I've got a GPS antenna with about 5 metres of coax (I think RG-59) plus an SMA connector. The antenna is quite light, but the cable is heavy, so it makes it tricky to put on my model aircraft.

Is it possible to shorten the cable to around 10 cm whilst maintaining its RF integrity and keeping the SMA connector?

 

Is the antenna end of the coax fixed to the antenna? If so, maybe it is soldered directly and you can unsolder it, cut the coax to the desired length, strip the new end, and re-solder to the antenna.

If you need connectors on each end, I wonder how hard it is to install new SMA connectors? Are they crimp or solder connection? Crimp might mean a ridiculously overpriced tool is required.

 

The antenna looks like this picture. I have two which are similar, so I'm okay to try something with one which might damage it, just for a test.

The cable is not removable on the antenna end (well, not without damaging the antenna.)

 

The image isn't high enough resolution for me to zoom in for detail, but is that heat-shrink tubing on the coax by the SMA connector? If so, it would be interesting to carefully cut the heat shrink tubing off to reveal how the coax is terminated to the SMA connector -- maybe by soldering? If you can't remove/re-terminate the coax, you may or may not be able to get proper heat shrink over the SMA, so you might have to suffer with electrical tape to restore it....

On the antenna end, it looks like you might have to dissect a plastic box. A job for some careful work with a Dremel and cutting wheel? Or, some careful Exacto-knife work? Or, can you crack it open at a plastic-weld joint? If you cut the antenna plastic enclosure cleanly, you can easily use some super-glue to put it together nicely at the end.

 

Inside all GPS antennas is a ceramic dielectric of some kind. It's quite delicate, so I can't go chopping anything near or inside the antenna. I'm prepared to buy some connectors and re-fit a connector on 10 cm of cable, if I need to.

 

Hello,

RG 59 is 75 Ohms as I recall.
RG 58 is 50 Ohms (thick).
RG 174 is also 50 Ohms (thin).
Maplin has crimp connectors for the cable:
http://www.maplin.co.uk/sma-crimp-plugs-26627
You will need the crimping tool too if you want to use these.

Bertus

 

Hello,

RG 59 is 75 Ohms as I recall.
RG 58 is 50 Ohms (thick).
RG 174 is also 50 Ohms (thin).
Maplin has crimp connectors for the cable:
http://www.maplin.co.uk/sma-crimp-plugs-26627
You will need the crimping tool too if you want to use these.

Bertus

Oh it's probably RG 174 then. Any guide on wire thickness?

What type of tool is a crimping tool, is it expensive?

 

Could you just get rid of the connector and solder cable directly to the board?

 

Could you just get rid of the connector and solder cable directly to the board?

I want to keep it expansible in case I need to change the GPS receiver or antenna.

 

Hello,

For the cable information take a look at this table:
http://www.pcs-electronics.com/guide_coax.php

This is a link from this EDUCYPEDIA page on RF cabling:
http://educypedia.karadimov.info/electronics/cablingrf.htm

As a crimping tool you can use this:
http://www.maplin.co.uk/coax-connector-crimping-tool-4234

Bertus

 

Ouch. That's very pricey . No easy way to do it without that, I guess?

 

Hello,

Farnell has some solder type connectors:
http://nl.farnell.com/te-connectivity-greenpar/1-1478908-0/plug-sma-straight-rg174/dp/1056357

(assuming it is RG174)

Bertus

 

Yeah, it's just a matter of economy... I can buy a GPS antenna with a fitted 10cm cable and SMA end for about £10, so I'll probably do that. I'd like to learn how to do it myself later, though.