[time-nuts] GPS Antenna Feed Line Decision
cautery at montac.com
Sat Sep 2 16:49:17 EDT 2017
HP 58516A GPS L1 Disribution Amplifier ( 4-way with external power
Clay Autery, KY5G
On 9/2/2017 3:38 PM, Pete Lancashire wrote:
> What are you using for a distribution amplifier ?
> On Sat, Sep 2, 2017 at 11:57 AM, Clay Autery <cautery at montac.com> wrote:
>> Having decision-making problems for the materials for my GPS main
>> feedline. Going to use a TM LMR stock, just can't decide how big to go
>> with it...
>> 26 dB 5vdc antenna on top of a 38 foot mast. Feed will come down the
>> inside/center of mast and exit near the bottom, thence routed through a
>> window and to the GPS distro amp. Antenna will feed GPSDO, NTP Server,
>> Blitzortung System Blue station, and one other device TBD.
>> Just cannot decide how big to go with the antenna to distro amp feed...
>> Assuming 50 feet total (38' mast + 12 feet to amp in shack) @ 1800 MHz
>> (closest to 1725 MHz), here are the losses from just this piece
>> (ignoring the amp to device jumpers):
>> -240 = 5.45 dB XXX - too much loss?
>> -400 = 2.85 dB
>> -500 = 2.30 dB XXX - too hard to find
>> -600 = 1.85 dB
>> -900 = 1.25 dB
>> Money not necessarily a consideration as this is a short run for a
>> permanent installation. Don't anticipate ever moving the GPS antenna to
>> the tower.
>> For 900 and likely 600, likely would not be able to do it in one piece
>> as routing it out of the mast and into the shack would get complicated.
>> Would likely bring it out of the mast at the bottom with a right angle
>> connector, and then use a smaller diameter jumper for the last 12 feet.
>> 500 is pretty uncommon stock wise and it and connectors are harder to find.
>> I already have the tooling for both 240 and 400... but I definitely
>> don't want to challenge ANY of the devices for signal gain.
>> So it mostly boils down to easy vs. more effort ($$ aside).... Is it
>> worth the additional trouble to move from -400 to -600 or -900? To NOT
>> lose the 1-1.6 dB additional?
>> I'd appreciate your recommendation and reasoning. Thanks in advance!
>> Clay Autery, KY5G
>> MONTAC Enterprises
>> (318) 518-1389
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> and follow the instructions there.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts