For improved top loading it is necessary for the parasitic elements of
a Yagi to be shorted to the boom. About three years ago there were a few
postings here regarding exactly that. In the summer of 2002 Natan of F12
sent one of us TowerTalkians a note that confirmed that shorting the
parasitics of their open sleeve designs to the boom would not adversely
impact the antennas' performance. You can probably find the posting in the
I have a Bencher Skyhawk that has a similar, if not identical, (ahem!)
feed design as the F12's. Bencher folk told me it would be OK to short
their parasitics to the boom, too. I shorted the parasitic elements (seven
out of ten elements) to the boom using self-tapping SS screws through the
center insulators, pieces of aluminum flashing and SS hose clamps. The
tower's performance on 160M is remarkable, plus my half-sloper on 80M works
I have no practical experience with loading effects of a tall mast, but
that might not be necessary. Try loading the tower on 160M and 80M with
just the Yagi as loading. You might not need to waste the aluminum for the
Gene Smar AD3F
----- Original Message -----
From: "Al Williams" <firstname.lastname@example.org>
To: "towertalk" <email@example.com>
Sent: Monday, November 01, 2004 11:51 AM
Subject: [TowerTalk] yagi top loading of tower
> I have two questions about using a 70' crankup with a yagi as a vertical
> radiator for 80m & 160m.
> 1. Will Force type yagis (insulated from boom) provide top loading;
> could the insulated yagi actually be detrimental?
> 2. Would extending the mast above the yagi be beneficial? I am
> thinking of some successfully smaller diameter aluminum tubing
> installed at the top of the mast perhaps 20 or 30'. Nothing
> attached to the extension or perhaps a small umbrella type hat.
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
> TowerTalk mailing list
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list