SDS100/SDS200: Missing Transmissions\ Dropping Off \ Front or End Clipping Help

[_DeS_]

I was wondering if someone might be able to help with my problem. I will describe this in as much detail as I can.
Firstly my problem. As the title suggests I miss the audio on my SDS100 that I pick up on either other scanners or radios for the specific system.
This may be in the form of the first transmission i.e Dispatch hailing a resource not being heard while the SDS100 stops on the transmission and I only hear the resource responding i.e. Go Ahead dispatch.

My set up is a SDS100, updated to recent firmware with a Remtronix antenna for the specific band I'm monitoring.

I'm monitoring the Maritime Public Safety Radio Network (MPSRN) in Nova Scotia, Canada.

I have my scanner set up to monitor only the sites in the network that would be geographically probable for me to receive as I travel around my area. These are all the sites listed as being located in Cape Breton in the network site list. While I'am stationary I turn off (ignore) the sites that would be farthest away from me and leave the closest sites enabled as well as a handful of VHF frequencies.

Geographically site strength for me switches between Site 64 Glace Bay & Site 63 Coxheath. As the crow flies, Site 64 is closer to me. If I use my TMR radio and force a site affiliation 9/10 it will affiliate with Glace Bay strongly. Now I know that a Radio designed for the network is different than a scanner but I mention just to give as much info as possible.

I have this problem if I scan both sites or turn one or the other off. I do not live in or around a "noisy" area and here is the current signal information for the sites mentioned.

My TMR Radio has affiliated with Site 63 with a RSSI 58.

SDS100 on Site 64 RSSI -80dbm steady with 0 D-errors strength bars remain constant and "DATA" is displayed constantly while on hold as well as all the sysinfo I want dispalayed stays in view.

SDS100 on Site 63 RSSI -90dbm fluctuates to -95, D-errors 20 ( would be an approximate average ) this fluctuates from 0 to as high as 90. I notice on this site as well that the signal strenght bars bounce around alot and the "DATA" is lost.

I think that about covers it...So my thinking is, now correct me if I'm wrong, I would be able to potentially hear more agencies if I scanned both sites, or is that completely wrong ?


So If anyone can point me in the direction of where to start looking at settings or what not I would greatly appreciate it. Just to give a example that just occurred, I have the SDS on hold on site 64 which is Glace Bay and seems to be the most stable and strong site, I could hear a unit in the field hailing Dispatch, I hear nothing, then I hear that same unit continue with their information, THEN I hear dispatch acknowledge that transmission. Bizarre.

Thanks for any suggestions !

 

[dazza0768]

Have you tried different filter settings? I find the more error and the further away they are it pays to fiddle with the filters.
Wide normal, wide invert and invert help me out alot. But it's all up to the individual as to what is good for them.

 

[_DeS_]

I have not...So what do you suggest scan both sites and change the filter settings on each and see what happens ? Is there somewhere that explains the filter settings ?

 

[hiegtx]

I have not...So what do you suggest scan both sites and change the filter settings on each and see what happens ? Is there somewhere that explains the filter settings ?

Not really. The filters serve to reduce or eliminate interference from other transmissions. But the setting will be pretty much specific to you and your location. Try each setting (wide, narrow, or normal, and/or inverted) to see what works best for you. Someone else in your area, monitoring the same system, might get better results with a different filter setting than what works best for you.

 

[Ubbe]

Is there somewhere that explains the filter settings ?

I tried to explain it in laymans terms here: SDS100: - SDS100&200 Global Filter Setting spreadsheet

If you are familiar with shortwave receivers then you probably have seen IF Shift on them. That's what Uniden uses but at 4 different fixed settings and not continously adjustable as they are in shortwave receivers.

The explanation probably doesn't help anyways as it is a trial and error process to find the correct filter for each frequency that has a problem at your location.

/Ubbe

 

[dazza0768]

I have no interference but the filters help massively.

 

[Ubbe]

It doesn't need to be a noticable interference as the SDS scanner adjust its sensitivity according to what it finds in the whole 10MHz window. If it finds a strong signal in that window it reduces the sensitivy of all signals, including the one you monitor.

The trick are to find a filter setting that blocks that strong signal, there are often several, that interfere with the automatic sensitivity adjustment system in the scanner. The reciever module in the SDS scanner are designed for static signals that doesn't change, like broadcast radio, television channels or sat dish signals and less suitable for dynamic signals like when you scan or different communication towers channels transmitters go on and off when they are in use and their frequencies happen to be within that 10MHz window.

