an other way to keep lightening damage away, to use one 1/4 wave length
stud, and bank on it, that the lightening will not transmit with full
power on the GPS frequencies.....that trick is widely used on TV
transmitter antennas, The only issue is that it is not very handy to
have piece of cable, cca 4cm long, and the length of the cable has to be
tried out with the available cable, -- with a piece of a semi-rigged
cable teflon isolated, the shorting factor is around 0,76.
If there is DC in the line, the end of the 1/4 wave length cable can
not be shorted, but connected to a large capacity -- up to 5µF ceramic
SMD brick-capacitor, that will prevent the short and also a spike to
travel on the line,
The stud length could be set with a network analyzer; the electrically
1/4Wave length, and at at the end shorted coax cable looks like open or
S11=0dB
73
KJ6UHN
Alex
On 8/14/2015 5:31 PM, Bob Camp wrote:
Hi
The GPS RX arrestors are something that come up from time to time.
They often have strange custom part numbers and very limited data.
Sometimes the only practical way to figure out what’s what is to buy one
and see. If it’s the right sort of unit once you check it out, the hope is that
there are still some left. An awful lot of these went into cell towers and
the install kits for them. The “give away” spec listed on the parts is often
only
that they cover the GPS band and not much else. The crazy thing is that
often the enclosed instructions have a few details (often as cautions like
“do not exceed 25V or 2W RF”) that let you know you have the right gizmo.
I really can’t complain a lot about that. Since they are “nobody knows” sort
of part they go for < $20 and not > $50.
Bob
On Aug 14, 2015, at 7:37 PM, Gregory Beat <[email protected]> wrote:
If anyone needs some if the Arrestors for outdoor GPS antennas
with "F" connectors (Trimble Bullet antenna) ... I think ai still have some
spares
In my installation parts boxes.
Love to trade for an "N" version (which I ran out of), or postage and offers.
greg
w9gb
Sent from iPad Air
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