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No talk power out #bitx20 #sbitx_v2

 

I Just upgraded the software to the latest on github. ?Then I Tried transmitting into a 10 watt dummy load and measuring power out on a qrp meter with various modes on 20m. With the drive set at 39 I was getting 7 watts out on CW, FT8, and PSK31 with both the radios meter and the qrp meter. Then I tried SSB with the supplied mic on various mic gain settings from 20-50. Neither of the power meters showed movement, although I could see what looked like random noise at a low level on the waterfall. I upped the drive but there was. still no power out.
I’ll try to look at the schematic tomorrow, but I have very limited skill in that area. Any ideas on how to fix this will be appreciated.?
73 Reed AA1RB
 

Can you try the 2 tone mode and check the power output? Is it possible that there is a problem with the mic? The low level RF indicates that there is marginal output from the digital parts.
I would try another mic. Do not attempt any calibration.
- f

On Fri, Jun 16, 2023, 7:19 AM JOHN BUMGARNER via <john.bumgarner=[email protected]> wrote:
I Just upgraded the software to the latest on github.? Then I Tried transmitting into a 10 watt dummy load and measuring power out on a qrp meter with various modes on 20m. With the drive set at 39 I was getting 7 watts out on CW, FT8, and PSK31 with both the radios meter and the qrp meter. Then I tried SSB with the supplied mic on various mic gain settings from 20-50. Neither of the power meters showed movement, although I could see what looked like random noise at a low level on the waterfall. I upped the drive but there was. still no power out.
I’ll try to look at the schematic tomorrow, but I have very limited skill in that area. Any ideas on how to fix this will be appreciated.?
73 Reed AA1RB

 

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I tried my Elecraft mic which I know works, with the same result.?

On Jun 15, 2023, at 10:08 PM, Ashhar Farhan <farhanbox@...> wrote:

?
Can you try the 2 tone mode and check the power output? Is it possible that there is a problem with the mic? The low level RF indicates that there is marginal output from the digital parts.
I would try another mic. Do not attempt any calibration.
- f

On Fri, Jun 16, 2023, 7:19 AM JOHN BUMGARNER via <john.bumgarner=[email protected]> wrote:
I Just upgraded the software to the latest on github.? Then I Tried transmitting into a 10 watt dummy load and measuring power out on a qrp meter with various modes on 20m. With the drive set at 39 I was getting 7 watts out on CW, FT8, and PSK31 with both the radios meter and the qrp meter. Then I tried SSB with the supplied mic on various mic gain settings from 20-50. Neither of the power meters showed movement, although I could see what looked like random noise at a low level on the waterfall. I upped the drive but there was. still no power out.
I’ll try to look at the schematic tomorrow, but I have very limited skill in that area. Any ideas on how to fix this will be appreciated.?
73 Reed AA1RB

 

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The Elecraft mics, I know, require bias or you get no output.

73,

-- Dave, N8SBE

On 2023-06-15 23:31, JOHN BUMGARNER via groups.io wrote:


I tried my Elecraft mic which I know works, with the same result.?
?

On Jun 15, 2023, at 10:08 PM, Ashhar Farhan <farhanbox@...> wrote:

Can you try the 2 tone mode and check the power output? Is it possible that there is a problem with the mic? The low level RF indicates that there is marginal output from the digital parts.
I would try another mic. Do not attempt any calibration.
- f

On Fri, Jun 16, 2023, 7:19 AM JOHN BUMGARNER via <john.bumgarner=[email protected]> wrote:
I Just upgraded the software to the latest on github.? Then I Tried transmitting into a 10 watt dummy load and measuring power out on a qrp meter with various modes on 20m. With the drive set at 39 I was getting 7 watts out on CW, FT8, and PSK31 with both the radios meter and the qrp meter. Then I tried SSB with the supplied mic on various mic gain settings from 20-50. Neither of the power meters showed movement, although I could see what looked like random noise at a low level on the waterfall. I upped the drive but there was. still no power out.
I'll try to look at the schematic tomorrow, but I have very limited skill in that area. Any ideas on how to fix this will be appreciated.?
73 Reed AA1RB




 

Farhan.
I tried the 2 tone mode this morning with the same conditions and got about 6 watts on the meter. I also tried the internal mic and got the same , almost zero power out , as with the supplied mic.?

73 Reed
 

I have the same problem: power OK on CW and two-tone mode but nothing with the MIC although the input to the WM8731 looks OK.
So my conclusion is, that it must be somehow software/ configuration related.?
--
73, Joerg - DB2OO
 

Joerg?
That would make sense, but so far you and I seem to be the only ones having this exact issue. Mine is the latest software (updated Friday) and software would affect everyone using that version. I see that there is maybe a common emitter transistor amplifier that takes the mic output before it gets to the audio codec chip. If I could get a clue on how ?to check it that would help.?

The way I have the ssb configured is with the mic gain set at the recommended level. I have tried other levels with the same result.?

73 Reed AA1RB
 

mine is the same..Minimal rf output on SSB with normal output on cw and 2 tone.. on cw and 2Tone about 22 watts on 17 meters and 2.1 watts at best on SSB.. software issue most likely..
 

