[Lowfer] Common Sense (was: 'CO' medfer will continue on 1704.8)

[John Davis]

A bit long, but I hope you'll find it worthy of consideration...

>No Medfer or Lowfer stations that I am aware comly with Part
>15.     {snip}
>> any Lowfer or Medfer system that can be
>> received 25 miles or  more away is most probably in violation.


One could attempt the same reductio ad absurdum on traffic laws:  The posted
speed limit in this neighborhood is 25 MPH.  But if you travel all 25 miles
of streets in this vicinity in one hour, you're actually in violation of the
law because there's also the "reasonable and prudent" clause, and there are
plenty of instances to show that backing out of your driveway at less than 1
MPH can cause an accident, so therefore it's neither reasonable nor prudent
for you to move your car in the first place.

This, of course, flies in the face of common sense and practicality.  As
Doug notes:

>As for
>Lowfer and Medfer operations, I think there is such a thing as common
>law based on tradition.  Our activities are a good example of it.  As I
>have told others, I am not critical of anyone who operates within our
>common law practices.

While I don't necessarily see the current Commission relying a lot on
tradition or common law, I do agreed with his point that they impart a
certain validity to our operations.

In broadcasting, for instance, the FCC used to have the Rules and
Regulations  which imposed specific limits on the parameters of a signal,
and a separate Standards of Good Engineering Practice which contained
practices that, if you followed them, were considered to put you in
compliance with the intent of the Rules.  Example:  The Rules stated that a
station of a certain class had to use an antenna efficient enough to produce
a certain field strength at one mile in order to be accepted for licensing.
Well, not many local stations would have been in an economically feasible
position to do a formal study to certify their antennas.  But the Standards
said (based in great part on the work of ol' Doc Brown of RCA) that if you
used a quarter-wave (or 3/8, or half, depending) vertical radiator over a
minimum of 90 radials, you would achieve the required field strength in the
vast majority of cases; so therefore, installing an antenna of that type was
deemed to comply with the Rule requirement, without the need for all the
measurements.  Here's a requirement--and here's a way we'll automatically
accept to meet that requirement.

The Rules and the Standards are now merged for broadcasting.  For Part 15
experimenting, all we have to go on for additional guidance is tradition,
PROVIDED the tradition doesn't start straying too far from the letter of the
rules.  This is where I would appeal for common sense to prevail.

I absolutely applaud Doug's desire to bring CO into accord with both the
letter of the Rules and common practice by moving the final to the base of
the antenna.  That's something the "microbroadcasters" who put 3m antennae a
hundred feet up a tower and feed them by transmission lines from
transmitters at the base, scoff at, for instance--the guys mentioned in the
Radio World letter.

I've missed a big chunk of correspondence over the past 24 hours from the
reflector, and possibly some direct correspondence as well.  So I hope Doug
didn't take offense when I mentioned those guys in some of my direct
correspondence.  I do not in any way equate his honest attempt to get on the
air with the cynical, calculated wiggling outside the letter of the law that
the makers of those commercial systems engage in!  To the contrary, I feel
his intent and that of nearly all MedFERs is well within the simple stated
limits of Part 15.

The catch with tradition:  One can go too far in *either* direction when
trying to interpret the Rules.

One could look at "the total length of the transmission line, antenna, and
ground lead (if any) shall not  exceed 3 meters" and be concerned about the
radials in their ground system, for instance.  One shouldn't.  The FCC is
not worried about it.  In previously published guidance on Part 15 operation
(such as those reproduced in various editions of the late Ken Cornell's
Handbooks), the FCC very clearly stated that "ground lead" means the
connection between the transmitting device and a water pipe, ground rod, or
other conductor going into the earth.  They do not care what's IN the
ground--only about the length of the conductor going to the ground.
Tradition and the FCC's past intepretation of their Rules agree quite well
on this one.

On the other hand, some folks look at that same requirement and yet don't
worry about the size of their tophat.  True, it doesn't radiate if it's
symmetrical; but it is part of the path taken by current leaving the
transmitter.  For that reason, 'traditional' tradition has included the
radius of the tophat in determining antenna length.  Less traditional
tradition looks to Ken Cornell's 3-meter-cylinder interpretation for
guidance; however, I would merely remind that the LWCA (through the umbrella
organization ANARC) did ask the FCC to formalize this interpretation in the
Rules during the big mid-nineties revision of Part 15, and they declined.

A thornier issue for some folks seems to be the loading coil.  I'd love to
dispense with this once and for all, but the FCC's Mr Reed (in the quoted
Radio World letter) really fouled the already-murky waters something fierce
with that "electrical length" blather*.  So let's first see if most of us
can agree on ONE simple point, after which some of us may have to simply
agree to disagree on the rest.

What we often loosely call a loading coil at ground level is, in most of our
home built devices, part of the tank circuit of the TRANSMITTER itself; and
in any case, is always part of the matching of the TRANSMITTER to the
attached load.  This requires no stretch of the imagination whatsoever.  You
wouldn't take the pi-L or dual-pi network in the final of your HF
transceiver and say, OK, this half is part of my transmitter and the other
half is part of the antenna.  If the matching inductor is part of your
TRANSMITTER design, then the output terminal of your TRANSMITTER is the
antenna terminal of your matching inductor, and that terminal is where the
antenna connection begins.  "Hook antenna here."  Simple.  Easy.  No foggy
interpretations required.

Now, for center- or top-loading coils in the antenna itself...yes, that's
where things get messier.  Most of those who have used such configurations
do include the physical length of the coil in their definition of antenna
length.  But what's this "electrical length" business?  *Blather is actually
the nicest term I can find for it.  Mr Reed is a professional engineer with
far heavier credentials than mine, but I defy him or anyone else to cite a
university-level engineering textbook or a section of any FCC Rule that
defines the "electrical length" of a coil.  I know about electrical length
of networks consisting of inductors, capacitors, and/or resistors, and how
to measure their phase response, group delay, and so on.  But I've never
encountered "electrical length" of a single, discrete reactance before.

In previous discussions on the reflector, we've had a lot of individual
interpretations of that, ranging from the physical length of the wire in the
coil when unwound (at which point it's no longer a lumped reactance of the
same value), to an arbitrary "90 degrees" (measured where and under what
condition?).  My own notion is that it's the same as straight-line physical
length from terminal to terminal, since that is the length that radiates.
But no one has yet cited an actual textbook definition you could use to
measure or calculate it in some conclusive way.  So in this one aspect
(loading coils incorporated into the vertical run of the antenna), various
traditions may significantly disagree, and I won't quibble with anyone who
chooses to approach it either way.

Bottom line:  I don't see any compliance problem for anyone who keeps to
simple, common-sense interpretations of the words in Part 15.  While the
Rules were set up to limit coverage, and hence interference possibilities,
they were also intended to provide reasonable flexibility.  If by taking
heroic measures with your ground system, you can extend that range--fine,
there's no prohibition in the Rules against it.  If you can gain range by
using CW instead of AM--go for it.  And by extension, of course, slow CW or
BPSK instead of CW--all the better.

The FCC is well aware of what we accomplish under Part 15.  As long as we
don't cause interference and don't *intentionally* start turning a blind eye
to the Rules and Regs, I believe all is well.

Regards,
John D.