SDS100 on DMR / Mototrbo - poor reception?

[RRR]

So I am trying to monitor a county (maybe 20 miles away) that has a 3 site Mototrbo system. I simply plugged in the frequencies, digital type of "DMR", and let it scan with my TRX-1 (RH77CA antenna)

On my SDS100, Same type antenna, running it about a foot or so from the TRX-1, I have it programmed conventional, with the proper frequencies as "Digital, Code search", also Conv. with "Digital" with the proper Color Codes, as well as "Mototrbo trunk", and also as "DMR One freq", with all the same frequencies, on DMR, and I hear a blip every now and then. I have them all seperated into different "Quick keys" and finally left them all 4 on, to see if I could pick up anything.

The TRX-1 is sitting here just a talking. The SDS100 is silent. When I stop the SDS100 on the exact same frequency that the TRX-1 is decoding, programmed as a DMR freq., it doesn't even make a hit on the signal bar.

(Yes, I have DMR and NXDN add-on's applied to the SDS-100, and have received DMR on it before)

I can't imagine the TRX-1 is that much more sensitive on DMR than the SDS100. The SDS100 sure does do a good job with the P25 Simulcast systems.

Any ideas?

 

[Australia4001]

I’m experiencing same issue on dmr

, side by side against sds and an old Moto dmr handheld , most of the time the sds is silent .

 

[buddrousa]

On the SDS you have to set the LCN so the scanner will track the trunking system.
If the LCN's are unknown use the LCN finder in the scanner to find the LCN's after you do this the Uniden will track the trunking system.
For what it is worth the Whistlers do not track the trunking system they scan the voice channels.

 

[RRR]

Well, the Whistler sure does pick up, where the SDS doesn't, in this case.

There are no LCN's on this system, they basically have 3 towers, around the county, with a different freq. each, that rebroadcasts everything together. I stopped the SDS100 on the clearest tower/site (frequency), same one that the TRX was picking up just fine, and still, nothing.

SDS sure does shine on P25 systems, especially simulcast. But so far, it is sorely lacking on DMR and NXDN.

Also, I tried the same programming on my SDS200 (mobile) with ext. (NMO roof mounted) antenna. Still nothing, but the TRX is just a yakking.

I can't have two totally different bad scanners. There has to be something up that I'm not doing right, I have tried them with "Any" slot, also with slot 1 then with slot 2, put the CC's in, and did search CC, still nothing. Are they really that de-sensitized on VHF and UHF DMR and NXDN?

 

[buddrousa]

I get a NXDN system 7 sites from over 20 air miles away and DMR Systems over 30 Air Miles VHF and UHF Repeaters non trunked.
I also get a 5 site 3 channel 800MHZ DMR T3 system over 30 Air Miles with no trouble 25 foot ST2 to a 4 channel stridsberg feeding 2 8 channel stridsbergs feeding 16 Uniden Scanners with 1 port of the 4 channel feeding a TRX-2 that does not hear the 800 DMR system but hears the VHF and UHF DMR systems. Just food for thought my SDS's, 536's and 996P2's all hear the same NXDN or DMR systems better than my TRX-2.

 

[Ubbe]

When I stop the SDS100 on the exact same frequency that the TRX-1 is decoding, programmed as a DMR freq., it doesn't even make a hit on the signal bar.

The signal bar indicates how much signal you actually are receiving. You have to receive something to be able to start to decode the digital data.

It seems to be a pure RF receive problem. You have to play with all the different filter settings, incl IFX on those frequencies or sites. If that doesn't help then your location have too much interference for the SDS to handle. An external antenna could help to move away from a problematic indoor situation with a lot of interfering signals from electronic devices, that the SDS series are more sensitive to compared to mainstream non-SDR scanners.

You could check that the antenna makes a proper connection to the scanner and also use the BNC adaptor and try the TRX antenna. Maybe you have, or could loan from someone, a magnet foot antenna that you could try at different places in the room, but preferable outside of the window.

/Ubbe

 

[RRR]

I appreciate the replies.

I did a lot of riding today, and I have a county with a DMR Con+ system, I had to be nearly 5 or 6 miles from the tower for it to start decoding correctly (LCN's set correctly on this) With a Pulse Larson multi-band 1/4 wave spring base antenna up on the roof. Showed the control channel full strength from about 15 miles away, but I heard nothing until I was within 5 or 6 miles (I did see an occasional blip of a slot and quick TG, but no audio during this time), but the TRX with the RH77CA antenna sitting in the cup holder was just a talking from 15 or so miles away (all this while moving, mobile).

Just for kicks, (I still have my BCD996P2 installed as well) it was hearing DMR at about 20 miles away. I programmed all the freqs in "Conventional" DMR, and let it scan.

Surely the SDS's can't be that desensitized?

Wish the TRX had GPS, then I could run the SDS for the 700/800 systems it blazes on, and the TRX on the DMR and NXDN ones. I'm not manually locking and unlocking agencies everytime I get within range of them.

