NS9710
Member
I’m still learning about the Uniden SDS100, one thing I never understood is how to properly implement a filter, which one to use in what situation, and if one is needed in a certain situation. Thanks
SDS100/SDS200: Question about proper use of filters.
- Thread starter NS9710
- Start date
There is a good amount of info in the wiki on filters here. I myself do not use the filters.
wiki.radioreference.com
SDS100 and SDS200 FAQ Page - The RadioReference Wiki
First and foremost - filters are only if you have RFI, (Radio Frequency Interference).
No interference, no filters needed.
Second: RFI is 100% location (and system/frequency) dependent. Even another room, or a few feet can change things. So, it 100% depends on YOUR location.
Third: The only way you are going to know is to experiment. There have been good write-ups on how to go about this here. (See #4 below)
Fourth: Search is your friend. Anytime you have a question - search first. Chances are very high it's been discussed and answered here in the past. There are many people here to help - and willing to do so. But, search first, then ask if you are still stumped. And when you ask, give as much information as possible. Your location, what system, what antenna, etc, etc, etc. Help us to help you.
There is a motto here :
No interference, no filters needed.
Second: RFI is 100% location (and system/frequency) dependent. Even another room, or a few feet can change things. So, it 100% depends on YOUR location.
Third: The only way you are going to know is to experiment. There have been good write-ups on how to go about this here. (See #4 below)
Fourth: Search is your friend. Anytime you have a question - search first. Chances are very high it's been discussed and answered here in the past. There are many people here to help - and willing to do so. But, search first, then ask if you are still stumped. And when you ask, give as much information as possible. Your location, what system, what antenna, etc, etc, etc. Help us to help you.
There is a motto here :
"Give a man a fish and you feed him for a day. Teach him how to fish and you feed him for a lifetime"
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- Feb 22, 2007
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When the radio was introduced, there were a lot of problems picking up Phase 2 tdma simulcast systems, my radio was about 400 off the line in 2018. I put it in the drawer as it didn't work and I relied on the Uniden product manager to address the obvious. He interacted with members of radio reference constantly.
The first firmware update had a minimal amount of filters and the second firmware update to follow up had all the filters we have today. I got very familiar with them very fast. It was a miracle and the SDS 100 came out of the drawer and worked perfectly on my County system.
Some will disagree but, if you're having a problem with a system like missed calls, dropouts and such.. get used to the menu system on the radio itself. Any filter adjustment should be done on the radio so you have real time results of reception indicators like error rate on a system. All you have to do when you're done is read the card in your radio to your profile and all of your keyboard entries will be preserved.
I believe that the default setting on global is for a reason. That filter is applied to every object on the radio whether it be a site or a conventional frequency. It's called normal for a reason.
Play with your radio with the keyboard and no computer and learn how to drill down to site options and Department options. That's your first step. By the way I do all of my adjustments on the run, when you get good at it it takes seconds to do as opposed to going home and hooking up to your computer and waiting for everything to set up, I'm being sarcastic.
Global filters are a way to sample a system or a series of conventional items quickly, avoid Auto wide and Auto. They sample every filter every which way and slow down scanning.
Sit on the system that you listen to if it is a phase 1 or Phase 2 system. Then go to Global filters and change it from normal to wide normal, then listen and look and see if error rate improves and do this with wide invert then with invert. For now ignore no filter option at all. For now.
If you see an improvement, remember the filter that did it, return Global filters you found in Settings to normal which is default for a reason.
I'm writing this to you, original poster, you're new at this, I've noticed most people ignore this method LOL.
Take the filter that works better and drill down on the menu on the radio with the keypad and apply it to site options, hopefully you have the least amount of sites that you need to hear your area.
I have often experienced one site having one filter and another site having another LOL.
If you apply a global filter to improve a specific system or conventional items, you're going to find that that new filter will probably screw up reception on so many other things that do well on.. normal.
The first firmware update had a minimal amount of filters and the second firmware update to follow up had all the filters we have today. I got very familiar with them very fast. It was a miracle and the SDS 100 came out of the drawer and worked perfectly on my County system.
Some will disagree but, if you're having a problem with a system like missed calls, dropouts and such.. get used to the menu system on the radio itself. Any filter adjustment should be done on the radio so you have real time results of reception indicators like error rate on a system. All you have to do when you're done is read the card in your radio to your profile and all of your keyboard entries will be preserved.
