On Tue, 11 Jan 2005 03:30:07 GMT, ml wrote:
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?

Hi OM,

As far as performance? Absolutely no difference to it even if it were
elevated 1000°F above that to compare.

- Well maybe someone with enough sophisticated equipment might notice
a dB difference - then they would whack the side of the gear to clear
that up - nope, no difference....

You need to come to terms with just how imperceptible 1 dB is (zilch,
in technical terms), and how much power it takes (about 12%, just more
$ to burn) to make that imperceptible difference. The dollar has lost
30% of its value in the world market in the last few years - have you
noticed? This may not be one way to appreciate 1dB, but it does
reveal how relative changes go unfelt.

73's
Richard Clark, KB7QHC

superconducting antenna?
 

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

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

Of course Mr. Clark, as usual, is "right on the money" in saying that 1db is
nothing. 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.

Double the transmitter power (3 db) , and you get a half an s-unit increase.

In many cases, it is more advantageous to raise the antenna 10 feet or more,
than it is to increase transmitter power, and it will often result in much
more signal in the receiver, since it gets the transmitter antenna "up in
the clear", where losses to the ground and surrounding obstructions drop
off..


"Richard Clark" wrote in message
...
On Tue, 11 Jan 2005 03:30:07 GMT, ml wrote:
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?

Hi OM,

As far as performance? Absolutely no difference to it even if it were
elevated 1000°F above that to compare.

- Well maybe someone with enough sophisticated equipment might notice
a dB difference - then they would whack the side of the gear to clear
that up - nope, no difference....

You need to come to terms with just how imperceptible 1 dB is (zilch,
in technical terms), and how much power it takes (about 12%, just more
$ to burn) to make that imperceptible difference. The dollar has lost
30% of its value in the world market in the last few years - have you
noticed? This may not be one way to appreciate 1dB, but it does
reveal how relative changes go unfelt.

73's
Richard Clark, KB7QHC

Zombie Wolf wrote:
Of course Mr. Clark, as usual, is "right on the money" in saying that 1db is
nothing.

Reminds me of an article in QST in the '50's titled
"One dB Doesn't Matter" or something like that. This
ham had one dB loss due to an old final tube, one dB
loss due to a dirty tank coil, one dB loss in the low-
pass filter, one dB loss in a bad solder joint, one dB
loss in the tuner, one dB loss in the transmission line,
and one dB loss in the antenna. He wondered why he
wasn't getting out very well. :-)
--
73, Cecil http://www.qsl.net/w5dxp


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Reminds me of an article in QST in the '50's titled
"One dB Doesn't Matter" or something like that. This
ham had one dB loss due to an old final tube, one dB
loss due to a dirty tank coil, one dB loss in the low-
pass filter, one dB loss in a bad solder joint, one dB
loss in the tuner, one dB loss in the transmission line,
and one dB loss in the antenna. He wondered why he
wasn't getting out very well. :-)
--
=============================

No he didn't. 7dB, about one S-unit, is not enough to come to anybody's
attention.

It's less than the difference between a G5RV plus coax, specially a 1/2-size
G5RV, and an ordinary dipole fed with open-wire line which most people never
seem to notice.
----
Reg, G4FGQ

I would argue over the simplification that below 1 db is "nothing."
If one cleans up his system then it is possible that those items
that lose less than a db could add up to something "meaningfull".
But DXrs say a little db is a lot and usually they are not casual operators.
A single increase in gain of a db of an antenna can infact supply more gain
at a lower
TOA where it enables the operator to make a contact where others fail!
On my antenna I am able to drive down the TOA by more than 3 degrees
where for comparison purposes it may only have the gain oif a normal four
element
yagi that has a TOA of 14 degrees. 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.
Regards
Art



"Zombie Wolf" wrote in message
...
Of course Mr. Clark, as usual, is "right on the money" in saying that 1db
is
nothing. 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.

Double the transmitter power (3 db) , and you get a half an s-unit
increase.

In many cases, it is more advantageous to raise the antenna 10 feet or
more,
than it is to increase transmitter power, and it will often result in much
more signal in the receiver, since it gets the transmitter antenna "up in
the clear", where losses to the ground and surrounding obstructions drop
off..


"Richard Clark" wrote in message
...
On Tue, 11 Jan 2005 03:30:07 GMT, ml wrote:
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?

Hi OM,

As far as performance? Absolutely no difference to it even if it were
elevated 1000°F above that to compare.

- Well maybe someone with enough sophisticated equipment might notice
a dB difference - then they would whack the side of the gear to clear
that up - nope, no difference....

You need to come to terms with just how imperceptible 1 dB is (zilch,
in technical terms), and how much power it takes (about 12%, just more
$ to burn) to make that imperceptible difference. The dollar has lost
30% of its value in the world market in the last few years - have you
noticed? This may not be one way to appreciate 1dB, but it does
reveal how relative changes go unfelt.

73's
Richard Clark, KB7QHC

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

Reg Edwards wrote:

No he didn't. 7dB, about one S-unit, is not enough to come to anybody's
attention. . .

Yet look at all the people who go to all the trouble of putting up a 3
element beam, then think that the 7 dB gain over a dipole actually makes
their signal louder. Or get a 500 watt amplifier for their 100 watt rig.
Silly fools! Old wives!

Roy Lewallen, W7EL

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.

This "over the top" expression speaks for itself. If a 12% drop is
outrageously "over the top," then there would be runs on the bank for
the 30% fall of the dollar's value in the world market. Back when we
had double-digit inflation (hmmmm, 12% is double-digit) the party now
in charge went ballistic about the state of the economy. Now that we
have outsourced inflation - 30% is cool. Merely a matter of who's ox
is being gored.

Well, so much for fun with numbers; let's look at "louder" signals.

What does it mean to be "louder" with a modern (post Depression era)
receiver? Is 1 dB perceived as being "louder?" Well, by definition:
just barely (IFF you turn up the volume control). Why do I
parenthetically add this constraint of a necessary active
participation of turning up the volume control? Because in a modern
receiver, the circuitry deliberately compensates for that 1dB boost by
depressing the gain by the same amount. Net result? Voila! 0dB by
perception and design. Well, by aural perception that is. So much
for "louder."

You "might" see (another perception) the S-Meter shift by something
less than one needle's width if that makes you feel that something has
been accomplished - in this case they could as easily calibrate the
meter in ego-Satisfaction units. Then again, maybe you would have
missed 1dB entirely (should we insist on a negative multipliers for
that ego reading?). The correct appeal is found in S+N/N where the
improvement adds clarity - merely bombasting about "loudness" is
provincial.

73's
Richard Clark, KB7QHC