Sorry to have been so pedantic, Ed.
In my drive to be thorough, complete, cover every aspect
including supplying the easiest answer I could give ("seek
out and make use of a portable SW radio utilizing a
ferrite loopstick on/near the band of interest") on the
subject (either brought up by me or others) I may have
crossed over into some covering some areas too deeply
thereby boring some and treading on the sacred ground of
others ... and here I go again, being pedantic (again!) and
I apologize.
Ed, I would stack up up my RFI tracking abilities
with the best, from LW through 1 GHz, incl. cellular,
AM broadcast; I've got my fair share of 'trophies'
hanging on the wall, both professionally and as a
ham. I also have one or two "white whales" that
have eluded me: notably, a case where I think a
secondary street light 120V source is 'modulating' (as
opposed to directly generating RF energy) the
AM broadcast RF field along a busy thorougfare
thereby imposing a distinct AM hum on any received
AM stations near where I drive daily ... and here I go,
being pedantic again, sorry.
I think, in the subject matter I covered, that I was
striving to cover several important subjects or topics
that I have found important in tracking down noise
sources, some subject areas that I have not seen
treated elsewhere including this list -
- such as using calibrated WB (wide band) peak-reading
TV field strength meters to DF noisesources (see, most
of the radios used in AM mode are average reading,
not peak reading, on account of the time constant
in the AGC used in the IF. Contrast this with the
inherent 'peak reading' of the old Stoddart RFI receivers
which had a quasi peak-reading meter function as well
as a comparator function where real 'peak' strengths
could be determined) ... there I go again, being thorough
and pedantic; pls forgive me.
Such concepts as 'correlation', (making mental note
of the audible sound charactersitics b/c hauling around
a scope or S/A is not feasable for most hams) of a
particular noise source that is active in spectrum
range of concern or effect into a higher, more easily
DF 'd band, specifically determining such factors as
"is the noise source observable in the VHF/UHF area
where I can use a unidirectional beam" as opposed
to doing it the hard way on the band of affectation has
been a specific point that I've stressed (I've even riggged
up portable 10 M dipoles to DF specific noise sources
that affected that band alone) ... hmmm, I've returned to
pedantics again, pls indulge a slighty pudgy old pedantic
ham one more time.
I've recently gone back to look at Maxwell's Equations
again, as they relate to radiation, propagation, since
he seems to have been the first one to quantify and
codify a number of the laws of magnetic and electric
field theory, some of which can even be used to
understand and explain the action of the various power
line noise sources we/some of us encounter.
On closing, If you ever wish to discuss a specific area of
noise, DFing, transmitter hunting et al off-list, my e-mail
box is always open; I may be delayed in responding
owing to work or personal schedules, but eventually
I will make the effort to respond.
Yours pedantically in the hobby,
Jim P -- WB5WPA --
----- Original Message -----
From: "Ed -K0iL" <eedwards@tconl.com>
To: "'Jim P'" <jvpoll@dallas.net>; <rfi@contesting.com>
Sent: Saturday, February 18, 2006 12:29 PM
Subject: RE: [RFI] RFI Direction Finding
> Jim,
>
> This has drifted far off from where the original question was, which was
how
> to make/use a loop on 40 mtrs to track noise. I was simply giving some
> "general" guidelines from my experience and those of other professional
> power company RI guys. You seem determined to dive off into specifics for
> which we haven't been given any information yet.
>
> Of course there are exceptions to the "rules", which are actually
> guidelines, not rules. But we don't have any info from the guy on the
> specifics since he's just getting started.
>
> Most of what you say is true: never start a search on UHF for a noise you
> hear on HF that could be far away; some FM radios do pick up impulse noise
> (which I stated), but usually at a lower sensitivity that a good AM rcvr
> would, and you have to take into account the limitations of your
equipment.
> I think you'll find I said the same things overall if you stop looking to
> tear apart each individual paragraph.
> ---
>
> Now back to the first question of tracking on 7 Mhz with a loop; some good
> things to look at before starting a PL noise search can be found in the
> "Interference Handbook" by William Nelson & Bill Orr. Even though the
> book's a bit dated, powerline technology has not change too much over that
> time. Fig 1 (pg 54) and Fig 5 (pg 58) shows the range of noise given
> different freqs/bands. Another is Fig 1 (pg 104) showing standing wave
> effects from a transimssion line. What's interesting here is a peak in
the
> horizontal is a null in the vertical and vice versa. Anyone tracking a
> source needs to keep these things in mind simultaneously when tracking a
> source.
>
> One limiting factor will always be the amount and type of equipment
> available to the investigator whether he's a ham or a power company
> employee. If a ham is trying to find the source to speed up response time
> and repairs, it's important that he get it right before calling the power
> company or he'll get a reputation that might hurt his response the next
> time.
>
> There was also an excellent article in QST last year or before that
> discussed a fast method of getting a kind of "fingerprint" of the
offending
> noise on a storage scope, then searching for that specifc noise in the
> field. I have the book by the same author at work (Marv Loftness). There
> are also some good tips on Mike Martin's site at
http://www.rfiservices.com/
> who teaches seminars on Loftness' tracking technique and does consulting
> work for power compaies.
>
> Just some things to think about before heading out with the HF loop. Good
> Luck.
>
> 73, de ed -K0iL
>
> -----Original Message-----
> From: Jim P
>
> > The FM broadcast wouldn't be affect on an FM radio since noise is
> > "Amplitude" in nature. FM rcvrs won't pick them up (usually, although
> some
> > rcvrs may).
>
> Bzzzzt!
>
> Not these cheap ratio-detector equipped FM radios with only
> 4 transistor IF stages - which I used to check this phenom (these
> radios aren't equipped with a full set of 'limiter' stages followed by
> the usual Foster-Seely discriminator).
>
> > Most powerline noise sources, when you are in the neighborhood, do emit
> into
> > VHF high-band real nice and sometimes even lower UHF portion locally if
> you
>
> Only a partial "Bzzzzzzt! on this one.
>
> An attempt on this basis to establish correlation of a particular source
> and it's 'effect' that one has in his shack may fail given a rock-hard
> assumption in this area.
>
> Take for example, again, where the ham who took his Two Meter
> Beam could not locate this source using VHF alone.
>
> > have a sensitive enough rcvr at those freqs. I am not referring to ham
> > bands here, just generic VHF (30-300Mhz) & UHF (300-3000). At work we
use
> > somewhere around 250-300Mhz and usually have to start turning the gain
> down
>
> I pointed out a specific case where a general assumption did not
> work; I just want to point out to people that there are no hard, fast
> rules to this game, there are exceptions..
>
>
>
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