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Alternate pop fix...

ajparent1/KB1GMX
 

While working with the uBitx V3 I finally got annoyed enough by the pop to fix it.
Basically copied from uBITX V4 but it still popped some..

Parts count 4:
2 1n4148/914 diodes.
1 10K resistor (any value from 10 to 100K really)
1 2n7000 mosfet

Why the second diode?  The TX line is relay switched 12V and relays are not instant
they take milliseconds to physically move contacts.  So the second diode to the T/R line
form the Raduino its the fast acting audio kill as that the command to the relay.  The
second diode resistor is the hold until the relay returns to RX position.

TX muting with no pop, no thump.  

Allison

schematic enclosed.

Skip Davis
 

Allison try moving the FET to the M1/C51 side and mute the audio preamp directly that is where I have it and I’m not experiencing any detectable pop in my headphones. Having said that, your results may very. 

Skip Davis, NC9O 

On Jun 16, 2018, at 16:28, ajparent1/KB1GMX <kb1gmx@...> wrote:

While working with the uBitx V3 I finally got annoyed enough by the pop to fix it.
Basically copied from uBITX V4 but it still popped some..

Parts count 4:
2 1n4148/914 diodes.
1 10K resistor (any value from 10 to 100K really)
1 2n7000 mosfet

Why the second diode?  The TX line is relay switched 12V and relays are not instant
they take milliseconds to physically move contacts.  So the second diode to the T/R line
form the Raduino its the fast acting audio kill as that the command to the relay.  The
second diode resistor is the hold until the relay returns to RX position.

TX muting with no pop, no thump.  

Allison

schematic enclosed.
<IMG_1834.JPG>

Skip Davis
 

Also move the parallel resistor/diode to the Raduino T/R and you won’t need the other diode you added.

Skip Davis, NC9O 

On Jun 16, 2018, at 18:06, Skip Davis via Groups.Io <skipnc9o@...> wrote:

Allison try moving the FET to the M1/C51 side and mute the audio preamp directly that is where I have it and I’m not experiencing any detectable pop in my headphones. Having said that, your results may very. 

Skip Davis, NC9O 

On Jun 16, 2018, at 16:28, ajparent1/KB1GMX <kb1gmx@...> wrote:

While working with the uBitx V3 I finally got annoyed enough by the pop to fix it.
Basically copied from uBITX V4 but it still popped some..

Parts count 4:
2 1n4148/914 diodes.
1 10K resistor (any value from 10 to 100K really)
1 2n7000 mosfet

Why the second diode?  The TX line is relay switched 12V and relays are not instant
they take milliseconds to physically move contacts.  So the second diode to the T/R line
form the Raduino its the fast acting audio kill as that the command to the relay.  The
second diode resistor is the hold until the relay returns to RX position.

TX muting with no pop, no thump.  

Allison

schematic enclosed.
<IMG_1834.JPG>

ajparent1/KB1GMX
 

Skip,

M1/C51 or the top of the pot are the same effect for this.
The spot I picked allowed an easier dead bug hookup.

Allison

ajparent1/KB1GMX
 

Hi Skip,

Also just having the Resistor and diode on the Radiuno was less effective
as you get the return to RX thump when DC is applied to Q70.  It only got the POP.
I wanted the TX release thump to go away.

This approach using the Raduino kills the RX audio before the relay actually moves so the key
down pop when power is applied to Q6 disappears completely.  The TX power resistor and diode
hold the audio off until after Q70 has power by a few milliseconds (1k*.1uf=about 1ms) and that
kills the return to RX thump.  FYI the cap needs about 3-4 RC time to release the mosfet as
the gate threshold us under 4V and we charge the cap to 12V.

Its a timing issue.  Relays are slow and there are enough capacitors in the switched lines
that nothing stops working immediately so we get RX/TX overlap.  

Muting this way is very clean and the audio comes back smoothly.  That and its well tested.
I finally got to writing it up.


Allison

Skip Davis
 

Yes it is the timing Allison I set mine to about 1.5 ms (I’d have to check my notes) and that solved both thump and pop. I played with the values too before settling on what I ended up with, using parts on hand. 

Skip Davis, NC9O

On Jun 16, 2018, at 19:25, ajparent1/KB1GMX <kb1gmx@...> wrote:

Hi Skip,

Also just having the Resistor and diode on the Radiuno was less effective
as you get the return to RX thump when DC is applied to Q70.  It only got the POP.
I wanted the TX release thump to go away.

This approach using the Raduino kills the RX audio before the relay actually moves so the key
down pop when power is applied to Q6 disappears completely.  The TX power resistor and diode
hold the audio off until after Q70 has power by a few milliseconds (1k*.1uf=about 1ms) and that
kills the return to RX thump.  FYI the cap needs about 3-4 RC time to release the mosfet as
the gate threshold us under 4V and we charge the cap to 12V.

