Interesting! I have some anecdotal experiences that support the "low inverted V
is better for local contacts" school.
I am mostly CW and tend to primarily chase DX and so have an F12 Sigma 80 OCF
vertical dipole for 80 m. It has a home-made 1:1 common-mode choke made from
two stacked 2.4" type 61 cores with about 24 bifilar turns of number 16
enameled wire. I see no evidence of RF in the shack and it doesn't get
noticeably warm at 1500 W.
I also have my Dad's old rigs, which are also the first ones I ever used: a WRL
Globe Champion 350 AM tx and a Hammarlund HQ-170 rx. I use these to
occasionally play with AM with some relatively local guys (within about 400
km).
The OCF vertical dipole performs uniformly poorly in this application: the
signals from me were poor and their signals were weak. Yet, I did quite well
with DX, often breaking through the pile in the first couple of calls.
When I put up my 80 m inverted v with the apex at 40 ft, my signals to and
received from the in-close guys became much better.
I can switch between the two antennas for A-B comparisons and most of the time
(not always) the inverted v does better for relatively close-in stuff and the
OCF vertical dipole is usually much better for DX. So, for what it's worth,
that's my experience.
73,
Kim N5OP
"People that make music together cannot be enemies, at least as long as the
music lasts." -- Paul Hindemith
> On Oct 6, 2015, at 18:22, Jim Brown <jim@audiosystemsgroup.com> wrote:
>
>> On Tue,10/6/2015 2:29 PM, Kim Elmore wrote:
>> Which should work better for domestic contests:)
>
> Not necessarily -- much of that is more urban legend than fact. It's a big
> country, and depending on conditions and the band you're working, many
> stations you want to work will be a low angle path. Also, inverse square law
> says that we lose 6dB per doubling of distance, so you need more signal to
> work those long distances than the shorter ones.
>
> W6GJB and I just built a loaded vertical dipole for 80M for use in CQP and on
> FD. It's designed so that old men can put it up without hurting themselves,
> with the objective of beating an inverted Vee with apex at 42 ft, which we
> have a good way of rigging. A few weeks ago, we set up both antennas in GJB's
> pasture and did a lot of RBN testing, and plotted the results vs distance.
> The low angle vertical beat the inverted vee at almost all distances. AND --
> many stations heard the vertical that didn't hear the inverted Vee, but only
> one or two heard the inverted Vee and didn't hear the vertical. Modeling
> predicted that the vertical would be 5 dB better, and the RBN clearly results
> showed that trend.
>
> To do our RBN testing, we alternated between antennas using a different call
> for each, making a couple of calls on a frequency, then QSYing and repeating.
> The purpose, of course, is to average out the results of QSB.
>
> Unfortunately, when we set it up for CQP, the Spiderbeam telescoping pole
> that made up the top half of the antenna broke in gusty winds that blew in
> late Saturday afternoon, so we didn't get to use it that night for the
> contest.
>
> 73, Jim K9YC
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