Topics

No audio driver

Michael Davis <maddmd818@...>
 

Hi again. I searched the site but couldn't find an answer to my new problem. The radio has been working just fine for awhile now. However after trying a few qso's with strong stations, I realized that I have no transmit audio. I suspected a bad wire from the electret mic to the board, but that doesn't seem to be it. I don't know how to test the mic element, as I only have a DMM and no scope. So far I have measured PA current and have the 100ma, however when I do the hallloooww thing, I get no increase in current. I also monitored my signal on my base hf rig and get no S meter fluxuation as I yell into the mic. I'm in the process of printing out the mic input circuit so I can start taking voltage and resistance readings. Any suggestions are always appreciated. WA1MAD

Randy Hall
 

Michael

Try swapping the wires on the back of the mic. The mic is polarity sensitive. The ground side may have a faint green color to it. You may hear then yourself!

Randy, K7AGE


On Sat, Apr 1, 2017 at 1:58 PM, Michael Davis <maddmd818@...> wrote:

Hi again. I searched the site but couldn't find an answer to my new problem. The radio has been working just fine for awhile now. However after trying a few qso's with strong stations, I realized that I have no transmit audio. I suspected a bad wire from the electret mic to the board, but that doesn't seem to be it. I don't know how to test the mic element, as I only have a DMM and no scope. So far I have measured PA current and have the 100ma, however when I do the hallloooww thing, I get no increase in current. I also monitored my signal on my base hf rig and get no S meter fluxuation as I yell into the mic. I'm in the process of printing out the mic input circuit so I can start taking voltage and resistance readings. Any suggestions are always appreciated. WA1MAD


John Backo
 

Mike. please realize that the hfsigs group aligns the BITX40 for RX (to 40m), but does NOT do any TX alignment.

There is one reference to TX and that is to increase the rig current by 100ma. with the PA connected.

Transmit involves the audio mic amplifier, the PA drive, and the PA output voltage. Most likely the mic audio
is ok, if connected properly. But the IRF510 gate voltage and the PA drive need to be set for proper operation.
This involves adjusting RV1 AND R136. Set the current up 100 ma. with the IRF510 connected. This is done
by adjusting RV1. NOTE WELL that the gate voltage on the IRF510 should not exceed 4v. or so.

Then, with the mic connected, try speaking into it in TX mode. Observe the current draw of the IRF510. It should
increase to about 1 amp or so. If it does not, the first thing top try is an adjustment to R136. Slowly increase R136
(the PA drive) until you see an increase in the current draw on transmit. This is the proper procedure to get into TX mode.

See the Topic "BITX40 Low Output Power" (message 23134 and following) for more information.

Jerry, perhaps a short paper on transmitter adjustment is in order? It should be on the same page as hookup
information.

john
AD5YE

Ashhar Farhan
 

I am trying to figure out a simple tx checkout procedure that doesn't need, say, "connect a 1ghz spectrum analyzer to point x". 
The difficulty with a good procedure to align the the tx is that, it needs to 'see' the RF at fairly low levels of 100 mv or so. This is quite difficult with a simple diode probe. The diode probes work only above 1v levels. One could add an RF amplifier to boost up the levels, but that is just too much complication.
does anyone have a better idea of a simple 2-3 component rf detector?

- f

On Sun, Apr 2, 2017 at 7:49 AM, John Backo via Groups.Io <iam74@...> wrote:
Mike. please realize that the hfsigs group aligns the BITX40 for RX (to 40m), but does NOT do any TX alignment.

There is one reference to TX and that is to increase the rig current by 100ma. with the PA connected.

Transmit involves the audio mic amplifier, the PA drive, and the PA output voltage. Most likely the mic audio
is ok, if connected properly. But the IRF510 gate voltage and the PA drive need to be set for proper operation.
This involves adjusting RV1 AND R136. Set the current up 100 ma. with the IRF510 connected. This is done
by adjusting RV1. NOTE WELL that the gate voltage on the IRF510 should not exceed 4v. or so.

