HI,
I worked at a Television station at the time and this was
a goof off middle of the night cure the boredom and curiosity
project.

What I did was amplify an RF signal spectrum using the vertical
amplifier on an oscilloscope. The TEK 465 for example had
a Vertical Amplifier out connector on the rear of the scope.

I took the amplified signal from the antenna and scope. I then
summed this signal with a black burst signal.

It might have been just been a HV sync signal. I then fed this summed signal
into the VCR input.

I then hooked an amplifier to the video out. I then feed this
signal into an AM radio receiver. You could then tune in various stations.


There were dropouts from the head switching wihch added a litlle bit
of a Darth Vader effect. In fact you could slow the audio down
without changing the pitch. It added an echo effect.

I used an old IVC 800 tape machine. BTW if you don't have a time
base corrector the frequency will move around do to tape stretch.

As AM doesn't respond to phase or frequency disturbances the
audio can be detected.


The military has been doing this for years for signal intelligence
work.

I was just goofing off at the time. You could do the same thing now
by using a fast A/D converter card storing the spectrum to disk
and replaying it back out using a D/A.

This is sometime used as a snapshot recorder. You then replay the
spectrum over and over until you extract the information. IE: The
intelligence
you want.

Norman



PCS Engineering
Norman Gillaspie
325M Sharon Park Dr. #210
Menlo park, Ca. 94025
Tel 650-854-5263
Fax 650-854-5445
KF6WHG
Email norman@pcseng.com


> -----Original Message-----
> From: Martin McCormick [mailto:martin@dc.cis.okstate.edu]
> Sent: Tuesday, February 08, 2000 11:25 AM
> To: norman@pcseng.com
> Subject: Re: [OT] Recording radio on a video recorder.
>
>
>       I always wanted to record a whole spectrum like that, but
> never actually did it.  How much trouble did you have with the loss of
> signal which would have occurred with each sync or vertical blanking
> interval?  One would need to amplify the band such that the strongest
> signals were in the 1-volt range to get the maximum signal to noise
> ratio.
>
> Martin McCormick