Adam Kumiszcza writes: > I've made a ca. 10.5 cm metal disc cut from an old car radio chasis and put > it under my gps antenna. It does not hang now, but lays on the window sill, > facing up.
That way you changed three variables in one go. You'd be better off changing one single thing each time so you can see what changes cause which results. You do have a patch antenna (rectangular flat shape), not a quadrifilar helix, do you? > I cannot see any difference between these positions. I've made 10 > measurement for each position, getting 12 SNR values for satellites for > each measurement and then calculated the average of these. Looking at your gpsmon pictures you seem to see the low elevation sats at very similar SNR as (most) high elevation ones. Any RF reflecting things around in your neighbourhood? Also, as David already mentioned, thermo-pane windows are actually damping RF quite significantly and even reflect them at low incidence angles. You might try a few minutes with an open window and otherwise unchanged antenna location to see what happens. > Hanging antenna had 25.18 SNR average (2.21 standard deviation). Antenna on > a ground plane had 26.10 SNR average (2.08 standard deviation). The constellation providing your fix (four satellites minimum) should probably all be well over 30dB, peaking in the mid 40dB SNR range. > If I take into account single high elevation satellite with good SNR > (satellite 26 in the examples), the new placement and ground plane even > lowered it :( You may have to experiment with antenna position a bit more. I have seen more than 15dB changes from rather small changes in antenna placement. It's definitely worth experimenting a bit to find one that is good over the full cycle of the GPS constellation. > I guess the real benefit of the ground plane would be if the antenna was > outside, or my measurement method was wrong? No, the ground plane (if your antenna needs one, not all do) is there to improve the gain in the forward direction and make the elevation pattern more uniform. Outside oir inside doesn't matter, but antennas are influenced by many things in their near-field region (at around 1.5GHz, a few wavelengths at most, so ~30…50cm). Again, you may be too close to the window pane for instance. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ Factory and User Sound Singles for Waldorf rackAttack: http://Synth.Stromeko.net/Downloads.html#WaldorfSounds _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.