Topics

A simple mod for the ptt pop squeal problem...

Mark <huitmarmottes@...>
 

Hi all,

I was googling around a bit, thinking of changing the gain on the lm386, and found a simple solution for the popping problem.

I found in some reading that pin 7 can be used for muting the amplifier. Muting will occur if either 0V or Vcc is applied to pin 7. So I simply installed a 1N4148 diode between the transmit supply line and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing of the ptt switch. There is still a small pop occuring after this mod, but it is reduced in magnitude by a great amount. I feel this is a nice mod and in keeping with the KISS theme of the BITX line :-)

I will put some photos up of my pcb after the mod, but it pretty easy to do on the backside as the 4-pin readymate connector header is just next to pin 7 on the lm386 and a diode reaches very easily between the two.

I also read that it is recommended, when using increased gain on the lm386 (like we are), to have a 1-10uF capacitor installed between pin 7 and ground in order to reduce power supply noise problems (see the second graph on the datasheet). This in itself helped a little bit with the pop problem (I tried this mod first) in that the pop sound changed from a "squeal" to a "crunch" which was a bit less unpleasant hi hi.

This mod is also easy to do on the backside as a small radial lead electrolytic or tantalum cap can be laid down along the pins of the IC and leads soldered between pins 7 and 2 (which is grounded).

Cheers and have a great day everyone!

Mark - N7EKU

Arv Evans
 

Mark N7EKU

Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.

Arv K7HKL
_._

On 09/13/2011 09:44 AM, Mark wrote:

Hi all,

I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.

I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)

I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.

I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.

This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).

Cheers and have a great day everyone!

Mark - N7EKU

Mark <huitmarmottes@...>
 

Any time Arv,

Let me know how it works for you...

73s,


Mark - N7EKU

--- On Tue, 9/13/11, Arv Evans <arvid.evans@...> wrote:

From: Arv Evans <arvid.evans@...>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@...
Date: Tuesday, September 13, 2011, 7:48 PM







 









Mark N7EKU



Nice mod. I will try it on the BITX20A that is lying on my workbench.

Thanks for the information.



Arv K7HKL

_._



On 09/13/2011 09:44 AM, Mark wrote:

Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU


[Non-text portions of this message have been removed]

redcatradio2000
 

Mark, Arv,

Would reversing the diode and picking up the PTT ground
work? That way the audio amp would be muted before the
transmitter was turn on. This might eliminate the pop
all together.

Frank - W4NHJ

On 9/13/11 6:29 PM, Mark wrote:

Any time Arv,

Let me know how it works for you...

73s,

Mark - N7EKU

--- On Tue, 9/13/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Tuesday, September 13, 2011, 7:48 PM



Mark N7EKU

Nice mod. I will try it on the BITX20A that is lying on my workbench.

Thanks for the information.

Arv K7HKL

_._

On 09/13/2011 09:44 AM, Mark wrote:

Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]



Mark <huitmarmottes@...>
 

Hi Frank,

Good idea, I think it should work -- the ptt jack is close so the connection should be easy.  I think I did test for muting using the diode either way with Vcc and Ground and both worked fine.  I also tried different diodes (silicon, germanium, schottky) to see if the different drops changed anything, but I couldn't tell a difference by ear anyway.

Maybe Arv can compare the two methods since he has a board on the bench!


Mark - N7EKU

--- On Tue, 9/13/11, Frank <w4nhj@...> wrote:

From: Frank <w4nhj@...>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@...
Date: Tuesday, September 13, 2011, 11:23 PM







 









Mark, Arv,



Would reversing the diode and picking up the PTT ground

work? That way the audio amp would be muted before the

transmitter was turn on. This might eliminate the pop

all together.



Frank - W4NHJ



On 9/13/11 6:29 PM, Mark wrote:

Any time Arv,
Let me know how it works for you...
73s,
Mark - N7EKU
--- On Tue, 9/13/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Tuesday, September 13, 2011, 7:48 PM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]






















[Non-text portions of this message have been removed]

kishore vagisetty
 

Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference.
73
v kishore
vu2-002swl

--- On Wed, 14/9/11, Arv Evans <arvid.evans@...> wrote:


From: Arv Evans <arvid.evans@...>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@...
Date: Wednesday, 14 September, 2011, 1:18 AM


 



Mark N7EKU

Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.

