VHF aerial and high VSWR

[MagicalArmchair]

I posted this on PBOs forum as it was a more general, non Bavaria specific, question - however, it appears to have grown into one...

https://forums.ybw.com/index.php?threads/ais-700-vswr-fault.533851/#post-7033155

The AIS 700 reports high VSWR. The final poster asks "Just a thought, do you have a deck connector? These can get water in and this would effect SWR as it changes impedance" - I am assuming the VHF aerial is all factory fit, I once again kick myself for not photographing every square foot of the boat last time I was on her (and I won't be back there for three weeks now, boo). Is there a deck connector? Anyone else had this issue and had to replace their VHF aerial? I sense a trip up the mast in the offing......

[Salty]

I have a masthead vhf transmitting and receiving aerial which used to be shared with a class “B” AIS transmitting system via an aerial splitter. Periodically the AIS system would show a High VSWR” warning notice on screen, but poking a button or two on the Icom AIS instrument usually resulted in the warning disappearing off the screen. I don’t know what caused it, but having had  a stern “A” frame fitted a couple of years after installing the AIS, I decided to fit a separate transmitting aerial for the AIS. That aerial is mounted on top of the “A” frame where it complies with the Icom recommendations regarding height above head and distance away from other transmitting or receiving aerials and human bodies and distance away from other instruments etc., and is connected directly to the transmitting output from the AIS. The splitter was taken out of the system such that the main vhf radio continues to use the masthead aerial while the AIS now has its own dedicated transmitting aerial.  The High VSWR warning previously seen has not returned.

[Symphony]

Neither of my Bavarias have had deck connections for the VHF, but in line with good practice the cable goes through a deck gland and the connection is a plug and socket inside the boat. Remove the panel in the deck head, usually around where the mast post is and you will find all the connections for all the mast cables. However if there is a leak through the gland water can of course get into the interior connections, but such leaks are usually pretty obvious as the water drips onto the panel and then into the boat!

It is of course possible that someone in the past has replaced the internal connection with a connecting deck plug, but think it most unlikely.

[MagicalArmchair]

I want to take a replacement PL 259 plug down to the boat, so I can eliminate the possibility of it being a bad plug/badly fitted PL 259. The RG cable, I remember, seemed quite thick to the VHF aerial (far thicker than the supplied patch from the VHF radio to the AIS 700). Is it RG 213 cable as standard factory fit? - It certainly seems too thick to be RG 6.

[MagicalArmchair]

I have found the culprit. As Sympony said, the cables travel through the deck via a gland. That gland leaks like a sieve, meaning the union between the RG8 connected directly to the VHF aerial and the RG213 cable that connects to the AIS unit was corroded to hell.

The offending deck gland:



The corroded union:



Added to that, the plug on the RG8 side just fell apart in my hands when I undid it from the union. The core had never been soldered into the plug. I went to refit the plug, only to find the the braid just fell apart in my hands. I cut a few inches off, and the coax improved a little. It was still very corroded though.

Corroded coax:



When I refitted the union and the PL259 to the RG8 cable, the VSWR was still too high, so its going to be a replace VHF/Coax job. Some questions for the sage panel of Bavaria experts:

• This is almost certainly the factory fit VHF aerial. Is the coax attached directly to the aerial at the top of the mast or is the a PL259 I can undo when I get there? I ran out of time to check when I was there yesterday.
• On changing the cable, is there a cable gland at the mast head that needs to be undone? Or can I simply tie a mousing cable to the old coax and pull it through without dismantling anything at the mast head?
• Is the deck gland factory fit also? I note the one on the transom was leaking also, so I took that apart and revealed it. Can you get a replacement rubber inner for it? How have others made these glands water tight?
• Does anyone have any photos of their head box?? Or their VHF aerial setup aloft please?

[SorinCT]

I had the same issue last week and ended up being a bad solder/connector installation. Just make sure everything is perfect down below before climbing up.

[Yngmar]

Is the deck gland factory fit also? I note the one on the transom was leaking also, so I took that apart and revealed it. Can you get a replacement rubber inner for it? How have others made these glands water tight?

The deck gland is factory fit, we have the same ones. These are designed to seal around a single cable and that's how it is from original. If used like that, they are watertight.

Someone must've replaced that single cable with a bundle of separate wires, probably due to replacements/upgrades. This doesn't work, because the wires are round and thus there are gaps between them, much like there are in a stack of cylinders.

