[RFI] Radar Engineers RFI Analyzers

Paul Christensen w9ac at arrl.net
Mon Dec 24 10:07:21 EST 2012

Seasons greetings to all...

There's been enough RFI at this QTH during the last decade that I'm looking 
to purchase a National HF Vector Gun and a used Radar Engineers (RE) RFI 
analyzer, model 240A or 242.  Or, in the alternative, a V/UHF Sadelco FSM 
with video output for use with one of the many oscilloscopes I have.


1) Apart from the usable frequency range, is there's much difference between 
the RE 240A and 242 models?

2) Loftness' book [1] goes into great detail concerning the interface he 
constructed to integrate his FSM and scope together -- right down to 
schematics and a parts layout diagram. I would opt for this approach since 
the display resolution is probably much better then the RE's LCD displays. 
My only concern is that the usual CATV FSM units only go down to about 50 
MHz, the lower VHF limit of TV Channel 2.  I would hate to expend a lot of 
time and trouble to construct an interface only to find another occurrence 
where RFI is lumped in one HF band well below the limit of the FSM.  In 
fact, this just happened to me where a utility pole about a half-mile away 
was arcing with greatest amplitude on 20m at an S9 level.  Very little RFI 
on AMBC and just a bit noticed on 10m as shown by Tresscot in Fig. 2 of his 
QST article. [2]

For those of you actively engaged in RFI abatement, have you found the FSM's 
limit of 50 MHz to be a drawback when using the scope system Loftness 

Many Tnx!

Paul Christensen
Jacksonville, Florida

[1] Loftness, M. (KB7KK), AC Power Interference Handbook, 2nd. ed. rev., pp. 
7/6, 7/12. ISBN 0-9653760-3-6.
[2]  Trescott, M. (K3QM), "Basic Steps Toward Tracing and Eliminating Power 
Line Interference," QST, Nov., 1991, p. 44. 

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