[time-nuts] GPS Antenna Feed Line Decision

Artek Manuals Manuals at ArtekManuals.com
Sun Sep 3 10:44:44 EDT 2017


Clay
LMR-400 is probably the best compromise , I doubt you will see any 
useful improvement in system performance as a result of the improved 
1.5db loss characteristics of the larger cables. Losses due to 
atmospherics, ionospherics and multi-path will be an orders of 
magnitude  higher than the additional 1.5 db of signal improvement with 
the larger cables. We are not talking comms with some guy in a space 
suit on Mars here :-)

AS for walking the mast  up I have done a number of installations of 
this sort and the use of a block and tackle at the eve point is not 
difficult, and will be appreciated more and more the older you get .  
Mechanical multiplicative advantages are easy to implement. Don't use 
block & tackles which can pivot since depending on the weave/braid of 
the rope they will twist around and bind.

Dave
manuals at artekmanuals.com

On 9/2/2017 7:48 PM, Clay Autery wrote:
> 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.
>
> 73,
>
> ______________________
> 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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-- 
Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com


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