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

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 <dan@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.

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 <kb8tq@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 <dan@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. >