Re: NEC-LIST: Coil-loading.

I think the original question, was, though, when a loading coil in the
middle of an antenna was suggested. This is somewhat different than loading
coils for phone lines, etc.

As a previous poster pointed out, early "wireless" transmitters used
inductors at the base of the antenna (in fact, I seem to recall seeing a
drawing in a recent IEEE Proceedings where the inductor was 'keyed'), but I
suspect that the use of a coil in the "middle" of the radiator is a more
recent invention.

The question would sort of revolve around whether it was discovered
empirically (gosh, boys, we don't have room for the loading coil here in the
transmitter room, let's put it outside in the antenna farm) or whether it
was proposed in the context of improving an existing design (say with
capacity hats, etc.).

I'd look for a copy of Terman and see what's in there about antennas with
loading coils.

An old handbook (by Henney) from the early 40s, late 30s vintage talks about
flattops and multiwires being "older". Certainly, by the thirties, the
theory of antennas was well developed enough that inductive loading in the
middle would have been analyzable and contemplated. For instance, there's
a reference to top loaded and sectionalized antennas of limited height and a
reference to a work by George Brown (1936).

However, for all that, there's no example of a center loaded antenna in
among the rhombics, fishbones, curtains, and so forth.
There probably wasn't much in the way of "mobile" operation back then.

A 1956 ARRL handbook has a fair amount of info on center loaded mobile
antennas (along with employment ads(!) from Lockheed Missile Systems in Van
Nuys, CA).

"Dr. Edward P. Sayre" <esayre_at_nesa.com> writes:
> Fellow Colleagues:
>
> The transmission loading coil was suggested by Lord Kelvin (J. J.
Thompson)
> for the improvement of the bandwidth of the second Atlantic cable. The
> first Atlantic telegraph cable suffered from poor risetime of response to
> telegrapher hand keyed code. The result was greatly reduced transmission
> speeds. By raising the inductance of the cable so that the time constant
of
> the L-G elements matched the time constant of the R-C elements, the result
> was the distortionless transmission line which suffers loss exponentially
> with distance but does not distort the waveforms. Hence the need for
> extremely high voltage at the transmitter location.
>
> Telephone engineers used a similar methodology, adding "loading coils" to
> produce "equalized cables" for much the same purpose, bandwidth
> improvement, this time for the 300 - 3000 Hz band. Today, at Gigabit
> speeds, cables are equalized using similar principles to improve the
> eye-diagram response. (see www.NESA.com for further information on
> equalized Gigabit cabling.)
>
> Sincerely,
>
> ed sayre
> ============================================
>
> At 06:33 PM 2/6/2005 -0600, rsmueller wrote:
> >Doug,
> >
> >I'm not certain, but, I believe that Marconi may have loaded his vertical
> >antennas with coils. If he did, he may have invented the antenna loading
> >coil. I have seen some examples of antenna loading coils that were
> >commonly being used in long wave radio stations in 1925, or so. The
> >earliest references to the term loading coils is in telegraph lines. I
> >believe that Oliver Heaviside first suggested their use in reducing the
> >transmission loss over long distances and some engineer at AT&T first
used
> >them in practice.
> >
> >I'm too young to know all this first hand, so, I'm not guaranteeing that
> >it's correct.
> >
> >I saw John Belrose at an IEEE Broadcast conference once. He did a good
> >job analytically and verbally disproving the CFA antenna performance
> >claims in front of the inventors there. I think that was about the last
> >time anyone ever talked about the CFA like it was somthing special.
> >
> >Best Regards,
> >Roland
> >
> >"D. B. Miron" <dbmiron_at_paulbunyan.net> writes:
> >>Good day,
> >>
> >>I recently read John Belrose's "Short Coil-Loaded HF Mobile
> >>Antennas..." in ARRL's "Vertical Antenna Classics". He
> >>claims the first analysis article in a 1953 issue of QST,
> >>which leads me to wonder who discovered or invented the idea
> >>and when?
> >>
> >>Thanks,
> >>Doug Miron
> >>
> >>--
> >>The NEC-List mailing list
> >>NEC-List_at_robomod.net
> >>http://www.robomod.net/mailman/listinfo/nec-list
> >
> >--
> >The NEC-List mailing list
> >NEC-List_at_robomod.net
> >http://www.robomod.net/mailman/listinfo/nec-list
> >
> >!DSPAM:4206b79f180831292113460!
>
>
>
>
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> | NORTH EAST SYSTEMS ASSOCIATES, INC. |
> | ------------------------------------- |
> | "High Performance Engineering & Design" |
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> | Dr. Ed Sayre e-mail: esayre_at_nesa.com|
> | NESA, Inc. http://www.nesa.com/ |
> | 235 Littleton Road, Ste 2 Tel +1.978.392-8787 |
> | Westford, MA 01886 Fax +1.978.392-8686 |
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
>
> --
> The NEC-List mailing list
> NEC-List_at_robomod.net
> http://www.robomod.net/mailman/listinfo/nec-list

-- 
The NEC-List mailing list
NEC-List_at_robomod.net
http://www.robomod.net/mailman/listinfo/nec-list