[time-nuts] Difference in GPS antennas

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Sat Aug 15 21:32:04 UTC 2009




On 8/15/09 8:27 AM, "Magnus Danielson" <magnus at rubidium.dyndns.org> wrote:


>> If you're near a harbor with fishing boats, you'll see plenty of quad
>> helices about a half a meter in overall height, used for VHF Weather
>> satellite reception.  They're also used on spacecraft (Mars Science Lander,
>> Mars Reconnaissance Orbiter, and Phoenix all have UHF quad helix antennas, I
>> think, for about 400 MHz)
> 
> Not used by the fishing vesels near me...

Really?  Practically all the fishing boats (mostly squid) boats going out
from Ventura Harbor (in Southern California) have big ol' quad helix
antennas up on the cross bar (as well as the usual HF SSB and VHF whips and
the radar).  Maybe it's a regional preference thing (or folks are going to
the 1.6 GHz band or something).



> 
> I didn't mean helixantennas as such, I was just asking myself the
> question if any of my *GPS* antennas was infact of the quadra-helix
> design, a few of them have the sizes that they *could* be that.

The one on my handheld Garmin (about 10 years old) is a quad helix.  I would
venture that any of the antennas that are about the size of your finger are
a quad helix.

Thinking of other antennas in that form factor (10-15 cm long, more than 1
cm in diameter) maybe Iridium or Globalstar phones use a quad helix?






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