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RE: circular polarized Arrow antenna



Hello Bob

> > Howard's analysis (I think it was his posting) showed that you'd need
> > arms 53cm long to be safe, direcly behind the antenna.  Maybe you
> > could stand in a null somewhere.
>
> Doesnt duration also factor into the equation?
> THe duty cycle for satelltie QSO's is extremely low....

Yes the fact that it's SSB and a number of other factors are taken into
consideration: modelling was using Stacey W4SM's RFWIN program, so it was
not at all tough to do.

I said back on 8 Aug 2001...
http://www.amsat.org/amsat/archive/amsat-bb/200108/msg00270.html

------******------

For interest's sake I tried the RFWIN program out with the above two
scenarios [HT and Arrow] to determine safe distances from the antennas'
lobes:

    @435MHz            Controlled  Uncontrolled
5W FM HT 1/4 wave         0.6'         1.4'
50W 20% SSB +10dBi (Main) 5.4'        12.2'
50W 20% SSB  +0dBi (Lobe) 1.7'         3.8'
50W 20% SSB  -5dBi (Lobe) 1.0'         2.2'
50W 20% SSB -10dBi (Lobe) 0.5'         1.2'

So unless you're pointing the antenna directly into your neighbor's window
at 12', I'd suggest you're safe. After all, there's not much point running
any more EIRP than this - I discovered last night that I _can_ set off LEILA
with this configuration.

------******------

...and in
http://www.amsat.org/amsat/archive/amsat-bb/200108/msg00317.html...

------******------

These are taken using the 'rules of thumb' operation with the RFWIN package
which includes stuff like typical % transmit cycle.

This includes 100% transmit during a 6 minute period for controlled exposure
and 67% transmit during a 30 minute period for uncontrolled exposure - well
within any satellite op's practices I'd have thought.

------******------

73 Howard G6LVB


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