Thanks, everyone, for a lot of thought-provoking advice. A couple of
specific comments.
At the base of the antenna I have 2 #31 cores each wound with 12 turns
of RG-400, in series. I think that may be about what Jim means by lots
more turns - I may even have gotten the spec from him.
It seems to me that moving the needed extra length to the far end of the
horizontal section may be about the best solution available. To support
the vertical section, I shot a line over a tall maple with a tennis ball
launcher and mounted a 2" diameter block with a Delrin pulley wheel to
the end of the line, with the antenna conductor (#14 stranded,
insulated) I appreciate the concern that over time, this may result in
the antenna conductor breaking due to movement of the trees on each end,
but this seemed like the easiest way to get the antenna up. I know that
I could, probably should have put a fixed insulator at the right place
in the antenna conductor, and run a rope from that over the pulley, but
since I don't really knowe how tall the tree is this seemed like the
simplest approach.
What I'm going to do is haul the pulley up as far as I can, measure how
much more length I still need, and then drop the end of the horizontal
section and dangle the appropriate length from the end insulator.
Now on to the RX antenna!
73, Pete N4ZR
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On 12/19/2021 2:50 PM, Jim Brown wrote:
On 12/19/2021 10:55 AM, Jeff Blaine wrote:
For 160 something around 8+ turns & type-31 are the "right" rule of
thumb answers.
Based on my research, a lot more turns. http://k9yc.com/2018Cookbook.pdf
Pete has received lots of good advice in this thread. I'll add this.
Base loading is a bad thing, because it places inductance at the point
in the antenna that carries the most current, and should be doing the
radiating. Better to remember that SWR is NOT a measure of antenna
performance, that as Jeff has noted, feedline loss is pretty low on
160M, and that what matters for moderate values of SWR most is whether
you amp can put power into it with the help of a tuner. And if
practical, I'd replace that length of RG8X with something the size of
RG8. OTOH, doubling the number of radials, realizing that length of
on-ground radials is not critical, would probably help TX signal more
than replacing that coax, and would change the feedpoint Z a bit.
While adding horizontal length is technically a great idea, sometimes
that isn't practical. I like Jeff's suggestion of an L-network at the
feedpoint, but the design requires either a lot of cut and try, or a
sweep of the feedpoint Z with a good vector analyzer whose data can be
ported to design software like SimSmith. I'll bet that Pete has
neighbors who can do that. And if Pete can send me a suitable sweep,
I'd be happy to do a design.
73, Jim K9YC
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