[AMRadio] Odd signals in lower 80 meters


Geoff/W5OMR ars.w5omr at gmail.com
Sat Dec 23 08:01:12 EST 2006


Jay Rusgrove wrote:
> Possibly the old NBVM (narrow band voice modulation) system debeloped by Dr. R.J. Harris and
> published in QST Nov. & Dec. 1978. There was a limited production run of commercial units, and a
> hard sell to the ARRL and commercial SSB users followed, however the concept never caught on.
> Imagine there are still units floating around.
>
> A brief overview of the system can be found here:
>
> http://www.qsl.net/vk5br/NarBandVoice.htm
>
> Details are in the QST articles. Being in on the original testing, I can say it was darn near
> impossible to get any intelligence from the 'folded over' signal.
>
> Jay W1VD
>   

There were some rigs used back in the late 70's and early 80's, where 
the police departments became more aware of those citizens that were 
listening on scanners at home, to keep abreast with what was going on in 
their community... and they knew (know) that the crooks use them too, to 
try to stay a step ahead of the law.

In Southern California, Pomona, specifically, there was a 'code' they 
used to go to the 'scrambled' mode;  'Gold'. 

"Unit so-and-so, meet unit so-and-so on city-wide tack 2, 'gold'."

Gold was the 'code' to 'go scrambled', so that no one else (outside of 
those officers who went and listened with their so-equipped rigs).
A little circuit inside the rig, activated by a miniature toggle switch 
was all that was required.

I've head these signals on 75m in the evening hours, and I thought that 
was -exactly- how it sounded.  If the high-end response is replaced by 
the low-end response, there won't be a high-end roll-off... you'd hear 
the equivalant of the low-end roll-off, and pretty much, it's fairly 
dramatic at around 100hz, in those commercial communication services.

Like most of y'all, though, I had never heard of that system being used 
on SSB.


Let the Pumkin Pie be served!  Pour the Egg Nog, and warm the filaments! 
It's time to celebrate! 
CHRISTMAS (_or_insert_your_celebrated_holiday_here_) Is here! It's time 
to enjoy the fellowship and commraderie of your fellow AM'ers.

It's RADIO TIME!

--
Ho Ho, Mo-Fo!
73 = Best Regards,
-Geoff/W5OMR



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