[AMRadio] A Sweaper from the early 70's

Mike Duke, K5XU k5xu at comcast.net
Thu Jan 21 18:08:34 EST 2010

I've heard the signals that have been discussed here today, but that 
discussion reminded  me of something I used to hear often in the early 
and mid 70's.

It would be heard here in Mississippi as low as 40 or 80 meters during 
certain times of the year, but mostly on the upper bands as high as 6 
meters  during the spring and summer.

When listening in the ssb or cw modes, the carrier sounded rather 
rough as it moved through the passband of my receiver.

When listening on AM or FM, it appeared to have a low level of 
modulation which sounded like a tone of around 400 cycles. During a 
summer job as a dispatcher for my local police department in 1974, I 
had to monitor 42.38, and 45.10. That's when I made several 

 1. The modulation was more noticeable on FM than on AM.

2. The closer the sweep came to reaching what I assumed to be the top 
of its range, the slower it would move. When it reached the highest 
frequency, it jumped back to the lowest point, and started over.

3. I learned to associate the sweep with pending band openings on 10 
and 6 meters. The higher and stronger the signal, the better the E 
skip opening signals would be.

I never learned what it was or where it was, but suspected some type 
of military radar.

Of course, in the early 80's there was the dreaded Russian Woodpecker, 
which I have also heard on 6 meters.

That one wasn't a sweeper; it was "broad band over radio!"

Mike Duke, K5XU
American Council of Blind Radio Amateurs

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