On 9/3/2013 5:23 PM, Jim Brown wrote:
The practical problem with sticking a ground plane on your roof is that
it needs at least two radials per band, but there are several multiband
antennas for those bands configured as vertical dipoles that work well
without radials. That's the basis of my earlier statement that a
roof-mounted well-designed multi-band vertical dipole is a far better
antenna above 20M than the 43 ft vertical.
I bought a GAP Titan, mainly for WARC bands, my low-band ladder-line fed
sloping vee [135' on a side] gets really complicated above 40m. I've
observed:
The GAP is about 1-2 S-units noisier. Not surprising, it's a vertical.
It works on the WARC bands, satisfying my need, I've never used it on
the "contest" bands.
I think it's a center-fed half-wave vertical dipole. It does have a
square wire loop thingy near the bottom that seems to deal with 40m,
pretty big.
No radials, but with the big square loop, it might as well have them.
I'm fairly convinced the shield of the coax plays a part on at least a
couple of bands, maybe all. They warn you to route the coax out a hole
in the side of the support mast, not out the bottom.
I installed it on a 3" riser pipe that goes straight up inside the wall
from a 2' square utility box in the wall under my radio desk. It has a
standard weatherhead on the top and carries the coax to the tower on a
steel messenger. This was a misteak. With the KPA500 at 500W, on 40m,
I get a lot of RF from the GAP screwing up things like the WinKey, the
laptop, and various other digital gadgets. Fortunately I don't use it
on 40m. It's directly over my head, I probably could have considered
that but of course didn't. On 160, my sloping Vee also keys several of
the irrigation control valves ... they're not exactly up to QRQ and the
pipes bang really bad.
I've modeled the 43' vertical, both on the ground and in the air. I've
tried one, on the ground with a not-too-shabby radial system. It
appears to me that it is:
A vertical
43' seems to garner some friendlier feed impedances on some bands than
some other lengths, and it's physically manageable in restricted spaces,
HOA or otherwise
It's a vertical
73,
Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