Anf for the record, I literally put the systems in (and locked out, and in, to see if either performed better) as DMR one freq, Conventional with the freqs set as DMR, and as DMR trunking (Can't find a way to program it as "Capacity plus" or "Connect plus" specifically)

Aside from sitting and going through every filter setting, in every county in the state while I am there until I find the perfect one, could I possibly be programming the SDS's wrong?

 

[buddrousa]

Did you adjust the filters

 

[RRR]

Yes.........

Many, many times. 100 and 200.

 

[buddrousa]

Not sure mine works with very little adjustments.

 

[tumegpc]

The TRX-1/2 receives DMR and NXDN way better than any Uniden Scanner.
Running Spectrum Sweeper with the TRX-1 will pick up NXDN and DMR without any special filters . Close Call on the SDS100 will just keep on searching.

 

[Ubbe]

Showed the control channel full strength from about 15 miles away, but I heard nothing until I was within 5 or 6 miles

That indicates that the signal strenght doesn't come from the actual tower but from a source of interference. You could probably hear that if you program that specific CC frequency as a fixed analog conventional channel and listen to it with your ears. It doesn't seem to be a desense issue from a strong nearby transmission but instead are a strong interference that blocks the signal from the tower. IFX would normally be the solution but if you're unlucky it could just switch in another interference source.

/Ubbe

 

[RRR]

Ok, but two things...

(1)- I am having the same issue with another DMR (multi site "roaming" system) that the TRX-1 picks up fine. (Stationary, at home)

(2)- I am pretty sure the signal strength was from the tower, it is over 200 ft. tall, and it was the "control" channel. And, again, the TRX was picking transmissions up, but the SDS wouldn't until it was pretty much line of sight.

I was hoping I had a programming error. And for the record, "Capacity plus", "Connect plus" and "Multi site roaming" are inherently set up differently, yet the SDS only gives me the option of "DMR one freq", "Mototrbo trunk" and "Conventional". Mototrbo trunking doesn't work very well on Con+ I am seeing, but if scanned as "conventional" I can actually get more traffic, however, I have to lock out the control channel, which hops around. Seems the SDS sits on the control channel, and hears very little, while the TRX is scanning, and hits on conversations. Very frustrating.

At this point, after some compelling research on my own, unless anyone can come up with something better than "it's the filters" or "too much interference" (I am pretty much out in the Country a vast majority of the time as I monitor, by the way) I can only make the presumption that either this will improve as the SDS line of scanners continue to evolve, or the SDS series are great on 700/800 P25 systems (especially on LSM) and pretty much are lacking on VHF/UHF, on DMR and NXDN.

 

[Ubbe]

A scanners decoding process should works as good at half signal strenght as at full, as long as it just is a faint background noise, and if your statement are correct that you have full signal strenght and still doesn't decode until you get very close to the site, then it is with 90% certainty that you have another signal blocking the one you are trying to receive. The receiver technology in a SDS scanner are very different from "normal" scanners and are highly suspect to be interfered from different kinds of sources at other frequencies, that doesn't even need to be powerful. Sometimes that other interfering frequency will be received just as strong as if you had selected to monitor it.

If you skip the normal control channel listening, that in this case might be an interfered frequency, and instead do conventional scan of the voice channels, that might not be interfered, you sometimes get a better result. So to me, it looks as both your observations point to an interfered control channel frequency.

The remaining 10% probability are that the J401 connector between logic board and RF board are faulty as that sometimes makes the signal strenght go haywire and the receiver doesn't get tuned properly to the frequency and the result of the decoding are missing bits of information that doesn't reach the logic board due to the faulty connector. It is easily confimed if you start a log session and look in the log file after a while of scanning and look for the signs of repeated data messages over several lines of log info.

/Ubbe

 

[wx5uif]

Have you verified that the talkgroups are not programmed with a short range or service type turned off? That has got me a time or three.

 

[IAmSixNine]

RRR on the uniden scanners Cap Plus and Conn plus are set up the same. Both have to have the proper LCN set up or it wont TRUNK properly.
Unidens trunk so you have to set it up properly. Whistlers do not trunk, they scan each voice channel independently so on busier systems you tend to miss more traffic. On Uniden, with a properly set up system, you miss no traffic because its monitoring the control channel and then assigning the proper frequency to monitor.
Your statement "Mototrbo trunking doesn't work very well on Con+ I am seeing, but if scanned as "conventional" I can actually get more traffic, however, I have to lock out the control channel, which hops around. Seems the SDS sits on the control channel, and hears very little, while the TRX is scanning, and hits on conversations. Very frustrating. " To me sounds like you do not have the proper trunking configuration set up. Cap Plus and Conn Plus should be DMR Trunking or MotoTrbo Trunking and the frequencies need to be assigned to the correct order. Only then will it pass audio properly. I feel like your confusing bad reception with bad programming.

I think i used properly to much. LOL

 

[RRR]

No, I absolutely appreciate the information.

