[aprssig] PSAT digipeater is ON

Stephen H. Smith wa8lmf2 at aol.com
Tue Jun 2 12:06:28 CDT 2015


On 6/2/2015 9:38 AM, Robert Bruninga via aprssig wrote:
> APRS activists:
>

> I don’t expect anyone to wear out their rotators tracking PSAT, no, just a
> simple vertical over a ground plane will do.  Either a 19” vertical whip over a
> large 6 foot square ground plane or even better, a 58” vertical monopole over
> the ground plane.  This ¾ wavelength vertical has almost 7 dBi gain and will
> pick up signals during the few minutes overhead.


I currently have an Icom AH-7000 discone monitoring 145.825 for the ISS 
digipeter running 24/7.

Go to <http://WA8LMF.net/map> and follow the links there.

It appears to be not very effective for high-elevation RX.   I assume the 
discone has more of a vertical dipole-like pattern that favors the horizon 
rather than over head, perhaps with slightly fatter lobes than a normal 
vertical dipole.  As I often say, it's equally poor at all frequencies from 
50-1000 MHz.....

I assume the 3/4-wave vertical, over an adequate ground plane, would have 
multiple lobes with one up-tilted substantially, and would favor high-angle RX 
better than the discone.  Albeit with still a null at at or near the zenith.

Any sense how the 3/4-wave compares with the discone?

I am considering building a Lindenblad antenna (four 1/2-wave dipoles arranged 
in a horizontal square with each one tilted about 30 degrees from horizontal) 
that supposedly creates a nearly hemispherical pattern that is circularly 
polarized at the zenith. Apparently the FAA uses these to communicate with 
aircraft anywhere from the horizon to directly overhead.

Anyone have experience with the Lindenblad for satellite downlinks on 2M?   How 
does it compare with the other two above?

___________________________________

Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page:          http://wa8lmf.net

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