SDS Filter Thread

[garys]

I know that there have been a lot of individual posts about how the filters work and what settings are best. I'm posting this in the hope that a moderator will make it a sticky and we can share filter settings, thoughts, questions, comments, etc... in one thread.

It would be nice to get a description of what each filter setting does so that we aren't just blindly trying them. Also, do particular settings work better with different modes?

I'm sure there are people here who understand the filters and can help those of us who don't figure out what we need to do.

 

[tampatracker]

Great idea!

 

[KK4JUG]

I'll be perfectly honest. I don't think Uniden fully understands the filters. There are some electronic adjustments that can be made but apparently they sometimes have a different effect even when applied to two similar systems. What I'm saying is, don't expect a lot of good information because everyone's experiences are different.

 

[KR7CQ]

I'll be perfectly honest. I don't think Uniden fully understands the filters. There are some electronic adjustments that can be made but apparently they sometimes have a different effect even when applied to two similar systems. What I'm saying is, don't expect a lot of good information because everyone's experiences are different.

Well said.

From what I've read, my understanding: Filtering above the target frequency is "normal", below is "invert", and with auto the scanner tries both to see which works best. The wide version of each is just that, a wider filter. Again, this just my limited understanding at this point but I'll share it for confirmation / correction by others.

As KK4JUG said, this is a trial and error situation for each user / situation. I'm not sure any "rules of thumb" can be agreed upon but this should be interesting.

Though I haven't gotten this in-depth, I would assume that the technically correct approach to finding the optimal filter settings might be having multiple scanners checking multiple frequencies from various systems at the same time, to determine when "interference" is occurring vs. when certain frequencies are transmitting, to determine what the offending frequencies are, and to determine what filter would be appropriate. Of course this would be some pretty tedious work, and it's probably a lot easier to just do orderly experimentation with each problem system (my approach).

 

[Hit_Factor]

What I'm saying is, don't expect a lot of good information because everyone's experiences are different.

Exactly.

Filters are all about what's happening at your exact location, at current propagation, and whatever is going on within reception range.

If you live near Bristol TN and there is a race going on, there will be signals that usually are not there. Drive over to the other side of a mountain in N.C. and everything will be different.

Propagation varies quite a bit between day and night.

About the best you can hope for is an easy way to change filters, if it helps great, if it doesn't try another one. After a while you will get the hang of it based on what you are hearing.

Don't forget the ifx function for images (hearing signals from a different freq).

73, K8HIT
Icom: IC-7300, IC-PW1, ID-5100A, ID-51A Plus 2, IC-R30, Hytera PD782G, Kenwood TH-D74, Uniden SDS100, DVMega, SDRplay RSPduo

 

[KevinC]

If Uniden would state exactly how the filters work I'd be happy to sticky it. Such as "Normal" is a HPF starting how far below the target frequency or "Invert" is a LPF starting how far above the target frequency. But without that info it would just be like every other post/thread concerning the filters and would encompass opinions, incorrect information and arguments.

 

[kruser]

If Uniden would state exactly how the filters work I'd be happy to sticky it. Such as "Normal" is a HPF starting how far below the target frequency or "Invert" is a LPF starting how far above the target frequency. But without that info it would just be like every other post/thread concerning the filters and would encompass opinions, incorrect information and arguments.

I agree. There appear to be way too many variables for any true sense of meaning for the filter settings for this to be a sticky with any valid meaning. I really do wish it was possible though when you look at the flood of posts asking the same basic thing about the filters.

