Hi, Gang,
Uncharacteristically, I'm moving to get ahead of winter's onslaught here in the
upper Midwest, and one of my tasks is to configure my back yard vertical. It's
one of the two "compromise" antennas I've managed to erect in the past year
since moving (vertical and a 100-foot doublet @ 35 feet fed with open-wire
line). I have accumulated several short towers (50-64 feet), but they won't
likely make it up until next summer. So, I will be using what I have until then.
My doublet works exactly as expected (which isn't fantastic), so it's a
relatively known quantity.
The vertical, which takes some 'splainin,' was very interesting last winter,
and I hope to improve it for this season. It was much quieter on RX than
expected (first vertical in 40 years on the air) -- which may indicate
something horrible -- but it put some DX in the log on 80 and 160, even at my
usual 5 W on CW, so it shows some kind of promise.
Staying the same: 32 on-ground radials, each 45 feet long, with four 70-footers
at the four corners of the compass.
Last year: Being a temporary installation, I used a 4x4 post to hold up a
14-foot length of weatherproofed, oak closet rod. Three wires, cut for Low SWR
on 80, 40 and 30 meters, ran up three "sides" of the post/pole and, at the top
of the pole, flared in three directions to three treetops. It was actually some
sort of "fan inverted-L." There was a lot of interaction between the elements,
and the SWR "swayed" in the breeze as the wires moved around, but I was able to
get it tuned up pretty well. The 40 and 30 wires slanted only a little, while
the 80-meter wire sloped the most. The antenna was fed with 110 feet of CATV
RG-6 quad shield, 12 turns of which were tightly wrapped around an FT-240-43
toroid, right at the feed point (about 24 inches above the ground).
This antenna would often hear stations that were inaudible on the doublet --
often with a HUGE increase in SNR -- but at 5 W, many of those stations
couldn't hear me.
MAX power for now is 100 W.
New ideas:
1. Replace the closet rod with a 20-foot aluminum mast and connect the "flared"
wires to a single tap at the top of the mast. This will add vertical height
keep the individual wires from running parallel down the wooden mast,
potentially lessening the interaction and the "SWR swaying in the breeze"
effect.
2. Add an SGC autocoupler to the feed point for maximum flexibility.
3. Add the autocoupler but leave only the 80-meter wire.
4. Add the autocoupler but use 2-3 switchable wires.
5. Eliminate the wires and add a 20-36 foot fiberglass pole to the top of the
aluminum mast (with internal 6-gauge aluminum wire "whip") to make a 40-56 foot
single radiating element.
BIG QUESTION: Can a Maxgain-type 40-foot fiberglass pole (deployed to 23-36
feet) be "walked up" during installation, or will it likely break? Weight-wise
it should be fine, but I don't know how much "horizontal" it can handle. I can
guy the top of the aluminum mast, etc, but I'd prefer the whippy part to not
be/need guying. If a winter hurricane is approaching I can always tilt it
down...
HIGH BANDS: K9YC's excellent presentation on the generally sucky results
obtained by ground-mounted verticals on 20-10 has me wondering whether having
the ability to cover those bands might be a complete waste. At 35 feet, the
doublet is at least minimally high enough for normal patterns and gain, and a
ground-mounted vertical probably won't match it?
160 METERS: The SGC will at least tune the 80-meter wire into submission on 160
meters, and it has to work better than using a shack-mounted antenna tuner to
load the 80-meter element on 160, right? I did that last year, but I was too
scared to calculate the insane SWR-mismatch losses! Despite the horror, during
a contest or two I managed to work a few Caribbean and Central/South American
superstations on 160 with 5 W CW...and that mess of an antenna. Imagine how
much better it will work without a 30-dB inline mismatch attenuator!
If I don't use the autocoupler I will have to load the 80-meter wire or the
40-56 foot single vertical element for use on 160. Because time is short, I'd
probably have to use some sort of base loading, which is the least efficient
way to do that (but perhaps the easiest). But, assuming the single vertical
element, what about adding a capacitance hat at the 20-foot level (where the
aluminum mast transitions to the fiberglass whip) instead of adding it at the
very top (which isn't practical for me)? Someone told me that such a low
capacitance hat would "divorce" the rest of the vertical, making the whole
thing essentially a 20-foot vertical. Is that correct? Cuz I could easily add
capacitance at that point if it might help.
Okay, clear as mud? :)
As always, your thoughts are appreciated. What's the "killer" way to maximize
this equation?
But please, no comments regarding the need for Radio Arcala hardware, cuz I'm
saving that for my next QTH! My budget is about $100, and I already have the
radials, main support post, the aluminum tubing, the ferrite ring, the feed
line, the autocoupler, etc. I don't have the fiberglass mast, however, and that
costs about $100... :)
Regards,
--Kirk, NT0Z Rochester, MN
My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com
and on the Amazon Kindle (soon)
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