[AMRadio] frequency sweeper

Paul Christensen w9ac at arrl.net
Thu Jan 21 11:54:41 EST 2010

> Apparently NOT an OTH radar, if it sweeps so
> slowly.

The 18 minute sweeps are coming from this ROTHR system.  Each of the three 
sites can be heard, all with different signal strength depending on your 
location relative to their transmitters.  The 18-minute cycle is not 
synchronized across all three transmitters.  For example, you may hear 
Virginia at the top of the hour, next followed by PR 45 seconds later, then 
followed by Texas perhaps 15 seconds later.  Once can record the signal 
strength from each of the sweeps then count 18 minutes and if propagation 
has not substantially changed, they are easily identified.

What I need is an 18-minute look ahead timer that automatically engages my 
20 dB attenuator for a split second!

Paul, W9AC 

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