SDS100/SDS200: SDS 100 having trouble with P25 simulcast

[NCFireman11]

I'm hoping someone can help me out. I have a nearby P25 Phase I simulcast system (Greensboro/Guilford P25) that is giving me trouble. When I'm on the outer edge of the simulcast (about 1-2 miles from the tower as the crow flies but not within the county), my SDS100 will pick up the control channel at -112 to-118 RSSI and then the control channel will drop altogether and the signal bar disappears. After several minutes, the signal will reappear at -70 to -80 RSSI but then level off back up to the -112 range with varying decode error rates. FWIW, I have the site filter set to Wide Invert and the attenuator off as this filter seems to work the best inside the county. As soon as I'm several miles in Guilford County, the signal vastly improves and doesn't drop at all. I realize simulcast P25 systems can be highly directional with the signals dropping off once outside the county but 1 to 2 miles seems a little unusual to me.

Any explanation on what's going on with my scanner? Is there a setting I should check? Or does this sound more like a radio system design?

 

[Whiskey3JMC]

Have you tried the (regular) Invert filter? I found this filter works best for me when I'm outside of a system's intended coverage area, YMMV. Also are you up to date on firmware?

 

[jtwalker]

Are you stationary when this occurs ? Like not even walking around or otherwise changing position/orientation of scanner ?

 

[nessnet]

Filters are meant to mitigate RFI in a specific environment, (location).
So, (assuming you are mobile), unless the RFI is coming from your vehicle, I suggest you set your filter(s) to off or normal.
(Remember, filters attenuate...)

Are you using the stock antenna - or if not, what are you using?

 

[KevinC]

(Remember, filters attenuate...)

You've posted that several times. How exactly do filters in the SDS-series attenuate?

 

[NCFireman11]

I have the REM-820 antenna, the latest firmware (1.23.05, Sub 1.03.05) and I am stationary when this happens. I'm not sure if I tried the regular Invert or not. Also, sometimes a TG will flash as active (non-encrypted TG) but no audio passes through the speaker with a high decode error. I really wish was there was a tried and true way to test which filter is best and works in 90% of situations, and not have to constantly tune or change the settings depending on location. It's really frustrating being close to a tower but the signal isn't reliable, especially since I don't live in Guilford County but try my best to monitor them.

 

[nessnet]

You've posted that several times. How exactly do filters in the SDS-series attenuate?

Reply:

If I am not mistaken, and from my experience, the filters actually decrease sensitivity - which is the OPs reported problem....

In a totally interference free environment they do. If set to Off it will have the best sensitivity. But any interference will usually reduce sensitivity and then the filter settings can actually increase performance, as well as the IFX function.

/Ubbe

Note:
I've also done my own bench testing and have found this to be true. But, as Ubbe states above, this is with no RFI. As soon as there is RFI, then it becomes case specific.

I don't have time to search right now, but Ubbe (?) did a very good write up on the functionality of the filters. Maybe someone has it archived and can post it again here?

 

[KevinC]

Reply:

In a totally interference free environment they do. If set to Off it will have the best sensitivity. But any interference will usually reduce sensitivity and then the filter settings can actually increase performance, as well as the IFX function.

/Ubbe

Note:
I've also done my own bench testing and have found this to be true. But, as Ubbe states above, this is with no RFI. As soon as there is RFI, then it becomes case specific.

I don't have time to search right now, but Ubbe (?) did a very good write up on the functionality of the filters. Maybe someone has it archived and can post it again here?

Ok.

 

[Ubbe]

Any explanation on what's going on with my scanner? Is there a setting I should check? Or does this sound more like a radio system design?

The receivers front end are wide like a barn door and will be interfered from transmitters many MHz away from your monitored one. If you buy the waterfall upgrade you can look at the spectrum and see when a strong signal appear and that will reduce the scanners sensitivity if it can be seen in that receive spectrum.

The receiver are actually designed to handle much wider channels, like satellite and TV that are 5MHz-8MHz wide so will not be particular suitable for NFM signals. It will need working with its filter settings and IFX to try and handle strong interfering signals within that wide bandwidth. I believe you can see the effect of those setting changes when looking at the spectrum display.

/Ubbe

 

[IAmSixNine]

Look around you, do you see a cell tower? Verizon 700 has been known to cause interference on my SDS00, Unication G4 and other devices.
I typically need to be fairly close for this to happen but none the less it happens.

 

[NCFireman11]

Look around you, do you see a cell tower? Verizon 700 has been known to cause interference on my SDS00, Unication G4 and other devices.
I typically need to be fairly close for this to happen but none the less it happens.

Not sure why I didn't consider that. From the map I can see two towers that belong to Crown Castle near the closest P25 tower. One of those is probably causing the interference and occasional signal drop out.

 

[NCFireman11]

The receivers front end are wide like a barn door and will be interfered from transmitters many MHz away from your monitored one. If you buy the waterfall upgrade you can look at the spectrum and see when a strong signal appear and that will reduce the scanners sensitivity if it can be seen in that receive spectrum.

The receiver are actually designed to handle much wider channels, like satellite and TV that are 5MHz-8MHz wide so will not be particular suitable for NFM signals. It will need working with its filter settings and IFX to try and handle strong interfering signals within that wide bandwidth. I believe you can see the effect of those setting changes when looking at the spectrum display.

/Ubbe

Thank you for the explanation. It looks like the culprit might be a cell tower. I guess I need to get the waterfall option, with more filter testing and maybe that will help my receiving capabilities.

 

[a417]

Thank you for the explanation. It looks like the culprit might be a cell tower. I guess I need to get the waterfall option, with more filter testing and maybe that will help my receiving capabilities.

Filtering > waterfall.

 

[SYZ1165]

I am having issues with my SDS 100. I am trying to monitor a simulcast system in the Bay Area and when I lock in on a channel, it seems like it’s clipping the transmissions and I do not hear a response or the first part of a conversation, I got this SCANNER thinking that it was supposed to take care of Simon issues as opposed to the Whistler Scanners am I doing something wrong as well or is there a firmware update that can be made like I said I recently recently purchased the SCANNER in August 2024 is there any assistance out there? Thank you. Oh by the way, it was programmed with two counties by SCANNER masters so should I ask them about my situation?

 

[doctordialtone]

I am having issues with my SDS 100. I am trying to monitor a simulcast system in the Bay Area and when I lock in on a channel, it seems like it’s clipping the transmissions

You probably have a Priority mode enabled?

Check the display for a clue. If it's cutting out at regular intervals, that's most likely the cause

Read here

 

[dmfalk]

I have the REM-820 antenna, the latest firmware (1.23.05, Sub 1.03.05) and I am stationary when this happens. I'm not sure if I tried the regular Invert or not. Also, sometimes a TG will flash as active (non-encrypted TG) but no audio passes through the speaker with a high decode error. I really wish was there was a tried and true way to test which filter is best and works in 90% of situations, and not have to constantly tune or change the settings depending on location. It's really frustrating being close to a tower but the signal isn't reliable, especially since I don't live in Guilford County but try my best to monitor them.

Update that puppy! I believe it's 1.23.07 & 1.03.06 (running off memory, atm), currently. Also follow the others' advice, too. Try your SDS's various filter options - Some have had more luck with wide invert, under your circumstances. And make sure Priority is turned off.