SDS100/SDS200: SDS100 - Squelch Not Opening Occasionally

[andy404ns]

My SDS100 has been having an issue where sometimes a transmission won't open the squelch. This occurs both in scan mode and hold mode. I originally thought it was limited to P25 One Frequency systems (and as those are known to be problematic I was mostly ignoring it) but I'm now seeing it on conventional channels. Most of what I listen to is P25 so I'm not entirely sure if it's limited to digital only.

I'm not 100% sure but it seems like it has been happening more frequently over time.

For troubleshooting, I have the SDS100 next to my BCD396XT and my BCD996T. All three are running off the same antenna that is split on a Stridsberg multicoupler. I confirmed that there are times where both of the BCDs will open squelch and receive transmissions while the SDS does not. Since the problem only happens occasionally, I know for sure that the programming is fine.

Has anyone experienced this type of issue before? I searched around the forums but most posts are "not receiving at all" type things. I wonder if there are any digital settings or filters that might be causing a problem?

Thanks in advance!

Andy

 

[trentbob]

My SDS100 has been having an issue where sometimes a transmission won't open the squelch. This occurs both in scan mode and hold mode. I originally thought it was limited to P25 One Frequency systems (and as those are known to be problematic I was mostly ignoring it) but I'm now seeing it on conventional channels. Most of what I listen to is P25 so I'm not entirely sure if it's limited to digital only.

I'm not 100% sure but it seems like it has been happening more frequently over time.

For troubleshooting, I have the SDS100 next to my BCD396XT and my BCD996T. All three are running off the same antenna that is split on a Stridsberg multicoupler. I confirmed that there are times where both of the BCDs will open squelch and receive transmissions while the SDS does not. Since the problem only happens occasionally, I know for sure that the programming is fine.

Has anyone experienced this type of issue before? I searched around the forums but most posts are "not receiving at all" type things. I wonder if there are any digital settings or filters that might be causing a problem?

Thanks in advance!

Andy

Simple question, what do you have the squelch set at on the SDS 100? It should be set at 2. Also do you have any priorities turned on? Make sure all service types are enabled.

How many systems are you listening to at one time? How many sites are enabled, could it be that the SDS 100 is just not cycling around to that talk group that the other scanners are hearing? Just some thoughts.

 

[andy404ns]

Squelch is set to 2. No priority channels. All service types are enabled.

I mentioned in the first post - this happens when holding on a channel as well as when scanning so it can't be the case that is just happens to miss them.

 

[Whiskey3JMC]

Take the SDS100 off the multicoupler and run it on its own antenna. Does the issue persist? How strong are the signals? If the applicable service types are turned on you can certainly experiment with different filters. May or may not yield any improvement. Is the same issue encountered when you tune into your local NOAA weather radio station?

 

[trentbob]

So poster, these are channels as in frequencies, not talk groups or part of a digital system?

You can experiment with global filters that are already set by default to normal filter where Global filters should always stay. If you want to use Global just as a sampling to see if things improve on a certain filter but then return Global to normal.

Go into department options and apply the better filter to the department of the frequencies that were not opening the squelch. It will affect all of the conventional frequencies in that group but that's okay. You can't apply a filter to just one frequency. It has to be a group of frequencies. Often similar.

You don't want to rely on just the global filter changing if it improves reception as that new Global filter will be applied to every object on the radio and may compromise reception on objects that do well on normal filter which should be returned to on Global filters. The new filter you applied to the conventional frequencies might improve the situation.

 

[pro106import]

Squelch is set to 2. No priority channels. All service types are enabled.

I mentioned in the first post - this happens when holding on a channel as well as when scanning so it can't be the case that is just happens to miss them.

Unfortunately, setting 2 is too tight for many situations. I have complained to @JoeBearcat and on the forums here for a few years. I doubt it will ever get fixed. I have to leave my squelch opened up all the way for some of the weaker systems I monitor. They need to make a 1 setting with the value set for #2 cut in half. It would be a simple fix if they ever do a firmware update. In the meantime, unfortunetly you have to open it to 1 or 0 (same difference).