Arv K7HKL
_._

On 09/13/2011 09:44 AM, Mark wrote:

Hi all,

I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.

I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)

I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.

I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.

This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).

Cheers and have a great day everyone!

Mark - N7EKU

[Non-text portions of this message have been removed]








[Non-text portions of this message have been removed]

Mark <huitmarmottes@...>
 

Hi Kishore,

You're very welcome!  I hope especially the cap added from pin 7 to ground should help with the hum -- that's what the datasheet shows it is for.

NOTICE!!!    I tried moving the muting diode to the ptt position (cathode to ptt and anode to pin 7) so it should conduct ground to pin 7 when the ptt is pushed however it was not very effective in this position.  I think it has something to do with large inductive energy in the relay coil.  I do have a protection diode in there, but I'm afraid I may have partially fried my lm386.  So, I wouldn't recommend using the muting circuit in this position!

The original location I had going from pin 7 to the transmit power line works pretty well so I recommend putting there if you want to try it.

Cheers and 73s,


Mark - N7EKU

--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...> wrote:

From: kishore vagisetty <kishorev001@...>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@...
Date: Wednesday, September 14, 2011, 3:39 AM







 









Dear Mark N7EKU,

thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think ur discovery should make some difference.

73

v kishore

vu2-002swl



--- On Wed, 14/9/11, Arv Evans <arvid.evans@...> wrote:



From: Arv Evans <arvid.evans@...>

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...

To: BITX20@...

Date: Wednesday, 14 September, 2011, 1:18 AM



 



Mark N7EKU



Nice mod. I will try it on the BITX20A that is lying on my workbench.

Thanks for the information.



Arv K7HKL

_._



On 09/13/2011 09:44 AM, Mark wrote:

Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU


[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]






















[Non-text portions of this message have been removed]

Arv Evans
 

Frank & Mark

After a bit of playing I find that it eliminates part of the change-over
noise, but not all.
Possibly some sort of RC network is required to delay un-muting when
going from Tx
to Rx.

Part of the click is apparently related to the LM386 output lead going
to ground when
the power is removed for Tx mode and then coming back up to 1/2 Vcc when
power
is re-applied for receive mode activation.

Now that Mark came up with mute for the LM386, maybe we should try
leaving it
powered up but muted during transmit mode?

This whole thing with muting the LM386 has some interesting options to
consider.
What about instead of using pin-7 we were to use a MOSFET to switch the two
inputs together when transmitting so that input would be common-mode,
and then
letting the alternative input pin revert to ground when receiving?
Normal audio is
input on pin-3 with pin-2 connected to ground. Pin-2 could be grounded
through a
resistor and then use a MOSFET switch to connect pin-2 and pin-3
together when
transmitting. This might avoid the DC offset transition when changing
from transmit
to receive.
Also might be able to use a MOSFET (2N7000...?) to short the LM386 input
pin (pin-3)
to ground during transmit.

I may have to build up another ugly-constructed BITXxxA because thoughts
now are
running toward adding MOSFET switches in series with C77 and C8 to
totally separate
send and receive audio from the BFO mixer. This might eliminate the
charge and
discharge cycling of C77 and C8 as their respective circuits are powered
up and down
when switching between receive and transmit. Disconnecting the mic amp
output
during receive and disconnecting the receive audio input during transmit
could allow
those two circuits to remain powered up instead of switching them up and
down
and causing the current surge through C8 and C77. This could also
provide a way
to add sidetone if adding a keyed oscillator for CW.

Arv
_._

On 09/13/2011 05:23 PM, Frank wrote:

Mark, Arv,

Would reversing the diode and picking up the PTT ground
work? That way the audio amp would be muted before the
transmitter was turn on. This might eliminate the pop
all together.

Frank - W4NHJ

On 9/13/11 6:29 PM, Mark wrote:

Any time Arv,

Let me know how it works for you...

73s,

Mark - N7EKU

--- On Tue, 9/13/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Tuesday, September 13, 2011, 7:48 PM



Mark N7EKU

Nice mod. I will try it on the BITX20A that is lying on my workbench.

Thanks for the information.

