SDS200 "Off Frequency" sound on some signals

[Vulcanccit]

I read this is normal on some frequencies... but ill give you an example... I listen to a lot of aviation... It seems to happen on some signals where at first the signal has some static, sounds off frequency (almost like listening to one of the sidebands)....then the signal gets stronger, full quieting and the "off frequency" sound slowly morphs into normal audio. I read a post from @trentbob (my alf buddy! hahha) suggesting to use the IFE filter on aviation which I will try later tonight. However, I think I heard this sound also on the medical and police bands....

As always, thank you for your responses and again, I love this forum

-Chuck

 

[a417]

but ill give you an example... I listen to a lot of aviation... It seems to happen on some signals where at

...and which modulation type is most prevalent on the air bands?

hint, it's not FM.

 

[Vulcanccit]

...and which modulation type is most prevalent on the air bands?

hint, it's not FM.

AM lol but using both sidebands with the center being what I am tuned to.... in the 108 -137 MHZ band.

 

[tvengr]

It is perfectly normal for aircraft signals to slowly fade in and out.

 

[buddrousa]

Aircraft and AM Sideband I am CONFUSED

 

[kruser]

In addition to trying IF Exchange, also try changing the Filter type.
I had that same experience when I first tuned the NOAA WX channels with my SDS100. They sounded horrible. In that case, it was just a matter of using the correct filter.

 

[Ubbe]

It seems to happen on some signals where at first the signal has some static, sounds off frequency (almost like listening to one of the sidebands)....then the signal gets stronger, full quieting and the "off frequency" sound slowly morphs into normal audio.

I know exactly what you mean by that. The receiver are full of internal spurious signals, carriers of different frequencies that usually are not exactly on the same frequency you are monitoring, it will be one or two KHz off and those signals change in frequency depending of IFX and filter settings. If you ever use a cheap SDR dongle and look at the spectrum over a 1MHz range you'll see those spikes, or you can use the bandscope program for SDS100/200 to see those signals live in your scanner.

Free Scanner Software | Hi all, here is the experimental SDS100/200 bandscope program | Facebook

/Ubbe

 

[dave3825]

I listen to a lot of aviation... It seems to happen on some signals where at first the signal has some static, sounds off frequency (almost like listening to one of the sidebands)....then the signal gets stronger, full quieting and the "off frequency" sound slowly morphs into normal audio.

Where is your antenna located and how many trees are between it and the open sky?

I can tell you from watching aviation in Sdr# that here by me in NY, I see a good amount of aircraft radios that are off freq. Majority are spot on but many are off quite a bit. Its clear as day watching on the spectrum.

 

[Vulcanccit]

It is perfectly normal for aircraft signals to slowly fade in and out.

im not referring to the fading, im referring to how it sounds when it is faded, it not just static, it is simply off frequency..... but then slowly come back in...very odd...based on the replies it seems to happen to others....it is not like it is every signal or often...maybe 1-2% of what I hear. Curious what @dave3825 and @Ubbe said about actually observing some of these radios being off frequency It does happen even in the Commercial Broadcast Transmitters, usually FM and older boxes...I had one be 2 channels off one day lol....fairly rare these days with PLL/computerized exciters. All of this is fun though, discovering these little quirks

 

[Vulcanccit]

Aircraft and AM Sideband I am CONFUSED

AM has sidebands.... any off of the center frequency is a sideband... now it is not modulated exactly like an FM subcarrier...

with AM Broadcast we routinely need to measure the sidebands to comply with NRSC Measurements...

 

[buddrousa]

I am fully aware of AM and what is upper and lower Sideband as I passed in 1978 my 2nd class general radio telephone license.
What you are talking about is plain old off frequency.

 

[Vulcanccit]

I am fully aware of AM and what is upper and lower Sideband as I passed in 1978 my 2nd class general radio telephone license.
What you are talking about is plain old off frequency.

ok cool, I guess I mistook your comment of being confused lol. 1978 is about when I got my 1st class, 2nd class was in 1977 I believe, somewhere in there lol.

 

[tvengr]

It does happen even in the Commercial Broadcast Transmitters, usually FM and older boxes.

If you are referring to the FM broadcast band, that should be programmed as WFM. If you use FM, it will sound off frequency and distorted.

 

[tvengr]

If you are referring to the FM broadcast band, that should be programmed as WFM.

Correction: It should be FMB for FM Broadcast band. WFM was good for analog TV audio.

 

[donc13]

I know exactly what you mean by that. The receiver are full of internal spurious signals, carriers of different frequencies that usually are not exactly on the same frequency you are monitoring, it will be one or two KHz off and those signals change in frequency depending of IFX and filter settings. If you ever use a cheap SDR dongle and look at the spectrum over a 1MHz range you'll see those spikes, or you can use the bandscope program for SDS100/200 to see those signals live in your scanner.

Free Scanner Software | Hi all, here is the experimental SDS100/200 bandscope program | Facebook

/Ubbe

It would seem that group may not be functional anymore. I say so because while I am not on Facebook (hate it) I did go ahead and create an account using an unused email address (which I verified the account with) but when I tried to join the group I get a screen saying the content can't be displayed. That could be because the group has to accept my request to join or because of other reasons.

Anyway, the point being that software may or may not be available any longer.

I will wait a few days and see.

 

[dave3825]

The software is there and available. I am joined with them and I did post asking questions but there has not been any response yet. I do know some of the users in the group are still around as I see them in other scanner groups. I wanted to know if live data should be being shown while stationary on an analog conventional channel with no active transmission.

 

[donc13]

The software is there and available. I am joined with them and I did post asking questions but there has not been any response yet. I do know some of the users in the group are still around as I see them in other scanner groups. I wanted to know if live data should be being shown while stationary on an analog conventional channel with no active transmission.

View attachment 120584

We'll, I will wait then.

Thanks!

 

[Vulcanccit]

I joined shortly after this post, I answered the question, and was accepted moments later, so someone was around. I did download the software, but I have not yet tried it.

 

[wtp]

i have a couple of radios and have heard what i think is the same 'off frequency' sound.
if i it to FM it comes in fine. and then the others sound horrible.
i have also used two radios at times when this happens and i am convinced that some (very few) aircraft radios are using FM. they just don't know it.
so, could you try FM next time and get back to us ?
thanks.

 

[donc13]

I joined shortly after this post, I answered the question, and was accepted moments later, so someone was around. I did download the software, but I have not yet tried it.

I still haven't heard back, but it is a brand new FB account and it did tell me the join request was sent to the group admin.

I have no idea how often the admin checks in.

I did note the acknowledge statement saying the software can't be distributed for non hobby purposes. And I did accept that acknowledge.