N6LF is also WD2XSH/20 whose 630m CW signal I copied up here. Rudy
moved a couple years ago to new property and has new antenna farm.
I believe his study of elevated grounds was published in QEX and later in QST.
Virtually all transmitting antenna for 630m will be "short" verticals
so his findings are useful if you consider getting on 630m. EZNEC-5
indicated my radiation resistance would only be 0.83 ohms with a
43-foot high top-loaded vertical. Actual measurement showed 18 ohms
so efficiency is 0.83/18 = 0.046. My ground plane is woefully too
small: four 70-foot by 2-foot wide runs of chicken wire on
ground. But most hams have too little acreage for anything even
close to 1/4 WL (521-foot).
My antenna consists of three parallel vertical wires spaced 1-foot
apart and shorted by a 1/2 inch copper tube at both top and bottom;
horizontal leg is two parallel wires spaced 2-foot and 122-foot long
(like-wise with copper tube shorting bars). The parallel wires lower
Q a bit to widen the SWR bandwidth which is about 5-KHz. Extra
horizontal wire increases top-hat capacitance which makes vertical look longer.
I will make a new webpage to show what I am using on 630m (old
webpage was hacked several years ago and I never resurrected the 600m page).
I may still get my inverted-L repaired and rehung with aid of my
prof. tower person, though winter wx is not far off up here (freezing
temps expected within a week).
73, Ed - KL7UW
I will probably play with running WSPR and the new FT8 digital modes on 630m.
Date: Tue, 19 Sep 2017 11:09:10 -0700
From: Jim Brown <[email protected]>
To: [email protected]
Subject: Re: [Elecraft] 630M Antenna
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=utf-8; format=flowed
N6LF's website should be required reading for anyone intending to
operate these new bands. He's done extensive work on antenna systems for
these bands.
73, Jim K9YC
73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[email protected]
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