Arv K7HKL

_._

On 09/13/2011 09:44 AM, Mark wrote:

Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]



Arv Evans
 

Mark, & others...

You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.

Arv
_._

On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,

You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.

NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!

The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to try it.

Cheers and 73s,

Mark - N7EKU

--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>> wrote:

From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM



Dear Mark N7EKU,

thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.

73

v kishore

vu2-002swl

--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...

To: BITX20@... <mailto:BITX20%40yahoogroups.com>

Date: Wednesday, 14 September, 2011, 1:18 AM



Mark N7EKU

Nice mod. I will try it on the BITX20A that is lying on my workbench.

Thanks for the information.

Arv K7HKL

_._

On 09/13/2011 09:44 AM, Mark wrote:

Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU


[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]

Mark <huitmarmottes@...>
 

Excellent advice Arv :-) 

Turns out my amp chip was OK.  For some reason now however (after trying the other diode position) I have a little leakage or noise from the mic circuit coming over the speaker at the beginning of transmit.  That wasn't happening before so I'm not sure what's up.  I had the chip in a socket already and switched it out but no change.  Not a big deal just wierd.  Maybe my mic wiring is running with different routing now since I had the set apart.

Yeah the mute mod didn't completely eliminate the pop for me either, but now it's pretty tolerable and is just a bit louder than the relay clicks on my set.

Cheers and lots of interesting ideas you have now Arv!



Mark - N7EKU

--- On Wed, 9/14/11, Arv Evans <arvid.evans@...> wrote:

From: Arv Evans <arvid.evans@...>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@...
Date: Wednesday, September 14, 2011, 5:08 AM







 









Mark, & others...



You could probably use a small transistor to switch Pin-7 and avoid

possibility of

damaging the LM-386 during the experimentation process. I routinely use a

socket for the LM-386, mostly because I like to tinker with things and

have fried a

few AF amp IC's. If you do have to replace a soldered-in-place LM386,

the easy

way is to cut all the legs off and then remove them from the PCB one at

a time.



Arv

_._



On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to try it.
Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]






















[Non-text portions of this message have been removed]

Arv Evans
 

Mark

Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on
raised the
board high enough for all wiring to be run under the board instead of
across the top.
This made it much easier to do measurements and to troubleshoot. And,
it looks
better with most of the wiring hidden under the board.

It might be interesting to try a large capacitor from pin-7 to ground on
the LM386?
Thinking is that this might slow down how fast this amplifier recovers
from power-
down during transmit and thus mask part of the changeover feedback
period. Idea
is that this could possibly act as a timed mute function. We could add
enough
components to do an actual time delay before allowing the LM386 to
activate but
that seems contrary to the minimalist concept of BITX design.

Arv
_._

On 09/14/2011 01:06 AM, Mark wrote:

Excellent advice Arv :-)

Turns out my amp chip was OK. For some reason now however (after
trying the other diode position) I have a little leakage or noise from
the mic circuit coming over the speaker at the beginning of transmit.
That wasn't happening before so I'm not sure what's up. I had the
chip in a socket already and switched it out but no change. Not a big
deal just wierd. Maybe my mic wiring is running with different
routing now since I had the set apart.

Yeah the mute mod didn't completely eliminate the pop for me either,
but now it's pretty tolerable and is just a bit louder than the relay
clicks on my set.

Cheers and lots of interesting ideas you have now Arv!

Mark - N7EKU

--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM



Mark, & others...

You could probably use a small transistor to switch Pin-7 and avoid

possibility of

damaging the LM-386 during the experimentation process. I routinely use a

socket for the LM-386, mostly because I like to tinker with things and

have fried a

few AF amp IC's. If you do have to replace a soldered-in-place LM386,

the easy

way is to cut all the legs off and then remove them from the PCB one at

a time.

Arv

_._

On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.

Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>

<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Marcel
 

Hello, maybe another idea:

I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop. 
It gave me no satisfaction, because the pop remained somehow.
My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais.
When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s. 
Now the pop has gone completely.

cheers and 73

Marcel - PE1LNX


________________________________
From: Arv Evans <arvid.evans@...>
To: BITX20@...
Sent: Wednesday, September 14, 2011 6:37 PM
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...