All,

I had the same issue with my DE sbitx.? I had to reload the image on the microSD card, do the update, and then reboot.? After that, the mic worked again.

Before I did the above, I checked that QD1 was operating with about 0.6 volts between the emitter and base.? I then verified that I got an audio signal on my oscilloscope on the collector when providing sound into the mic.? Both tests confirmed that the mic preamp was working.

That was the 3rd time I had to reload the image and redo the software.? I had a fourth just the other day after I had not reset the current limit on my bench supply which caused a low power input to the sbitx.? If, after an unexpected or unclean shutdown, there is a significant chance that the microSD card has been corrupted.

The above are my experiences.? Others may be different.
73
Evan
AC9TU

73
Evan
AC9TU
 

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I did do the update, but I’ll try again.?
Also, is there any reason the Elecraft KX3 Mike shouldn’t work. ? ?Does the mic jack provide any biasing voltage?


On Jun 18, 2023, at 10:36 PM, Evan Hand <elhandjr@...> wrote:

?All,

I had the same issue with my DE sbitx.? I had to reload the image on the microSD card, do the update, and then reboot.? After that, the mic worked again.

Before I did the above, I checked that QD1 was operating with about 0.6 volts between the emitter and base.? I then verified that I got an audio signal on my oscilloscope on the collector when providing sound into the mic.? Both tests confirmed that the mic preamp was working.

That was the 3rd time I had to reload the image and redo the software.? I had a fourth just the other day after I had not reset the current limit on my bench supply which caused a low power input to the sbitx.? If, after an unexpected or unclean shutdown, there is a significant chance that the microSD card has been corrupted.

The above are my experiences.? Others may be different.
73
Evan
AC9TU

73
Evan
AC9TU

 

John,

I did a full SD card image overwrite, not just an update.

The tip of the plug does provide a bias voltage.? It is a static 12 volts, with a 10k resistor in series.

Did you measure the voltage of the pins of QD1 to verify that the transistor was operating?? ?Also, you can verify the input and output of the transistor preamp.

73
Evan
AC9TU
 

Are there detailed instructions anywhere on how to do the sd card overwrite?
73 Reed AA1RB
 

have tried 4 different mics? ?two of them were sbitx mics.. same results low SSB power output... odd some have it and others do not..voltages are good.. QD1 is working...has to be some variable thats common between all the rigs that have this issue..rewriting firmware does not fix it...
digital and cw works fine.Just low SSB output regardless of mic settings
Steve N3KDN
 

The test report that came with my V2 (#166) dated May 15 said the SSB output on 7 mHz was 127 with external mic and 118 with the internal one. I assume the units were volts PEP , the same as reported for CW and other modes. However I haven’t gotten any SSB power out since I received delivery. Maybe there was a software change between the time of testing and delivery.?
 

any one have any luck yet with the low SSB power issue.. I restored my V2 by replacing finals and doing pa bias cal and meter and tx calibration and have good power out on cw and digital by still dismal on SSB
 

I replaced my finals also and firmware.
Set bias and my SSB was ok.
Note before firmware it would put out 50 watts on 7 mhz.
After firmware about 28. I'm using a external pep reading wattmeter and dummy load.

I did not do power calibration.

Perhaps your bias needs a relook?
Wd8axa?
 

rechecked the pa bias 225 ma from resting reading...annoyed about the SSB output...not a digital mode person here...wanted for POTA use
 

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Do you have an external watt meter?

charles

?

From: [email protected] On Behalf Of Steve via groups.io
Sent: Wednesday, June 21, 2023 4:19 PM
To: [email protected]
Subject: Re: [BITX20] No talk power out #bitx20 #sbitx_v2

?

rechecked the pa bias 225 ma from resting reading...annoyed about the SSB output...not a digital mode person here...wanted for POTA use

 

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Yes external pep meter..? been tested with 2 separate meters….

?

Sent from for Windows

?

From: charles
Sent: Wednesday, June 21, 2023 4:42 PM
To: [email protected]
Subject: Re: [BITX20] No talk power out #bitx20 #sbitx_v2

?

Do you have an external watt meter?

charles

?

From: [email protected] On Behalf Of Steve via groups.io
Sent: Wednesday, June 21, 2023 4:19 PM
To: [email protected]
Subject: Re: [BITX20] No talk power out #bitx20 #sbitx_v2

?

rechecked the pa bias 225 ma from resting reading...annoyed about the SSB output...not a digital mode person here..wanted for POTA use

?

AEFEEEC0DCD44A12B1E48B94DF530E45.png
D66CBE428DEC4D6B8A7A2BAE0272D8B4.png

 

Just a FYI . I had low power output only on SSB. tried using two different sbitz supplied mics.. opened up the mic case.. i removed the black sticker over the mic element.. seems that it blocked totally any sound from entering the mic element as when elemnt tapped SSB power increased.. now with sticker on mic element removed SSB power is at rated and expected power..?
just a FYI
Steve N3KDN

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