Once upon a time I was challenged that my homemade ladder line
was somehow radiating so much that it made a neighbor's garage door, two
houses away, go up and down by itself. A local 'telephone man' lived nearby
and claimed my feed line was to blame. (After all this was an electronics
guy and he knew all about electronics.)
This led to some testing where it was demonstated that when matched very
little (if any) radiation could be detected in the vicinity of the feed
line. I had expected a little bit, but there was none. The resident 'expert'
said a simple FSM was insufficient and dragged over some lab equipment.
After a bunch of testing, the readings were so low as to be inconsequential.
Yet, I still got the 'blame' because after all I had to be 'hiding' or 'doing'
something.
Luckily, for me, this was even happening when I was not even at home, but
nevertheless -- the ham gets the blame. It was finally discovered that one
of the family pets was 'nosing' the actuator button which was located next
to a shelving unit in their garage. Of course, no apology.
73 de Phil - N8PS
-----
Quoting Jim Brown <k9yc@audiosystemsgroup.com>:
> On 1/27/2012 5:10 AM, Steve Hunt wrote:
>> The ladderline loss figures quoted in the Antenna Book - which I believe
>> are also repeated in TLW - are out by a factor 2. It's very easy to
>> demonstrate that with a simple I^2R loss calculation. I'm happy to show
>> the sums if you need convincing.
>
> Based on verbal correspondence with two ARRL technical editors I trust
> and know well, there's considerable content in ARRL publications that
> has been there for a long time, and doesn't get as much (if any) review
> as is needed. AFAIK, N6BV is responsible for TLW (and HFTA). Several
> years ago, I was studying some of the discussion in the ARRL Antenna
> Book, which he edited, on the topic of the fields associated with
> vertical antennas and the radial system. It was quite good, but fairly
> dense, and in using figures and drawings to follow it, noted some typos
> that made it impossible to follow. I also spotted some other typos.
> Those errors had been for at least one edition back, as were a few
> others I pointed out to him.
>
> When I was working with N0AX a few years ago on updates to the Handbook,
> although he liked what I had written and most of it was incorporated,,
> we were stonewalled by "the old guard" in their defense of existing
> Handbook content on EMC that is wrong and/or seriously outdated, and the
> old stuff remains. At my insistence, the disputed content was
> subsequently submitted for peer review, and last I heard, my material
> was supported by that panel.
>
> The lack of competent technical review for ARRL publications, along with
> the dumbing down of content, have gotten to the point that I cringe at
> least several times at the gross errors in every month's QST. There
> USED TO BE very good stuff in QST that you could sink your teeth into.
> Now, N0AX's regular contributions are almost the only thing you can
> trust in the magazine.
>
> One of the major deficiencies in published data for transmission lines
> is good numbers for loss and shielding effectiveness in the MF and HF
> spectrum. Loss is most often quoted in dB/100 ft and rounded to one
> decimal place. This yields values of 0.1 dB/100 ft and 0.2 dB/100 ft for
> most coax at 1 or 2 MHz, which is lousy resolution (0.1 dB is the result
> of rounding between 0.05 and 0.149; 0.2 the result of rounding from 0.15
> to 0.249). Now, loss at 1 or 2 MHz is quite difficult to measure, first
> because it is small, but also due to termination effects (that is, Zo is
> not a constant 50 ohms, but rather varies with frequency and is
> increasingly reactive below HF, but generators and loads are a pure 50
> ohms resistive). I've attempted it, and you've got to measure at least
> 500-1,000 ft to get reasonable precision. Why does this matter? Several
> reasons, Some hams need to run 500-1,000 ft to their antennas, so the
> difference can matter. Second, many hams are spending big bucks for
> premium coax when they may not need to.
>
> And when have you seen data for shield transfer impedance for ANY coax?
> Or a definition for it? Yet it is a fundamental property that
> quantifies shielding effectiveness and allows computation of actual
> numbers for how much RF gets through a shield!
>
> 73, Jim Brown K9YC
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