I live in a very rich RF environment here in the west county area of St Louis, MO. What works for me does not work for my buddy who lives in the south county area of the same county. His RF environment is much tamer than mine is. He has no strong paging signals nor is he near any of the counties P25 800 MHz towers for example. I myself am saturated by all those types of signals so what works for me is totally different than what works for my buddy. My elevation in comparison to my buddies is much higher so my area is prime for radio towers when it comes to LMR systems of all types. This can make it tough for all but the best professional grade receivers and especially tough for designs like GREs with overly sensitive front ends. Same type problems with the typical TV Tuner SDR sticks sold on eBay for cheap or the SDS series Uniden's that also use a similar cheap TV Tuner chip in their design.
Granted, Uniden's introduction of user controllable filters did make my SDS100 very useable where it was totally unusable before the filter settings came out was a very welcome change in the radios firmware but like I said earlier, the same filter settings that made my SDS100 work very well do not work at all for my buddy who is less than 13 miles away from me. He monitors the same systems as I plus uses an SDS100.

 

[ansky]

I live in the highest RF environment in the US (right outside NYC). My SDS200 is virtually unusable on the NYPD frequencies. No combination of filters and/or IFX makes any difference. All the frequencies just bleed over each other.

 

[kruser]

I live in the highest RF environment in the US (right outside NYC). My SDS200 is virtually unusable on the NYPD frequencies. No combination of filters and/or IFX makes any difference. All the frequencies just bleed over each other.

I feel your pain.

 

[sparklehorse]

I live in the highest RF environment in the US (right outside NYC). My SDS200 is virtually unusable on the NYPD frequencies. No combination of filters and/or IFX makes any difference. All the frequencies just bleed over each other.

Have you tried turning on the Attenuator for any of these channels? Also a different antenna might be helpful, or if using the collapsible antenna that came with the radio try collapsing it all the way. Less signal is often better when it comes to overload problems.
.

 

[werinshades]

Unless you know the exact cause of each intermod, bleedover, cellular tower interference of each and every one of us, an exact filter setting for each system will turn into a debate. For me, Wide Invert/Attenuator ON for a P25 Phase 1 Simulcast Trunking System, Wide Normal/FM for some analog systems, Wide Normal/NFM for another analog systems, Wide Invert for Aircraft band, Wide Normal for a NXDN Trunking System, Wide Normal MotoTRBO Trunking system...

Now...someone will come on and have opposite results because our sources of intermod vary. I don't quite understand why it's difficult to experiment IF you're having an issue. You have the capabilities to try each filter setting to see what works. No harm or damage will come to the scanner...just do it!

 

[bravo14]

What I'm using is Wide Normal for UHF/VHF 700/800 Wide Invert for Edacs/provoice. Global Auto set at Wide Normal. When I go visit back home I'll test filters see if they work and don't work. Where I'm at I get alot of interference on all bands seems like in my complex.

 

[werinshades]

Now...just imagine when the filters came out if Uniden said" for optimum results on P25, use this filter setting". What if that filter setting made your reception worse...the cries of "Uniden SDS scanners suck!/I'm calling repair!/ Recall...it's defective!" choir would have been screaming from the pulpit. Instead they wisely gave a brief synopsis of what the filters do, and "trial and error" is what most of us have found to work best. 6 filter settings, 1 OFF setting, and you can set Global to a setting if you find it works best for most/all of your systems. What part are some of you missing? How much more technical does it have it to be? If it works, you found your setting. If it doesn't, find another one. Uniden engineering could not have made it simpler.

 

[Ubbe]

Upman has mentioned that Uniden will not give more details about the filters as it is Uniden propriatary information.

/Ubbe

 

[Anderegg]

Upman has mentioned that Uniden will not give more details about the filters as it is Uniden propriatary information.

/Ubbe

Why bother to even LABEL them then...just make the menu say "Filter 1, 2, 3, 4" etc, about as proprietary as the XT P25 adjust levels.

Maybe this is a stupid question, but for a thread suggesting it become a sticky, it has not been discussed here. If the "filters" filter out anything other than the desired and received frequency, why are they not just "on" all the time, what is the disadvantage of filtering out unreceived frequencies?

Paul

 

[garys]

This thread is actually working out much as I hoped it would. I'm learning a lot about the mysterious filters and how they work. In some cases, it seems that "Off" might actually be the best setting.

