Low audio output in AM mode

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  • Updated 3 years ago
I recently purchased a used Flex-6500 to replace my mortally wounded 5000A. The unit works FB, and is everything I'd hoped for, except for one small issue.
When switching to AM or SAM mode, the audio output to powered speakers drops to nearly nothing. Audio out to headphones is adequate, but not like unto other modes. 

Audio out is fine in all other modes.

Any ideas? There are so many software switches in SmartSDR that I may be missing something, but I'm beginning to think it's an problem, not a glitch.

I've tried this with DAX enabled and not enabled, no difference.

BTW, I'm running 1.9.13.
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Posted 3 years ago

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Jim Gilliam

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I have ALWAYS noticed a reduction in audio on my 6500, 1500, 3000, and 5000 in the AM modes. Perhaps Flex will address this issue some day.

Jim, K6QE

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N5LB - Lionel B

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I asked a similar question a few months ago regarding my 5000.  I've decided it is part qualitative, demodulated AM vs SSB audio seems relatively muffled, or low level; many ham AM stations themselves seem to be running some low level modulation, look at voice peaks vs carrier level;  there may be something in the way AM is being demodulated, but I don't know why or how.  

Listening to AM SW some of the stations have great audio, others sound a lot like the ham AM on 80m.  I suspect that the older SW transmitters use a better modulation scheme, whilst the newer ones do not.  A few times I've listened to a Johnson Valiant on AM, a totally different quality of audio; clear and booming. Hmmm. 

I think some AM just isn't very good, starting at the transmitter.   There may be some changes that would help in software; I don't know nearly enough.  But Jim is right about the reduction in audio recovered. 
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I used AM broadcast band signals as a test. Most of them have adequate modulation, but I picked out the stations that were truly booming it out there. In the headsets, it was a very nicely modulated signal, with very good audio quality. In the speakers? Nada. Zilch. Well, maybe a whisper. But next to nothing.

So in this case, it seems that the path the audio is taking has an effect on volume.

Again, in all other modes, not an issue.
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Larry - W8LLL

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You really shouldn't be having any receive audio issues in AM mode, i use it often. Make sue your volume controls on the very top right for speakers and head phones are turned up. Also you can gain audio loudness using the rx eq. Also make sure the agc slider is up enough.
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I agree with Larry - I run a lot of AM and don't have any issue. SSB's audio response tends to be somewhat narrower, so could it be that the predominately higher audio freq characteristics of SSB "seem" louder? Also, many of the stock boat anchor radios tend to be under modulated, so weaker signals do often sound down in the mud.
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Sounds like it's time to try a hard-reset of the 6500?
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Yup. Good suggestion.
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Tim - W4TME, Customer Experience Manager

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This may be related to a previously reported issue related to how the AGC interacts with demodulated AM (and SAM).  The issue is defect #2077 and it is tentatively scheduled to be addressed after the final release of SmartSDR v1.10.
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Thanks for the info. A hard reset made no noticeable difference.
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While waiting for #2077 to be resolved, you might switch your AGC decay to FAST instead of MED or SLOW.  I notice FAST increases the audio amplitude in the AM or SAM modes on my 6500.
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Did that. Thanks.