SDS200 Garbled Audio...

[n1chu]

I doubt the filters are even needed for conventional analogue or digital VHF/UHF systems. They were offered primarily for the simulcast problem.

 

[Ubbe]

I doubt the filters are even needed for conventional analogue or digital VHF/UHF systems. They were offered primarily for the simulcast problem.

Filter settings, as well as IFX and attenuator, are purely for RF interference purposes, that could happen regardless of system type and modulation.

For "normal" receivers the IFX and attenuator are enough to fight those problems but the SDR receiver chip in SDS scanners have such poor RF performance that additional tools are necessary and the filter settings where added, and works well if the interfering signal are either above or below the monitored frequency. If there's interferences coming from both sides then that will be a problem, as well as too strong signals within a 10MHz window.

/Ubbe

 

[n1chu]

By “IFX” I assume you mean those filter settings. While I accept your understanding of the problem the OP is expressing, I doubt it’s a needed corrective action in this case. (I question not seeing much in the way of previous postings regarding the same issue that we’re corrected using IFX and attenuation settings.)

The OP further states the scanner was using the “Normal” filter settings and it worked but then reverted back to some other setting that exhibited the problem-but they don’t state what that setting was?

The OP should start anew, reprogram the scanner using the auto download feature, (that will eliminate any fat-fingering while programming), with all filter and attenuation settings turned off, record the results and if the problem still occurs, try what you suggest. Because it’s my belief the OP is not all that familiar with the programming process (which, it turns out, is the problem in most cases.)

One question; If the problem still exists, and it’s due to signal overload, as I expect you are suggesting, might trying “Close Call” help, just to see if the attenuation when using “Close Call” helps?

 

[doctordialtone]

By “IFX” I assume you mean those filter settings.

No.

It's a settling that switches the IF Frequency that's used.

" Press Func then 7(IFX) to toggle Intermediate Frequency Exchange "

 

[n1chu]

No.

It's a settling that switches the IF Frequency that's used.

" Press Func then 7(IFX) to toggle Intermediate Frequency Exchange "

Ok. Isn’t that used to change the IF when the radio has a birdie?

 

[doctordialtone]

Ok. Isn’t that used to change the IF

It's used to change the IF for any reason needed

Re-read this:

Filter settings, as well as IFX and attenuator, are purely for RF interference purposes, that could happen regardless of system type and modulation.

For "normal" receivers the IFX and attenuator are enough to fight those problems but the SDR receiver chip in SDS scanners have such poor RF performance that additional tools are necessary and the filter settings where added, and works well if the interfering signal are either above or below the monitored frequency. If there's interferences coming from both sides then that will be a problem, as well as too strong signals within a 10MHz window.

 

[nessnet]

I realize this may sound like a stupid question but were you actually driving around town with your SDS 200 in your vehicle when you noticed these changes?

It isn't a stupid question when dealing with someone that really sounds like they are at the very beginning of the 'learning curve' on these SDS radios.

So, to reinforce the subject: The filters and IFX are to mitigate RF interference at a CERTAIN LOCATION. When leaving that location, the RF environment also changes, meaning the need for a certain filter or IFX also changes.

 

[Ubbe]

Upman where smart enough to add the auto settings for filters that you'll have a use for when travelling and going between different locations that you have yet to figure the proper filter settings for.

/Ubbe

 

[rbritton1201]

Initially, I noticed the garbled noise as I was driving around town listening to the scanner remotely via my cell phone. I rarely actually monitor my scanner at my radio desk. I have Proscan installed on my radio room computer, where the scanner is located and connected for remote access. I don't have the scanner in my vehicle. So, the answer is yes, I initially did notice this garbled noise issue occurring when I was mobile, which prompted me to change to the "Normal" filter setting at the scanner itself, which is stationary. The scanner worked fine with the "Normal" filter setting for at least 24 hours, then I noticed that it was not receiving anything the next day via that same Favorite List via remote access via cell phone nor at the scanner itself.

I realize this may sound like a stupid question but were you actually driving around town with your SDS 200 in your vehicle when you noticed these changes?