I believe that the default setting on global is for a reason. That filter is applied to every object on the radio whether it be a site or a conventional frequency. It's called normal for a reason.
Play with your radio with the keyboard and no computer and learn how to drill down to site options and Department options. That's your first step. By the way I do all of my adjustments on the run, when you get good at it it takes seconds to do as opposed to going home and hooking up to your computer and waiting for everything to set up, I'm being sarcastic.
Global filters are a way to sample a system or a series of conventional items quickly, avoid Auto wide and Auto. They sample every filter every which way and slow down scanning.
Sit on the system that you listen to if it is a phase 1 or Phase 2 system. Then go to Global filters and change it from normal to wide normal, then listen and look and see if error rate improves and do this with wide invert then with invert. For now ignore no filter option at all. For now.
If you see an improvement, remember the filter that did it, return Global filters you found in Settings to normal which is default for a reason.
I'm writing this to you, original poster, you're new at this, I've noticed most people ignore this method LOL.
Take the filter that works better and drill down on the menu on the radio with the keypad and apply it to site options, hopefully you have the least amount of sites that you need to hear your area.
I have often experienced one site having one filter and another site having another LOL.
If you apply a global filter to improve a specific system or conventional items, you're going to find that that new filter will probably screw up reception on so many other things that do well on.. normal.
Perfectly written… and in the simplest terms. Especially the caution about once selected, the filter should only be applied to that system by screwing down in the menu and assigning that filter to only the system or channel where you see an improvement, and NOT Global. Yes, it’s a hassle to devote the time choosing a correct setting for your location. But given the numerous variances that can occur with the many systems we monitor it’s necessary if you experience issues. The filters are applied locally, meaning your findings may not be the best for the neighbor next door. They are location specific… and that location can be as sensitive as a mere foot! What works for you at your location may not work for someone else monitoring the same system elsewhere. “Your results may vary” is one way of putting it. I personally haven’t used the filter settings. I am one of the lucky ones who has no trouble with the scanner right out of the box! I say lucky but for how long? There will come a day when I will need to experiment with them also.
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- Feb 22, 2007
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Eureka!! By jove, I think you've really got it. This is such a frustrating topic for me. I stopped responding a long time ago, I read Paul's brief comments regarding the filters and I got it.. I got it right away.. the scanner came out of the drawer with invert filter, worked even better with wide invert. I had been using a system hold of over 300 seconds for those who know what that means.
The extremely expensive doorstop came out of the drawer and remains on my desk or in my car till now. I personally fixed the rotary dial problem.
Original poster, I hope I kept this as simple as I possibly could. Any questions just ask.
Trentbob, Excellent explanation …I agree on the way to experiment above, but will throw out another maybe more labor intensive for those more experienced. I did this a while ago so I hope I have my details correct.. If there are frequencies not in a trunked system, just set up in sentinel a separate favorites group with different filter entries for the same frequency in separate departments and then switch between them when active…I did this with a list of vhf freqs and was able to determine a good setting on at least 20 freqencies over a period of time when they became active. without too much work. I had 4 departments(filters) since I did not use auto or off. I know many people have mostly trunked but we have a large number of single channel vhf still very active. If trucked, this is a bit more complicated probably requiring separate duplicate favorite lists and settings. If all of this seems too complicated, just follow trentbob’s advive!! 😨😳😳
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- 6,744
Yes I've experimented with different things, setting a filter to a specific conventional object is not possible as you know, you have to set a filter to department options. It usually works out, as for example, you might have a group of marine frequencies or aircraft frequencies alone together in the same Department and the more favorable filter would apply to that group.
Your system definitely will work, conventional objects you have to wait until they transmit to see if a filter makes an improvement, that can be tedious.
I have occasionally used no filter at all on a specific group of conventional objects. I understand that if you don't have a lot of interference in a rural setting no filter at all would theoretically be advantageous but with a system, the system itself might respond better to a filter due to the way it's set up, configured or tweaked.
Your method sounds very plausible. I personally am one of those people that faithfully lives by the KISS principal😉
Yes, agreed. Strangely in my semi rural area there is very little interference and no towers within quite a few miles from me but in most cases, wide invert definitely improves reception for me. I too am a KISS follower!(not the band!)
