Reconnecting UHF coax

[nevillebartos]

I'm going to have to cut the coax to get my antenna off it's old mounting spot and into a new one, am I right to just solder the inner and outer wires back together? Will I mess up the shielding / create a big loss by doing so? Any best method I should be using?

[Gearloose]

If you can post some pics of the antenna base that would be good. You may be able to de-solder the coax from the antenna base and re-route it.
If the coax has been in there for a few years it might be worth replacing the entire length anyway.
If you have to cut and join it, use a proper 50 Ohm coaxial joiner, or a couple of 50 Ohm connectors (like male and female BNC connectors).
Just soldering the centre and braid will affect the impedance, the tuning, and create losses. (The spacing between the centre and braid, type of insulation between them and thickness are some factors that affect it's impedance). It'll still work, but the performance will be degraded and you risk damaging the output stage of the radio due to reflected power.

Cheers

[nevillebartos]

Tricky to get to it for a pic at the moment but it's this kind of thing https://www.ryda.com.au/index.php/gm...uCQaAu7R8P8HAQ

Doesn't appear to be any way to de/resolder at the base.

Hasn't been in there long, maybe a month or two. Not too keen on running an entire new length right now but when I get around to fitting a work light back there I could run one at the same time.

I reckon the 50 Ohm joiners will hold me down for the time being, easy enough to come by?

[Gearloose]

A crimped connection – bugga. The best way would be to remove the PL-259 connector at the radio end (which should be a solder type or can be replaced with one), and then re-route the cable from the new antenna mounting position.
PL-259 connectors are pretty easy to fit, lots are just crimped these days and no soldering required.
Any join in the cable introduces some amount of loss, so better to have one continuous length where possible. If you have any cable left over, rather than coil it up, chop it out. The longer the cable the more loss.

For joining...
If you're handy with a small soldering iron and fiddly bits, then Jaycar should have a pair of BNC connectors – 1 x male and 1 x female (to suit RG-58 coax cable), and fit them about 150mm from the antenna base. The parts would cost about $10 or less, and maybe half an hour to fit. Crimp type are cheaper and faster, but you'd also need the correct crimp tool for the job.

This pdf link shows how to fit the male connector...

http://www.solidsealing.com/technical/documents/ns10551.pdf

Otherwise a quote from a radio shop or competent hobbiest to fit them might be easier.

[Redemptioner]

What gearloose said.

Only caveat I would add is aim for a joiner as the BNC connectors are much larger and tend to have slightly higher losses.

You loss per connector is around 1/3 of power output for each connector so you are better cutting off the one at the end of the cable (transmitter end), feeding it where it is needed and then add a new one back on the end. Same goes for each meter of cable so try and cut this down as short as possible.

[nevillebartos]

What gearloose said.

Only caveat I would add is aim for a joiner as the BNC connectors are much larger and tend to have slightly higher losses.

You loss per connector is around 1/3 of power output for each connector so you are better cutting off the one at the end of the cable (transmitter end), feeding it where it is needed and then add a new one back on the end. Same goes for each meter of cable so try and cut this down as short as possible.

Woah thats a huge loss for both connectors and cables. I run it down the back at the moment so a fair bit of additional cable length vs up front. Although that way the noise from engine bay is mostly avoided.

I'm now thinking about relocating up front, shortening cable and crimping new connector, what you guys reckon?

[Redemptioner]

Woah thats a huge loss for both connectors and cables. I run it down the back at the moment so a fair bit of additional cable length vs up front. Although that way the noise from engine bay is mostly avoided.

I'm now thinking about relocating up front, shortening cable and crimping new connector, what you guys reckon?

What "noise" do you believe the engine making that will affect the antenna/output from your UHF?

And yes thats a lot of loss that can add up really quickly, not only shortening your range but also potentially doing damage to the UHF, I take it you know not to ever remove the antenna when the UHF is turned on?

Remember you need approximately 4 times the output power to double your range so it does not take much to shorten it drastically, the less connectors and cable the better, you will also find cables ain't cables and there can be a bunch of loss just from lower grade cable. In most cases running double shielded cable is recommended for 4x4 applications due to having to run the antenna cable past high current power cables, yes it will cost twice as much but the results are worth it.

Keep in mind if you are not going long distances out into woop woop or being a convoy lead/tail then the loss in range is probably not going to affect you much as you only want to go a couple of hundred meters to your mate up the road anyways.

[Gearloose]

Agree mostly with Redemptioner, although should perhaps clarify that the loss figures would also depend on the type of connectors used. Some of the cheap Chinese ones make good attenuators. But the losses between a typical in-line PL-259 connector (good up to about 300MHz) will be greater than using BNCs (good to beyond 1GHz).
No need to say it... us detail-nazis take a lot of criticism for being pedantically PC OCD.

Anyhoo...

....
I'm now thinking about relocating up front, shortening cable and crimping new connector, what you guys reckon?

<style type="text/css">p { margin-bottom: 0.25cm; line-height:
</style>Relocating up front sounds like a good idea, shorter cable length, and there are plenty of solderless PL-259's available.

I haven't heard of Jeeps having this problem, but some car computers generate a lot of noise and spurious RF. Don't know if there's any EMI specs the manufacturers have to meet, but some VHF and UHF channels consistently register a signal until the ignition is off.

If you can thread the coax through the inner guard cavity from the firewall to the front of the vehicle and away from any other cables it can help provide some EM shielding and keep some radiated engine heat off the coax as well.
Don't neglect cleaning the earth ground points.

Depending on the set-up, type of antenna, etc, you could probably expect to get about 5~10kms range vehicle to vehicle over flat ground.
You can receive on just about anything from a piece of wet string to licking your finger and sticking it into the antenna socket. Safety Tip: If someone transmits on the radio (with said finger still in the antenna socket) you'll likely get a nasty RF burn, so don't transmit without the proper antenna connected or hold on to it if someone is transmitting.

[nevillebartos]

Thanks guys, going to give this a go now