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

Bob Camp lists at rtty.us
Sun Sep 15 21:19:03 UTC 2013


Hi

Worth noting: 

The "mid class" antennas are not a lot different electrically than the "low end" antennas. The main differences are mechanical:

1) You get a much more weather tight housing
2) You get a rational way to mount the antenna 
3) There's a connector on it so you can put a good piece of coax on it
4) The housing *may* be more immune to snow / ice buildup and bird nests

RDR Electronics on the usual auction site appears to be selling some nice ones at the moment.

Bob

On Sep 15, 2013, at 4:36 PM, Hal Murray <hmurray at megapathdsl.net> wrote:

> 
> 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.
> 
> 
> 
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