How to Check VHF cable/antenna

[exapp]

Hello,

Have a new Ray54e and Antenna. VHF reception is a little noisy and can't hear as much chatter as i would expect (but that could be the rain keeping the fairweather types at home).

Is it possible to check a VHF cable with a multimeter?

Should i get continuity, what resistance should i expect ?

Regards,

Exapp

 

[ShaunG]

Multimeter won't tell you much i am afraid. The only way to test your aerial and cable is with a VSWR meter, you can pick them up starting from £10, it will be invaluable in sourcing aerial problems, people are always asking to borrow mine.

Good luck

 

[savageseadog]

Sometimes there is a dead short between inner and outer I'm sorry to say. It's not a short at VHF frequencies.

 

[exapp]

thanks for info how does a VSWR meter work? Does it check antenna and cable or just antenna? Where would i get one ??? Maplins??

Exapp

 

[DaveS]

I bought a VSWR meter a few days ago from Waters and Stanton for £30 on the advice of another poster (search previous threads for link). I have yet to try it, but it looks the biz. I thought that was a good price (RS's cheapest was £120) but if, as has been suggested, you can get one (right frequency?) for £10 then you might want to seek further.

(Edit - haven't answered the rest of your query!)

Basically you plug it in between the radio and the cable to the antenna, transmit, and it shows the power being sent down the cable and the power being reflected back. In an ideal world all transmitted power would go down and none would come back, but the meter will show how far away from this ideal your setup actually is, and give an indication as to whether you need to worry / do something.

 

[wotayottie]

it checks how much of the signal you send up the wire on transmit is reflected back down to the set and how much goes out into the ether. more reflection = worse aerial. cant tell cable from aerial but then I would not recommend replacing cable alone unless you know what you are doing.

the aerial would need to be really duff to affect reception - transmission always fails first. if you can transmit and be received then your aerial is good enough to receive.

 

[Billjratt]

If you don't have a SWR meter, do you have an ammeter on the boat? When you press transmit on high power (25watt) you should draw about 5amps. Less than this would indicate the radio sensing high SWR and shutting down the power to stop damage (self destruction). You don't need to whistle or anything, just press the mike key and look at the amps drawn.
If you don't get a good current draw, it's most likely the aerial cable or connections are poor. If you take a plug apart and the wire is black instead of copper coloured, you're on the way to trouble.

 

[brianrunyard]

I've got VSWR meter, where are you?

 

[st599]

[ QUOTE ]
cant tell cable from aerial but then I would not recommend replacing cable alone unless you know what you are doing.

[/ QUOTE ]

If you replace the Antenna with a 50 ohm load, then you can check the cable. NB. the load must be rated to above the transmit power.