Good comments by Bob. I run 100 ft of Rohn 45 and then have a stack of rotatable antennas at that point. 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. Regards Paul. WB8TSL
On Fri, Jun 16, 2017 at 2:38 PM, Bob kb8tq <kb...@n1k.org> wrote: > Hi > > 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. > > Bob > > > On Jun 16, 2017, at 1:17 PM, Dan Kemppainen <d...@irtelemetrics.com> > wrote: > > > > 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 > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.