Then, with the mic connected, try speaking into it in TX mode. Observe the current draw of the IRF510. It should
increase to about 1 amp or so. If it does not, the first thing top try is an adjustment to R136. Slowly increase R136
(the PA drive) until you see an increase in the current draw on transmit. This is the proper procedure to get into TX mode.

See the Topic "BITX40 Low Output Power" (message 23134 and following) for more information.

Jerry, perhaps a short paper on transmitter adjustment is in order? It should be on the same page as hookup
information.

john
AD5YE




 

How about this Farhan?

http://www.ebay.com/itm/182209512477

It should do, very economical RF probe!

73 Raj

At 02-04-2017, you wrote:
I am trying to figure out a simple tx checkout procedure that doesn't need, say, "connect a 1ghz spectrum analyzer to point x".Â
The difficulty with a good procedure to align the the tx is that, it needs to 'see' the RF at fairly low levels of 100 mv or so. This is quite difficult with a simple diode probe. The diode probes work only above 1v levels. One could add an RF amplifier to boost up the levels, but that is just too much complication.
does anyone have a better idea of a simple 2-3 component rf detector?

Lawrence Galea
 

Farhan
how about measuring voltage changes in supply or emitter resistors?
Regards
Lawrence

On Sun, Apr 2, 2017 at 8:54 AM, Ashhar Farhan <farhanbox@...> wrote:
I am trying to figure out a simple tx checkout procedure that doesn't need, say, "connect a 1ghz spectrum analyzer to point x". 
The difficulty with a good procedure to align the the tx is that, it needs to 'see' the RF at fairly low levels of 100 mv or so. This is quite difficult with a simple diode probe. The diode probes work only above 1v levels. One could add an RF amplifier to boost up the levels, but that is just too much complication.
does anyone have a better idea of a simple 2-3 component rf detector?

- f

On Sun, Apr 2, 2017 at 7:49 AM, John Backo via Groups.Io <iam74=rocketmail.com@groups.io> wrote:
Mike. please realize that the hfsigs group aligns the BITX40 for RX (to 40m), but does NOT do any TX alignment.

There is one reference to TX and that is to increase the rig current by 100ma. with the PA connected.

Transmit involves the audio mic amplifier, the PA drive, and the PA output voltage. Most likely the mic audio
is ok, if connected properly. But the IRF510 gate voltage and the PA drive need to be set for proper operation.
This involves adjusting RV1 AND R136. Set the current up 100 ma. with the IRF510 connected. This is done
by adjusting RV1. NOTE WELL that the gate voltage on the IRF510 should not exceed 4v. or so.

Then, with the mic connected, try speaking into it in TX mode. Observe the current draw of the IRF510. It should
increase to about 1 amp or so. If it does not, the first thing top try is an adjustment to R136. Slowly increase R136
(the PA drive) until you see an increase in the current draw on transmit. This is the proper procedure to get into TX mode.

See the Topic "BITX40 Low Output Power" (message 23134 and following) for more information.

Jerry, perhaps a short paper on transmitter adjustment is in order? It should be on the same page as hookup
information.

john
AD5YE





Ashhar Farhan
 

The transistor current stays the same in all the class A amplifiers. It won't do. It should be something simple that is available in every shack. probably, a slightly forward biased diode will do it.

- f

On Sun, Apr 2, 2017 at 2:50 PM, Lawrence Galea <9h1avlaw@...> wrote:
Farhan
how about measuring voltage changes in supply or emitter resistors?
Regards
Lawrence

On Sun, Apr 2, 2017 at 8:54 AM, Ashhar Farhan <farhanbox@...> wrote:
I am trying to figure out a simple tx checkout procedure that doesn't need, say, "connect a 1ghz spectrum analyzer to point x". 
The difficulty with a good procedure to align the the tx is that, it needs to 'see' the RF at fairly low levels of 100 mv or so. This is quite difficult with a simple diode probe. The diode probes work only above 1v levels. One could add an RF amplifier to boost up the levels, but that is just too much complication.
does anyone have a better idea of a simple 2-3 component rf detector?