 

[nessnet]

Initially, I noticed the garbled noise as I was driving around town listening to the scanner remotely via my cell phone. I rarely actually monitor my scanner at my radio desk. I have Proscan installed on my radio room computer, where the scanner is located and connected for remote access. I don't have the scanner in my vehicle. So, the answer is yes, I initially did notice this garbled noise issue occurring when I was mobile, which prompted me to change to the "Normal" filter setting at the scanner itself, which is stationary. The scanner worked fine with the "Normal" filter setting for at least 24 hours, then I noticed that it was not receiving anything the next day via that same Favorite List via remote access via cell phone nor at the scanner itself.

RFI can be caused by all sorts of things.... and some may certainly be intermittent.
Not just nearby strong radio signals. Microwaves, cordless phones, bad florescent ballasts, bad digital power supplies, another scanner, etc, etc, etc... - even a poorly shielded computer or poorly shielded card within can be the culprit(s). It is a process of elimination.

BTW, try the off filter setting for yucks.
It is no filtering at all and it will give you the strongest (raw) signal.

 

[rbritton1201]

So, I decided, before changing the filter selection from "Normal" to "IFX," I would simply reboot the scanner first. I know how such reboots are necessary with computers, cell phones, etc...I was skeptical that it would work to restore reception on the Favorites List that was otherwise dead. But, what do you know?

A simple reboot worked, and I am now receiving signals via the Favorites List that had formerly been silent. What I don't understand is that the Favorites Lists, Systems, and Departments all showed up on the readout as it was scanning, but there was absolutely no reception on the scanner on that particular Favorites List that formerly had the garbled audio, and signals were no longer being received.

After the reboot, I decided that I should continue to test the reception, and it seemed to be working as it had a couple of days ago with the "Normal" filter activated. I haven't heard any garbled noise from the scanner so far today. But, I did hear one short scratchy transmission, just one over the last 14 hours. I don't know, that might be a common characteristic of almost any radio, so I decided that I'm just going to continue to monitor to see if the garbled noise returns, if the scratchiness becomes more prominent, or if the scratchiness occurs more often. I'll test a little longer, and I'll probably try "IFX" in a few days, just to see if it improves reception in general.

I notice that digital transmissions have always been a little more garbled than analog transmissions at times, but I think that's characteristic of digital signals in general. So, with an eye toward potentially improving the P25 digital signals, I'm looking forward to testing the "IFX" filter on both the analog and digital systems that are programmed into the scanner.

 

[Ubbe]

BTW, try the off filter setting for yucks.
It is no filtering at all and it will give you the strongest (raw) signal.

Actually there are always a filter in line, either one for 265MHz or one for 380MHz IF frequency that both are some 10MHz wide and which one that are used depends of the frequency but you can manually switch to the other filter using IFX. Ideally filters should only be as wide as necessary, perhaps 25KHz, but are impossible to produce at 265MHz frequencies and instead cheap 10MHz wide filters are used that will pass a lot of unwanted signals that could cause interference.

The receiver are receiving a frequency that then are mixed with an oscillator signal to create two intermediate frequency signals, IF. One is receive frequency plus the oscillators frequency and the other is receive frequency minus the oscillator frequency. IF filters are used to pick only one of the two IF frequencies.

IF filters have its least attenuation in the center of it's 10MHz frequency range and more at the ends. The naming of the filters are not really telling the truth and only adds to the confusion, perhaps deliberately. The Off setting are using the filters center position, as a "normal" scanner, and Normal and Invert use the filter at the far ends of it, also adding some more attenuation that sometimes can be a good thing, and Wide use the filter halfway out to the edge of it's frequency range.

Instead of Off, Normal, Invert, Wide-Normal and Wide-Invert maybe the settings could be called Center or Bandpass, Highpass, Lowpass, Semi-Highpass, Semi-Lowpass to more accurately explain what they do, but would anyhow be of no help to users to understand what filter setting to apply when there's a reception problem.

I would suggest to always try to activate the attenuator first, if the signal strength allows it, as that will generally help the receivers ability to handle interferences and can be used on a single conventional channel or a single site. Then try IFX as that can be applied to a single frequency. Filters can only be set for a whole conventional department or a whole site.

When trying any of the Att, IFX or filter settings then look at the Noise level for analog signals and digital error count for digital channels and the value should be as low as possible. For Noise the value will increase with modulation, when someone speaks, so might be a bit difficult to use. If problems are intermittent then the only solution are to try one setting and then wait and see if it helped.