 
Mark

Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on
raised the
board high enough for all wiring to be run under the board instead of
across the top.
This made it much easier to do measurements and to troubleshoot. And,
it looks
better with most of the wiring hidden under the board.

It might be interesting to try a large capacitor from pin-7 to ground on
the LM386?
Thinking is that this might slow down how fast this amplifier recovers
from power-
down during transmit and thus mask part of the changeover feedback
period. Idea
is that this could possibly act as a timed mute function. We could add
enough
components to do an actual time delay before allowing the LM386 to
activate but
that seems contrary to the minimalist concept of BITX design.

Arv
_._

On 09/14/2011 01:06 AM, Mark wrote:

Excellent advice Arv :-)

Turns out my amp chip was OK. For some reason now however (after
trying the other diode position) I have a little leakage or noise from
the mic circuit coming over the speaker at the beginning of transmit.
That wasn't happening before so I'm not sure what's up. I had the
chip in a socket already and switched it out but no change. Not a big
deal just wierd. Maybe my mic wiring is running with different
routing now since I had the set apart.

Yeah the mute mod didn't completely eliminate the pop for me either,
but now it's pretty tolerable and is just a bit louder than the relay
clicks on my set.

Cheers and lots of interesting ideas you have now Arv!

Mark - N7EKU

--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM



Mark, & others...

You could probably use a small transistor to switch Pin-7 and avoid

possibility of

damaging the LM-386 during the experimentation process. I routinely use a

socket for the LM-386, mostly because I like to tinker with things and

have fried a

few AF amp IC's. If you do have to replace a soldered-in-place LM386,

the easy

way is to cut all the legs off and then remove them from the PCB one at

a time.

Arv

_._

On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.

Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>

<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]








[Non-text portions of this message have been removed]

Mark <huitmarmottes@...>
 

Nice solution Marcel!  Builders have some nice options now :-)

Mark - N7EKU

--- On Thu, 9/15/11, Marcel Jacobs <pe1lnx@...> wrote:

From: Marcel Jacobs <pe1lnx@...>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: "BITX20@..." <BITX20@...>
Date: Thursday, September 15, 2011, 8:04 PM







 









Hello, maybe another idea:



I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop. 

It gave me no satisfaction, because the pop remained somehow.

My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais.

When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s. 

Now the pop has gone completely.



cheers and 73



Marcel - PE1LNX



________________________________

From: Arv Evans <arvid.evans@...>

To: BITX20@...

Sent: Wednesday, September 14, 2011 6:37 PM

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...



 

Mark



Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on

raised the

board high enough for all wiring to be run under the board instead of

across the top.

This made it much easier to do measurements and to troubleshoot. And,

it looks

better with most of the wiring hidden under the board.



It might be interesting to try a large capacitor from pin-7 to ground on

the LM386?

Thinking is that this might slow down how fast this amplifier recovers

from power-

down during transmit and thus mask part of the changeover feedback

period. Idea

is that this could possibly act as a timed mute function. We could add

enough

components to do an actual time delay before allowing the LM386 to

activate but

that seems contrary to the minimalist concept of BITX design.



Arv

_._



On 09/14/2011 01:06 AM, Mark wrote:

Excellent advice Arv :-)
Turns out my amp chip was OK. For some reason now however (after
trying the other diode position) I have a little leakage or noise from
the mic circuit coming over the speaker at the beginning of transmit.
That wasn't happening before so I'm not sure what's up. I had the
chip in a socket already and switched it out but no change. Not a big
deal just wierd. Maybe my mic wiring is running with different
routing now since I had the set apart.
Yeah the mute mod didn't completely eliminate the pop for me either,
but now it's pretty tolerable and is just a bit louder than the relay
clicks on my set.
Cheers and lots of interesting ideas you have now Arv!
Mark - N7EKU
--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM
Mark, & others...
You could probably use a small transistor to switch Pin-7 and avoid
possibility of
damaging the LM-386 during the experimentation process. I routinely use a
socket for the LM-386, mostly because I like to tinker with things and
have fried a
few AF amp IC's. If you do have to replace a soldered-in-place LM386,
the easy
way is to cut all the legs off and then remove them from the PCB one at
a time.
Arv
_._
On 09/13/2011 10:29 PM, Mark wrote:
Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.
Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]






















[Non-text portions of this message have been removed]

Arv Evans
 

Marcel - PE1LNX

That is a good positive solution to the problem.