- f

On Sun, Apr 2, 2017 at 7:49 AM, John Backo via Groups.Io <iam74=rocketmail.com@...o> wrote:
Mike. please realize that the hfsigs group aligns the BITX40 for RX (to 40m), but does NOT do any TX alignment.

There is one reference to TX and that is to increase the rig current by 100ma. with the PA connected.

Transmit involves the audio mic amplifier, the PA drive, and the PA output voltage. Most likely the mic audio
is ok, if connected properly. But the IRF510 gate voltage and the PA drive need to be set for proper operation.
This involves adjusting RV1 AND R136. Set the current up 100 ma. with the IRF510 connected. This is done
by adjusting RV1. NOTE WELL that the gate voltage on the IRF510 should not exceed 4v. or so.

Then, with the mic connected, try speaking into it in TX mode. Observe the current draw of the IRF510. It should
increase to about 1 amp or so. If it does not, the first thing top try is an adjustment to R136. Slowly increase R136
(the PA drive) until you see an increase in the current draw on transmit. This is the proper procedure to get into TX mode.

See the Topic "BITX40 Low Output Power" (message 23134 and following) for more information.

Jerry, perhaps a short paper on transmitter adjustment is in order? It should be on the same page as hookup
information.

john
AD5YE






Al Duncan VE3RRD
 

If you now have no output when you speak into the mic, but the receive is OK (but everything worked OK previously); then another component to check is Q13. Although Q13 is in the TX path, it is left in the circuit during RX. If you have transmitted on another 100W or higher power rig while the Bitx40 was in RX mode on a nearby antenna,then there is a good chance you have blown Q13 - if you didn't install the two 1N4148 protection diodes between K1 pin 12 and ground. The picture in the following message shows the location on the board:

https://groups.io/g/BITX20/message/22844?p=Created,,,20,1,0,0::Created,,minimum+mods,20,2,40,4415405

Placing them between pin 12 and ground means they are only in the circuit during RX; you might not want an extra couple of non-forward biased diode junctions in the TX path during transmit that could generate noise, harmonics etc. Q13 can be replaced by a 2N3904.

Jerry Gaffke
 

Could use the diode probe if a signal is injected into the amp with some kind of probe, giving a response 2 or 3  times bigger than it normally is.


On Sun, Apr 2, 2017 at 06:01 am, Ashhar Farhan wrote:

The difficulty with a good procedure to align the the tx is that, it needs to 'see' the RF at fairly low levels of 100 mv or so.

 

Jerry Gaffke
 

Actually, a germanium (and likely even schottky) diode probe can work down below 100mv if the current is kept low enough (if the voltmeter is at least a megaohm or so).  That curve is exponential, not two straight lines meeting at a "knee" as we (and LTSPICE) usually think of it.  Below 100mv the results can be repeatable though certainly not linear.  If we use an analog input to the Nano as the voltmeter, then everybody will have about the same voltmeter input impedance to better compare results.

> The diode probes work only above 1v levels.

Soundararajan Ra.
 

I hope we can use RF probe with germanium diode when set righting a nonworking BITX by comparing working BITX rig..

On Sun, Apr 2, 2017 at 8:23 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

Actually, a germanium (and likely even schottky) diode probe can work down below 100mv if the current is kept low enough (if the voltmeter is at least a megaohm or so).  That curve is exponential, not two straight lines meeting at a "knee" as we (and LTSPICE) usually think of it.  Below 100mv the results can be repeatable though certainly not linear.  If we use an analog input to the Nano as the voltmeter, then everybody will have about the same voltmeter input impedance to better compare results.

> The diode probes work only above 1v levels.


