2 Types of signals on one frequency

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smurf_cat

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I am trying to listen to WNUD964 in Los Angeles, specifically 462.13750. I have an inexpensive hand held scanner that is several year old. On this frequency I can clearly hear maintenance workers, but there are other transmissions that I believe are security guards that sound unclear. Sometimes I can understand a word or 2 but it sounds off, wavy, sampled funny or narrowed in frequency; words fail me.

Could they be using modulation or some other type of transmission technique to put 2 types of traffic on one frequency? It does not sound encrypted or digital. It is not trunked.

If I were to upgrade my scanner, what features would I look for to be able to listen to the frequency?

thank you,
Smurf Cat
 

commstar

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If you can post an audio sample the answer would probably be way to get more immediate and definitive answers to your question. a recording is worth 10,000 words and all that.....

Heres a guess:

I know you said it is not encrypted but what you describe almost sounds to me like low grade analog voice encryption. That wavy undecipherable speech description is what leads me to think that. Posting an audio sample would quickly rule that in or out.

Listen to the 400 series on this list- somewhat like you are hearing?
http://www.transcrypt.com/products/scramblers/audio

As for weeding out all the other co-channel users in the purchase of a new radio, purchasing a scanner with pl tone/ctcss capability may get you where you want to be.

It is the one of the prime reasons that PL tones exist - to have different users on different PL tones hearing the same frequency- so they cannot hear one another.

Conversely, when you listen to the same frequency with your scanner you hear all the
users. Many newer scanners have PL capability allowing one to hear one users on a specific channel with a specific PL tone.

If conversely, 'they' are in fact using even low level analog encryption then there is no scanner made to my knowledge that will support decoding that signal.

I imagine Largely because unauthorized decryption is illegal (i will leave that for you to deal with), but, secondarily because there are so many different types of encryption protocols out there and next to no marketable/legitimate call for this capability in a scanner in addition to the cost of licensing the use of each encryption protocol.

These are my best guesses based on your description

Posting a recording will almost certainly get you better answers and I would encourage you to do that.

Regards,
Mike
 

smurf_cat

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Yes, it does sound a lot like the 400 low security analog encryption on that page. I was unaware that such encryption was available legally to users of the public airwaves. I will post a link to an audio sample in the next day or so. Thank you.
 

commstar

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Affirm, that is analog voice encryption. I do not have the expertise to tell what manufacturer it belongs to. No legal way to monitor without thier permission.Would like likely need radio equipment set up the same as thiers as no current scanner will support this stuff. Most of the transcrypt stuff I have played with has MDC1200-esque signalling in it and I do not hear that here......

There used to be voice inversion 'decoder' boxes made but congress put a stop to that years ago. I THINK Grove used to make/sell one but like I said no more. dont think it would work regardless. If you lived somewhere where it was legal to decode this signal and found such a decoder box at a garage sale (long shot) it would be worth a try.

On a side note, do you happen to know what brand/model radios they are using? That might give one some insight into the manufacturer of the encryption.
 

rescue161

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Ramsey sells a kit that will decode it. It's called the SS70. There is also software available that will do it, but the SS70 is a stand alone unit that you hook to your scanner.
 
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