[time-nuts] Req: Decent GPS Antenna Active/Passive Recommendation

Hal Murray hmurray at megapathdsl.net
Sun Sep 15 16:36:31 EDT 2013


john at westmorelandengineering.com said:
> Well, I need something that I can put outside, in the weather, with my
> verticals, and other antennas.  I am a Ham radio enthusiast, and I want
> something I can properly mount and can be an all-weather device and can live
> happily 'in the farm' so to speak. 

I split GPS antennas into 3 clumps.

At the low cost end are the small "mouse" or "hockey-puck" type units, 
usually with a magnetic mount.  They typically come with 10 or 15 feet of 
thin (lossy) cable.  Ballpark price is $10.

In the middle are the typical cones that you see on cell phone stations.  The 
Lucent 26 dB ones are common on eBay.  Ballpark price is $50.  The same or 
very similar thing is also available with different brand names.  Some of 
them come with a pipe mounting setup such that the coax and connector is 
inside the pipe and out of the weather.
  http://www.megapathdsl.net/~hmurray/time-nuts/Lucent-Antenna.jpg

At the top end are the choke ring antennas intended for surveying.  They are 
mostly out of my price range so I haven't looked carefully.

----------

I haven't seen a GPS antenna without an amplifier, but I haven't been 
looking.  They also include a filter.  See the LightSquared flame-wars for a 
discussion of filters.

I think the choke ring antennas usually let L1 and L2 through while most 
others are L1 only.

The other important consideration is the sensitivity of your receiver.  Every 
couple of years a new generation comes out that is a few dB better than the 
previous ones.  (Has anybody seen a Moore's Law type graph?)

Modern receivers are sensitive enough to work indoors with a non-fancy 
antenna, at least most of the time.  YMMV etc, and "indoors" probably doesn't 
include buildings with a lot of steel.  It doesn't cost much to try.

If you have an old recycled GPSDO such as a TBolt or Z3801A, the receiver is 
much less sensitive and a good antenna position helps a lot.  Of course, it 
also depends upon what you want to do and/or how nutty you are feeling.

There is yet another dimension.  GPS receivers come in two modes: navigation 
and timing.  Navigation units need 3 or 4 satellites to figure out where (and 
when) they are located.  The timing units assume they are not moving and that 
they know their location.  They should be able to maintain timing with only 1 
satellite.


-- 
These are my opinions.  I hate spam.





More information about the time-nuts mailing list