Jerry Gaffke
 

I haven't had reason to play with diode RF probes.  But here's a quote from  http://www.tuberadioforum.com/t4138-simple-rf-probe-for-my-dmm  suggesting they work well enough at far far lower RF voltages than you might think:

  This one is a bit more sophisticated. It is still a passive probe, but can be calibrated in both output and linearity. Its minimum sensitivity is about 2.3 mVrms input, and in testing so far, has an essentially a flat response from high audio frequencies to about 30 MHz I have not gone beyond that, but it should be good to 100 MHz or so.  The main difference with this RF probe is the fact that it is just about dead on 1:1 RMS input to DC output from 150 mV to past 15V. Again, it should continue to be linear, but I have not tested its voltage response beyond about 26 dB.

Most of the RF probe designs out there use the meter's internal resistance in series with a resistor in the RF probe to convert pk-to-pk into rms voltage.  Careful with that if using an external meter, as they can have an order of magnitude difference in internal resistance.  

Another point often not mentioned is that the probes use that series resistor in the probe plus any stray capacitance inside the meter to form a low pass filter, creating the DC voltage that gets measured.


On Sun, Apr 2, 2017 at 07:53 am, Jerry Gaffke wrote:

Actually, a germanium (and likely even schottky) diode probe can work down below 100mv if the current is kept low enough

 

ohwenzelph
 

anyone have a better idea of a simple 2-3 component rf detector?

- f


Well, not as cheap as the eBay one but could this be useful?


Jer AA1OF

Sent from my iPad

Jerry Gaffke
 

If you must have a log amp, I'd make pads for an optional AD8310 (the improved and cheaper AD8307)  on the main board and have it drive a Nano analog input.  Make a dandy S meter when not being used to troubleshoot the Bitx or perhaps other gear.  Those that want it could go out and buy one, or you could make the extra part a buying option at hfsigs.

Of course, we'll quickly run out of Nano pins.  I still like the idea of the Si5351 on the main board, a connector off to the microcrontroller/display of our choice.  I'd go Teensy 3.2, likely never run out of pins or anything else (mips, flash, ram, ADC bits, serial ports, ...).

On Sun, Apr 2, 2017 at 01:12 am, Raj vu2zap wrote:

How about this Farhan?  http://www.ebay.com/itm/182209512477 It should do, very economical RF probe! 


 

Jack Purdum <econjack@...>
 

Dennis and I are finishing up work on an AGC board, from which we grab the S meter data. By having the takeoff for the AGC in the RF chain, Dennis has a pretty good S meter (i.e., not a VU meter). I've also added a little more detail to the S meter graphic to make it look more like an S meter. I'll let the group know where we're done hacking away!

Jack, W8TEE


From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: BITX20@groups.io
Sent: Sunday, April 2, 2017 11:52 AM
Subject: Re: [BITX20] No audio driver

If you must have a log amp, I'd make pads for an optional AD8310 (the improved and cheaper AD8307)  on the main board and have it drive a Nano analog input.  Make a dandy S meter when not being used to troubleshoot the Bitx or perhaps other gear.  Those that want it could go out and buy one, or you could make the extra part a buying option at hfsigs.
Of course, we'll quickly run out of Nano pins.  I still like the idea of the Si5351 on the main board, a connector off to the microcrontroller/display of our choice.  I'd go Teensy 3.2, likely never run out of pins or anything else (mips, flash, ram, ADC bits, serial ports, ...).
On Sun, Apr 2, 2017 at 01:12 am, Raj vu2zap wrote:
How about this Farhan?  http://www.ebay.com/itm/182209512477 It should do, very economical RF probe! 

 


Lawrence Galea
 

You are right Farhan.
Regards
Lawrence

On Sun, Apr 2, 2017 at 3:01 PM, Ashhar Farhan <farhanbox@...> wrote:
The transistor current stays the same in all the class A amplifiers. It won't do. It should be something simple that is available in every shack. probably, a slightly forward biased diode will do it.

