SDS100/SDS200: RFI or something else?

[SummarElm]

So I have been having a problem picking up the Niagara County P25 phase 1 simulcast system got it programmed and and working well however I am having a problem with a particular frequency specifically 423.93750 and its a voice channel not a control channel and it seems to have a really bad interference source on that frequency I have tried IFX to no avail also tried the attenuator setting and that just kills the signal completely as well as changing the filter and I found that normal is the best setting so if anyone has any suggestions as to a fix that would be greatly appreciated.

 

[n1chu]

Try narrowing down the source of interference. Run your scanner on battery and while you experience the interference, turn off the main for your house electricity. That should shut EVERYTHING within your house down. Do you still hear the interference? If yes, it’s not something within your house that is the cause. If the answer is no, and the interference goes away, it’s something within your house, something that is fed from your breaker panels. Try to isolate the offending device by unplugging suspected devices one at a time. Don’t forget to turn the main back on and reset all your clocks. If you determine the interference is not being generated from within your house, look outside for the cause. Take a walk away from your house in all directions. Does the problem worsen or get better in one direction? Now walk in the opposite direction… you get the idea. It may be a transformer on the utility pole. Call your power company. Tell them what makes you suspect it’s their problem. They should check it out for you.

 

[nessnet]

Another possible way to track it (RFI) down.
An RTL-SDR and SDR# or SDTTrunk (and other programs?) give you a spectrum analyzer that visually shows what is going on.

 

[KevinC]

I would apply IFX to that frequency and see what happens. The SDS-series sometimes act weird in the UHF band.

 

[SummarElm]

I would apply IFX to that frequency and see what happens. The SDS-series sometimes act weird in the UHF band.

I have actually tried that and it didn’t work

 

[SummarElm]

Try narrowing down the source of interference. Run your scanner on battery and while you experience the interference, turn off the main for your house electricity. That should shut EVERYTHING within your house down. Do you still hear the interference? If yes, it’s not something within your house that is the cause. If the answer is no, and the interference goes away, it’s something within your house, something that is fed from your breaker panels. Try to isolate the offending device by unplugging suspected devices one at a time. Don’t forget to turn the main back on and reset all your clocks. If you determine the interference is not being generated from within your house, look outside for the cause. Take a walk away from your house in all directions. Does the problem worsen or get better in one direction? Now walk in the opposite direction… you get the idea. It may be a transformer on the utility pole. Call your power company. Tell them what makes you suspect it’s their problem. They should check it out for you.

Went outside my house today and it still did it but not as bad I did flip the breaker and it didn’t seem to do anything

 

[SummarElm]

Figured I would give an update so whenever it lands on the voice channel frequency where it says data link P25 that stuff totally disappears once it lands on that frequency and goes silent just figured I would throw that out there

 

[n1chu]

Went outside my house today and it still did it but not as bad I did flip the breaker and it didn’t seem to do anything

Ok. You’ve narrowed it down to something outside of your house, maybe… you say you flipped a breaker… that’s just one circuit. You have many breakers but only one main switch. Throw the main-that divorces ALL power coming into your house. If you meant to say you turned off the main then you can definitively rule out any offending device you have control over inside your house. Since you also say you’ve tried the IFX fix with no luck, my guess is it’s coming from a neighbor’s house? Or, it’s a utility, either the light company, cable service or land line phone? Any one of them can act as a conduit, bringing interference into your house and surrounding areas.

Your particular issue may also be caused by your SDS100. Do you experience the problem when you go away from your neighborhood? This is where the other posts suggesting you look at the band scope could help, or not. I am not familiar with the scope so I can’t help there. If you can put your hands on another scanner, preferably the same as yours, you could see if it’s something inherent to that make/model. But I’m just spitballing now and I will defer to those more knowledgeable. I am out of ideas and will bow out, but ask that you please keep us informed as to how you make out.

 

[Ubbe]

I have actually tried that and it didn’t work

If you do Channel+423.93750+Channel do you see the IFX indicator, if that particular display field are enabled in your configuration?
You can also go to Sentinels Profile setting and the Miscellaneous tab and that frequency can be entered in the Review&Edit table and then programmed to the scanner.

If you move further away from your house, look at the dBm signal strength value, if you have that field configured in the display, and see what signal strength change you see on the other voice channels on that site. If they go down the same amount as the interference then it's not coming from your house.

If you see a difference using different filters then it's a mixing product inside the receiver. While in that Ch+Fq+Ch mode and SQ at 0, go into the scanners menu and to Global filter setting and try different filters. Listen to when that interference are the weakest, but check only when that voice channel are not in use.

/Ubbe

 

[JoeBearcat]

I have to wonder if the filters might change things.