[30m] Re: Screwdriver Antenna Problem

[Thomas Giella KN4LF]

Antenna theory must have been dropped from the new Extra Class course study 
materials?

A vertical antenna needs a good ground radial system to operate properly. A 
minimum number of recommended 1/4 waves would be 16, 32 better, 64 best, 
after 64 pretty much a waste of time and copper wire. Laying them on the 
ground surface and tacking them down is more efficient than burying them in 
the soil.

# 1/4 Wave Radials/Efficiency%

4/63
16/85
32/91
64/96
120/98

120 1/2 wave radials 100%

If you can raise the base of the vertical up high above ground to say 
approximately 45 feet then 4 1/4 waves would be fine, as you would be 
reducing capacitive coupling loss between antenna and ground and improve 
efficiency of collected ground return currents.

I have a website published on the WWW about vertical antenna theory at 
http://www.kn4lf.com/kn4lf2.htm

--... ...--,
Thomas F. Giella, KN4LF
Lakeland, FL, USA
Grid Square EL97AW
kn4lf at arrl.net

KN4LF Amateur & SWL Radio History: http://www.kn4lf.com
Radiowave Propagation Yahoo eGroup: 
http://groups.yahoo.com/group/radiowavepropagation

I apologize for yesterday's no-show.  I have an antenna problem that I
STILL haven't been able to diagnose.  And I have a dirty little secret:
I'm the most incompetent antenna installer to ever earn a license.
Other people can work the world with double digit SWR, a dummy load, or
a piece of scrap metal lying around.  On the other hand, I can't radiate
anything unless everything about the antenna is just perfect.  (Well, at
least I didn't shoot my hunting partner.)

I'm using a DK3 Screwdriver antenna in the backyard.  When I adjust the
coil for minimum SWR (as shown by my antenna analyzer), I transmit and
find that the SWR is extremely high.  I switch back to the antenna
analyzer and find that the SWR has gone back up to 4 or more.  What's
more, the SWR shows no minimum when I tune through the frequencies.  In
fact, disconnecting the antenna from the coax doesn't seem to change the
SWR in this case.  When I bring the antenna analyzer outside and connect
it directly to the antenna (bypassing all of the coax, the ICE surge
suppressor, and the balun), I still find the same behavior but at a
higher SWR (presumably because of the elimination of coax losses).

The problem doesn't come up when I connect the antenna-end of the coax
to a dummy load.  So it has to be the antenna.  I tried using alcohol
wipes to clean the parts of the antenna where the wires leading to the
balun are attached.  I checked the connection between the upper whip and
the lower mast unit and couldn't find a problem.

HELP!  What could my problem possibly be?

Jason Hsu, AA0II 



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