SDS100/SDS200: SDS100 AM Audio quality through headphone jack

[dispatchgeek]

I've been recently trying out my SDS100 in my vehicle. I've hooked up a generic bluetooth transmitter with a 3.5mm stereo patch cable. This is paired with a bluetooth speaker I used formerly with other scanners.

FM, P25 and DMR all work well, audio is at a volume I would expect it to be. AM airband is a different story. At the beginning and end of each AM transmission, I get a small pop or click at the volume I would be expecting. Voice traffic however is quiet with rapidly varying volume. I threw my BC125AT in this morning as a test- through the same setup, audio is what I would expect it to be and much more intelligible.

What makes this more mysterious is that I have been using this SDS100 as a base scanner, remotely monitored through Proscan. Headphone jack was hooked up to a USB soundcard. AM audio volume there is constant and similar in volume/quality to all other transmissions.

I'm at a loss here. Any ideas to further diagnose or fix this?

 

[Ubbe]

Try it with its own speaker in the vehicle with the engine off. Try it at home with the BT attached and listen with what BT device you have, maybe your phone. Then you can probably figure out if the scanner has gone bad or the BT does something to the AGC in AM mode, or its just a fluke that it happened to AM and its actually having the same issue intermittently in all modulation modes.

/Ubbe

 

[dispatchgeek]

I did some further trouble shooting using the built in recorder. The linked audio file is straight from the SDS100.

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I believe the audio peak distortion was causing the inbuilt gain control on the speaker to misbehave. It appears to only be on local/strong transmissions. This aircraft was fairly close on this recording. Vehicle was running at highway speed during this recording.

I have a couple of next steps to try here:
*Filter settings. The recording was on Normal Filter. I'll try Wide Normal/Wide Invert next.
*I have an FM trap in line at home. I will add one into my mobile setup as well just to rule that out. (I pass several big FMs on my commute.)
*Add an inline audio isolation transformer to dull out the audio amp on/off spikes.

I can still observe this behavior with the vehicle off and in my home. I think the audio setup with proscan plus inline RF filtering in my home setup helped to mitigate some of the audio issues.

With the findings above, I did some additional searching on the RR forums and found out I'm not alone with the distortion issues. Frustrating, but I'll keep digging at it.

Thanks for the suggestions @Ubbe !

 

[nessnet]

*Filter settings. The recording was on Normal Filter. I'll try Wide Normal/Wide Invert next.

Please remember filters are to mitigate RFI, specific to a certain location. In a mobile environment, unless the RFI is coming from the vehicle, they probably are not a solution...

 

[dispatchgeek]

Please remember filters are to mitigate RFI, specific to a certain location. In a mobile environment, unless the RFI is coming from the vehicle, they probably are not a solution...

RFI from the vehicle is part of the question. I'm not expecting wonders, but I do know I have some noise in the 150-160 range from my vehicle, so air band is also not out of the question.

 

[nessnet]

RFI from the vehicle is part of the question. I'm not expecting wonders, but I do know I have some noise in the 150-160 range from my vehicle, so air band is also not out of the question.

Just keep in mind, filters attenuate.

 

[Ubbe]

With the findings above, I did some additional searching on the RR forums and found out I'm not alone with the distortion issues. Frustrating, but I'll keep digging at it.

Yes, it's a known issue with SDS100, and probably SDS200 that uses the same receiver, and AM mode when receiving strong signals.

Reciever question

hey I'm mostly an airband and adsb guy, but want a portable receiver that does p25 for local and state frequencies across mighagan along with repeaters and occasionally swl .but like I said mainly aircraft im thinking of getting a r30 I use a 706 mk2 in my shack any thoughts

forums.radioreference.com

SDS100 missing conversations on DMR Trunk

I have similar issues with simplex analog transmissions. If I monitor a conversation that goes back and forth between two users the SDS100 sometimes, maybe 25% of the time, opens up squelch late so that one or two words disappears that are heard in another scanner connected to the same splitter...

forums.radioreference.com