[GreenKeys] Re: M20-RO

Wed, 05 Feb 2003 08:22:43 +0200

Howard,

Wasn't the 16 kHz bandwidth on the R-390 and other receivers for
a slightly different purpose, not just for a tone pack?  The 
tone pack should go down a 4 kHZ VF grade phone circuit just 
fine.

I recall way back that there were some point-to-point systems
that needed that kind of bandwidth, carrying two VF grade phone
circuits on one side band and one VF grade phone circuit and
a 16 channel tone pack on the other side band.  I never worked
with this equipment, but I did see it.  Usually a pair of R-390s,
a CV-157 (I think it was) with the Maxson(?) or Manson(?) frequency 
stabilization system for frequency control.  The USB and LSB audio, 
each with a 8 kHz wide spectrum, was then sent to another pair 
of units, TD-98, perhaps.  I have notes that indicate
the receiver system was an FRR-39(V)/

My notes indicate that TD-97 was the two channel MUX and the TD-98 was
the two channel demux, and may have been replaced with a TD-410 and
TD-411 series units.

Anyway, the TD units may have been over in the tech control
facilities and not at the TX or RX sites, and were used to multiplex
two VF grade circuits into an 8 kHz audio signal, and then that
was fed into the wideband audio inputs on the ISB exciters.

The reverse on receive, two 8 kHz wide signals off the receiver, 
one USB and one LSB, and then each was fed to a matching demux
box, which broke the audio down to regular 4 kHZ VF grade circuits.

And Howard is absolutely correct on using the FSM for checking the
levels of "audio" signals in the baseband of the carrier or microwave
system, in the good olde days of frequency division multiplex.  
Sierra 125 seems to stand out as a workhorse in that vintage, the
1960s and 70s.  Maybe it was a 126.  Oh, that just jogged another
memory cell regarding a unit, the envelope delay test set, which 
measured phase shift and jitter across the VF grade circuit.  I 
believe Howard can tell I am showing my age!  (Hello 32 Deltas!)

73
Sheldon

"Howard R. Weeks" wrote:
> 
> I have in a different life..
> Assuming you have a receiver with enough bandwidth all the way through the
> audio section
> (now you know what that 16KC BW position on the R390 is for), you can use a
> frequency
> selective voltmeter to tune and demodulate each of the many subcarriers that
> may be there.
> The FSM will have to have detectors appropriate for the type modulation used
> on the subcarrier.
> Have also used them to demodulate the various channels on the baseband of
> microwave systems.
> Howard Weeks K5JCP
> Harlem, GA
> ----- Original Message -----
> From: Chuck Swiger <[email protected]>
> To: <[email protected]>
> Sent: Tuesday, February 04, 2003 9:44 AM
> Subject: Re: [GreenKeys] Re: M20-RO
> 
> >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?
> 
> For more details see the Utility Net at
> http://www.wunclub.com/digfaq/signals.html
> and scroll down to MULTI-CHANNEL/BUZZSAW like signals (1-I).  I'm always
> hopeful of picking up printable intelligence thru the aether. I sure miss
> George's
> RTTY station - It seems like the FCC can't do anything right!
> 
> --Chuck
> kb4new
> 
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