SDS100/SDS200: Debug Help needed with new Motorola Phase 2 system

[Ubbe]

It drops to -105 to -110 with ATT on. Enabled that with and without the ATT on and it didn't affect anything.

I need to have -100dBm to be able to decode a digital signal. That -105 and -110 are too low to get a reliable result. But if it goes from -40 without Att to -105 with Att then it has to be a huge adjacent channel that interfere. If everything was normal it should show -85dBm without Att.

Unfortunately Uniden scanners signal bars show full signal at levels around -90dBm so that 996 scanner will indicate that it has full signal strength.

That short video indicated that the control channel where working but it was the voice channel used at that time, 852.3375, that where interfered. Does it work better when the other voice channels are in use?

If you have played around with IFX and filters then it's probably not much to do, as trying to notch out a 850Mhz signal could be difficult. If you can look at the whole spectrum using a SDR dongle it might show the exact frequency you will need to attenuate and then check with PAR Electronics if its possible to make a suitable filter that will cost something like $150, if you really need to monitor that system using your SDS scanner.

/Ubbe

 

[R0am3r]

That signal level of -40dBm is pretty much the maximum that it can display.

I have seen -35dBm on 151.010 while driving by a CNYICC tower. Interestingly, my SDS100 worked fine while monitoring that specific CNYICC P25 system near the tower. I have routinely monitored other VHF signals (to include receiving Close Call hits) within a couple of miles from that CNYICC tower without issue. Parking under the tower likely yields different reception results.

 

[devicelab]

That short video indicated that the control channel where working but it was the voice channel used at that time, 852.3375, that where interfered. Does it work better when the other voice channels are in use?

It seems slightly better on 851.6625.

I did make a little progress. I was wondering why my new rubber duck was no longer able to receive the CC -- I was certain it was working but I had not used it since I received it. I discovered the SMA-BNC adapter I was using went bad. I trashed it and installed a new one. (I have a proper SMA torque wrench so it's firmly installed.)

With the now-working rubber duck antenna, the signal is approximately -90dBm and the bad voice channel is decoding. D-Error stays at "6" while on 852.3375. To be clear, I'm still seeing the issue but the rate is about one error every ten minutes.

I do think this is a failure of the SDS-100. The hardware should be able to handle an external signal.

FWIW, the BCD325P2 works just fine on this system with the external antenna.

 

[Ubbe]

I do think this is a failure of the SDS-100. The hardware should be able to handle an external signal.

Yes, it's a failure to handle strong signals as the receiver are not of the best quality. You can buy the receiver chip it uses for 85 cent from china, if you buy only one. The price goes down when you buy 10 or more. I've made some measurements and it's a lot worse than a $20 RTL-SDR dongle receiver. SDS100.mp4

/Ubbe

 

[devicelab]

Random question: In the old 325/996 firmware there was the AGC setting for analog and digital. These don't exist on the SDS-100. I downloaded ARC536 and noticed the above setting in their software after I read the scanner. I was able to set this and write to the radio. It seemed to retain it -- but Sentinel (or the scanner firmware) shows nothing about AGC. Has anyone confirmed if this does anything or is it just a bogus setting?

 

[Ubbe]

Has anyone confirmed if this does anything or is it just a bogus setting?

Uniden removed AGC from Sentinel and in the SDS scanners menu. So it's probably an oversight from Butyl that he didn't hide the AGC option when you select a SDS scanner in the ARC536 menu.

But the mystery are why SDS scanners cannot have AGC. Is it the different DSP that handle I/Q demodulation that hasn't got any AGC but the older BCD scanners have a DSP that include that function? It's a bummer that such an advanced and expensive scanner doesn't have audio AGC like it was from the 80's.

/Ubbe

 

[MStep]

Uniden removed AGC from Sentinel and in the SDS scanners menu. So it's probably an oversight from Butyl that he didn't hide the AGC option when you select a SDS scanner in the ARC536 menu.

But the mystery are why SDS scanners cannot have AGC. Is it the different DSP that handle I/Q demodulation that hasn't got any AGC but the older BCD scanners have a DSP that include that function? It's a bummer that such an advanced and expensive scanner doesn't have audio AGC like it was from the 80's.

/Ubbe

I have to agree with Ubbe's assessment. For those who have been following my Whistler TRX-2 adventures, apparently the Whistler unit does have an AGC function that works on digital signals. As I have commented, although the TRX-2 cannot handle P25 Phase II properly in my area, all the other digital modes sound quite a bit better on the TRX-2 than on my SDS radios.

As we have lamented many times here, some type of AGC algorithms might have been planned for future firmware upgrades were it not for the untimely death of Paul.

 

[devicelab]

Uniden removed AGC from Sentinel and in the SDS scanners menu. So it's probably an oversight from Butyl that he didn't hide the AGC option when you select a SDS scanner in the ARC536 menu.

SGTM.

 

[taz911]

I have to agree with Ubbe's assessment. For those who have been following my Whistler TRX-2 adventures, apparently the Whistler unit does have an AGC function that works on digital signals. As I have commented, although the TRX-2 cannot handle P25 Phase II properly in my area, all the other digital modes sound quite a bit better on the TRX-2 than on my SDS radios.

As we have lamented many times here, some type of AGC algorithms might have been planned for future firmware upgrades were it not for the untimely death of Paul.

I have found the TRX-2 handles P25 Phase II very well up until the latest firmware update. I live in TN and monitor the TN statewide P25 system, and just recently the HwyPatrol in our area have started using Phase II, the audio is very loud compared to non phase II audio. Anyone have any solutions that could be used to offset the audio on this particular talkgroup??

 

[werinshades]

I have found the TRX-2 handles P25 Phase II very well up until the latest firmware update. I live in TN and monitor the TN statewide P25 system, and just recently the HwyPatrol in our area have started using Phase II, the audio is very loud compared to non phase II audio. Anyone have any solutions that could be used to offset the audio on this particular talkgroup??

Volume Offset works for me.