Thread: NVIS and VHF?
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Old May 23rd 11, 07:51 AM posted to rec.radio.amateur.antenna
Jeff[_14_] Jeff[_14_] is offline
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First recorded activity by RadioBanter: Dec 2010
Posts: 87
Default NVIS and VHF?

On 22/05/2011 19:04, 'Captain' Kirk DeHaan wrote:
I'm living in a wooded area and am trying to hit our club repeater
reliably. It's cloudy now so I'm and getting a bit of ducting but I have
a lot of trees, mostly poplars, in the direct path. I would have a line
of sight if not for the trees as I'm up enough in altitude. I can cut
the trees, they're mine, but finding the right ones is difficult and i
don't want to waste the whole grove.

I go from keying the repeater with no intelligible signal to not being
able to hit it. Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? I have only seen references to it being
applied in HF.

'Captain' Kirk DeHaan
N6SXR


If you have line of sight to the repeater I find it hard to believe that
a few trees will cause you problems at 2m.

NVIS will not work at vhf it is an HF mode. 2m signals go straight
through the atmosphere they are not reflected back down.

You don't say how far away the trees are, but if they *really are* the
cause of you problems, if they are at any distance then they will
probably all have to go to give any sort of Fresnel zone clearance at 2m.

A simple map and compass will give you the bearing to the repeater, but
perhaps you would be better off running a propagation prediction program
such as Radiomobile to see if it is actually the terrain rather than the
trees that are the problem.

73
Jeff