Simplest fix for your situation is to squeeze some sealant between the individual wires in the bundle, but very carefully as it's easy to make a mess of it. Or install a different type of deck gland or waterproof plug/socket.

[Lyra]

From your pictures it seems that the coax cable is a non  tinned type - so could be corrosion of the copper strands (inner and sheath) - you may be surprised as to how deep into the  insulation this corrosion creeps so cutting several cm at the ends do not help much.
I know that on my boat I took great care in making the connections and it did not help much with the VSWR - my plan is to replace the cable from mast top into the cabin.

[SorinCT]

One radio enthusiast told me there are tools and different ways how to troubleshoot and pinpoint the cause of a high VSWR, although best practice is to check the wiring and connectors yourself as you get more familiar with the setup and start to find problems you did not know you had 

[MagicalArmchair]

Now I am resolved to go up the mast at the weekend, I have my new VHF aerial plus coax. It's one of these (or one very like it):

http://www.glomex.it/leisure/eng/antenna-vhf-RA106SLSSB25.php

It has a RA106 solderless connector at the base of the antenna, one of these: http://www.glomex.it/leisure/front/upload/usermanual_RA106solderless.pdf

I don't fancy making the connection whilst aloft, so the order of the day will be the below, I think, unless anyone can spot anything daft about it.

• Make up the RA106 connection in the garage, so we will be feeding the coax DOWN the mast, as opposed to pulling it UP the mast.
• Prepare by using binoculars to look up the mast, and hope the bracket already there will fit the new aerial. Cut the plug off the bottom end, pull it through the cable gland, and get it the bottom of the mast, on deck, ready to be pulled down (I'd rather do it this way as that gland will offer up a lot of friction when pulling the cable through).
  
• Climb up the mast, don't fall off the mast.
• Remove old VHF aerial
• (optional) If the old VHF bracket does not work with the new VHF, drill out rivets and rivet on the new Glomex one with monel rivets, being sure to use TEF-GEL to stop any galvanic corrosion.   
• Attach the new aerial to the bracket
• Cut RG58 cable off the old VH aerial, attach the end of the new coax to the end of the old coax using whipping twine. Wrap the connection in electrical tape making sure the width of the cable stays broadly the same.
• Hope the lovely assistant can spare 30 seconds away from stopping the three kids down below from jumping overboard, ask said assistant to pull the cable through. I'll give the cable a light coat of silicone lube to help it along its way. Feed the cable down the mast from the top as Liz pulls it from below.
• Climb down the mast, don't fall off the mast.
• Post cable end through deck.
• Attach plug.
• Test.
• Seal up deck gland.

Have I missed anything? There is a distinct possibility I'll need to come down to pull the cable through as the first mate might be busy with the crew. Anything daft anyone can spot?

I'll go up on the spare main Halyard, with the spinny halyard as my backup line with my fall preventer on it.

[Yngmar]

That looks a lot like the original(?) one we got our mast, so you might be in luck with the bracket.

Don't use Tef-Gel, it's a scandalous rip-off and Duralac is far better suited for the job (although not exactly cheap either - buy smallest tube as it does go off after a couple years and you only use a bit usually).

Use liquid soap instead of silicone grease as temporary lubricant. It'll wash away in the future, which is desirable. Silicone grease will stay forever and the cable ends up coated in dust/dirt and/or forever greases anything else it may touch in there.

Squeeze any connectors full of silicone grease before plugging them in, then wipe off excess squeezeout - it'll keep any moisture out and thus prevents corrosion. This tip makes a huge difference on boats I've found.

Good luck, especially with the not falling off part 

[Symphony]

Rather you than me! Pity your children are so young as once they get to teenage they become the modern equivalent of chimney boys as they seem to love going up the mast. Better having two people doing the pulling through bit as the top one will need to feed the new cable through and keep a bit of tension on to keep it straight. Probably better the lower one is on deck as well rather than inside as pretty sure there will need to be communication between the two.

[MagicalArmchair]

Secretly, I quite enjoy going up the mast. I have some good, solid kit which helps with the general anxiety related to the downsides of gravity (no pun intended).

The boy setting up my kit on my old boat .



Typical, Saturday is now going to be a howling gale with 40mph gusts and rain - not ideal for going aloft. Sunday is looking a better day for it.