As far as I have been able to determine, the source of the clicks and pops,
and the 20 ms of carrier that gets sent when starting to transmit, is a
combination
of the power bypass capacitors for each stage holding some amount of voltage
after the power feed has been switched off, and the audio-to-mixer
coupling caps
charging & discharging causing temporary unbalance of the BFO mixer.

Arv K7HKL
_._


On 09/15/2011 02:04 PM, Marcel Jacobs wrote:

Hello, maybe another idea:

I've also played around with transistors and FET's at the input of the
LM386 of my BITX v3 to get rit of the pop.
It gave me no satisfaction, because the pop remained somehow.
My solution is a small SMD relais at the output of the LM386. It
switches the output between the speaker and an 8 Ohm resistor. The
relais gets his power from the TX signal via a diode and a C, in
parallel to the relais.
When keyed, it is activated immediately, but when de-keyed, it remains
active for 0,5s.
Now the pop has gone completely.

cheers and 73

Marcel - PE1LNX

________________________________
From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Sent: Wednesday, September 14, 2011 6:37 PM
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...


Mark

Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on
raised the
board high enough for all wiring to be run under the board instead of
across the top.
This made it much easier to do measurements and to troubleshoot. And,
it looks
better with most of the wiring hidden under the board.

It might be interesting to try a large capacitor from pin-7 to ground on
the LM386?
Thinking is that this might slow down how fast this amplifier recovers
from power-
down during transmit and thus mask part of the changeover feedback
period. Idea
is that this could possibly act as a timed mute function. We could add
enough
components to do an actual time delay before allowing the LM386 to
activate but
that seems contrary to the minimalist concept of BITX design.

Arv
_._

On 09/14/2011 01:06 AM, Mark wrote:

Excellent advice Arv :-)

Turns out my amp chip was OK. For some reason now however (after
trying the other diode position) I have a little leakage or noise from
the mic circuit coming over the speaker at the beginning of transmit.
That wasn't happening before so I'm not sure what's up. I had the
chip in a socket already and switched it out but no change. Not a big
deal just wierd. Maybe my mic wiring is running with different
routing now since I had the set apart.

Yeah the mute mod didn't completely eliminate the pop for me either,
but now it's pretty tolerable and is just a bit louder than the relay
clicks on my set.

Cheers and lots of interesting ideas you have now Arv!

Mark - N7EKU

--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM



Mark, & others...

You could probably use a small transistor to switch Pin-7 and avoid

possibility of

damaging the LM-386 during the experimentation process. I routinely
use a

socket for the LM-386, mostly because I like to tinker with things and

have fried a

few AF amp IC's. If you do have to replace a soldered-in-place LM386,

the easy

way is to cut all the legs off and then remove them from the PCB one at

a time.

Arv

_._

On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.

Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>

<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to
pin 7.

So I simply installed a 1N4148 diode between the transmit supply
line

and pin 7 of the lm386 so that it conducts Vcc to the pin upon
closing

of the ptt switch. There is still a small pop occuring after
this mod,

but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty
easy

to do on the backside as the 4-pin readymate connector header is
just

next to pin 7 on the lm386 and a diode reaches very easily
between the

two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed
between pin

7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less
unpleasant

hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of
the IC

and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]

k4dsb
 

I used a reed relay in series with the LM386 output driven by the TX voltage bus...

Reeds are known for their low power and fast switching time...also very low ohmic resistance

I do hear a tiny, almost a light click when switching to transmit...NOTHING like the POP I heard before.
Arv and I had a discussion on an early thread on the same subject...
A transistor would work but much more complex

K4DSB
Dean




To: BITX20@...
From: pe1lnx@...
Date: Thu, 15 Sep 2011 13:04:41 -0700
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...






