I've recently bought a PRO-95 and am enjoying scanning.....

Several times now, while listening to our local police/sheriff channel,
I'll run receive an unintelligible message. The voices are very high
pitched, sounding like a cross between Minnie Mouse and Alvin the
Chipmunk, and I know they're talking but I can't quite understand what
they are saying. Superimposed over this is a loud ticking sound.

What have I run into??

Wayne
Port Townsend, WA

Wayne Howell wrote:

I've recently bought a PRO-95 and am enjoying scanning.....

Several times now, while listening to our local police/sheriff channel,
I'll run receive an unintelligible message. The voices are very high
pitched, sounding like a cross between Minnie Mouse and Alvin the
Chipmunk, and I know they're talking but I can't quite understand what
they are saying. Superimposed over this is a loud ticking sound.

What have I run into??

Rolling code voice inversion, the "tick" is the sync telegram. Should
be near to impossible to decode this, sorry.

Transcrypt is a common manufaturer of such toys, also AFAIK Daxon.

Wayne
Port Townsend, WA




regards - Ralph

--

Want to get in touch? http://www.radio-link.net/whereisralph.txt

Voice scrambling of the audio.

"Wayne Howell" wrote in message
...
I've recently bought a PRO-95 and am enjoying scanning.....

Several times now, while listening to our local police/sheriff channel,
I'll run receive an unintelligible message. The voices are very high
pitched, sounding like a cross between Minnie Mouse and Alvin the
Chipmunk, and I know they're talking but I can't quite understand what
they are saying. Superimposed over this is a loud ticking sound.

What have I run into??

Wayne
Port Townsend, WA

Wayne Howell wrote in news:tZ-dne4xfrIHPDjfRVn-
:

I've recently bought a PRO-95 and am enjoying scanning.....

Several times now, while listening to our local police/sheriff channel,
I'll run receive an unintelligible message. The voices are very high
pitched, sounding like a cross between Minnie Mouse and Alvin the
Chipmunk, and I know they're talking but I can't quite understand what
they are saying. Superimposed over this is a loud ticking sound.

What have I run into??

Wayne
Port Townsend, WA

A 2-way conversation between Alvin the Chipmumk & Minnie Mouse ?

If it's voice inversion, even if the base freq shifts about, should be
pretty straight forward to decode. Any .wav (or whatever format) samples
on the net available to download and examine?


B.




Ralph A. Schmid, DK5RAS wrote:
Wayne Howell wrote:


I've recently bought a PRO-95 and am enjoying scanning.....

Several times now, while listening to our local police/sheriff channel,
I'll run receive an unintelligible message. The voices are very high
pitched, sounding like a cross between Minnie Mouse and Alvin the
Chipmunk, and I know they're talking but I can't quite understand what
they are saying. Superimposed over this is a loud ticking sound.

What have I run into??


Rolling code voice inversion, the "tick" is the sync telegram. Should
be near to impossible to decode this, sorry.

Transcrypt is a common manufaturer of such toys, also AFAIK Daxon.


Wayne
Port Townsend, WA





regards - Ralph

bob wrote:

If it's voice inversion, even if the base freq shifts about, should be
pretty straight forward to decode. Any .wav (or whatever format) samples
on the net available to download and examine?

How do you want to find out what inversion frequency is used at what
moment?



regards - Ralph

--

Want to get in touch? http://www.radio-link.net/whereisralph.txt

First you have to determine ow many 'base' frequencies are utilized.
it's likely a small number, likely 8, 16 at the most. If it's a variable
scale, it could be a larger number, but again, not an impossible task.

You will have to determine how the key is sent, or if it's a rolling
sequence. (a rolling sequence would not require continuous sync pulses,
so it's likely the receiver looks for the next key (base freq) and
changes the mix frequency accordingly.

To analyze it manually (to at least get some details about the
transmission format) just grab a small (perhaps a few seconds) sample
and tear it apart manually. Break it up with a computer sound editing
program and play each slice repeatedly into a frequency inversion
circuit (Ramsay sold one, there are also a few schematics floating about
the net) until you recover natural sounding snippits of audio. Splice it
all back together and see how it sounds. Document each mixer freq
needed, and compare them to each 'tick' data byte. (you'll need a data
slicer for this, again, see the net.) This will give you a good
selection of raw data.

Just to clairfy things, when I said "...it should be pretty
straightfroward to decode." I was not suggesting it would not be labour
intense. It could turn out to be a royal pain in the a$$, however, if
it's simply inversion with a variable mixer freq, there's no real
security there. It would be inconvienent to analyze, but again, the
process is straightforward. To automate it will also take a lot of time,
but again, unlike with digital ciphering, you're not up against large
numbers and even larger permutations.

Is there a sample of the audio somewhere on the net that could be
downloaded?

B.




Ralph A. Schmid, DK5RAS wrote:
bob wrote:


If it's voice inversion, even if the base freq shifts about, should be
pretty straight forward to decode. Any .wav (or whatever format) samples
on the net available to download and examine?


How do you want to find out what inversion frequency is used at what
moment?



regards - Ralph

bob wrote:

roward to decode." I was not suggesting it would not be labour
intense. It could turn out to be a royal pain in the a$$, however, if
it's simply inversion with a variable mixer freq, there's no real
security there.

The problem may be that the tick usually has nothing to do with the
number of frequency changes. The inversion frequency may change
several hundred times per minute, and the tick is just used to keep in
sync.



regards - Ralph

--

Want to get in touch? http://www.radio-link.net/whereisralph.txt

Okay, so if it's several hundred times per minute, that would definitely
change everything. However, if that's the case, would it not be most
likely they're employing some sort of sinewave (or sawtooth, or
stepwave) 'seed' signal into a VCO which supplies the mixer freq?

It's not impossible, but it may be unlikely the mixer freq changes that
often. If it changes too much, then it itself starts to become a
problem, because the switching itself will begin to encroach into the
audio spectrum. The mathematical limit would be 3000 seed changes per
minute, as this would impose a 50Hz noise on the information. I suppose
part of the problem is my not ever hearing this type of signal, so I'm
only able to imagine what it sounds like. Is the system is truly an
analog mangling of the source material? Also, there was another system
out back in the 70's where they took the passband, inverted it, sliced
it up, and shifted the pieces about. It think Radio-Electronics did a
feature on it, including a project for one that broke 300Hz-3000Hz into
4 pieces, mangled them a bit and out popped your encoded audio. It was a
symmetrical system.

The more I think about it, it could be a nasty chore to straighten it
out. Harris has a system for HF that's straight analog but certainly not
easy to decipher, but their's is not straight inversion either. If
however, the mixer truly shifts about that much, it's simply not worth
the effort, unless you don't mind placing your sanity at risk...






Ralph A. Schmid, DK5RAS wrote:
bob wrote:


roward to decode." I was not suggesting it would not be labour
intense. It could turn out to be a royal pain in the a$$, however, if
it's simply inversion with a variable mixer freq, there's no real
security there.


The problem may be that the tick usually has nothing to do with the
number of frequency changes. The inversion frequency may change
several hundred times per minute, and the tick is just used to keep in
sync.



regards - Ralph

The tick that started this thread is at a one second interval......

These scrambled (?) messages occur quite infrequently (perhaps 2-3 times
a day) and it is always in incoming message. The dispatcher usually
(but not always!) responds in plain talk.

About half the time, from the context of the dispatcher's message, I can
identify which field radio the scrambled (?) speech is coming from.
And, in those cases I will have heard the same radio in clear speech and
will hear it later on also.

Wayne Howell
Port Townsend, WA