Where do you get the 35'?
Wes N7WS
On 3/25/2021 9:08 AM, Dave Cuthbert wrote:
An EZNEC model of your antenna (height of 35') shows it to be resonant at
1865 kHz. The minimum SWR was adjusted to 2:1 by adding GND loss of 8 ohms.
SWR is all you need to tune the antenna. Is minimum SWR at 1977 kHz?
I would add more wire and tune the length for minimum SWR at your frequency
of interest. While doing that feedpoint shunt inductor (about 4uH is a
start) can be added to achieve a 1:1 SWR. That does not improve the SWR
bandwidth though and as I like to roam about the bottom 100kHz in contests
I don't bother. The antenna tuner takes care of that.
Dave
On Thu, Mar 25, 2021 at 5:07 AM N4ZR <n4zr@comcast.net> wrote:
I have been trying to replace my inverted L, which broke a few weeks
ago, and am having all sorts of puzzlements. Please be kind - I was a
history major.
1. The inverted L broke at the turn, so I went looking for sturdier
wire. I wound up with some #14 insulated recommended by our local RF
maven, and put up 140 feet initially, figuring I would prune it *up*
into the CW part of the band. Imagine my surprise when it showed up
resonating at 1977 KHz (on an AA-55 Zoom). Does insulation have such a
profound effect on velocity factor?
2. My feedpoint arrangement has 17 turns of RG-400 as a common mode
choke, with the radial field connected to the RG-400 shield at the
antenna end. Initially I tried measuring the resonance without the
radial connection. No resonance and infinite SWR. I connected the
radial field (8 X 70-foot radials on the ground) and that's when I saw
the 1977 KHz resonance (X crossing zero). SWR at minimum was above
2:1. Does this make sense? I know the radial field is inadequate for
good performance, but...
--
73, Pete N4ZR
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