Hello, maybe another idea:

I've also played around with transistors and FET's at the input of the LM386 of my BITX v3 to get rit of the pop.
It gave me no satisfaction, because the pop remained somehow.
My solution is a small SMD relais at the output of the LM386. It switches the output between the speaker and an 8 Ohm resistor. The relais gets his power from the TX signal via a diode and a C, in parallel to the relais.
When keyed, it is activated immediately, but when de-keyed, it remains active for 0,5s.
Now the pop has gone completely.

cheers and 73

Marcel - PE1LNX

________________________________
From: Arv Evans <arvid.evans@...>
To: BITX20@...
Sent: Wednesday, September 14, 2011 6:37 PM
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...


Mark

Adding 1/4 inch spacers under the PCB for the last BITX20A I worked on
raised the
board high enough for all wiring to be run under the board instead of
across the top.
This made it much easier to do measurements and to troubleshoot. And,
it looks
better with most of the wiring hidden under the board.

It might be interesting to try a large capacitor from pin-7 to ground on
the LM386?
Thinking is that this might slow down how fast this amplifier recovers
from power-
down during transmit and thus mask part of the changeover feedback
period. Idea
is that this could possibly act as a timed mute function. We could add
enough
components to do an actual time delay before allowing the LM386 to
activate but
that seems contrary to the minimalist concept of BITX design.

Arv
_._

On 09/14/2011 01:06 AM, Mark wrote:

Excellent advice Arv :-)

Turns out my amp chip was OK. For some reason now however (after
trying the other diode position) I have a little leakage or noise from
the mic circuit coming over the speaker at the beginning of transmit.
That wasn't happening before so I'm not sure what's up. I had the
chip in a socket already and switched it out but no change. Not a big
deal just wierd. Maybe my mic wiring is running with different
routing now since I had the set apart.

Yeah the mute mod didn't completely eliminate the pop for me either,
but now it's pretty tolerable and is just a bit louder than the relay
clicks on my set.

Cheers and lots of interesting ideas you have now Arv!

Mark - N7EKU

--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@... <mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM



Mark, & others...

You could probably use a small transistor to switch Pin-7 and avoid

possibility of

damaging the LM-386 during the experimentation process. I routinely use a

socket for the LM-386, mostly because I like to tinker with things and

have fried a

few AF amp IC's. If you do have to replace a soldered-in-place LM386,

the easy

way is to cut all the legs off and then remove them from the PCB one at

a time.

Arv

_._

On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,
You're very welcome! I hope especially the cap added from pin 7 to
ground should help with the hum -- that's what the datasheet shows it
is for.
NOTICE!!! I tried moving the muting diode to the ptt position
(cathode to ptt and anode to pin 7) so it should conduct ground to pin
7 when the ptt is pushed however it was not very effective in this
position. I think it has something to do with large inductive energy
in the relay coil. I do have a protection diode in there, but I'm
afraid I may have partially fried my lm386. So, I wouldn't recommend
using the muting circuit in this position!
The original location I had going from pin 7 to the transmit power
line works pretty well so I recommend putting there if you want to
try it.

Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>> wrote:
From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me with 50hz hum. i think
ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>

<mailto:arvid.evans%40gmail.com>> wrote:
From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com> <mailto:arvid.evans%40gmail.com>>

Subject: Re: [BITX20] A simple mod for the ptt pop squeal problem...
To: BITX20@... <mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is lying on my workbench.
Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of changing the gain on the
lm386, and found a simple solution for the popping problem.
I found in some reading that pin 7 can be used for muting the
amplifier. Muting will occur if either 0V or Vcc is applied to pin 7.
So I simply installed a 1N4148 diode between the transmit supply line
and pin 7 of the lm386 so that it conducts Vcc to the pin upon closing
of the ptt switch. There is still a small pop occuring after this mod,
but it is reduced in magnitude by a great amount. I feel this is a
nice mod and in keeping with the KISS theme of the BITX line :-)
I will put some photos up of my pcb after the mod, but it pretty easy
to do on the backside as the 4-pin readymate connector header is just
next to pin 7 on the lm386 and a diode reaches very easily between the
two.
I also read that it is recommended, when using increased gain on the
lm386 (like we are), to have a 1-10uF capacitor installed between pin
7 and ground in order to reduce power supply noise problems (see the
second graph on the datasheet). This in itself helped a little bit
with the pop problem (I tried this mod first) in that the pop sound
changed from a "squeal" to a "crunch" which was a bit less unpleasant
hi hi.
This mod is also easy to do on the backside as a small radial lead
electrolytic or tantalum cap can be laid down along the pins of the IC
and leads soldered between pins 7 and 2 (which is grounded).
Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been removed]


