Re: NEC-LIST: Coil-loading.

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
>>
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