On 2/24/2013 8:43 PM, tom wrote:
On 2/23/2013 11:41 PM, Sal wrote:


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're
still up
there.

If I were to continue in that vein, I could weld (torch solder,
really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)



A good source is VE7BQH, Lionel. He has a lot of info related to EME
antennas that are as well engineered as possible for obvious reasons.

I've never looked at his correction factors as I have ones for through
the boom insulated that I know work for my build type. My corrections
are from WB0TEM.

What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR


I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea.
And it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR