SparkFun Forums 

Where electronics enthusiasts find answers.

Tips and questions relating to the GPS modules from SFE
By fgcity
#49978
Hi everyone.

I have an Active antenna on a GE 863 module.

Works fine.

But i want to make the reception a bit more powerful.

If i put an LNA between the antenna and the module will the reception be stronger?

Please help out.
User avatar
By leon_heller
#49979
An active antenna already has an LNA.

Leon
By fgcity
#49981
yeah, i know. but if i put another one will that make a difference?

Are there any other tricks i could use to make the signal a couple bars more?
User avatar
By leon_heller
#49984
It'll probably overload with another amplifier, or you'll just introduce more noise. You could try a higher gain active antenna, or shorten the lead if the length is excessive.

Leon
By fgcity
#49986
it's actually not a normal active antenna. It's this:

http://www.taoglas.com/docs/ap-12a.pdf

It has 24db+

There are others which are a bit bigger with 14 and 15db+

Those would get better reception you think ?
User avatar
By leon_heller
#49992
I think I've got a couple of those, you probably won't find anything better. You need about 25 dB gain for most GPS modules.

Leon
By scalegps
#50101
Dimka,

Adding an extra LNA would help somewhat, but it's not that easy to do. You have to make accomodations for a bias-T for the new LNA, and also pass voltage through to the LNA in the antenna. Doable, but more trouble than it is worth. What kind of C/No values are you getting now? If most of them are in the high 30's to low 40's you should be fine.

An EASY way to add 3-4dB to the C/No's on these small patch element antennas is to add a groundplane behind the antenna itself. Without the groundplane the side lobes are substantial, and you are giving up a lot of sensitivity in the direction you want. The plane can be as simple as a piece of aluminum foil behind the LNA can on the antenna. 1" to 2" in diameter will help quite a bit. As you get up to 4-5" or so you won't see much more improvement, but that first 1-2" is REALLY important.
By signal
#53060
Most Active Antenna LNA Gain is 24 - 27 dB,

I've tested Active Antenna with 55dB Gain LNA,

here's several results

GPS Module without LNA + 55dB Active Antenna = Best

GPS Module with LNA (27dB well designed automatic gain ) + 55 dB Active Antenna = superior than the regular one

GPS Module with LNA (27dB poor designed) + 55 dB Active Antenna
= worst among 3 <- because LNA-LNA saturation.

MTK3318 module without LNA from GTOP was best one with

55dB Active Antenna from www.fis4her.com

I have nothing to do with fis4her

best regards
By no first name supplied
#53064
You'd be better off choosing a GPS module with better sensitivity than the GM-863. The SiRF III modules (EM-406 etc) are great, and the 5th gen u-bloc are even better. Of course you would lose the GSM integration.