Which GPS antenna: whip, patch soldered to module, or amplified

[kbosak]

Hi,
I have observed that most of us are using GPS ceramic patch antennas that are directly soldered to module, placed either on top of the fuselage after the wing (far from radio modem and wireless TV), or at wingtip (when using high powered TV).

But there are other solutions, say 15-30USD powered, amplified antennas sold for vehicular use, in waterproof casing, usually with some 2-4m of cable.
With cable shortened, they would weight under 100g. I think such antenna would be beneficial allowing more robust fix.

Another idea is to use horizontal whip antenna for max range. Whip antennas wave blind spots but give nice max range, so I would use it for secondary GPS receiver, preferably placed on wingtip, dragging the (stiff) whip antenna.

With the receivers being cheap, my idea is to use two GPS receivers for UAV/FPV:
one SirfIII based, one on another chipset (example: ETEK EB-85A uses mysterious SV3301 as depicted in 'GPS Locator Utility').
In hope their artifacts will average at least partially, and in cases when one would see max 3 satellites, the other could see 5.

To date I haven't identified what mass-market GPS receivers are operating over 60.000 feet, a few are known by the balloonists, f.ex venerable Geko 201 is capable of such flights. Are there special antenna considerations for such altitudes (say amplified&powered antenna could fail due to low temp and commercial grade electronics?)

Any experiences to share?

[Peter Seddon]

I have a U-blox with a simple wire loop antenna that seems to work fine.

regards Peter

[kbosak]

I have a U-blox with a simple wire loop antenna that seems to work fine.

regards Peter
Wire loop you say... do you mean 10 inches of dangling copper wire :eek: ?

[Blue Sky]

You'll need to be careful.
Modern GPS modules have very sensative front ends and could easily be swamped by
using an amplified antenna, esp. if the cable is shortened.

-Dave

[Jack Crossfire]

Combing multiple GPS modules for better accuracy got a bad rap before.

http://www.gpsinformation.net/main/poordgps.htm

Doubt multiple modules in the same location would improve matters, since the errors are atmospheric & 9 satellite reception is typical. Maybe the extra wing loading would improve stability.

[kbosak]

Combing multiple GPS modules for better accuracy got a bad rap before.

http://www.gpsinformation.net/main/poordgps.htm

Doubt multiple modules in the same location would improve matters, since the errors are atmospheric & 9 satellite reception is typical. Maybe the extra wing loading would improve stability.
I was not dreaming about averaging the 2 receivers because the errors in them are not independent, they are very dependent in fact.
What I am trying to eliminate are rather post-processing artifacts introduced in GPS chipset modules, let's say one chipset will report invalid groundspeed when the plane is climbing almost vertically, the other will report huge DOP when the plane decelerates from 80 to 60mph while descending.
By combining 2 receivers I want to smooth out failure conditions, which by default very sharp: invalid, 2D, 3D , speed OK or completely unavailable etc.

Note that one antenna setup can be swamped by reflection from something passing by, what would shuffle the almanach or something like that, while the other GPS could stay calm.

What matters for me is not to halve the DOF nor even slice 5% of it, just to make VERY IMPROBABLE that inflight the only onboard GPS will go crazy for 1 minute until it reacquires everything. It could be even some electronics problem, suddenly broken ESC, oscillating voltage. The processors and everything onboard can reset and restart in 1s, EEPROM will hold constants (I design it this way, all constants will have 2 shadows in EEPROM with simple correction code for each etc), but no sensor should die for more than a few seconds.

[kbosak]

Here it is
http://www.sparkfun.com/commerce/product_info.php?products_id=8234
20 Channel EM-408 SiRF III Receiver with Antenna/MMCX
that has soldered ceramic patch antenna AND external antenna connector.