[RFI] Oscilloscope requirements for power line noise locating

N1BUG paul at n1bug.com
Sat Dec 29 16:10:09 EST 2012

I have some more questions. I have been re-reading relevant sections 
of Loftness' book on using an oscilloscope with a Sadelco (or 
similar, presumably) field strength meter but it isn't all coming 
together for me.

For this purpose, what are the minimum scope specifications for 
acceptable performance (bandwidth and otherwise)? The two scopes 
referenced in the book appear to be 40 and 60 MHz units. I don't see 
why that bandwidth would be needed. Is it?

I don't yet understand exactly how he triggered or set up the scope 
to obtain a stable trace in the field. I do NOT have extensive 
experience with scopes so I may be missing something basic here. 
Using my HP 1980B scope at home, I had to resort to external 
triggering from the AC line to get a stable display when viewing 
power line noise pulse groups from my station receiver. However that 
scope has digital controls and sweep rate is not infinitely 
adjustable. I wouldn't be able to trigger off the AC line in the field.

Would anyone have recommendations for inexpensive scopes suitable 
for this purpose that can run from internal batteries? Everything I 
use in the field ABSOLUTELY MUST be 100% portable and able to be 
hand-carried. Anything that is not is useless to me.

I am considering selling off part of my ham station to assemble a 
noise locating system with a field strength meter (providing video 
output), oscilloscope, and log periodic dipole array antenna. But 
first I need to get a better picture of what it's going to take.


Paul Kelley, N1BUG
RFI Committee chair,
Piscataquis Amateur Radio Club

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