Both diameters are really, really small relative to a wavelength at
80m. After a point the effect of the differences isn't a big deal.
The model is really simple ... just one straight wire fed in the
middle. If you trust EZNEC+ at all it's pretty difficult to mistrust
that model.
No, I can't explain why you saw an improvement in bandwidth with 10
gauge wire on your 80m Inverted-V, but I'd be interested in what "much
wider" actually was if you still have the figures available. One thing
that does scale fairly linearly with diameter is capacitive coupling to
surroundings. Possibly (just speculating here) there was some resulting
loading effect from that for your antenna.
73,
Dave AB7E
On 1/5/2020 10:57 AM, Jim Thomson wrote:
Date: Sat, 4 Jan 2020 14:37:10 -0700
From: David Gilbert <xdavid@cis-broadband.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80M antenna wire size
<According to EZNEC+, an 80m dipole at 100 feet (resonant and matched at
<3.7 MHz) has a 2:1 SWR bandwidth from 3.55 MHz to 3.87 MHz with #10
<copper wire and from 3.57 MHz to 3.86 MHz with #18 copper wire. Much
<thicker conductors or similar conductors at higher frequencies would
<make more difference of course (I've modeled 12 inch diameter wire cages
<for 80m and they make a usable improvement in bandwidth), but in spite
<of what somebody just posted the advantage for #10 wire on 80m does not
<seem significant to me for bandwidth.
<Dave?? AB7E
## 10 gauge wire is .102 inches in diameter.
18 gauge wire is .0403 inches in diameter.
## .102 / .0403 = 2.531
## 10 gauge is 2.531 x the circumference of 18 gauge wire. Thats a
bunch.
Thats a huge difference in Length to diameter ratio.
## I have never tried a 80m wire dipole at 100 ft, but have
used a full sized wire inverted vee on 80m.
## 10 gauge wire provided for a much wider BW, vs the 16 +18
gauge I tried previously.
2 other folks here in town tried the same experiment...with same
results. Again, inverted vee used.
Is EZNEC modeling your dipole correctly ?
Jim VE7RF
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