[time-nuts] GPS Antenna Feed Line Decision

Clay Autery cautery at montac.com
Sat Sep 2 19:48:52 EDT 2017

Thanks for the response...

Not sure why you and the other guy both recommended RG-6 75-Ohm cable
and F-connectors, when the nominal impedance of literally everything
else in the system is 50 Ohm, including the antenna and the HP GPS
Distribution Amp....  And then adding N to F adapters?

Doesn't make any sense unless one has $$ as a top priority, already has
a spool of RG-6 quad shield, etc...  but I specifically stated that $$
is not a top priority....  Not really even in the top 5 or 10...

The whole point of this exercise is to put up a semi-permanent SINGLE
antenna/feed-line install that will supply all 4 ports of the HP amp
with the least compromised signal within reason.... 4 now, and 8
whenever I can find the HP 8-way distro amp with external power input.

Strain relief solution:  Really depends upon which cable stock I end up
using....  Obviously, the larger the cable, the more weight will be
suspended under the antenna (approx. 38 feet, depending on where I pull
the cable out of the mast at the bottom.  (The mast is on a tilt-base of
my own construction....  which brings up a valid consideration.  it is
already a chore to walk the mast up manually.  The more weight added at
the top and inside the mast, the more difficult a manual walk-up will
be.  I'd prefer to keep this a manual tilt for now...  at least until I
add the tri-band vertical dipole)

LMR-400 would be less than 4 lbs total weight...  I'd likely suspend the
cable by the connector alone. (although, it wouldn't be JUST the
crimp...  The connector would have at a minimum, 1 layer of
adhesive-lined shrink tube... probably 2, with the second, overlapping. 
Then a nice wrap of self-fusing tape and then electrical tape over that.
Even LMR-600 could be suspended by the connector alone, at 5 lbs max in
the 38 foot max vertical section.
I do have several methods of secondary suspension within the top (and/or
second) mast section though if I decide I need it.

Also prefer to keep all the connectors N-type as much as possible since
that is the station standard.


Clay Autery, KY5G

On 9/2/2017 6:07 PM, Mike Naruta AA8K wrote:
> Clay, you may wish to consider using a quality RG-6 with F
> connectors.  Grounding blocks are readily available for the base of
> your mast and the entrance to your house.  Also, off-the-shelf
> over-voltage protectors (Zap-Tech) are available. I even found an
> F-to-N adapter for the antenna on Amazon.  Watch out for the ones with
> metric N threads though.
> For my 25 meter run I was going to use an existing one inch Heliax,
> but pulled a run of Belden RG-6 instead after learning that Trimble
> used RG-6.
> It worked well directly connected to a Trimble Thunderbolt; now it is
> connected to a Symmetricon 58535A GPS L1 distribution amplifier.
> My Blitzortung System Red station has been running fine in my attic
> (Michigan) on a Motorola 97 Oncore patch antenna fastened against the
> roof underside.  It is looking through wood, shingles, and nails (and
> a tree and antennas and utility lines).
> How are you planning to do strain-relief on the vertical run of coax
> inside of your mast?
> Mike - AA8K
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