SDS100/SDS200: hang on frequency in search mode

[serial14]

Lately I've been doing more hunting of new frequencies than just scanning of known frequencies. I've observed an unexpected behavior on the SDS200 in search mode. I'm wondering if it's a known behavior issue and if there are any work arounds.

Setup:

• In search mode( as opposed to Scan mode of a Favorite list or DB )
• Custom Search utilized, Banks 6,7,8, default bank definitions
• Squelch level set to 2, it's always been a reasonable value for my area.

Observation:

• SD200 is scanning each of the Custom search banks as expected
• SDS200 will stop on a frequency and just stay there.
• Nothing heard audio wise
• No RSSI reported on screen
• Remote Serial command( GSI XML response ) also indicates the scanner isn't receiving a signal
• Scanner will stay on that frequency until you Lock it out or rotate the main knob to continue scanning

Question:

• Why is the scanner stopped and won't continue.

Expectation:

• Scanner doesn't stop if a signal is below the squelch setting

Playing around:

• Adjusting the squelch higher( bigger number ) doesn't help the issue.
• Adjusting the squelch to zero( always open ) does reveal a faint digital voice signal. But with a lot of hash/snow
• Scanner doesn't decode the digital voice signal. It's not registering as P25 or DMR( I have that license ). I don't have the license for NXDN or ProVoice
• Once the squelch is open, GSI XML response of course conveys the signal information.

 

[slhbeard]

I had a similiar problem with a BCD536HP. Turned out that after I reformatted the SD card, it fixed the problem.

 

[Ubbe]

• Why is the scanner stopped and won't continue.

It's two types of squelch action in a SDS scanner. One that indicates it is receiving a carrier and another that controls the audio mute.
When you receive a frequency not exactly on the displayed frequency it often stops scan but doesn't unmute. This usually comes from an interference from another frequency and needs IFX or different filter settings to move that interference to another frequency that you are not monitoring. Any signal that are -80dBm or stronger might interfere with another frequency you are monitoring. If you set squelch to 0 and tune around you will probably hear a lot of distorted signals, that you don't hear on a "normal" scanner, that potentially could stop scan but will not unmute due to its too much distorsion for the audio squelch to open. SDS100.mp4

/Ubbe

 

[sonm10]

A few thoughts...

Could be a birdie, or a signal generated internally by the scanner
Could be an open carrier caused by a high noise floor or stuck transmitter
Could be distant signals that don't open squelch
Could be improper decoding of digital signals
Could be hanging on digital data signals i.e. digital control channels, data blips, etc.

The last one is the most probable
When in search mode try a negative delay. This will force a resume. also try adjusting digital wait time. I find 0ms wait time works best but ymmv

Just as an aside, I have always have had trouble with decoding digital signals when in search mode. The digital wait time has troubles switching from analog to digital.

 

[Ubbe]

The digital wait time has troubles switching from analog to digital.

It's only setting how long the audio should be muted when you go to a new channel and has nothing to do with the scanners way how it decodes signals.

/Ubbe

 

[wtp]

take the antenna of and try again.
birdies usually don't change.
it could be a really local (in house) thing that is generating a signal.

 

[serial14]

I haven't had time to dive into all the suggestions, but some, and worth and update. I will of course follow up with the others as I gain more hobby time.

I have duplicated the behavior with my BCD536, though the BCD536 doesn't get hung up as often as the SDS200 does. A year ago when I did this sort of activity with my BCD996P2 I never had the problem. Perhaps its worth duplicating the experiment with the 996.

In doing the experiment again with the 536, I spot checked the frequencies where it was getting hung. Of note, there were some that were faint Digital Voice modes when I opened up the squelch all the way, just like the initial report on my SDS200. But there were also FSK/AFSK signals from well-known M2M telemetry links in the area that would trip up both radios. Again, the squelch was set higher than the FSK signal level and both radio's stayed stuck. The FSK used by these M2M telemetry links is certainly something the Unidens can't decode as Digital Voice, so I'm still puzzled there.

Regarding the comments about birdies and noise signals. I don't think that is the BULK root cause of my observed behaviors. I maintain a pretty good lockout list in all my scanners and have for years. So the well known / constant ones have been taken care of. Also, when I spot check these frequencies that the scanners hang on, there is a purposeful modulated signal. But of course, there are always new signals so that probably accounts for some of them. What I'm really asking about is the difference in observed behavior vs expected behavior on a pretty straight forward signal like the FSK telemetry case I mentioned above.

 

[sonm10]

Scanners don't decode fsk telemetry signals. Digital signals that are supported are P25, DMR, and NXDN. If you are really interested you might MultiPSK.

 

[wtp]

that was supposed to say "take the antenna OFF"

 

[serial14]

Scanners don't decode fsk telemetry signals. Digital signals that are supported are P25, DMR, and NXDN. If you are really interested you might MultiPSK.

Yes, I understand that. I'm not trying to decode the FSK signals at all.

I'm trying to figure out why the scanners are stopping on that signal even though its below the squelch level. It doesn't get hung up on analog NFM signals below the squelch level, only digital signals that are below the squelch setting.