VHF cable

[Jegs]

Can anyone tell me how to identify one co-axial cable from another?
I've got a drum of cable that I used when installing a satellite dish which I think is RG 58 & hope this may be suitable.

Many thanks

John G

 

[Salty John]

Satellite/TV cable is 75 ohm, VHF cable is 50 ohm.

 

[wotayottie]

RG58 cable has it printed on the outside. the output stage of your vhf radio will be 50 ohm impedance and ideally you will want the cable to match this. 70 ohm is used for vhf (your old tv was vhf) but the mismatch to your radio would cause a loss of signal at best and might even blow the output stages though I doubt the latter.

 

[MM5AHO]

Size is also a help to identification. (but not a failsafe)
Measure the outside diameter. If its about 5mm, then its likely RG58, 6mm Mini8 (a superior 50 ohm cable than RG58), about 10mm it could be RG213. (even better)
Colour of the outside: brown - probably TV or satellite and not suitable for Marine VHF, black probably OK, Grey probably OK.
Another key to quality is to check the amount of braid. Strip some of the outer insulation off (this is a destructive test, don't do it to a part you need, or a length thats only just long enough), and see how dense the braid is (outer mesh of copper). If you can easily see through it, its el-cheapo. If its fairly thick - can't see the inner insulator though it, then its better stuff.

 

[colvic987]

rg58 is the cable you require, more info about marine vhf and accessories here

http://www.glomex.it/files/glomex-2007-en.pdf

 

[William_H]

A bit depends on how long the VHF cable run is going to be. If it is really short run 1 or 2 metres it won't matter much but if you are running a cable up to the top of a mast 10 metres then there will be a lot of losses and the characteristic impedance of the cable becomes the main load for the transmitter. So more losses as transmitter throttles back due to incorrect load.

So you need to confirm it is the correct cable (usually written on the cable) If you are not sure buy some new stuff. If it is a long run then go to RG8U heavy cable with much less loss. olewill

 

[Jegs]

Many thanks for your informative & helpful replies.

John G