Posted by
Jim Brown-10 on
Mar 14, 2020; 12:31am
URL: http://elecraft.85.s1.nabble.com/Off-Topic-Your-advice-suggestion-about-antenna-tp7658892p7658906.html
On 3/13/2020 3:05 PM, Lyn Norstad wrote:
Hi Lyn,
IL is a state I know fairly well, having spent 41 years in Chicago and
one in Cairo.
I don't work nets like you do, but I do a lot of contesting, including
80 and 160M, and if you're paying attention, can teach a lot about
propagation. I have several interesting observations about 160M. First,
ANY horizontal wire that we can rig is electrically very low, so ground
losses are high.
When I first moved to NorCal in 2006, I had an 80 ft Tee vertical with a
lot of radials and a dipole at about 110 ft. During contests, I switched
between them a lot. The dipole rarely "won." 160M contests start at 2PM
local, so our first 2.5 hours are in broad daylight. During those hours,
I soon learned that, running legal limit CW, I could reliably work out
to 800 miles or so on the vertical, but not even get "QRZ?" on the
dipole. Clearly, there's a difference between horizontal and vertical
propagation under these conditions! When that 150 dipole bit the dust in
a major storm several years later, I didn't bother to restore it.
In addition, the bigger stations as far east as VE3 and W8/W9 are solid
copy here as early as 3:15 pm local, but are almost impossible to work.
At least two reasons are at play: 1) they're using RX antennas aimed to
EU for more points per QSO and for multipliers; and 2) they have noise
propagated from the east, while I have mostly local noise.
While I haven't really answered your question, I do suggest that you try
to rig some sort of top-loaded vertical with as much of a counterpoise
as you can manage. Some years ago, I put together an app note on 160M
antennas and counterpoise/radial systems, all of it the summary of very
good work by others. All the advice for 160 scales for 80M. Two of the
more interesting ideas are K2AV's folded counterpoise and Rob Sherwood's
improvised ground screen.
http://k9yc.com/160MPacificon.pdfThis slide deck shows what I did in Chicago. The antennas I used there
are shown beginning on page 10. I found that the 80/40 loaded dipole
worked on 160 as a Tee vertical (fed with vintage 75 ohm "KW twinlead),
and it worked better fed as a vertical on 80 than it did fed as a
dipole. Thanks to the loading coils and the length of the feedline, it
was pretty easy to load on both bands. That discussion starts on page
30. My counterpoise was a wrought iron fence that ran around my front
yard. :) That antenna had no problem working anyone within 800-1000 miles.
http://k9yc.com/LimitedSpaceAntennasPPT.pdf73, Jim K9YC
>
> One question I have relates to NVIS. In the case of my 80 meter EDZ, the
> plan was to make it workable for NVIS operation. It has succeeded in that
> regard very nicely in that I can cover the entire state of Illinois (which
> is primarily a N-S pattern) very well on both 80 and 160. We operate a
> state wide ARES/RACES net on 80m, but there has been some fear that as
> propagation continues to worsen for a period, the MUF for NVIS will require
> a higher frequency than non-NVIS and one that actually approaches the MOF at
> that time - due to the angle of radiation. In other words, using an NVIS
> antenna when the MUF is 4.0 MHz might actually require an MUF of 12 - 13 MHz
> which would be closer to the MOF at that same point in time.
>
> Have you observed that at any extremely low spot in the cycle?
>
> We have seemingly remedied that by setting up and operating a successful
> 160m net and passing digital traffic.
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