Re: [IRCA] Perseus captures from 1991

[Sylvain Naud <sylvainnaud62@xxxxxxxxx>]

This is very interesting Mark.

I'll certainly look forward for your Perseus converted files.

Sylvain Naud
Portneuf, QC


Le 2014-02-21 16:55, Mark Connelly a écrit :
> I finally got around to going through a box of VHS videotapes from the 
> late '80s / early '90s spectrum capture experiments, as originally 
> developed by Craig Healy (NG1U), and mentioned in this article:
> http://chowdanet.com/markc/webpage/WA1ION/vcrdx.pdf
>
> There were about 6 tapes in the box.  Two of these, when played into a 
> receiver, had reasonable performance.
>
> One of these was the tape Craig had originally supplied me.  This was 
> made at his QTH near Providence, RI.  The whole AM band is captured.  
> Sensitivity on the lower half was quite low so it's primarily the 
> local stations such as 630, 790, and 920.  Some skip signals can be 
> heard on the upper half of the dial.  I still have to review the tape 
> to determine the exact date and times of recording.  Items on a news / 
> sports station, possibly with some Google follow-up, will nail down 
> the date.  At some point in the recording there should be a time check 
> on one station or another. I looked into the lower shortwave spectrum 
> but noted little in the way of "real" (non-birdie) signals, so no CHU 
> or WWV assistance on the time.
>
> The second tape was one I made at Billerica, MA in April 1991 during 
> the "wee hours" of the morning: 0643-1043 UTC.  Because 50 kW WRKO on 
> 680 is only 2.8 miles / 4.5 km from the receiving site, a notch filter 
> for 680 was inserted ahead of the VCR input. Usable sensitivity for 
> the capture came in starting around 800 kHz and up.
>
> One thing that must be kept in mind is that this primitive version of 
> spectrum capture had a rather small dynamic range: only about 30 to 40 
> dB from a hashy noise floor up to the level of a strong local on the 
> verge of causing distortion and spurs.  The tapes, obviously, are not 
> going to produce much in the way of weaker signal DX.
>
> Before the tapes have a chance to deteriorate, I'm porting at least 
> some of the contents over to Perseus files.  This also gives a ready 
> method for sharing the experiment results with others.  I reset the 
> computer date/time so that the Perseus time-stamping is relatively 
> close to the occurrence of the original recordings.
>
> After I get all this stuff digitized, I'll go over it for any 
> interesting audio clips.
>
> Though the "VCR DX" method became known to the MW DX world about a 
> quarter century ago, it is widely believed that, as far back as the 
> JFK administration, "spook" agencies such as the NSA were able to 
> store substantial RF bandwidths for later review.  Broadcast studio 
> grade videotape, or something similar but custom-designed, was used.  
> Converters allowed any chunk of spectrum to be heterodyned to the 
> baseband range (0-3 MHz?) the tapes could accommodate.  The late 
> Gordon Nelson (WA1UXQ) seemed aware of it. Maybe some tapes will show 
> up at a Fort Meade, MD fleamarket / yard sale so we can tune around 
> and hear stuff like Belize 834 and Bermuda 1235 once again, as well as 
> Murray-the-K on WINS proclaiming his status as the Fifth Beatle.
>
> Mark Connelly, WA1ION
> South Yarmouth, MA

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