[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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