[RFI] Frequency-Specific Interference

KD7JYK DM09 kd7jyk at earthlink.net
Tue Feb 28 11:29:04 PST 2012

Back in 2004 I ran a beacon, RPG, on 13,555.430 KHz.  It genrated a bit of 
broadband hash from the Epson oscillator so I would shut it down when I 
wanted to monitor HF.

Sometime around December of 2004, there had been some driving sleet and I 
began to heard a strong  pulsating broadband hash similar to to what my 
beacon oscialltor would created, however it was one second on, one second 
off.  It was from a few tens of KHz to at least 30 MHz, the upper limit of 
the receiver I had at the time.

I have a rotatable 10m dipole and tried to get a bearing on it, but it was 
very strong with a faint null to the South.  This made sense to me at the 
time because with the dipole facing South, my beacon was off the tip.

I hiked out and shut off my beacon.  Upon return to the shack, the noise was 
still present.  I thought that perhaps the odd-ball power supply I used had 
capacitors in it I didn't know about and due to the low current draw, my 
beacon was still operating.

I went back out and disconnected the transmitter and just in case, shorted 
the input leads due to its own capacitors.

Still a broadband sound.  I went back out to the beacon, this time with a 
portable HF receiver.  As I got closer, the sound increased!  Now I'm really 
getting confused!  I ran my little receiver with it's ferrite bar antenna up 
and down the beacon antenna and mast, yep, noise everywhere near the beacon, 
still a null to the South, very strange.

The sound last for about three hours, then stopped and hasn't been heard 

It was a couple of years later when passing through a portion of the Nevada 
Test site and looking at some rather unobtrusive large metal sheds that I 
recalled a story form a fellow I had spoken with one evening several years 
earlier.  His comment was something like this:

"You know those large metal sheds, they have simulators in them that can 
create the conditions of outer space.  We can put a device under a vacuum 
and blast it with most any type of radiation, thermal, electromagnetic, even 
nuclear.  Right now we have a spy satellite in the chamber and we're 
blasting it with RF, CW, from a few Hz to GHz with pulses up to three 
MegaWatts.  This will go on for days".

Fast forward a few more years, I run into another fellow from the NTS and 
make a brief comment, "Did you have an instance a few years ago with one of 
your chambers that may have generated external RFI?", "Yes, we had a loose 
door for a few hours".  I told him my general location and that I had been 
blasted, resulting in my equipment being rendered near useless for that 
period.  He provided me with a phone number to call and told me "we REALLY 
need to know when there is a problem detectable from outside, call this 
number, when a person answers, tell them, "check your simulator doors""


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