/Ubbe

 

[rbritton1201]

Well, today the garbled transmission returned briefly with the "Narrow" filter turned on. The department within this particular Favorites List dispatches law enforcement on one VHF frequency, and they also dispatch Fire/EMS on another different VHF frequency.

I've heard the garbled signal manifest itself on both the law enforcement frequency and the Fire/EMS frequency in the past. Both frequencies have had their different CTCSS code squelches activated while the "Normal" filter has also been activated. Actually, the CTCSS tone squelch codes have always been turned on at times when the "Global" filter was turned on in the past.

With today's garbled transmission episode, the garbled transmission manifested itself on the Fire/EMS frequency only, but not on the law enforcement frequency. The law enforcement frequency was perfectly readable today in a transmission that was very close in proximity of time, several seconds only, to the garbled transmission that was heard on the Fire/EMS channel.

I guess the next step will be to activate the IFX filter to see if it eliminates the garbled transmission issue...

 

[rbritton1201]

So, since changing to the IFX filter, that seems to have solved the garbled interference sounding transmissions. I haven't heard the issue over the last several days.

 

[rbritton1201]

So, the ugly garbled transmissions came back today, not quite as bad as when I started this thread. I actually have two SDS200s in the shack, positioned about 2 feet apart from one another on the same shelf. So, I isolated each of the scanners to the same agency (System), where I've been experiencing the garbled transmissions. The garbled transmissions were exhibiting on both scanners, but not on the VHF/UHF transceiver programmed to the same frequencies as the agency in question.

Each scanner is plugged into a common 8-position internet switch, which runs to the router, which is upstairs, in order to facilitate connection to Proscan for remote monitoring via cell phone or laptop. I noticed that the garbled transmissions I was hearing seemed to correlate almost rythmically with the two lights on the front of each of the scanners, as they blinked from being plugged into the switch, indicating they are connected through the switch to the router.

Initially, I put coax "quick connect" ferrite cores on each of the respective cables running between the switch and each of the respective scanners, thinking there was some kind of mixing occurring between the cables. But, that did not resolve the issue.

When the ferrite cores didn't resolve the issue, the rythmic correlation of the blinking lights on the scanners had me wondering if the "noise" was being generated by the locations where the cables where plugged into the switch. Sure enough, the cables were plugged into the switch right next to one another. I separated them, including the incoming feed from the router, all equal distant from one another, and the garbled "noise" went completely away.

So, if using Proscan to remote monitor your scanner, depending on your internet setup, be especially aware of the internet connections between a switch, and perhaps even a router, or it may introduce an illusive transient into your connections that may cause what sounds like garbled transmissions on your scanner.

The odd thing is, the garbled noise only manifested itself on one particular agency (system) programmed into the SDS200s, and not on the other system favorites programmed into the scanners. I have both analog system favorites programmed into the scanner, and digital system favorites programmed into the scanner. The anomaly only presented itself on the one analog system, not on any other analog systems, and not on any of the digital systems programmed into the scanner. Very strange...The switch must not have much in the way of isolation from bleed over.

Now, I just made these adjustments, and it seemed to correct the issue so that all transmissions are being received perfectly right now. But, I still need to sample the situation over a couple of weeks to be absolutely sure this resolved the issue. If I find it did not ultimately work, I'll be back...

 

[rbritton1201]

What I also don't comprehend is why the anomaly only manifests itself on certain days, sometimes a couple of weeks apart. Maybe one of you internet configuration gurus can enlighten me as to why if the anomaly was being caused by the positioning of the cables into the switch, why it wouldn't be manifesting itself continually, and not just occasionally. I was elated that I seemed to have fixed it today by merely repositioning the cables into the router so they're separated. But, because the issue manifests itself at weird times, sometimes a week or two apart, I'm a little skeptical that the repositioning of the switch cables is truly the cause of the issue, or whether I'm setting myself up for a disappointment by assuming I resolved it today with such a simple fix.

 

[nessnet]

Ethernet cables contain twisted pairs of wires - specifically to cancel out any induction caused interference.
Or... if it is the switch, I'd immediately chuck it and replace it - NO ethernet device should do this.