[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

Mark <huitmarmottes@...>
 

Hi Dean,

I saw you earlier mod and some of the others with relays and transistors. I just thought the diode mod might be usefull for those without a lot of parts - just a throw away quality doide works fine for the mod - one part and cheap and works fairly well :-)


Mark - N7EKU

--- On Fri, 9/16/11, Dean Blake <dsblake1@...> wrote:

From: Dean Blake <dsblake1@...>
Subject: RE: [BITX20] A simple mod for the ptt pop squeal problem...
To: bitx20@...
Date: Friday, September 16, 2011, 11:45 AM

I used a reed relay in series with the LM386 output driven
by the TX voltage bus...

Reeds are known for their low power and fast switching
time...also very low ohmic resistance

I do hear a tiny, almost a light click when switching to
transmit...NOTHING like the POP I heard before.
Arv and I had a discussion on an early thread on the same
subject...
A transistor would work but much more complex

K4DSB
Dean




To: BITX20@...
From: pe1lnx@...
Date: Thu, 15 Sep 2011 13:04:41 -0700
Subject: Re: [BITX20] A simple mod for the ptt pop squeal
problem...


 



Hello, maybe another idea:

I've also played around with transistors and FET's at the
input of the LM386 of my BITX v3 to get rit of the pop.
It gave me no satisfaction, because the pop remained
somehow.
My solution is a small SMD relais at the output of the
LM386. It switches the output between the speaker and an 8
Ohm resistor. The relais gets his power from the TX signal
via a diode and a C, in parallel to the relais.
When keyed, it is activated immediately, but when de-keyed,
it remains active for 0,5s.
Now the pop has gone completely.

cheers and 73

Marcel - PE1LNX

________________________________
From: Arv Evans <arvid.evans@...>
To: BITX20@...
Sent: Wednesday, September 14, 2011 6:37 PM
Subject: Re: [BITX20] A simple mod for the ptt pop squeal
problem...

 
Mark

Adding 1/4 inch spacers under the PCB for the last BITX20A
I worked on
raised the
board high enough for all wiring to be run under the board
instead of
across the top.
This made it much easier to do measurements and to
troubleshoot. And,
it looks
better with most of the wiring hidden under the board.

It might be interesting to try a large capacitor from pin-7
to ground on
the LM386?
Thinking is that this might slow down how fast this
amplifier recovers
from power-
down during transmit and thus mask part of the changeover
feedback
period. Idea
is that this could possibly act as a timed mute function.
We could add
enough
components to do an actual time delay before allowing the
LM386 to
activate but
that seems contrary to the minimalist concept of BITX
design.

Arv
_._

On 09/14/2011 01:06 AM, Mark wrote:

Excellent advice Arv :-)

Turns out my amp chip was OK. For some reason now
however (after
trying the other diode position) I have a little
leakage or noise from
the mic circuit coming over the speaker at the
beginning of transmit.
That wasn't happening before so I'm not sure what's
up. I had the
chip in a socket already and switched it out but no
change. Not a big
deal just wierd. Maybe my mic wiring is running with
different
routing now since I had the set apart.

Yeah the mute mod didn't completely eliminate the pop
for me either,
but now it's pretty tolerable and is just a bit louder
than the relay
clicks on my set.

Cheers and lots of interesting ideas you have now
Arv!

Mark - N7EKU

--- On Wed, 9/14/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>> wrote:

From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>>
Subject: Re: [BITX20] A simple mod for the ptt pop
squeal problem...
To: BITX20@...
<mailto:BITX20%40yahoogroups.com>
Date: Wednesday, September 14, 2011, 5:08 AM



Mark, & others...

You could probably use a small transistor to switch
Pin-7 and avoid

possibility of

damaging the LM-386 during the experimentation
process. I routinely use a

socket for the LM-386, mostly because I like to tinker
with things and

have fried a

few AF amp IC's. If you do have to replace a
soldered-in-place LM386,

the easy

way is to cut all the legs off and then remove them
from the PCB one at

a time.

