...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."
John,
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
product.
Paul, W9AC
----- Original Message -----
From: "John Brosnahan -- W0UN" <shr@swtexas.net>
To: "Paul Christensen" <w9ac@arrl.net>; <rfi@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
have.
Questions:
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
W9AC
[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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