Its a timing issue.  Relays are slow and there are enough capacitors in the switched lines
that nothing stops working immediately so we get RX/TX overlap.  

Muting this way is very clean and the audio comes back smoothly.  That and its well tested.
I finally got to writing it up.


Allison

ajparent1/KB1GMX
 

What's not seen and didn't make a difference to pop/thump was I removed k3 from the audio path
(K3 contacts 1,3,5) so I could use them to ground the RX path during TX and use K1 to switch
the antenna and Q90 to the output/input of the 30mhz low pass filter.  This relieves the filter
and receiver of Q90 base resistor (100 ohms) from the path on RX and helps improve sensitivity.

There are many mods most will not do or feel are not needed for them.  Most of what I am doing
are to suit my wishes eclectic as they may be.

Allison

davedt1e@...
 

Excellent!   Thank you Allison!  And thanks for the diagram too!

 

Alison :

Doesn't it kill the CW Sidetone with your mute connected to VOL-H ?
Ashar has his V4 pop circuit connected at M2(R70) with the value of R70 increased to 1K ohms.  I think that this option still allows you to
hear CW sidetone.

Skip (NC9O),  M1/M2 is connected via relay (RX voltage) so I would think that you would want to mute at M2 rather than M1/C51 to isolate the
input of the audio amp from the relay opening and closing. 

Michael VE3WMB 

P.S. Alison ... thanks for this it is very timely as I was just about to build a pop fix for my V3 board ! 

ajparent1/KB1GMX
 

Michael,

It would if I were using CW and sidetone.  Remember my last line on eclectic choices...
>> Most of what I am doing are to suit my wishes eclectic as they may be.<<<
I do what I did for my application.  If you do it the other way it should allow sidetone.

My build excludes support for CW, completely.  I rarely use it and I have several
QRP CW transceivers [love my 1W] that are optimum for the mode and far less
battery hungry.

Since I wish to have 10M I've planed a bandpass filter for the band (extra switching). 
I do not need or use wide tuning so there is a band change button that takes me to
the last frequency in a given band and the band list is 80/40/20/10M because for
portable ops those are more useful and I have many monobanders, Argonaut 505, and
a FT817.  The menu system is out the door and there are separate buttons for band
select, VFO, Split enable, fast tune, RX agc, TX alc, and so on.  Eclectic choices but
what I favor as its a modders delight radio.

Allison

 

Allison :

Therein lies the beauty of building/customizing your own radio .. you choose to make it work the way you want it to.
If you don't plan to use it for CW, then there is no need to worry about sidetone ! 

This also applies to my philosophy on enclosures. There are some very nice commercially made uBITX enclosures out there but I would rather 
"roll my own" as I then I am free to determine what goes on the front panel and where it is located. Some people don't care, some do ... it is nice
to have the choice. 

Thanks again for sharing your mods ... 

Cheers

Michael VE3WMB 

 

I built up Allison's (KB1GMX) anti-pop circuit on a small piece of single-sided copper-clad board, using Manhattan building techniques and MEPADS (www.qrpme.com
and I must say that it does an excellent job of suppressing the pops on both the RX to TX and the TX to RX transitions.

The idea of using the second diode connected to the Raduino T/R line is brilliant as it gives the circuit a head-start on muting the audio before the relays are engaged on TX.
Bravo ! 

I ended up having to play with the value of the capacitor as I was still getting some noise on the TX to RX transition. For whatever reason I ended up with an extra
1uF paralleled with the specified 0.1 uF. I haven't really had a minute to go back and look in detail at why this was necessary, but the end result is that I can now use
headphones with my uBITX without hurting my ears so that is all that matters. 

I have attached a picture of my little board. 

BTW, since I do plan on using the rig for CW and thus did want to preserve sidetone, I replaced R70 (100 ohms located on the far right edge of the board about half way back) with a 1K resistor as Farhan has done on the V4 boards.  

I connected the drain on the 2n7000 to the M2 end of R70 (the end furthest back). 
I connected a ground wire (twisted together with the above wire) to end of D8 closest to the right edge of the board (D8 is very close to R70).

The 5 v T/R input  is connected via a single wire to the junction of C150 & R150 on the back left corned of the board (between relay K1 and P1 - the power connector). 

The TX input  is connected to the end of C150 closest to D13 (this is 12v on TX). 

Cheers

Michael VE3WMB 

P.S. BTW the bulges in the wires are ferrite beads covered in heat shrink tubing.
Overkill, but I like to try to keep RF out of where it doesn't belong and I ended up with a life-time
supply of mix 43 beads as I needed one and had to order 100 so I figured that I might as well use them ;-)