VHF Antana Debugging

[Andrew_Trayfoot]

I have a spare patch l

Have you checked the cable from mast base to radio to be sure you have no circuit between centre pin and outer shell on all your connectors?
Most likely causes are corroded cable and badly fitted connectors.

Will double check there is no continuity between the core and shell on the patch lead between the radio and the mast foot.

I have a spare lead which I can try when the mast is back up.

 

[Boathook]

Any way to test the cables?

Cable from mast foot to aft end of port cuddy in the main cabin
Cable from aft end of port cuddy to bulkhead panel (back of the radio).

Cables are connected with barrel connectors and PL259's


With a multi meter the continuity of the non mast cables look ok0 or 1 to 2 ohms

Any suggestions?

That is a lot of connections. If the connector at the foot of the mast is in one of those plastic housings, water does get in and corrode the cable. When I renewed my aerial last winter I also renewed all the internal wire due to corrosion and moved the connection at the foot of the mast to inside the boat complete with a drip loop just incase water got past the water tight deck gland.

 

[cpedw]

I built this SWR meter. It's probably not an exact science but I use it each season and compare the results with last year. While they don't change much, I'm happy. A major limitation is power input - switch to 1 watt before use!

Derek

 

[Andrew_Trayfoot]

That is a lot of connections. If the connector at the foot of the mast is in one of those plastic housings, water does get in and corrode the cable. When I renewed my aerial last winter I also renewed all the internal wire due to corrosion and moved the connection at the foot of the mast to inside the boat complete with a drip loop just incase water got past the water tight deck gland.

Mast foot connection is actually below deck.
So new cable from there to the radio rooms like a good plan.

 

[langstonelayabout]

A CB radio SWR meter won't give you the correct reading. A meter covering the correct (marine) frequency will set you back about £120.

The glaring issue seems to be the bit betwixt the installed radio and the top end of the coax connector. connectors hide every evil known to mankind when it comes to problems.

Your simplest solution is to re-run the cable from the antenna at the top of the mast (the best place) continuously to the radio inside the cabin, via a cable gland in the deck that allows you to retrieve the cable from inside the cabin without removing the fastener. Your problems will go away and you won't need to SWR the antenna (not that many need SWRing anyway).

Make sure you use a decent cable. Try something from these people: Cables, Leads & Plugs – Nevada Radio

And seeing that Salty John is in this thread, I'll mention that I've bought my last 3 VHF antennas from him (the Metz ones) and they are excellent. Worth you considering...

 

[GTom]

A CB radio SWR meter won't give you the correct reading. A meter covering the correct (marine) frequency will set you back about £120.

The glaring issue seems to be the bit betwixt the installed radio and the top end of the coax connector. connectors hide every evil known to mankind when it comes to problems.

Your simplest solution is to re-run the cable from the antenna at the top of the mast (the best place) continuously to the radio inside the cabin, via a cable gland in the deck that allows you to retrieve the cable from inside the cabin without removing the fastener. Your problems will go away and you won't need to SWR the antenna (not that many need SWRing anyway).

Make sure you use a decent cable. Try something from these people: Cables, Leads & Plugs – Nevada Radio

And seeing that Salty John is in this thread, I'll mention that I've bought my last 3 VHF antennas from him (the Metz ones) and they are excellent. Worth you considering...

I was wondering how much use <£40 SWR meters have? This one claims to cover the VHF range: SURECOM SW-33 Mark II Mini Digital VHF UHF Radio Handheld Power SWR Meter 781055984964 | eBay

 

[Skylark]

I was wondering how much use <£40 SWR meters have? This one claims to cover the VHF range: SURECOM SW-33 Mark II Mini Digital VHF UHF Radio Handheld Power SWR Meter 781055984964 | eBay

I'm a pre-digital person so I wouldn't want one as a gift. I'm sure that it's fine for people who wish to boast of an VSWR of 1.65873425890267345:0.9999999999

I like to watch a needle move. Even better, two needles, one for radiated, one for reflected power. A Google search finds them for less than £40.

This is a bargain, albeit second hand. It will give you the required information at a glance.

SML SWR-25 Swr And Power Meter | eBay

 

[GTom]

I'm a pre-digital person so I wouldn't want one as a gift. I'm sure that it's fine for people who wish to boast of an VSWR of 1.65873425890267345:0.9999999999

I like to watch a needle move. Even better, two needles, one for radiated, one for reflected power. A Google search finds them for less than £40.

This is a bargain, albeit second hand. It will give you the required information at a glance.

SML SWR-25 Swr And Power Meter | eBay

That one is below 150Hz but got the idea

 

[Catalina36]

A technical discussion here far beyond my knowledge and understanding.

Are you able to test it with a different microphone? I had one go faulty probably because it was knocked or dropped in use.

 

[Andrew_Trayfoot]

A technical discussion here far beyond my knowledge and understanding.

Are you able to test it with a different microphone? I had one go faulty probably because it was knocked or dropped in use.

pretty sure it is an antenna problem as it appears to work better on my separate AIS antenna.

 

[Skylark]

That one is below 150Hz but got the idea

Absolutely not a problem for the purpose of problem solving marine vhf aerial & connector issues.
Remember that you’ll also need a dummy load and a couple of patch leads.
I’ve had one of the model that I linked since the early 1980s and can vouch for its usefulness.