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Very low ssb output for v5

 

CW output appears to be fine. The mic and its connection is not the problem. The info I need is a table of of test point voltages with the radio settings appropriate to measuring them. I have seen references to such a table but cannot find it. I also need some direction to help visually inspect the areas of the board that may be causing this problem.

The audio is a little tinny but acceptable. I switched the provided LM386 with a known good National Semiconductor LM386N-1 which improved weak audio. I feel that there is a fault in the board or a bad component, I have no access to a scope and/signal generator.

Thanks in advance for your help.

Tom? AB6TN
 

Hi Thomas,

The schematic can be found here: . It lists all of the test points etc, so you should be able to find all the points worth checking :)


Reed
 

I would start with a BFO calibration.? The BFO will affect both receive AND SSB transmit, as the 11.092 MHz crystal filter and BFO need to be aligned in both directions.

The best way that I have found to set the BFO is to tune to a clear frequency with static, then use HF Signals web page to "listen" to the audio.? You would then go to the BFO calibration setting and adjust to get the "plateau" between the red lines.



Be sure to mark down the new setting before setting.? There is no way to save what is the current, other than to do a factory reset.

CAUTION:? The v5 stock firmware will go into transmit at 10 MHz if you go to the master calibration setting.? This should only be done with a dummy load connected.? Unfortunately, a dummy load may not generate enough white noise ("static") to do the BFO calibration.? If the rig does go into transmit, power down immediately.? Do not save the setting, as it will go back to a default that will not be correct.? Just be sure you are in the BFO calibration and you will be fine.

Note: Every time you go into a calibration, the old value is overwritten, and I do not know of a way to go back to a prior setting.? This is a limitation of the v5 stock firmware.? One of the reasons I went to the KD8CEC firmware, as there is a separate Memory Manager program that can be used to set and save the values, including a save to file option.

Above are my experiences, others may be different. Please use with caution and at your own risk.
73
Evan
AC9TU
 

To answer your request for the voltage measurements, You can use the v4 values for the SSB transmit side, as there are only minor differences.? The audio receive and bandpass filters are the significant differences, with only the audio section being able to be measured with a volt meter. There is a change in the IF/SSB filter frequencies, however this again will not show up in voltage measurements.

/g/BITX20/files/VU2ZAP/uBitx4%20voltages.xlsx

To help, download the v4 and v5 schematics to compare.




If you compare the two, you will see that the Q6 mic preamp sections are the same.

The most likely issue for low SSB transmit power after the BFO calibration is the mic gain.? There have been varying reports on the supplied mic performance.? Most have required a preamp to boost the signal.? On the three that I have built, I have found the provided mic to be inadequate to drive to full power without distortion.?

Hopw\e this helps and have fun!
73
Evan
AC9TU
 

Evan, please study thevpost? PA? lpf for 40m band. Let us take sch values as correct. Tro take out the coils one by one? ( you can do without removing the board) and check for inductance and do some trimming. The 40m band power increases.
All the best
Sarma vu3zmv

On Mon, 13 Jan 2020, 10:57 am Evan Hand, <elhandjr@...> wrote:
To answer your request for the voltage measurements, You can use the v4 values for the SSB transmit side, as there are only minor differences.? The audio receive and bandpass filters are the significant differences, with only the audio section being able to be measured with a volt meter. There is a change in the IF/SSB filter frequencies, however this again will not show up in voltage measurements.

/g/BITX20/files/VU2ZAP/uBitx4%20voltages.xlsx

To help, download the v4 and v5 schematics to compare.




If you compare the two, you will see that the Q6 mic preamp sections are the same.

The most likely issue for low SSB transmit power after the BFO calibration is the mic gain.? There have been varying reports on the supplied mic performance.? Most have required a preamp to boost the signal.? On the three that I have built, I have found the provided mic to be inadequate to drive to full power without distortion.?

Hopw\e this helps and have fun!
73
Evan
AC9TU

 

Evan -
The tuning aid site appears to be not working. I gather it is some sort of audio analyzer. I will try to find substitute. TNX for help.
 

Do you have a microphone attached to the device you are using to access the web page?? It will not work without a mic, and it will not give you a reason, just a static page without the graphics.

If you have a smart phone or tablet, those will work as well and will have a mic.

73
Evan
AC9TU

HFSignals BFO Tuning Page.pdf
HFSignals BFO Tuning Page.pdf

 

Thomas, et al,

"Spectroid" by Carl Reinke, or any audio spectrum display available for a smart-phone or tablet, works. While I applaud HF Signals for making a utility available for the purpose, it's chiefly just a graphic display of the audible sound range.?

You'll have to self-impose the 300 - 3,000 hz SSB window on the display, doing your best to set the BFO to fill that range more or less equally.? Me? I like to put just a little higher than lower by a thin margin so as to drop my voice lows and favor the highs,? for punch though the QRN.?


Ted
K3RTA
Mark - N7EKU
 

Hi Thomas,

You need to use Chrome or a Chrome-based browser.? Vivaldi browser works fine on my computer.

73,


Mark.

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