Thanks to everyone who has replied so far, and apologies - I did a lousy
job of describing the antenna. First off - I set out to make it 1/4
wave (approximately 128 feet) long, and the starting length of wire
(what I actually put up) was 140 feet. Vertical portion is about 55
feet, and the horizontal part is more or less level. The feedpoint choke
is wound on a #43 core (I think), which may make it a bit more
credible. The measured minimum SWR is 2.2 at 1925 KHz, and resonance (X
crossing zero) is at 1983 KHz. All measurements made at the base of the
antenna
Now here's the part I *really* don't understand - at X=0, the R measures
119 ohms. Working from memory, I think the old L was resonant about 1875
KHz, and the R was on the order of 35 ohms, which I was told made sense
for a quarter-wave with a lossy ground plane. The new numbers make no
sense at all to me.
73, Pete N4ZR
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On 3/25/2021 12:26 PM, Artek Manuals wrote:
Technically the insulation should electrically lengthen the antenna
about 1.5-2 % (lower the frequency)
As Wes said the dimensions would be helpful. is the flat op horizontal
or does it slope down if it slopes how low is the far end?
I dont think 17 turns of RG400 is doing much for you on 160M but with
a ground mounted radials (IMO) not likely needed...what is the "R" at
X=0.
�Are you measuring R+jX at the antenna or at the shack end of the
coax? How long is the coax
Dave
NR1DX
On 3/25/2021 11:54 AM, Wes wrote:
How long is the vertical section?� The insulation should have minimal
effect.
Wes� N7WS
On 3/25/2021 8:07 AM, N4ZR 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...
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