Re: [Paparazzi-devel] Tiny V2.11 GPS Antenna

[Martin Mueller]

Hi Bryan,

> I am rather new to the Paparazzi system and am thoroughly enjoying it so
> far. I currently have the Tiny V2.11 with the integrated GPS but I will
> be using a modded airframe that will have a carbon fiber fuselage that
> fosters the autopilot and a camera. However, with this I am worried that
> I will not get the good GPS signals that I would like in order for
> automated takeoffs and landings.

first thing would be to check how much the carbon affects the GPS 
signal/noise ratio in the gcs inside and outside the fuselage.

> Thus, I would like to try to use a different GPS antenna than the one
> provided with the Tiny set-up and was wondering if anyone has done this
> before or is more familiar with this. The current GPS antenna I have
> uses a SMA male connector; so my thought was to un-solder the current
> antenna, solder in a coaxial cable in the Tiny to run a SMA adapter to
> the GPS antenna (which is a 3 to 5 volt active antenna).

You could solder a SMA connector. But also you have to feed the DC 
voltage into the RF link. Guess your Tiny is fitted with a LEA-5H. This 
module does have circuitry inside to separate the RF from the DC supply. 
You have to apply the antenna voltage to V_ANT through a resistor as 
described in chapter 2.6.2 of the hardware manual [1] (currently that 
signal is grounded on the Tiny).

> If anyone is more familiar with using a different GPS antenna for the
> Tiny V2.11 any help would be appreciated (or if you would recommend
> switching to the Lisa or TWOG model).

Not sure that anyone has done that before. You should probably only try 
that if you are familiar with high frequencies and a little adventurous.

Another solution is to use an external GPS receiver on J7 DOWNLOAD with 
the TWOG as you described or even with the Tiny. You can disable the 
on-board GPS receiver by pulling GPS_RESET low. It does not sound like a 
clean solution...at least u-blox said it does not harm the GPS receiver.

Martin

[1] 
http://www.u-blox.com/images/downloads/Product_Docs/LEA-5_NEO-5_TIM-5H_HardwareIntegrationManual%28GPS.G5-MS5-09027%29.pdf