Hi All of the ones I've opened up or seen dis-assembled have had the ceramic plate antennas in them. That very much surprised me early on, since I *assumed* they had something fancy inside based on their shape.
No argument about the filtering, I'm not sure if the temp-co of filter delay on an exposed antenna makes it a plus or a minus…. Bob On Sep 15, 2013, at 5:48 PM, Robert Atkinson <[email protected]> wrote: > Hi Bob, > Many of the midrange antennas have one or more significant differences from > the cheap "pucks". Firstly they generally have better filtering, many pucks > have none. This is important if you are co-located with transmitters. > Secondly many use quad-helix antenna elements rather than the off-set feed > ceramic patches in the pucks. The heical elements have better control of the > radiation pattern and along with a larger radome are less likely to be > affected by external contamination. I also wonder how the tuning of a cheap > ceramic patch holds up over the range of temperatures seen by a fixed > antenna. Modern receivers compensate well for poor antennas, try using an > early receiver on an internal patch and you won't get great results. > > Robert G8RPI. > > > > > ________________________________ > From: Bob Camp <[email protected]> > To: Discussion of precise time and frequency measurement <[email protected]> > Sent: Sunday, 15 September 2013, 22:19 > Subject: Re: [time-nuts] Req: Decent GPS Antenna Active/Passive > Recommendation > > > 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 <[email protected]> wrote: > >> >> [email protected] 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. >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