- f

On Sun, Apr 2, 2017 at 2:50 PM, Lawrence Galea <9h1avlaw@...> wrote:
Farhan
how about measuring voltage changes in supply or emitter resistors?
Regards
Lawrence

On Sun, Apr 2, 2017 at 8:54 AM, Ashhar Farhan <farhanbox@...> wrote:
I am trying to figure out a simple tx checkout procedure that doesn't need, say, "connect a 1ghz spectrum analyzer to point x". 
The difficulty with a good procedure to align the the tx is that, it needs to 'see' the RF at fairly low levels of 100 mv or so. This is quite difficult with a simple diode probe. The diode probes work only above 1v levels. One could add an RF amplifier to boost up the levels, but that is just too much complication.
does anyone have a better idea of a simple 2-3 component rf detector?

- f

On Sun, Apr 2, 2017 at 7:49 AM, John Backo via Groups.Io <iam74=rocketmail.com@...o> wrote:
Mike. please realize that the hfsigs group aligns the BITX40 for RX (to 40m), but does NOT do any TX alignment.

There is one reference to TX and that is to increase the rig current by 100ma. with the PA connected.

Transmit involves the audio mic amplifier, the PA drive, and the PA output voltage. Most likely the mic audio
is ok, if connected properly. But the IRF510 gate voltage and the PA drive need to be set for proper operation.
This involves adjusting RV1 AND R136. Set the current up 100 ma. with the IRF510 connected. This is done
by adjusting RV1. NOTE WELL that the gate voltage on the IRF510 should not exceed 4v. or so.

Then, with the mic connected, try speaking into it in TX mode. Observe the current draw of the IRF510. It should
increase to about 1 amp or so. If it does not, the first thing top try is an adjustment to R136. Slowly increase R136
(the PA drive) until you see an increase in the current draw on transmit. This is the proper procedure to get into TX mode.

See the Topic "BITX40 Low Output Power" (message 23134 and following) for more information.

Jerry, perhaps a short paper on transmitter adjustment is in order? It should be on the same page as hookup
information.

john
AD5YE







John Beasley
 

First off. Thank you for the repair information on this.

 

I had the pleasure of replacing my Q13 a few nights ago after using my Kenwood to make contact on 40 meters without turning off the BitX40. I replaced the SMD transistor with a standard one I had in my parts box and my TX is back to normal. Last night I tried the protection diode hack below but then when attempting to Transmit I had no power output. As soon as I removed the Diodes everything went back to normal.

 

My understanding is that this diode configuration  works the following way. Please correct me if I am wrong. When the current coming in from the antenna goes above a certain threshold the protection (switching) diode would drop it to ground protecting the circuit. So why did I loose TX power with the diodes installed exactly like the picture below?

 

I don’t have a picture of the terminals on the board under the relay but from the diagram I can only assume that I must have installed the diodes at K1 from 14 to 16 instead of from 12 to 16? I was going to give it another go tonight but thought I might ask for a little assistance before I cook something that isn’t an easy fix.

 

Thanks Again,

John Beasley

KG7UMN

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Al Duncan VE3RRD
Sent: Sunday, April 02, 2017 7:10 AM
To: BITX20@groups.io
Subject: Re: [BITX20] No audio driver

 

If you now have no output when you speak into the mic, but the receive is OK (but everything worked OK previously); then another component to check is Q13. Although Q13 is in the TX path, it is left in the circuit during RX. If you have transmitted on another 100W or higher power rig while the Bitx40 was in RX mode on a nearby antenna,then there is a good chance you have blown Q13 - if you didn't install the two 1N4148 protection diodes between K1 pin 12 and ground. The picture in the following message shows the location on the board:

https://groups.io/g/BITX20/message/22844?p=Created,,,20,1,0,0::Created,,minimum+mods,20,2,40,4415405

Placing them between pin 12 and ground means they are only in the circuit during RX; you might not want an extra couple of non-forward biased diode junctions in the TX path during transmit that could generate noise, harmonics etc. Q13 can be replaced by a 2N3904.

Jerry Gaffke
 

No "picture below", I have no idea what you did.

K1 is pinned out as if it is a 16 pin dip on 0.1" centers, pin 1 is nearest the "TUNING1" connector.

