Metz marine band VHF antenna

Ian_Edwards

Ian_Edwards

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The mast is being stepped and I want to do a quick check on the Metz, with a multi meter.
Should it check out open circuit or low resistance?
I think it should be low resitance, because it has an inductor in the base
Is this correct?
 
Check everything you can. Note the results, test when the mast is vertical. Next time the mast is down test and compare the results.
 
Not quite what I was looking for.
The imast is down and has been all winter.
I want to check it before it's stepped, it's much easier to do something about it before the rig goes in.
I will check it this morning, and note it in the log, but I still won't know if there is a problem until the mast is stepped and I can test it.
Just trying to avoid going up the mast.
I have checked with a Google search, looking for a data sheets, but without success.
 
Ian_Edwards said:
Not quite what I was looking for.
The imast is down and has been all winter.
I want to check it before it's stepped, it's much easier to do something about it before the rig goes in.
I will check it this morning, and note it in the log, but I still won't know if there is a problem until the mast is stepped and I can test it.
Just trying to avoid going up the mast.
I have checked with a Google search, looking for a data sheets, but without success.
Click to expand...
You need to 'baseline' the individual antenna. You can also check the wiring.

You can use a SWR meter, if one is available.

I had a marine electrician tell me that my Metz antenna was not working, when questioned what testing he had done he replied none! Clearly, a psychic electrician, but wrong. Returning to basic principals it worked perfectible when I did a test call before departing the yard. The resulting email to his boss, I hope, raised a laugh.
 
Thanks for the link, I've emailed them.
I have SWR meter, and I'll check it when the mast is back in.
But if I can do an obvious simple test to see if there is something wrong, before the mast goes in, it'll save a lot of time and hassle. If it is supposed to be low resistance, and I find it's open circuit ..... then I know something is wrong. The air draft is about 22.5m and I don't want to go up there unless I really have too.
 
The most likely fault will be in the coax/connectors.
Disconnect the plug at the bottom of the antenna and on the radio. Measure the resistance between the pin and shell of the connector which should be open circuit i.e. more than 10Mohm. Anything less and you might have water in the coax.
Then short the pin and shell at one end and measure the resistance between the pin and shell at the other end. It should be a couple of ohms which is the resistance up the centre wire and back down the braid screen. The actual reading will depend on the type and length of the coax.
Here are typical DC resistance figures for RG58
1648451403734.png

If all is well , replace the antenna plug with some grease/contralube and cover with self amalgamating tape.

You really need a VSWR meter to properly check the antenna.
 
Some aerial designs will show a dead short between centre pin and outer casing of plug , "N" PL259 or BNC, if checked with a multi meter on continuity. This is OK.
More likely to fail will be coupling connections in any extended cable run,
In extreme cases over many years moisture will enter the cable to the extent that the internal braid will corrode and eventually literally disappear.It will ooze out of the cable at the bottom and in some cases actually get into the radio with not very good results.
Undo any joint protecting tape and check for bright clean dry connections and then test continuity between central conductor/ braid. If any doubt new cable and plugs.
Avoid your local chandler and search out a local amateur radio outlet . Any good quality cable and plugs will do, braid quality/quantity important but no need for arm and a leg exotic low loss magic stuff.
Avoid cheapo chinese rubbish.
Preferably soldered even if you do have the correct crimp tools and know how to use them.


If you can still receive distant stations with the mast down then its probably OK if you can still talk to them its almost certainly OK.
 
Last edited:
andsarkit said:
The most likely fault will be in the coax/connectors.
Disconnect the plug at the bottom of the antenna and on the radio. Measure the resistance between the pin and shell of the connector which should be open circuit i.e. more than 10Mohm. Anything less and you might have water in the coax.
Then short the pin and shell at one end and measure the resistance between the pin and shell at the other end. It should be a couple of ohms which is the resistance up the centre wire and back down the braid screen. The actual reading will depend on the type and length of the coax.
Here are typical DC resistance figures for RG58
View attachment 132379

If all is well , replace the antenna plug with some grease/contralube and cover with self amalgamating tape.

You really need a VSWR meter to properly check the antenna.
Click to expand...
Quite hard to short the pin and the outer without climbing the mast!
 
You could look at a NanoVNA for such tests - it will plot SWR vs Frequency (without need of a VHF radio)

Some of the newer models can also measure the time of reflection, which, with a little maths, tells you where in the system the problem causing the reflections is.
 
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