/Ubbe

 

[dazza0768]

I find it helps with distant sites. I have site which can be nearly 100kms away and changing the filter to invert or wide invert gives it greater signal bars and decodes it nicely.
With filter off or normal I get nothing.

 

[Ubbe]

That's how it is supposed to work. An interfering signal will reduce the gain in the scanner and you'll hear less. Filtering out that offending frequency will restore full sensitivity.

/Ubbe

 

[_DeS_]

Very interesting. I will certainly play with the filter settings and see what I come up with. Thank you all for your input.

 

[dazza0768]

That's how it is supposed to work. An interfering signal will reduce the gain in the scanner and you'll hear less. Filtering out that offending frequency will restore full sensitivity.

/Ubbe

That's the weird thing, I have no interfering signals at all. Our spectrum in NZ is not that busy at all.

 

[Ubbe]

Do a search between the frequency and 10Mhz lower. Invert filter mode will filter lower frequencies and pass the higher ones. As invert wide also works it should be something between 5-10Mhz lower in frequency that makes the AGC gain react to it.

/Ubbe

 

[pro106import]

I have the same problem on my local state simulcast system. Even if I hold on one site and a quick key with just a few talkgroups, I miss the calling unit usually. A big delay with the radio. Nothing to do with the signal. I get the system with an rssi of -75 db
0 errors. It's just the radio.i have it in id scan mode also. Not Id search mode. This happens on all different P25 simulcast systems by the way
And I receive many. In 4 different states

 

[Ubbe]

I have the same problem with trunked DMR systems with my BCD536 scanner, the only trunked system type I have at my location. It just misses some transmissions when scanning from the control channel. If I program a sites voice channels as conventional non-trunked, so that it will stop scan on the carrier and then begin to decode the data, it seems to always work. My DMR Tier II radios and Whistler scanner also do only voice channel scanning and always catch all DMR transmissions.

It's some kind of bug that dates long back in time and the SDS scanners got its firmware ported from the x36 series and then would have the same bugs that the x36 series had at the time when the development of the SDS series where done.

/Ubbe

 

[zl1dfa]

That's the weird thing, I have no interfering signals at all. Our spectrum in NZ is not that busy at all.

You would be surprised. Broadcast FM (80-108MHz), paging (156-157MHz), cell towers (Spark 870-885 MHz), etc are very strong and can de-sense the scanner.

For example, search in RSM for licenses between 870 & 885 MHz. See the power of those Spark cell sites ... 40dbW. That's 10,000 watts EIRP. If you have one of those near you it's not going to help your reception on 800MHz. Likewise if you are near an FM broadcast transmitter - maybe 45dbW = 32,000 watts EIRP. Poor scanner would be sticking its fingers in its ears!

This is why we have FM band stop filters and other types of filters, especially if you are using a preamp.

D.

 

[rvacs]

I am just throwing this out there because it took me a while to find for SDS radios on P25.

I was loosing lots of P25...then later found my squelch should be set to 0 or 1. WOW big difference.

Can you check your squelch setting?

 

[_DeS_]

Going to have a boo at the squelch settings now...Thanks. Currently set @ 2

 

[_DeS_]

I have the same problem on my local state simulcast system. Even if I hold on one site and a quick key with just a few talkgroups, I miss the calling unit usually. A big delay with the radio. Nothing to do with the signal. I get the system with an rssi of -75 db
0 errors. It's just the radio.i have it in id scan mode also. Not Id search mode. This happens on all different P25 simulcast systems by the way
And I receive many. In 4 different states

Thanks for the info, this system isn't simulcast.

 

[pro106import]

Going to have a boo at the squelch settings now...Thanks. Currently set @ 2

Yes Setting 2 is too tight and 1 is open. See my Radioreference thread here:

SDS100/SDS200: - Service mode?

I'm pretty sure the answer will be a big no, but I'll put it out there anyway. Is there a "service mode" for the sds100 or any other way to tweak the default squelch presets? There are situations for me where preset 2 is a little too tight for my liking, and unlike a radio with a pot for the...

forums.radioreference.com

Bob

 

[_DeS_]

Yes Setting 2 is too tight and 1 is open. See my Radioreference thread here:

SDS100/SDS200: - Service mode?

I'm pretty sure the answer will be a big no, but I'll put it out there anyway. Is there a "service mode" for the sds100 or any other way to tweak the default squelch presets? There are situations for me where preset 2 is a little too tight for my liking, and unlike a radio with a pot for the...

forums.radioreference.com

Bob

I have set it at 1 and 0...Possibly helps. I will give it a few days. Thanks for your input !