Here is my 2 cents on this.
If it were the cables/switch/whatever LAN network component, it'd be on ANY signal, not just a specific one and it'd happen at all times, and not be intermittent. Me thinks you have a coincidence here.

I suppose you could try CAT6 cables - and ditch that POS switch....

 

[rbritton1201]

I don't know...below is the switch. It seems to be highly rated, 43,000 reviews, 5 stars, and it's brand new. I mean no product is perfect, but this one seems pretty highly rated, and it's working as it's intended with respect to it's general purpose. I'm always skeptical of Amazon ratings, and of their quality, as I've seen a lot of pirated crap come out of Amazon. But, I wouldn't know which switch would be better to replace it with, and from which more expensive reliable source to obtain a switch that is as highly rated, so Amazon it was.

My cables between the scanners and the switch are flat cables. I'm not sure how that would be for isolation, which may be the issue. But, there again, if so, the ferrite cores didn't seem to work at all. As I pointed out, and I agree with you, if the noise is coming from some kind of mixing effect between the scanners, cables, or switch, it should manifest on all frequencies.

When I separated the cables the noise totally disappeared immediately. It's difficult for me to believe that was a mere coincidence. Today, there is still no garbled noise on the scanner whatsoever, so time will tell. But, if by moving the cable positions on the switch solved the problem, I can't explain why doing so would resolve the issue.

Perhaps with Proscan, a computer program interfacing with two radio receivers also in the mix, I should have used dedicated cables for each scanner running directly from the router upstairs to their respective scanners. That's the only thing I can think of, provided the separation of cables at the switch solved the noise problem. But, there again, why should it? I already had the cable in place to employ a switch instead of running separate cables between floors, and I was too lazy to run two dedicated cables from the router to each respective scanner, but maybe I should have.

Ethernet cables contain twisted pairs of wires - specifically to cancel out any induction caused interference.
Or... if it is the switch, I'd immediately chuck it and replace it - NO ethernet device should do this.

Here is my 2 cents on this.
If it were the cables/switch/whatever LAN network component, it'd be on ANY signal, not just a specific one and it'd happen at all times, and not be intermittent. Me thinks you have a coincidence here.

I suppose you could try CAT6 cables - and ditch that POS switch....

 

[RT48]

What category are those flat cables? I think the suggestion of replacing them with CAT6 cables is the way to go. I can't picture a flat cable as having the same amount of crosstalk protection as a round, high quality CAT6 cable.

 

[nessnet]

I don't know...below is the switch. It seems to be highly rated, 43,000 reviews, 5 stars, and it's brand new. I mean no product is perfect, but this one seems pretty highly rated, and it's working as it's intended with respect to it's general purpose. I'm always skeptical of Amazon ratings, and of their quality, as I've seen a lot of pirated crap come out of Amazon. But, I wouldn't know which switch would be better to replace it with, and from which more expensive reliable source to obtain a switch that is as highly rated, so Amazon it was.

My cables between the scanners and the switch are flat cables. I'm not sure how that would be for isolation, which may be the issue. But, there again, if so, the ferrite cores didn't seem to work at all. As I pointed out, and I agree with you, if the noise is coming from some kind of mixing effect between the scanners, cables, or switch, it should manifest on all frequencies.

When I separated the cables the noise totally disappeared immediately. It's difficult for me to believe that was a mere coincidence. Today, there is still no garbled noise on the scanner whatsoever, so time will tell. But, if by moving the cable positions on the switch solved the problem, I can't explain why doing so would resolve the issue.

Perhaps with Proscan, a computer program interfacing with two radio receivers also in the mix, I should have used dedicated cables for each scanner running directly from the router upstairs to their respective scanners. That's the only thing I can think of, provided the separation of cables at the switch solved the noise problem. But, there again, why should it? I already had the cable in place to employ a switch instead of running separate cables between floors, and I was too lazy to run two dedicated cables from the router to each respective scanner, but maybe I should have.

View attachment 126328

Flat cables...... maybe(?) an issue, not sure on that one. I'd still consider different (better) Ethernet cables (Cat 6 or at least 5) to eliminate them as the issue. If Ethernet is functioning properly, there would be no need for 'home runs' for the cables.

As to Netgear switches. I've uses many of them and never had any issues. In fact, I have 200s connected to one and I have had no issues.