GPS module, long ANT wire

i recently got this GPS module., its was working fine in 3.3V and got sattelites fix very fast.

In my current project i need to transfer the ANT outside of the plastic Box i have , So i cut the wire and i solder an extra long cable 10cm , i made the connections very good,
the problem is that i get response from GPS UBLOX module , but i got no sattelites, is like the ant is not workign any more, and i am thinking that maybe the current isn’t enough sould i try powering it with 5v…is this cable working like attenuator?

(This module Supports 3.3v-5V)

Unless you use good quality RF SMA connectors and coax cable with low attenation at GPS frequencies you very well could get worst or no reception then just leaving it on board inside case. The greater then 1GHz frequency that GPS uses almost an art form to design and build antenna, lead wire, (software type would just not understand :wink: ). Be aware on those external GPS antennas that there is a + DC voltage needed on the wire to power the internal RF amplifier in active antennas and not for passive antennas.

Lefty

Thanks Lefty , so i was thinking very wrong when i decide to extend it , it is just not possible

i will solder the same type cable as the stock one, but sorter , as sorter as possible ,
then i will transfer the entire module where i want it , and i will extend the 3v,gnd,tx,rx connectors

Do you think it will operate normal again , or i have to purchace a new replacement ant?

Unfortunately, without special tools it is very difficult to repair that type of antenna cable and have it function as well as when it was new.

Show a picture of the soldering and tell us what kind of cable you used, then we can give a guess on if you destroyed the module.

Extending GPS antennas with cable is always a very, very bad idea. That is why almost all GPS antenna have the electronics embedded, and the cable running from them is just for power and the serial NMEA stream. This you can run many feets without issue. No quite so with 1 GHz+ signals.

// Per.

Zapro:
Show a picture of the soldering and tell us what kind of cable you used, then we can give a guess on if you destroyed the module.

Extending GPS antennas with cable is always a very, very bad idea. That is why almost all GPS antenna have the electronics embedded, and the cable running from them is just for power and the serial NMEA stream. This you can run many feets without issue. No quite so with 1 GHz+ signals.

// Per.

I don't agree with that statement. While most modern GPS antenna modules are 'active' in that the have internal RF amplifiers to amplify and filter the GPS RF signal (that is why they require a positive DC voltage applied to the center pin) they do not have the circuitry that can process/decode the RF signal and generate a NMEA stream, that is the function of the board the active antenna is cabled to.

Lefty

I think he means take the entire GPS module with antenna and circuitry, put it in a sealed box, and put it outside.

So, as he says, only power, ground, and data are required to run a long distance.

polymorph:
I think he means take the entire GPS module with antenna and circuitry, put it in a sealed box, and put it outside.
Maybe, but he stated " That is why almost all GPS antenna have the electronics embedded....."
So, as he says, only power, ground, and data are required to run a long distance.

Sending arduino TTL level serial data has limits to how long and/or how fast before data becomes a problem. Line driver/receiver chips can extend the distance.

You can safely extend the serial TTL connection without an extra transceiver if some care is used.

I think the default data rate for NMEA data is 4800 baud which is slow. Use shielded twisted pair like CAT5e and you should be able to get 50' - 100' without using additional transceivers.

Connect RX and gnd to one pair and TX and gnd to the other pair. Do not put RX and TX on one pair. They do not share return currents. Meaning that the the TX signal wire would try to use the RX signal wire as part of the return path and a little bit of the signals will appear on the wrong wire, called crosstalk. At some point that would cause problems. Connect power and ground through the extra pairs that are not being used for data.

I have done something like this before with a GPS receiver and it worked well. I do not remember the exact distance but it worked over a longer distance than expected.

If it does not work and you need it to work over longer distances at higher speeds, you can use the same CAT5e and add a DS8921 transceiver.

MIDI transceivers also give long distances, good noise immunity and they are inexpensive to build. I understand that MIDI is still used for wiring stage lighting controllers.

GPS is at 1.5GHz and 1.2GHz. RG6 and F connectors from the local hardware-mart would probably be (barely) useable for short runs at this frequency. The GPS unit is most likely matched to 50-ohms. 75-ohm cabling would not be too terrible a match. If you built a good antenna, I could see it working at the end of 10m of RG6 without too much trouble. Here's a possible fixed outdoor antenna design:

If you went farther afield than Home Depot, you could lay your hands on LMR400 and SMA or N connectors that would be better suited.

I'd like to see pix of what the O/P was attempting.

Sounds like a minimum requirement is teflon insulated silver-plated coax (low loss
at GHz frequencies) and good impedance-matched joins (with thin coax that's real
tricky without using the right kind of coax connector).

GPS signals are close to the noise-floor, you cannot afford to attenuate them more
than a fraction.

i repair it successfully with a spare cable for ANTs ...