SDS100/SDS200: Is Their A Problem With My SDS100 - Poor reception?

[Ubbe]

So, why do we hear the radio described as “mediocre” on the VHF/UHF bands so many times? Maybe it’s more susceptible to one or more variables I mention.

A 150MHz signal will be 15dB stronger than a 900MHz signal transmitted with the same power. In the 150MHz band it can be some high powered pager transmitters or any of those NOAA transmitters.

As soon as the received signal in a SDS scanner gets stronger than -60dBm it will create intermod signals inside its receiver chip and generate interference that could make the monitored signal distorted or totally disappear. If a received signal inside a 10MHz bandwidth are too strong, like -40dBm or stronger it will desense a SDS scanner. Intermod and desense at these levels are not happening to other scanners. If you have RF issues at your location then it will be a SDS scanner that will notice it first.

Attenuation can be individually set to conventional frequencies and trunked sites and will help if your monitored signal are always -80dBm or stronger.

/Ubbe

 

[sfb88]

Just an idea. Check if there are any local ham radio clubs that you could attend. Maybe someone there will have a signal generator and would be willing to inject signals at various frequencies and strengths into your scanner to determine if the receiver is working independent of any antenna issues.

 

[lightninhopkins]

Just picked up an SDS100 yesterday. I've been using 4x RTL SDRs for many months now with the same antenna setup outside a high-rise balcony overlooking LA on the 30th floor, 2 blocks from a major LAPD antenna. I've had no issues with the SDRs, but with the SDS100 I get random garbled digital signal.

When the decode has no issues, it's at maximum quality, but it randomly goes garbled for minutes on end. Very odd. Thought about the overload issue, but even with the stock antenna indoors and doors closed, it's the same. It's definitely an issue on my end with the SDS100, because the internet feed playback is perfect on the same channel. No issues with non-P25 either.

With my external antenna, I get an RSSI of -40dBm, and with the stock antenna indoors it'll drop to -80dBm to -100dBm. Same issue with both methods.

Anyway, thought I'd chime in. Latest firmware. Tried different filters, no change. Can't imagine what the issue is.

 

[lightninhopkins]

I'm trying to monitor the RSSI more closely while listening, and I noticed an interesting pattern. During one dispatch that became garbled (with a stronger signal of -35 dBm), the RSSI started fluctuating between -35 and -105 dBm within the same broadcast. The audio completely garbled whenever the fluctuation occurred in this range.

Using the stock antenna, the signal tends to stay around -70 dBm, and the issue happens less frequently. Interestingly, I’ve also heard solid calls at -105 dBm where the attenuation remained stable.

It seems this issue mostly occurs during the abrupt variations in dBm levels. I assume the receiver might be getting overloaded, causing it to drop the attenuation.

 

[IAmSixNine]

You could be overloading the front end of the sds100 which is why its working a bit better with the stock antenna.
Since these are digital channels also try adjusting the filters.

 

[crippledchicken]

Enabling the digital error count on the display is a good indicator to watch.

 

[lightninhopkins]

Enabling the digital error count on the display is a good indicator to watch.

Thanks. No matter what I do, I get garbled broadcasts (keep in mind this is random, but enough to be frustrating). My SDRs seem more stable. Mind if I ask how to show the error count? I have detailed view on display. Thanks.

 

[lightninhopkins]

Found it! Menu - Display Options - Customize - Set Detail Trunk

Thanks a lot.

 

[crippledchicken]

Found this online I have the sds200 might be different. To enable the digital error count on a Uniden SDS100 scanner, navigate to the menu, then select "System Settings" and choose "Digital Error Count" to toggle it "On" Seems a lot easier than my 200 but, worth a try. I deal with garbled audio too, it is irritating. I live in a poor signal area outside antennas don't help a whole lot.

 

[lightninhopkins]

Found this online I have the sds200 might be different. To enable the digital error count on a Uniden SDS100 scanner, navigate to the menu, then select "System Settings" and choose "Digital Error Count" to toggle it "On" Seems a lot easier than my 200 but, worth a try.

Thanks a lot. Got it running. D-ERROR is zero on some calls. Then getting 50-95 on the garbled signal.

 

[lightninhopkins]

Hey guys. Good news! First of all, thank you for all the information on the signal overload and telling me to add the D-ERROR. So I removed the antenna and still had good reception on the P25 LAPD transmission (couple blocks from tower).

I fixed it by replacing the antenna with a small wire tie-strap. First time that every single transmission has been solid. Only issue is, other signals are weak. Anyway, it's good for now. Thanks again.

 

[crippledchicken]

Glad to hear that!

 

[buddrousa]

You could try the Attenuator on the LAPD with the regular antenna or add another scanner.

 

[lightninhopkins]

I only piggy-backed on this thread because it sounded similar to my issue. Hope more people can see this if they know what the issues might be.

