VHF aerial checks?

[Graeme9]

Is there any way to check the integrity of the VHF aerial while the mast is off?

Our VHF radio transmissions were not working before the season ended. We checked the radio using our emergency antenna. I have checked the cable for continuity and insulation resistance and the cable all appears ok throughout the run from the radio to the top of the mast. The aerial connection is a solderless connection and I can't see any way to check that this connection is good.
I would like to get this sorted before the mast is replaced.

All help and advice gratefully received.

 

[Alpha22]

An SWR meter would give you an indication of power out and reflected power. Make sure you are using one for VHF (144-145khz. Typical Ham radio spec) not a £10 CB radio one.

Ask a local radio ham... its right up their street and they may well have the gear already.

 

[Twister_Ken]

Something similar happened to us a couple of seasons back. Turned out the aerial was at fault. One of those slightly whippy ones with a Windex sleeved over it. There was, apparently, a break in the aerial core so that only a few cms of it where actually collecting and radiating signals. Free replacement by embarrassed supplier who also refunded the installer's costs.

 

[Martin_J]

As Alpha22 says... Try and find a local radio Ham to bring their SWR meter.. They should also be able to tell you how much power your radio is actually putting out, what precise frequency your aerial is tuned around, how much is being reflected and perhaps even how much (in the way of millimeters) to shorten the aerial by to bring the max power out at the Channel 16 frequency.

 

[Martin_J]

Your profile doesn't say where you are...

If you knew the make of the aerial and whether the cable is removable (from the base of the aerial), then someone might be local to you and have a spare cable/aerial of similar design that you could try whilst the mast is down.

 

[lw395]

An SWR meter would give you an indication of power out and reflected power. Make sure you are using one for VHF (144-145khz. Typical Ham radio spec) not a £10 CB radio one.

Ask a local radio ham... its right up their street and they may well have the gear already.

Wiki:
Marine VHF radio refers to the radio frequency range between 156.0 and 162.025 MHz, inclusive.
The trouble with VSWR measurement is that a lossy coax will often have a fairly good VSWR, as the power is absorbed not reflected.
VSWR will help find breaks and shorts.
A comparative reception test is as good as you can do, if you can borrow a known good aerial.

 

[Martin_J]

A radio HAM might use something like the MFJ-259B...
http://www.mfjenterprises.com/Product.php?productid=MFJ-259B
This will measure cable loss, length of co-ax and distance to a short or open circuit as well as the resonant frequency of the whole antenna system.
I guess it's more than just a simple SWR meter...