Arv

_._

On 09/13/2011 10:29 PM, Mark wrote:

Hi Kishore,
You're very welcome! I hope especially the cap
added from pin 7 to

ground should help with the hum -- that's what
the datasheet shows it

is for.
NOTICE!!! I tried moving the muting diode to the
ptt position

(cathode to ptt and anode to pin 7) so it should
conduct ground to pin

7 when the ptt is pushed however it was not very
effective in this

position. I think it has something to do with
large inductive energy

in the relay coil. I do have a protection diode
in there, but I'm

afraid I may have partially fried my lm386. So, I
wouldn't recommend

using the muting circuit in this position!
The original location I had going from pin 7 to
the transmit power

line works pretty well so I recommend putting
there if you want to
try it.

Cheers and 73s,
Mark - N7EKU
--- On Wed, 9/14/11, kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>>
wrote:

From: kishore vagisetty <kishorev001@...
<mailto:kishorev001%40yahoo.co.in>

<mailto:kishorev001%40yahoo.co.in>>
Subject: Re: [BITX20] A simple mod for the ptt
pop squeal problem...

To: BITX20@...
<mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, September 14, 2011, 3:39 AM
Dear Mark N7EKU,
thanks for info !! my BITX20 ver3 troubles me
with 50hz hum. i think

ur discovery should make some difference.
73
v kishore
vu2-002swl
--- On Wed, 14/9/11, Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>

<mailto:arvid.evans%40gmail.com>>
wrote:

From: Arv Evans <arvid.evans@...
<mailto:arvid.evans%40gmail.com>
<mailto:arvid.evans%40gmail.com>>

Subject: Re: [BITX20] A simple mod for the ptt
pop squeal problem...

To: BITX20@...
<mailto:BITX20%40yahoogroups.com>
<mailto:BITX20%40yahoogroups.com>

Date: Wednesday, 14 September, 2011, 1:18 AM
Mark N7EKU
Nice mod. I will try it on the BITX20A that is
lying on my workbench.

Thanks for the information.
Arv K7HKL
_._
On 09/13/2011 09:44 AM, Mark wrote:
Hi all,
I was googling around a bit, thinking of
changing the gain on the

lm386, and found a simple solution for the
popping problem.

I found in some reading that pin 7 can be
used for muting the

amplifier. Muting will occur if either 0V or
Vcc is applied to pin 7.

So I simply installed a 1N4148 diode between
the transmit supply line

and pin 7 of the lm386 so that it conducts
Vcc to the pin upon closing

of the ptt switch. There is still a small
pop occuring after this mod,

but it is reduced in magnitude by a great
amount. I feel this is a

nice mod and in keeping with the KISS theme
of the BITX line :-)

I will put some photos up of my pcb after
the mod, but it pretty easy

to do on the backside as the 4-pin readymate
connector header is just

next to pin 7 on the lm386 and a diode
reaches very easily between the

two.
I also read that it is recommended, when
using increased gain on the

lm386 (like we are), to have a 1-10uF
capacitor installed between pin

7 and ground in order to reduce power supply
noise problems (see the

second graph on the datasheet). This in
itself helped a little bit

with the pop problem (I tried this mod
first) in that the pop sound

changed from a "squeal" to a "crunch" which
was a bit less unpleasant

hi hi.
This mod is also easy to do on the backside
as a small radial lead

electrolytic or tantalum cap can be laid
down along the pins of the IC

and leads soldered between pins 7 and 2
(which is grounded).

Cheers and have a great day everyone!
Mark - N7EKU
[Non-text portions of this message have been
removed]

[Non-text portions of this message have been
removed]

[Non-text portions of this message have been
removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]




   
        
          
 

[Non-text portions of this message have been removed]



------------------------------------

Yahoo! Groups Links


    BITX20-fullfeatured@...


bryan
 

Reading Marcel`s report on PTT Noise Fix .
I tried the relay fix but may be I got the wiring wrong
Did Marcel  switch both + and - leads of the speaker to  ground
or just the + lead  to speaker to a 8 Ohm resistor to speaker ground
or to board ground ?

I have had no luck with switching + line to speaker to speaker ground through an 8 Ohm resistor .
Still a very loud pop.
Bryan vk7kwb