The two 1n4148 diodes suggested by Raj months ago should be between K1-12 and ground.  That trace between K1 and K2 is only used during receive.  It's a 50 ohm environment, so the voltage would have to rise up to around 0.7 volts peak before the diodes start to conduct a significant amount of current, and that would be an extremely strong received signal.   The diodes do not "switch on" like an SCR would, instead they just conduct when the voltage exceeds the 0.7 Volt level, and hold it to 0.7 Volts max.

That 0.7 Volts peak would also be an extremely strong transmitted signal for the node at K1-14 going into the Q13 stage of the final.   I would not expect two diodes between K1-14 and ground to totally kill your transmitter power.  In post   https://groups.io/g/BITX20/message/22764  I report seeing 0.4 volts peak to peak around ground (so 0.2 Volts peak) at that node during transmit.

Jerry, KE7ER


On Thu, Apr 13, 2017 at 08:29 am, John Beasley wrote:

My understanding is that this diode configuration  works the following way. Please correct me if I am wrong. When the current coming in from the antenna goes above a certain threshold the protection (switching) diode would drop it to ground protecting the circuit. So why did I loose TX power with the diodes installed exactly like the picture below?

 

I don’t have a picture of the terminals on the board under the relay but from the diagram I can only assume that I must have installed the diodes at K1 from 14 to 16 instead of from 12 to 16? I was going to give it another go tonight but thought I might ask for a little assistance before I cook something that isn’t an easy fix.

 

John Beasley
 

Jerry,

 

Thank you for the explanation. The picture I was referring to is the following link from an earlier post:

https://groups.io/g/BITX20/message/22844?p=Created,,,20,1,0,0::Created,,minimum+mods,20,2,40,4415405

I soldered the two diodes on exactly as this gentleman showed in the diagram and had no output power. After removing them it went back to normal.

 

With your information I will tackle this again tonight with the hopes of not inadventingly blowing Q13 if I leave the bitX on and TX out of my other radio at 100 watts.

 

I also will place my cheap DSO on the line to investigate the p2p voltages.

 

Thanks

John Beasley

KG7UMN

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Thursday, April 13, 2017 8:59 AM
To: BITX20@groups.io
Subject: Re: [BITX20] No audio driver

 

No "picture below", I have no idea what you did.

K1 is pinned out as if it is a 16 pin dip on 0.1" centers, pin 1 is nearest the "TUNING1" connector.

The two 1n4148 diodes suggested by Raj months ago should be between K1-12 and ground.  That trace between K1 and K2 is only used during receive.  It's a 50 ohm environment, so the voltage would have to rise up to around 0.7 volts peak before the diodes start to conduct a significant amount of current, and that would be an extremely strong received signal.   The diodes do not "switch on" like an SCR would, instead they just conduct when the voltage exceeds the 0.7 Volt level, and hold it to 0.7 Volts max.

That 0.7 Volts peak would also be an extremely strong transmitted signal for the node at K1-14 going into the Q13 stage of the final.   I would not expect two diodes between K1-14 and ground to totally kill your transmitter power.  In post   https://groups.io/g/BITX20/message/22764  I report seeing 0.4 volts peak to peak around ground (so 0.2 Volts peak) at that node during transmit.

Jerry, KE7ER

 

On Thu, Apr 13, 2017 at 08:29 am, John Beasley wrote:

My understanding is that this diode configuration  works the following way. Please correct me if I am wrong. When the current coming in from the antenna goes above a certain threshold the protection (switching) diode would drop it to ground protecting the circuit. So why did I loose TX power with the diodes installed exactly like the picture below?

 

I don’t have a picture of the terminals on the board under the relay but from the diagram I can only assume that I must have installed the diodes at K1 from 14 to 16 instead of from 12 to 16? I was going to give it another go tonight but thought I might ask for a little assistance before I cook something that isn’t an easy fix.

 

Al Duncan VE3RRD
 

Note that if the two diodes are installed as shown in the picture, they are not in the circuit during transmit and thus should not have any effect on the TX signal.