[VHFcontesting] Re: VHFcontesting digest, Vol 1 #8 - 6 msgs

Fred Lass fredlass at global2000.net
Fri Jul 27 23:48:21 EDT 2001

> Hi Dave;

In my experience you need two basic antennas, one high angle for short
sporadic-E/nearby meteor scatter, and one low angle for ground wave/long one hop
sporadic-E/long meteor scatter.  Two hop sporadic-E may peak on either antenna
depending on the location of the clouds that day.  My favorite antenna for high angle
is a pair at about 20'/40'.  This gives maximum ground gain for the less than 1000 mile
paths.  You may do the math yourself if you assume that the height of a typical
sporadic-E cloud is 50-60 miles up.  The low angle antenna depends on your preference
of stacks vs long booms.  My preference is as used on Greylock, 4/4/4/4.  The upper two
rotate simultaneously, and the lower two on a side mount rotor.  The ULB box can select
upper 4/4 or lower 4/4.  There is little to be gained from stacking all 4 except for
angle diversity.  However, on Greylock the 4/4/4/4 tends to minimize line noise
eminating from the nearby valley.

As a matter of information there is nearly no ground gain available in useful
directions on Greylock from the location  that we are allowed to set-up.

73,  Fred  (K2TR)

> Message: 1
> Date: Fri, 27 Jul 2001 01:09:57 -0400
> To: vhfcontesting at contesting.com
> From: k8cc <k8cc at mediaone.net>
> Subject: [VHFcontesting] Suggestions on Antenna Heights for 50 MHz
> Since our new reflector has been "broken in" by its first thread ("Software
> Questions"), I'd like to start another.
> K9TM and I are putting together some gear and antennas to have a permanent
> VHF setup here at K8CC.  In the past, the constraints of underground
> feedlines (or rather, the lack thereof) lead to temporary summer lashups
> that had to be ripped down once the HF contest season arrived in the fall.
> One of the main questions to be answered here concerns the preferred
> heights for the 50 MHz antennas.  I've looked at the 50 MHz setups from the
> K8GP and W2SZ web sites, but their mountaintop locations offer advantages
> my QTH doesn't have.  I found some interesting 50 MHz configurations at the
> W5KFT web site, but Texas and Michigan are somewhat dissimilar in terms of
> the available target audience.
> I think I understand HF wave angles, antenna heights and stacking pretty
> well, but my feeling is that VHF is a different thing.  50 MHz might share
> *some* characteristics of 28 MHz, so some of those techniques might apply
> if the propagation modes are known.
> My location is essentially flat terrain, and I have towers that go up to
> 120'.  My thinking is that really tall heights are not necessarily needed,
> since anything above 80' (four wavelengths) is essentially free
> space.  I've been told that a 30' antenna can be a real killer at times for
> summer E-skip, so I was thinking about identical yagis at 60' and 30' with
> upper/lower/both switching for wave angle control and the ability to spray
> RF in different directions.
> Thanks for any suggestions.
> 73,
> Dave/K8CC

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