"matt weber" wrote in message
...
On Sun, 12 Oct 2003 01:33:19 GMT, "Frank Dresser"
wrote:


"Dale Parfitt" wrote in message
...

For HF, I totally agree. My passion is 1296 MHz Moonbounce- and silver
plated
cavities are a must for high efficiency.

Dale W4OP

Got news for you. skin depth IS a big deal at SW freuquencies as well.
For copper is it roughy 6.6/(f^.5) in cm....

The skin depth at 1 Mhz in copper is a whopping .066 mm. That is about
2 mils (1/500th of an inch). That is why copperweld wire (copper
over steel) works as well as pure copper for an antenna.

Well, thanks for the newsflash. I guess that means that skin effect isn't
worth worrying about for 99% of the work SWLs do. Like antennas and ground
wires.


And yes, it is a bigger deal 1Ghz, but a 1 micron silver plate is
about all it takes. Skin depth in copper at that frequency is .0021
mm, or about .07 mils, one 15,000th of an inch in copper, in Silver it
would be more like 1/20,000th of an inch.


Wow. That must mean that skin effect makes a difference in the hair fine
wires oftentimes found in IF and RF transformers used in SW radios. Maybe
1% of SWLs will be dealing with such things.

Even at 60hz, it doesn't pay to use a conductor larger then an inch in
diameter. Skin depth at 60Hz in copper is .85cm
Sure. Skin effect is a big deal at 100 times a typical SW frequency.
It's
also important inside IF and some RF transformers. Have you ever seen ads
for those expensive audio cables in which they make a big deal the skin
effect? To paraphrase some comedian -- "Being an audiophool is God's way
of
saying you have too much money".

Frank Dresser



Frank Dresser