[time-nuts] Spring cleaning and antenna placement

Magnus Danielson magnus at rubidium.dyndns.org
Mon Apr 20 01:58:38 UTC 2009


Magnus Danielson skrev:
> bg at lysator.liu.se skrev:
>>> If you are in Scandinavia, the GPS birds will not spend much time (if
>>> any?) to the north of you. Slide 12 of
>>> http://web.ics.purdue.edu/~ecalais/teaching/geodesy/Satellite_orbits.pdf
>>> suggests that the most northerly orbital point is at the latitude of
>>> Denmark.
>> With a decent antenna siting you see plenty of SVs to the north. Magnus
>> problem is that there are lots of rather close by trees and stuff. These
>> trees are also much taller than the antenna position.
> 
> Indeed. The southbound sats goes almost over the head, but I also get 
> long tracking periods for sats way up to the north.
> 
> Since the house sits partly in a valey and the neighborhood is rich of 
> trees there is plenty of foilage. To the north is a building, two 
> stories high and ground level for it is just above the upper of mine, 
> which pick up the extreme north direction.
> 
> The location also requires an antenna mast forr the TV reception. With 
> modern digital transmission it is best to have a good margin for 
> reception, or there is no TV at all.
> 
> If I had a flat roof I might just put a ladder up to the antenna, but 
> unfortunately not so.
> 
> Sky-view of GPS antennas was not of concern when picking this house. 
> Maybe it should be for the next.

To follow up on this... I have now received my LNAs and I have installed 
one. The LNA gives me a 16 dB boost, but lack of a bias tee force me to 
use a passive splitter to act as the bias tee, and that sets me back 6 
dB, so I effectively only gets 10 dB of boost, but the effect is 
certainly there, the Z-12 tracks significantly better.

Just goes to show that LNA may come to assistance. Thought this may be 
useful to some. A second LNA could boost me up even more, but using a 
proper bias tee should give me about 6 dB.

Cheers,
Magnus



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