On Wed, 12 Jan 2005 15:55:12 -0800, Richard Clark
wrote:

|On Wed, 12 Jan 2005 18:46:52 GMT, "
wrote:
|So I consider the statement that 1db is insignificant
|a bit over the top when one is working with antennas and what one can
|achieve what others can't.
|
|Hi all,
|
|This "over the top" and other straining to get a "louder" signal begs
|a real number - like 1dB. Such testimonials (negative or positive)
|are emotional comparisons.


One of the biggest thrills I've had in my amateur radio career was
pressing the key and 2.5 seconds later hearing my signal returning
from the moon. I will confess, this was an emotional response [g].
One dB does make a difference. One dB difference in transmission line
loss or antenna gain makes a hell of a difference.

I also got emotional when VU4RBI barely came up out of the noise and I
worked her a few days before the great flood or last night when 3G0YM
gave me a 59 report on 20M and not being able to tell him he was S0, I
fibbed and gave him a 53.

Zombie Wolf wrote:
. . .To get a 1 unit s-meter difference on the average receiver, it
actually takes 6 decibels more signal, or 4 times the power, from the
transmitter, to produce that signal increase. . .

I'd be very interested in seeing the basis for that statement. Or are
you simply and mistakenly assuming that the ficticious 6 dB "S-Unit" so
fondly and inexplicably used by amateurs actually represents a division
on a typical receiver S meter? Have you checked your receiver's S meter?

Roy Lewallen, W7EL

A number of superconducting antennas have been built and the results
published. The ones I recall seeing were using the newer high
temperature superconductors, although it can be done with conventional
superconductors also.

It doesn't seem to be generally known that superconductors have zero
resistance only at DC. Their resistance is finite at any frequency above
zero. It increases with frequency, and it also increases as the
temperature rises toward the critical temperature (at which the material
ceases becoming a superconductor).

The resistivity of copper drops pretty dramatically at cryogenic
temperatures, so copper becomes pretty hard to beat at RF, particularly
if the temperature is getting anywhere near the critical temperature of
the competing superconducting material.

The potential advantage to be gained from a lossless antenna is that a
very small, efficient antenna can be made. The problems a

1. You have a really tough matching problem, and will have severe loss
in your matching network unless it's also superconducting.
2. If you do keep the antenna and matching network losses to a small
value, a very small antenna will be very narrow banded.
3. You'll have to keep the temperature far below the critical
temperature if you want to do much better than copper. This probably
means cooling to a few degrees Kelvin, which is expensive and not
compatible with putting antenna high and in the clear, let alone making
one that can be rotated, for example. And the advantage of a small
antenna is likely to be negated by the size of the cooling equipment.
4. Because the antenna will have finite resistance and presumably a
small size, application of transmitter power will cause heating. This
heat has to be removed by the refrigeration equipment to avoid raising
the temperature too much.

A google search on "superconducting antenna" will bring you a lot of
papers, but probably not much in the way of commercial products. While
interesting in the laboratory, the above problems limit the practicality
of the idea.

Roy Lewallen, W7EL

ml wrote:
i just wonder does anyone know of any links to articles on a small
superconducting antenna say for hf frequencies



what would happen if i build say i'd have to stay physically small , so
say a 1/4wave verticle on 10m and then made that antenna
supercondutive?

the antenna would technically have like no resistance that i know then
i get fuzzy


wonder what happens both technically speaking and if anyone tried it,
was it a 'great' antenna rx or tx wise?? any pro's con's of such a
design

aside from the obv cost and impracticaliaty of pumping Lhydr/liq helium
or nitrog into it etc

Perhaps the cost/benefit ratio is not viable
because of the expense to keep the antenna cold ?

On spacecraft missions to the outer plantes,
the antenna were not supercooled but the
space environment was very cold !

Wefax_Dude wrote:
Perhaps the cost/benefit ratio is not viable
because of the expense to keep the antenna cold ?

It's certainly more economical to increase the
transmitter's power output than to supercool a
dipole.
--
73, Cecil http://www.qsl.net/w5dxp


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In article , Cecil Moore
wrote:

?

It's certainly more economical to increase the
transmitter's power output than to supercool a
dipole.

it think this statement is not totally correct, as if someone manages to
build an antenna that serves some pourpose that achieves it's built p
goal, then it's worth the expense for certain additionally...

who knows maybe sombody might invent somthing that is more efficient or
discover something like a benificial offshoot..

who knws what the cost will be one day to supercool a antenna, of which
dipole is one of many kinds

On Fri, 14 Jan 2005 01:53:31 GMT, ml wrote:
who knows maybe sombody might invent somthing that is more efficient or
discover something like a benificial offshoot..

Who knows indeed? It may be the next penicillin for diesel knock.

who knws what the cost will be one day to supercool a antenna, of which
dipole is one of many kinds

Who knws undeed! It could pcost as much as the national debt of
Liechtenstein which isn't big enough to field a full sized 16 KHz
superhip antenna for communications to their solar powered submarine
fleet. But if the fate of whirled peas hinges upon their sacrifice,
cost be DAMNED!

73's
Richard Clark, KB7QHC