[time-nuts] GPS Antenna on Tower.

Dan Kemppainen dan at irtelemetrics.com
Fri Jun 16 13:17:19 EDT 2017

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!


More information about the time-nuts mailing list