So I still have random decode error problems and I don't think it's an overloaded signal (at least not consistently). I also rolled back a firmware and that didn't help either.

I discovered a new thing:

Let's say the transmission starts on a P25 LAPD channel. Once I get the massive decode errors, when I hit scan again and it immediately comes back to the same channel (only a handful of channels on the favorites), it will have zero decode errors.

 

[scanman1958]

I would like to chime in here too. Just to chime in. I too have reception issues with VHF reception with my SDS100. I have eight systems programmed. All of them but one are digital systems. Overall I get better than average reception on them. Great scanner for digital. One system is VHF high band. Probably 25 or so frequencies programmed. I have received reception on only 3 channels. Ever. Just to cover any bases....I have used multiple antennas. Mobile and base. All good antennas covering different bands. Compared scanners with the same antennas above with great reception. I too have constant poor (at best) VHF reception with the 100. Did all the att stuff. Making sure the squelch is right. Etc etc. Some people get perfect reception on VHF with the 100. That's great! But for many of us it just doesn't work. Which leads some of us to believe it is the scanner.

BTW. I bought a BCT 15(x?) primarily for VHF reception and that specific scanner also sucks of VHF. Same results with same antenna comparison. Not one antenna, even one designed for VHF high improves the VHF reception on the 15.

Been scanning for 50yrs. Things are really complicated now days with scanners.

Happy scanning...if you can.

 

[Ubbe]

BTW. I bought a BCT 15(x?) primarily for VHF reception and that specific scanner also sucks of VHF. Same results with same antenna comparison. Not one antenna, even one designed for VHF high improves the VHF reception on the 15.

What other scanner/receiver are you comparing it too?

/Ubbe

 

[buddrousa]

Then you have the ANALOG SYSTEM setup wrong is it TRUNKING or LTR?
Can you point to this System in the RR Database?
Did you setup this system yourself?

 

[scanman1958]

For my VHF high comparisons....the two antennas are a VHF 5/8 wave mobile with added ground plane using RG-6 coax. The other antenna is an old Radio Shack tri band using RG-6 Quad Shield coax. Both in my attic. The scanners used are the old 895 and 898 table top scanners, my trusty BCD396xt, 325P2, 125AT, BCT15, BCD996 and the SDS100. I have pretty much swapped around all the combinations that I can.

"In general"... the newer, more advanced digital scanners don't receive VHF very well. I am "guessing" that they are designed heavily for the digital trunking systems. "In my case" the SDS100 and BCT15 VHF reception is nearly dead.

With the older 895 and 898, along with the 125AT and 396XT, using those above mentioned antennas, I can regularly receive rural county sheriffs, EMS and fire, 60 plus miles away. (Much further before narrow banding).

I know the limitations of rubber duck type of antennas. Thats a given.

As I said before, some people have no problem what so ever with VHF reception on the SDS100. Thats great! But there are enough people here that "do" have issues and nothing we/they/I do seems to fix the problem.

You can ask 274 questions about what we did, how did we do it, what settings, etc., hoping for the magic question. For some of us (as Bill Murray chanted in the movie Meatballs) it just doesn't matter.

Thanks for letting me chime in. Have a great rest of the week.

 

[lightninhopkins]

I probably just have bad luck. The frustration isn't worth it anymore and I've tried everything. Even for anyone with decent technical troubleshooting, this issue appears to be random. Couldn't find one specific combo of things that resolved it fully.

Since I don't use the SDS100 for portability, I'm just going back to my sdrtrunk on the computer. Even did a test with both of them on the same channel, and the SDS100 would have decode-errors (randomly) where the SDR didn't. Even with similar antenna swapped during testing. I've tried almost everything.

The BIGGEST thing that sticks out to me when I get decode errors, and scan again to reacquire the SAME exact dispatch broadcast, the decode error drops to zero. This happened every single time, 100% of the time. So if a dispatch call is 10 seconds long, it would start, 2 seconds in I'd get errors, I'd rescan and reacquire the same dispatch that didn't end yet, and it's perfectly reset to zero decode errors. Appears since the transmission is still ongoing, and the signal conditions might slightly differ (or improve), the scanner can lock onto the signal correctly, decoding it without errors.

Once again, I sincerely appreciate everyone's help! Just seems odd to me.

 

[Ubbe]

The BIGGEST thing that sticks out to me when I get decode errors, and scan again to reacquire the SAME exact dispatch broadcast, the decode error drops to zero. This happened every single time, 100% of the time.

The exact same issue as another user @rdxny are having. I believe it to be a firmware bug. I don't know if he managed to get thru to @JoeBearcat about this issue but you should definitely try as it will affect all users but they might not be as observant as you are and don't notice it, or thinks it their own fault with some setting issues and doesn't need to be reported.

/Ubbe