Please take a careful look at what HyGain and Cushcraft do for their AV-640
and R6000
They use a 3/8 wavelength radiator for the low bands and have 3/8 wavelength
stubs attached just above the feedpoint for the high bands.
I use the AV-640 and it is a whopping success. Don't get me wrong, I use
yagis also. But there have been a few times that I needed to use the
vertical on high bands and I was pleased with it.
The takeoff angle for 3/8 wave is lower than 1/4 wave. The antenna has a
fixed matching unit to match 50 ohm line to 200 ohm antenna. Works on all
bands. Never had any problem with RF in the shack using it. I think there is
also a RF choke in the matching box. And you do not need to command the box
to perform a match. It is always a match from 50 to 200 ohms.
They also now make versions that include 80 meters but it is a narrow
bandwidth on 80. So, you adjust the antenna for the band segment of
interest, CW or Dig or SSB segments.
Best Regards
Dan Schaaf
=================================
K3ZXL www.k3zxl.com
=================================
-----Original Message-----
From: Jim Lux
Sent: Tuesday, April 08, 2014 9:06 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Fwd: Hustler 6-BTV installation
On 4/8/14 4:25 AM, john@kk9a.com wrote:
I just read the Joel Hallas, W1ZR article - "The 43 foot vertical monopole
- What's the magic?". It was very interesting! The coax losses are worse
than I imagined, up to 8dB though 100 feet of RG-213, and as my model
showed the radiation is very high above 20m. Certainly a relay to
electrically shorten the antenna would help 15m and 10m.
I'm of the general opinion that one should be putting the matching
components at the feedpoint of the antenna (base in the case of a
vertical), so the coax loss isn't going to be a factor.
However, the radiation pattern from an overlong antenna is an issue.
This brings up an interesting idea. What if lengths of elements between
traps and trap design were not driving towards getting a 50 ohm match at
the feedpoint, but rather, just getting the effective radiator length right.
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