[time-nuts] GPS Antenna on Tower.
paulswedb at gmail.com
Fri Jun 16 15:12:45 EDT 2017
Good comments by Bob.
I run 100 ft of Rohn 45 and then have a stack of rotatable antennas at that
I have the antenna some 3-4 ft off the tower at 90' feeding with 1/2"
line.(Because I had it) The trees have grown to 90' so that gives a nice
clean view south. Works totally fine. Reason to keep it a bit lower is to
allow other things to take the static that can build up. Most of the other
stuff is just metal.
I also have a backup antenna at the 50' level using 75 ohm hardline.
the great thing today is just about anything works pretty well.
On Fri, Jun 16, 2017 at 2:38 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> Will there be an effect? Yes. Are roughly 99% of all GPSDO’s run with
> antennas mounted that way
> by “pros” ? Yes again.
> If you are setting up a reference site for high precision survey work,
> don’t do it that way. For a GPSDO,
> you should be fine.
> > On Jun 16, 2017, at 1:17 PM, Dan Kemppainen <dan at irtelemetrics.com>
> > Hi All,
> > Fair Warning: Nuts Mode Engaged. :)
> > Recently we've moved to a new house and am in the process of getting the
> antennas back up for various things. One of these is the GPSDO(s), and an
> obvious location is somewhere on a Roan 25 tower set up just south of the
> house. At about half way up the tower, there is clear sky view in all
> directions and the GPS antenna is temporarily parked there about a foot off
> the tower. The GPS antenna is on the south side of the tower and we're
> ~47N, so most of the GPS birds should be visible. Single band GPS antenna,
> nothing special.
> > My guess is this will be fine. However, I'm still wondering what sorts
> of multi-path or reflections could be expected off the tower itself. And
> are these enough to worry about? If there is multi-path what sorts of
> things would help prevent this? (Mounting the antenna further off the
> tower, etc.)
> > Once I get the tower guy lines redone, I'm thinking about putting the
> GPS antenna on the tip of the mast (No rotator on this tower). That's at
> about 75 feet with nothing close by. That would be slightly above the tree
> line, with a 360 degree sky view.
> > FYI, currently the GPS antenna wire is "Priority Wire and Cable" RG-6/U.
> Did some measurements last night. It measures as 85 Ohm, with a velocity
> factor of ~.86. It looks pretty lossy, but it should still work.
> > Any ideas and comments welcome!
> > Thanks,
> > Dan
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