[GreenKeys] Re: M20-RO

[Sheldon Daitch]

Well, guess what, you both may be right, and here is why they 
will sound differently.

Without some data on the exact tone frequencies, I can't 
tell you if the Lenkurt 25A system was indeed the same
tone channel layout as the normal 16 channel tone pack.  
I just don't have any literature on the 25A system.  
But, I think they were.

Does anyone have this information?

Two reasons the UPI or the AP tone packs might not sound
as the FDM tone packs on HF is that in most cases the
tone package for the wire services were not fully occupied
with all 16 channels, thus the individuals tones were much
easier to pick out by here.

But here is why I believe they really sound different.
When listening to the "buzzsaw" tone pack on HF, you are
generally listening to a SSB signal with the tone pack
that is, the modulation of a signal without a carrier.

I think you will find the difference between a tone pack
on a phone line and off the air as an FDM tone pack, is the
same as voice audio on a phone line and the same voice audio
on a SSB transmitter, listening in the AM mode.  If you listen
to the FDM tone pack on HF in the SSB mode, and tuned to the
correct channel frequency, the tone pack should sound pretty 
close to what you would hear on an audio pair.

Now, I am making the assumption that the "buzzsaw" tone packs
on HF are indeed some type of TTY/data tone pack running
multiple channels.  Obviously, other "data" would should
differently.

73 
Sheldon
WA4MZZ









"Charles Ring, W3NU" wrote:
> 
> Chuck Swiger wrote:
> 
> > >And more from memory, so if I am wrong on a detail or two,
> > >someone add to this.  I think the basic AP Lenkurt system was
> > >a 16 channel AFSK multiplex system, that would allow 16 channels
> > >of data on a voice grade phone line.
> >
> > Gang - just curious, is this anything like FDM signals on shortwave?
> >
> >  From what little I've picked up thru the years there are or used to be
> > 'buzzsaw' sounding signals that were reportedly multiplex feeds - has anyone
> > here ever decoded those?
> 
> I listened across the UPI line (same Lenkurt system as AP) at the radio station
> I worked for, and it didn't sound at all like a buzzsaw, just a number of AFSK
> signals with different mark and space tones all mixed together.
> 
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