> 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
To: <vhfcontesting@contesting.com>
> Date: Fri, 27 Jul 2001 01:09:57 -0400
> To: vhfcontesting@contesting.com
> From: k8cc <k8cc@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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