RE: [amsat-bb] FD, VX5R, FM38-39

[Tony Langdon <tlangdon@xxxxxxxxxxxxxxxxxx>]

> This is too broad of a statement to let stand as is.  THis 
> statement is
> TRUE for a terrestrial vertical designed for gain at the 
> horizon, but I
> disagree completely beyond that.  a 3/4 wave 435 MHz vertical 
> whip over a
> good groundplane has almsot 8 dBi gain above 30 degrees.  I 
> have found NO
> other  "omni" antenna that can get even close to that.  And 
> the downlinks

This is true, though I'm yet to realise this in practice.  I did try the 3/4
wave trick on a 50 degree UO-14 pass once, while mobile, and ended up
getting better results from a handheld 1/2 wave rubber duck.  I guess it
depends on circumstances.  I think this idea probably suits APRS style
operation better, because of the greater number of total pass opportunities
(more chance of one bird going overhead), and the short transmissions give
frequent opportunities for access in the short central window, where the 3/4
wave is effective.

> of all existing birds are predominatly vertical.  You cannot afford to
> give up the 3 dB by going to any cross polarized "omni".

UO-14 often shifts rapidly down here, just ask anyone who was on the 12:38z
pass over VK last night - we had some _really_ crazy shifts going on, was
spinning the beam in quick time (the LP-Texas Potato Masher became a blender
:) ). :-)

> No, it does not work to the horizon, but the bird is 6 dB further down
> there anyway, and NO OMNI can hear the weak UHF downlinks  there
> either...
> 
> Just another opinion...

All opinions are appreciated. :)
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