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[aprssig] flying digipeater?

Robert Bruninga bruninga at usna.edu
Mon Apr 18 23:14:56 UTC 2005


>Have you considered just putting the antenna up ... from 
>the baloon with the antenna wire running down to a digi 
>on the ground?

big problems here.  The loss in the long coax will be far
worse than any height gained.  This is a common error
for dreamers with high towers.  We have access to a 600'
tower.  But in 10 years still have nothing on it:

1) Remember that height gain only goes up 6 dB with
each doubling in height.  Thus the 600' tower is only
6 dB better than a 300 foot one.  If the 300 feet of coax
to get to the top has more loss than 6 dB, then it is almost 
pointless to go higher.

2) That is why, those heights need coax as big around
as your arm costing $15 a foot and weighing about
a Lb every foot too... and we cant afford it.  We built 
a small solar powered digi, but I got too old to sneak up
the tower at night to install it..

Using lightweight RG-174 as a feed line to any antenna
at 2 meters is pointless beyond about 20 feet.  At that length
you lose 3 dB or 50% of your signals.

But getting above the tree does sometimes make it worthwhile
to have a slingshot and some coax...    Bob




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