[TowerTalk] GPS Receivers

[N7KA@comcast.net]

I think the question about the GPS receivers was to help set up a 5 GHz backbone.

Now the discussion has been the ability of a GPS receiver to assist in this effort.

I would think that depending on the distance between the 2 positions (antenna locations) that a few feet would NOT make any difference.

We just recently did a 10GHz shot over a 100 mile distance and the GPS helped to get "ball park" locations then the antennas on both ends were rotated for maximum signal strength.  Each end taking turn peaking the RX signal.  I would doubt that either antenna being proposed has a rotation indication that would be able to resolve a few feet of placement of antenna on the other end of the link. Besides do the antennas to be used have a very sharp narrow pattern? Our antennas were 2M in diameter BTW.

I use a GPS receiver when I am 4X4ing.  In most cases the ISGS Topo maps are fairly accurate when the GPS coordinate is over layed onto the map. (Digital mapping and track logs are great, BTW).  Just using Topo maps would allow placing both ends of a link with enough accuracy except for the VERY narrowest of beam patterns from the antenna.  I do agree with others that altitude on the "consumer" GPS receiver does leave a LOT to be desired.  I only use altitude as a "ROUGH" reference and not for any other navigation purposes. However I WILL depend on my GARMIN 2+ for location.  Have driven in on a trail then driven out the same or next day and GPS readings were the same. This is very evident when you make a track log going in then follow that route coming out.  BTW, did this in full darkness on one trip and I had 100% confidence in what the GPS was telling me.

One thing to be careful of is to make sure any map DATUM compares to the DATUM on the GPS.  Most folks use WGS84 on the GPS, whereas most topo maps have NAD27 (or even earlier).  There will be some difference in location but its not much, under 100 meters in most cases.

This might be a case of ditch the technology and just go to work.

73 de Arne N7KA