 

[trentbob]

I agree with @pro106import, the squelch is tight, unfortunately if you're scanning and putting it on zero it only works with conventional frequencies that are protected by a tone squelch like a PL tone, otherwise it will just sit on a frequency with an open squelch.

I also agree that it will never be addressed, the last productive, useful and impactful firmware updates were in April 2019.

I think the best approach is to try to improve the reception on the objects that don't open the squelch, your options are filters or maybe getting your antenna higher.

You can sample your p25 system with global filters also and just use the reception indicators like RSSI, noise level and error rate, if you find a better filter on global then return Global to normal and go into site options and apply the new filter directly to the sites, sometimes a better RSSI can indicate a higher noise level but sometimes your best indicator is your ears.😉

 

[pro106import]

I agree with @pro106import, the squelch is tight, unfortunately if you're scanning and putting it on zero it only works with conventional frequencies that are protected by a tone squelch like a PL tone, otherwise it will just sit on a frequency with an open squelch.

Yes, and even with the PL tones in there, the scanner will scan much slower. So, I only use my SDS-100 for P25 trunked systems. Such a shame that what should be a great scanner has limited use. I wish these scanners had the old analog squelch pots like the Whistler TRX-1 and WS1088. Yeah I know the old cost argument is always the excuse. Then make the values user settable with the EZ-Scan like you can do with commercial radios. You can set the battery meter levels and the RSSI levels with EZ-Scan. Why not the squelch preset values?

 

[andy404ns]

I doubt it's the squelch setting. This happens on _all_ channels, including the PD that has a tower 1/2 mile from me that I can receive without an antenna. Regardless, I'll play around with the setting to see if anything changes.

I'll also switch up the filters to test that.

 

[trentbob]

I doubt it's the squelch setting. This happens on _all_ channels, including the PD that has a tower 1/2 mile from me that I can receive without an antenna. Regardless, I'll play around with the setting to see if anything changes.

I'll also switch up the filters to test that.

Yeah filters will only improve poor reception as if signal was not strong enough to open the squelch. This is a real head scratcher.

If it only happened on p25 even sitting on a talk group I would think maybe you're rolling through too many sites until you get to the one that you need but if it's happening on conventional stuff too, I don't know what it is.

 

[pro106import]

I doubt it's the squelch setting. This happens on _all_ channels, including the PD that has a tower 1/2 mile from me that I can receive without an antenna. Regardless, I'll play around with the setting to see if anything changes.

I'll also switch up the filters to test that.

OK give it a shot. Just hold on a system and put the squelch to zero. I monitor 3 P25 systems from NYC, about 70 miles from me. With the squelch set at 2, the scanner just scans away and never stops, even though the signal level is about -95 to -100db. When I set the squelch to 0, every system comes in 100% with no data errors.

 

[werinshades]

I haven't seen the attenuator mentioned...make sure it's not on inadvertently, or try turning it on per site/department in addition to filter(s) usage.

 

[trentbob]

I haven't seen the attenuator mentioned...make sure it's not on inadvertently, or try turning it on per site/department in addition to filter(s) usage.

I thought of it but, thought the poster would already know about that, definitely a possibility.

 

[andy404ns]

Attenuator is definitely not on

 

[werinshades]

Attenuator is definitely not on

Maybe try turning it on with or without a filter and strip it down to the stock antenna and work your way up. Nothing to lose I say.

 

[Ubbe]

My SDS100 has been having an issue where sometimes a transmission won't open the squelch.

The demodulator filters are programmed very narrow in the DSP compared to other scanners. Setting the modulation mode manually to FM will help a bit.

