About Us

John S · November 8th 14, 06:37 PM posted to rec.radio.amateur.antenna

[email protected] · November 8th 14, 07:12 PM posted to rec.radio.amateur.antenna

Lostgallifreyan wrote:
wrote in :

The resistivity of stainless steel is about 35 times that of copper and
about 20 times that of aluminum.

This will make a big difference for a wire antenna, but less for one
of fat tubing or rod, however stainless tubing is both heavy and expensive.

It would all be a bunch of engineering trade offs that would depend on
what one wants to accomplish.

If it happens that your brother-in-law can get you stainless at a good
price...

I have no brother-in-law. But I usually have a bit of stainless steel
around.

Ok, so no high current transmitters unless some sturdy mechanical design is
used. What about QRP? I understand that high efficiency and a large antenna
is best for very low power transmitters, and given the lower currents
involved, would I^2R losses be low enough to be pretty much as viable as for
reception? This strays from the short antenna subject, but I'm interested
enough to ask anyway.

Loss is loss, whether receiving or transmitting.

The only difference is loss on receive can mostly be made up for by
an amplifier in front of the receiver, a technique used in the small
directional loops often used for receive on the lower bands. The
directionality and low bandwidth of the loop reduces the noise and
signals from other directions.

Can't hurt to try and the free demo version of EZNEC can be used for
simple antennas and will show you the effects of using stainless.

--
Jim Pennino

Lostgallifreyan · November 8th 14, 08:32 PM posted to rec.radio.amateur.antenna

[email protected] · November 8th 14, 10:31 PM posted to rec.radio.amateur.antenna

Lostgallifreyan wrote:
wrote in :

Loss is loss, whether receiving or transmitting.

Yes, but as you say, if the SNR is ok, then an amp can help on receive. What
I wondered was if the losses being a lot lower with lower current (I^2R
suggesting a significant inverse-square reduction as current falls), whether
a low power transmission justifies 316 stainless where a higher current would
not. To put it another way, if there is, is there some crude rule to suggest
a current (transmitter power) that makes it better to go with copper? (I'm
assuming a half-wave dipole for now, not the small antenna the subject
indicates).

Loss is a multiplicative thing; 50% of 100W is 50W, 50% of 10W is 5W.

As for a 1/2 wave dipole in particular, unless the stainless is very
thin it is unlikely to make enough difference to notice without test
equipment.

I'm not ready to trust my use of NEC yet, I've been visiting people about
amplifier repairs and such, my sight's bad enough that I'm limiting my
computer time deliberately for a while to see if that helps.

Have you thought about purpose dedicated glasses?

I have three pair; one for everyday, one for target shooting, and yet
another for flying.

--
Jim Pennino

Lostgallifreyan · November 9th 14, 11:05 AM posted to rec.radio.amateur.antenna

Lostgallifreyan · November 9th 14, 11:08 AM posted to rec.radio.amateur.antenna

Lostgallifreyan · November 9th 14, 11:11 AM posted to rec.radio.amateur.antenna

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
LF Antenna Design	rickman	Homebrew	12	December 3rd 12 12:42 AM
LF Antenna Design	rickman	Antenna	11	November 26th 12 10:25 PM
New antenna design	Art Unwin	Antenna	36	September 6th 09 09:04 AM
Short 80m antenna, suggestions??	MD	Antenna	18	August 17th 05 02:08 AM
Short lot 80 and possible 160 antenna suggestions	Rick Scott	Antenna	6	January 31st 05 08:53 PM