[RFI] Radar Engineers RFI Analyzers

Paul Christensen w9ac at arrl.net
Mon Dec 24 10:56:22 EST 2012

>...Or skip the CATV FSM and go directly to the dongle (less than $40)
and upconverter.  This will limit your expense to less than $100
(plus portable computer) and you have an SDR with a noise
calibration/reference source in the upconverter."


Sounds like a slick concept although I need to get the results into a time 
domain - rather than spectrum.  The essence of the Loftness and RE designed 
systems is to sweep with a sync generator at a 60 Hz rate, then look for a 
distinctive signature of two pulse trains, indicative of a spark/arc 
occurring at the positive and negative peaks of the 60Hz AC cycle.  When 
sparking is symmetrical, two pulse trains appear on the screen (i.e., 120 Hz 
sparks). Folks like Mike Martin, Frank Haas, and Ed Hare seem to live by 
this tracking method as it can produce some fast results in the hands of the 
properly trained.

I do use an SDR-IQ and notebook PC for use when hunting down SMPS noise 
while on foot.   That works well since localizing SMPS noise works best in a 
spectrum domain rather than time.

In researching this more, it appears that as broadband/CATV companies have 
upgraded to HDTV/QAM, they have jettisoned most of their older Wavetek and 
Texscan FSMs.  Many of them go down to 4 MHz and have a video output for the 
scope.  So, that may be an alternative to the limitation of the Sadelco FSM 

Paul, W9AC

----- Original Message ----- 
From: "John Brosnahan -- W0UN" <shr at swtexas.net>
To: "Paul Christensen" <w9ac at arrl.net>; <rfi at contesting.com>
Sent: Monday, December 24, 2012 10:39 AM
Subject: Re: [RFI] Radar Engineers RFI Analyzers

> Paul--
> One option to see HF with your VHF only CATV FSM is to use an HF 
> upconverter designed for SDR dongles like the FunCube.  This puts the 
> entire HF spectrum into the low VHF band.
> Do a search on Amazon or Google and you will see them for about 50 bucks.
> Ham It Up v1.0 - NooElec RF Upconverter For Software Defined Radio.
> Or go directly to the nooelec website and get it for $40
> nooelec.com/store/software-defined-radio/sdr-accessories/ham-it-up-v1-0-rf-upconverter-for-software-defined-radio.html
> Or skip the CATV FSM and go directly to the dongle (less than $40) and 
> upconverter.  This will limit your expense to less than $100 (plus 
> portable computer) and you have an SDR with a noise calibration/reference 
> source in the upconverter.
> nooelec.com/store/software-defined-radio/eztv668-dvb-t-usb-set-for-sdr.html
> John  W0UN
> At 09:07 AM 12/24/2012, Paul Christensen wrote:
>>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 
>>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 describes?
>>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.
>>RFI mailing list
>>RFI at contesting.com

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