Ubbe
Member
Any frequency withing 10MHz of your monitored one could interfere if it has a -80dBm signal strength or more. What exact frequency that interfere will change depending of what filter and IFX you are using. If you have signals that are -60dBm or stronger in your frequency band they could trigger the automatic RF gain feature and desense the scanner.
/Ubbe
Ubbe
Member
The monitored frequency in a SDS scanner are mixed to another IF frequency of either 265.55MHz or 380.75MHz by injection a oscillator signal.
To simplify lets say that the IF is a 250MHz one and you monitor a 500MHz signal, then the oscillators frequency could be 250MHz to produce a 250MHz result, 500-250=250. But it will also produce an equal strong signal from 750MHz, 500+250=750. To prevent the 750MHz to be received there are two filters in the SDS scanners, one for each of the two IF frequencies, that are 10MHz wide so that the unwanted 750MHz signal are suppressed.
What IF frequency of the two to be use are decided by the scanner depending of the frequency monitored but you can sometimes manually switch to the other filter by the IFX function. Sometimes the IFX function will instead change the oscillator frequency. For that 500MHz monitored frequency it could be using a 750MHz oscillator with the same 250MHz filter, 750-500=250.
The frequency response of the filters could look something like this:
When you have the filter set to Off the monitored IF signal are in the middle of the filters frequency response, at the filled red triangle.
The Normal setting are a low pass filter and the monitored IF frequency are then at the non-filled triangle to the right. The Invert setting have the frequency pass the filter at the left triangle. Wide settings are halfway between the filled and a non-filled triangle.
For the Off setting it could be the highest signal level through the filter and at the edges it could be attenuated more with a worse sensitivity. Filters used are the cheapest one possible and tolerances could differ and also could be different for the 265 and the 380 one, one gives a higher signal level than the other.
Lets say you monitor at the center at the filled triangel and you have an interfering signal at the right triangle that might be 5MHz higher in frequency and will perhaps desense the scanner. Then if the monitored signal are moved 5MHz higher to the right triangle by using the Normal filter setting, that will actually change the oscillator frequency 5MHz to accomplish this, the interfering signal will also move 5MHz up and will be outside of the filters frequency range and will be suppressed.
But the filter will then receive much more of the frequency range below the monitored frequency and will be more vulnerable to any strong signals in that lower frequency range. Sometimes going halfway by using Wide can be a solution.
/Ubbe
To simplify lets say that the IF is a 250MHz one and you monitor a 500MHz signal, then the oscillators frequency could be 250MHz to produce a 250MHz result, 500-250=250. But it will also produce an equal strong signal from 750MHz, 500+250=750. To prevent the 750MHz to be received there are two filters in the SDS scanners, one for each of the two IF frequencies, that are 10MHz wide so that the unwanted 750MHz signal are suppressed.
What IF frequency of the two to be use are decided by the scanner depending of the frequency monitored but you can sometimes manually switch to the other filter by the IFX function. Sometimes the IFX function will instead change the oscillator frequency. For that 500MHz monitored frequency it could be using a 750MHz oscillator with the same 250MHz filter, 750-500=250.
The frequency response of the filters could look something like this:
When you have the filter set to Off the monitored IF signal are in the middle of the filters frequency response, at the filled red triangle.
The Normal setting are a low pass filter and the monitored IF frequency are then at the non-filled triangle to the right. The Invert setting have the frequency pass the filter at the left triangle. Wide settings are halfway between the filled and a non-filled triangle.
For the Off setting it could be the highest signal level through the filter and at the edges it could be attenuated more with a worse sensitivity. Filters used are the cheapest one possible and tolerances could differ and also could be different for the 265 and the 380 one, one gives a higher signal level than the other.
Lets say you monitor at the center at the filled triangel and you have an interfering signal at the right triangle that might be 5MHz higher in frequency and will perhaps desense the scanner. Then if the monitored signal are moved 5MHz higher to the right triangle by using the Normal filter setting, that will actually change the oscillator frequency 5MHz to accomplish this, the interfering signal will also move 5MHz up and will be outside of the filters frequency range and will be suppressed.
But the filter will then receive much more of the frequency range below the monitored frequency and will be more vulnerable to any strong signals in that lower frequency range. Sometimes going halfway by using Wide can be a solution.
/Ubbe
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