And please remember, this is on my SDS100 AND SDS200 that does this. I can go outside and turn the exact same "system" on in my mobile setup (SDS200), and still get a lack of decoding, that the TRX picks up. -And on different systems, my original post was in reference to a "Roaming" Mototrbo system, where each site has one frequency, using random Timeslots, and TG's as needed. But the same conversations are on all 3 sites. I can put the TRX1 on the closest site, pause it, and have it searching T/S and T/G and hear everything passing, the SDS just sits there, nothing. (Unless I am very close to the transmitter) I haven't found anything else within range of me and that tower on a spectrum monitor that would be close enough to interfere.

I also am currently using "ID searching" on everything until I verify for sure the TG's in use. I have tried with proper Color codes, and color code search also.

On Connect plus, I understand the control channel hops around. Basically, a radio transmits, and the conversation occurs on that frequency, the other radios that are "logged in" are then moved to another frequency. This is different from a dedicated control channel type of system.

If I am incorrect, please let me know.

 

[IAmSixNine]

If its a single frequency system with multiple towers it sounds like a LCP, Linked Capacity Plus. No problem.
The color code will not change and the TG will still be the same. The Time Slot, Slot 0 or 1, or is it 1 or 2. LOL either way that is what is changing. So its not random. the site controller is assigns the time slot based on the seed channels in the Motorola radios. Your lucky, company i used to work for had 3 site with 4 frequencies (8 voice paths) per site. In this case its still MotoTrbo Trunking and you program in the LCN as 1 OR you can use LCN finder. I would recommend programming up the system and then running LCN finder on it just in case the radio shop put the seed channel on 2 or 3 or 4 and not 1. BUT because the unidens actually (properly) trunk the system it has to have the channels in the proper order.
This goes back to Whistler not actually trunking the system but scanning each and every voice channel to pass audio. Where the Unidens listen to the control channel and based off that then tell the scanner what freq and slot to go to.
A conventional DMR channel is based on Slot 1 or 2. So if TG 1 S1 is active and TG 2 S1 wanted to talk it would not work since S1 is busy. S1 being Slot 1. So single channel trunking basically says hey TG1 needs to talk, The controller assigns the free time slot and bam it works, now if someone else keys up it uses the other time slot until one is free, that then becomes the new control channel. Thats also why Cap plus pulses every few seconds, its sending out a beacon and timing to keep the radios in sync. On top of that its linked to 2 other sites that do the same thing on different frequencies. At least in your example. Try to focus on the site closes to you and experiment with programming and LCN finder with your SDS and once you have the programming correct it should pass audio more reliably, assuming its in coverage.
I am hoping someone can chime in and correct any mistakes i have made.

I tested a SDS100 for a few weeks about 2 months after they came out. I monitored a Connect Plus UHF system with about 9 frequencies, a rather busy system, and was able to receive it roughly 20 miles away. Testing it against my WS1080 (both stock antennas) the SDS100 picked it up much better. With that said as i got closer to downtown the SDS100 started to have some issues with front end overload. It still worked better as the WS1080 was scanning all the frequencies and was missing conversations.
In the heavy down town environment my BCD436 worked better on the UHF Connect plus system, followed by the SDS100 and last was the WS1080. But in the suburbs the 436 and SDS were neck and neck with the WS1080 struggling.
I ended up using my WS1080 parked on a single TG on a P25 single site system. It works well there.

 

[bravo14]

DMR in my area if it is simplex you need to be very close by. I live across a school and I don't hear them on DMR on the sds100/200 and DSDPlus. It will pick up if there is a repeater just fine so I don't know why DMR simplex is deaf........

 

[XTS3000]

My experience with the SDS100 is that it is not as sensitive from the FM broadcast band to the T band UHF frequencies compared to my 396XT. SDS100 is about equal in the 7/800 MHz bands vs the 306XT. Never tested either below the FM Broadcast bands - no interest honestly.

YES I HAVE PLAYED AND ADJUSTED THE SDS100 FILTERS TO NO AVAIL IN GREATER SENSITIVITY OR SELECTIVITY!

I can limit search on both the SDS100 and 396XT on either VHF or UHF, and the SDS will just search and search without stopping, yet the 396XT will stop on many signals.

I’ve hooked up the 396XT and 2 SDS100’s to the service monitor. The 396XT can hear down to -118dBm, while the same signal quality on the SDS100 can only hear down to -110dBm. So we’re talking about a 8dBm signal difference. 8dBM difference can be the difference of hearing a digital signal and not hearing it. YES I HAVE PLAYED AND ADJUSTED THE SDS100 FILTERS TO NO AVAIL IN GREATER SENSITIVITY! This test was performed at 155.500mhz and 460.500Mhz.

Close call on the same thing. 396XT would hit on a signal at -75dBm, while the SDS100 would hit on the same signal at -66dBm. So it takes a 11dBm stronger signal to close call hit on the SDS100. So those wondering why they don’t get many CloseCall hits on the SDS100, it’s because it’s not as sensitive to lock onto a signal.

I really want to like the SDS100!!! It’s a magic box that does and decodes nearly everything. It’s just the low sensitivity that makes me grab my 396XT or G5 rather than my new SDS100.