If I measure my SDS100 with a clean analog unmodulated signal near its sensitivity level at -100dBm it is noise free but as soon as I modulate with a tone the noise starts to increase and at max modulation the noise could make the squelch close. Making the filter wider in FM instead of using NFM will allow a higher modulation level without the noise becoming too dominant for the squelch. Nothing of this modulation noise issue can be noticed in conventional scanners with a "normal" demodulator.

/Ubbe

 

[trentbob]

Maybe try turning it on with or without a filter and strip it down to the stock antenna and work your way up. Nothing to lose I say.

Certainly could be an overload from a nearby Tower but.. how do we explain the conventional stuff?

OP. . Stay with this, I don't believe it's a defect in the radio nor do I think it's programming other than, if you want to solve your problem, give me the exact, location, hometown, county, state p25 systems and, some of the conventional frequencies that this has been occurring on.

You've got some pretty smart people covering this thread, give more details on the p25 system and some of the conventional frequencies you're skipping.

 

[andy404ns]

Location is Rockingham County, New Hampshire. I am not monitoring any trunked systems at all. The majority of what I monitor is P25 conventional. Those P25 conventional frequencies are where I see the problem. It might happen on the analog as well but I don't monitor them very often so it's hard to say for sure:

Rockingham County, New Hampshire (NH) Scanner Frequencies and Radio Frequency Reference

Scanner Frequencies and Radio Frequency Reference for Rockingham County, New Hampshire (NH)

www.radioreference.com

There was a part of this that I intentionally did not mention earlier because I didn't want to lead the responses but here goes: I will often be holding on a P25 frequency and see that the SDS100 is not opening squelch despite my other scanners doing so. In other words, I know there is an active transmission but the SDS100 isn't doing anything. If I simply use the scroll knob to rotate up one channel and then immediately go back to the problematic channel... voila! The problem is solved and the squelch opens. That sounds ridiculous so as it was happening today I took a video. In it you can see my SDS100 side by side with my BCD396XT. Both are holding on Derry Fire Dispatch / Operations (see Rockingham county link above). The quality of the video isn't anything to write home about unfortunately but such is life.

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[Ubbe]

The received signal level are indicated as being -30dBm on the SDs100. I believe that to be the max value it can show.

It's clearly overloaded by some signal. What happens if you engage the attenuator? It it then indicates lower than -60dBm then it is another frequency that creates the problem. But if it indicate -60dBm or stronger then it seems to be your 153.9950 signal that are that powerful. But it's probably a nearby NOAA transmitter or a pager system at another frequency that are the problem.

/Ubbe

 

[andy404ns]

There's a tower 1.25 miles from my house that, among other things, is used by my local PD and FD (not Derry as shown in my video). It's quite tall and there are a bunch of other antennas on it as well (cell? radio? I don't really know). I do use the attenuator on my local PD because that does overload when they transmit sometimes. So when my local PD transmits, if I don't have the attenuator turned on for them, I'll often get high digital error rates on their frequency.

But I'm not totally sure what to do here which is in part a lack of my understanding in how the attenuator works. So I attenuate my local PD but they definitely weren't transmitting during that video I posted. It could be something else blasting out from that tower. Here's my question:

If I were experiencing overload from some frequency transmitting off that tower, would I generally see very strong RSSI values for most frequencies I have programmed? In other words, does the overloading frequency impact the RSSI value of everything I'm scanning? For the most part, the stuff I regularly scan is all within a 20 mile radius of me and from what I'm seeing, the RSSI values are all between -30 and -60.

A few more specific questions:

1. If this is overload from something on that tower, how do I figure out which frequency it is so I can attenuate it? I've been meaning to buy an FM notch filter from Stridsberg just to see if it helps but haven't grabbed it yet.

2. If the offending frequency is, for example, 155.8125, and I have that stored in a department/group on the SDS100, will simply attenuating that channel fix the problem for everything? My mind has trouble believing that attenuating one programmed frequency will do anything when the scanner is off scanning another system.

Very much appreciate the time y'all are spending on these responses!