Keep posting folks.

 

[kruser]

This thread is actually working out much as I hoped it would. I'm learning a lot about the mysterious filters and how they work. In some cases, it seems that "Off" might actually be the best setting.

Keep posting folks.

I have exactly one favorite list or system where Off works well. My others require a various mix of All the other filter settings with none of them really used more often than the others. It's purely hit or miss for my location. I have no filters that work better than the others on average.
When I'm working on figuring out what works best for a system, I'll give it a FL name starting with something like 001 so that FL appears at the top of the list when I go into Manage Favorites. That makes it easy and fast for me to get to that system and edit its site(s).
When done, I take the 001 prefix back out of the name and then do the same for the next FL I need to work on.
Definitely time consuming but it does usually pay off. I do wish we could access the Filter setting option with the press of the Function Knob and one of the other keys. Much like you can turn ATT on or off. That would sure speed up trying the different filters in my case where each system is often different.
I also have a couple UHF (450) systems that are not very strong signals. No Filters work for those systems at all. The SDS100 will simply never lock onto the CC. The other radios like any of the x96XT or x36HP models all work fine on those trouble UHF systems. So these filters are Not a cure all for all systems that different users may encounter. Being these UHF systems are generally weaker signals, I can't play with attenuation. All I can try on these are external notch filters to try and notch out offending powerful UHF transmitters near me. So far, I've not found any offending UHF signals though. It seems like it may be strong signals from other bands that kill my weak signal UHF systems.
That's my next project, put external band stop filters in place before the SDS100 and see if I can figure out what band is killing UHF systems on the SDS100.

 

[werinshades]

I have exactly one favorite list or system where Off works well. My others require a various mix of All the other filter settings with none of them really used more often than the others. It's purely hit or miss for my location. I have no filters that work better than the others on average.

I also have a couple UHF (450) systems that are not very strong signals. No Filters work for those systems at all. The SDS100 will simply never lock onto the CC. The other radios like any of the x96XT or x36HP models all work fine on those trouble UHF systems. So these filters are Not a cure all for all systems that different users may encounter. Being these UHF systems are generally weaker signals, I can't play with attenuation. All I can try on these are external notch filters to try and notch out offending powerful UHF transmitters near me. So far, I've not found any offending UHF signals though. It seems like it may be strong signals from other bands that kill my weak signal UHF systems.

Another example of filters being "trial and error" per user.

We have similar systems near us. I submitted debug files thinking it was firmware related and while I was disappointed with the response of "weak signal/interference" etc., I have the 536hp around for any problematic systems. Most of these involve "low-power" digital systems that the SDS scanners just can't grab on to due to too much/too little sensitivity.

 

[woodpecker]

Unidens filter settings are most likely altering the bandwidth of the R836 tuner IF filter, the R820T/T2 which is very similar can be adjusted as discussed in the link below. The problem with using a cheap TV tuner chip designed for 6-8MHz bandwidth is that it can easily saturate the ADC if there are multiple strong signals in the IF bandwidth. Reducing that bandwidth may improve the dynamic range but could decrease the sensitivity depending upon many things such as the filter shape etc.

If you sat in the same spot all day everyday the RF environment will constantly change, a filter that works now may not work 1 minute later, it seems kind of ridiculous expecting end users to have to play and trial and error like this.

R820T

 

[garys]

For the various complaints about analog being a secondary consideration when the SDS was designed, I have overall very good results on analog VHF and UHF. There is a LTR UHF trunk used by one of the local private ambulance services. I get very good reception on that. Also, the Mass. State Police run a statewide Smartnet 800 trunk system and I get very good reception on that. Both of those systems are set to "Normal" filtering, so I'm not going to mess with that.

I'm getting very good reception on a 700Mhz P25 system operating in the Boston area as well.

I will say that analog UHF is a bit inconsistent. Audio processing is overall very good, but occasionally will be better if the signal is a bit weaker. Odd.