Re the soap, I'm away's shy just in case there is something eventually corrosive in it (such as a scent additive for example), I want this cable to still be fine in 20 years time. What about something made for the job like https://www.screwfix.com/p/ideal-yellow-77-wire-cable-pulling-lubricant-950ml/44462 - then I have it in stock for future use too?

Good idea re the silicon grease!

[MagicalArmchair]

At the weekend I went up the mast, all the way to the top, twice (my quads and shoulders are telling me all about it today!).



The old aerial bracket will fit the new aerial, so that is the good news, the bad news is that the splice on the spare halyard means I can't get quite to the top without standing with locked knees in the stirrups, making it quite hard to work, and any work on the aerial is done at full extension.

To try and get the nut off the bottom of the aerial, I gripped the top section with my mulgrips. As the plastic split (I gripped a bit too high up the aerial to start with) water poured out of the body, showing water had managed to enter the aerial body itself - it had probably then travelled all the way down the coax, destroying it as it did. I, rather stupidly, didn't tie the mulgrips on to bosuns chair, they slipped and fell straight into the water (thankfully not the deck! (or onto any hapless passer by...)), however, with no mulgrips, with the spanner on the nut, the aerial just span no matter how hard I tried to grip the top section with my pliers. I did consider drilling out the bracket and replacing that too, however I had forgotten my Duralac also, so I didn't want to start that process. Drilling fully extended didn't feel desperately sensible at any rate...

I am left ordering new mulgrips, and going back to have another try in a few weekends time when my quads have recovered. What is my best option? I'm surprised that nut has galled so badly onto the body of the aerial/the bottom of the bracket (Alley onto Stainless I suppose?) 

• Use some Plusgas, spanner and mulgrips should get it undone do we think? Or am I wasting time there?
• A nut splitter just won't work as too much force will be required. What about a Dremel with a cutting disc? Sounds more dicey than just drilling off the bracket?
• Do I get on with it and just drill out and replace the bracket and stop messing around? Installing monel rivets at height using my long, levered, riveters, is not for the faint hearted. 

Either way, I'm going to try and pull a bit of that splice into the mast (without getting it wedged), to try and get a bit higher up... come to think of it, I could always cut the splice off and replace it with a Bowline?? The primary use for this halyard will be going aloft anyway?

[Yngmar]

Dremel would do the job, or simply a small hacksaw down the slot of the bracket.

When doing jobs up the mast I find it helpful to do the entire job in my head first. Not just plan it, but do every move. Usually that helps me find three more things I need to take up there with me

[MagicalArmchair]

The heat generated from the Dremel grinding disc might help break the galling of the nut onto the aerial also if it doesn't free off easily this time.

I'm going to chop the splice off the end of the rope. I am uncomfortable (on reflection) going up on someone else's splice anyway (it looked pretty good mind you), so I'll chop the end off the spare 12mm Halyard and join it on to my 10mm climbing rope with a Flemish bend and two stopping knots, and that should let me get a good foot higher, making the whole job a lot easier and safer. The knot I joined my climbing rope to the halyard with was a double bowline finished with two half hitches (which I've always used when climbing masts), however, reading around it, eventually that knot might kill me .

New Mulgrips get delivered today! This time I'll remember to tie them on to myself.... probably....

[Symphony]

Suggest you replace the splice with a Selden halyard knot to a shackle. This knot is less than 50mm long, much less than a splice and will butt right up to the sheave. I have no splices on any of my running rigging.

[MagicalArmchair]

Suggest you replace the splice with a Selden halyard knot to a shackle. This knot is less than 50mm long, much less than a splice and will butt right up to the sheave. I have no splices on any of my running rigging.

Interesting. I could put one of these on the end of my halyard I use to pull my "climbing" rope up with (with the TopClimber gear, you must ascend on a 10mm braid on braid, so you hoist that first, before climbing that rope), and one on the climbing rope itself, shackling the two together and then seizing the shackles? This would make it quicker to set the kit up in future too I suppose.

[MagicalArmchair]

Up I went again at the weekend, and after an hour of swearing up the mast, and a number of bags up and down the mast of tools from the long suffering first mate, the VHF aerial was replaced and the wire pulled through! Huzzah thought I. Job done.

I connected the aerial coax to the boats internal coax at the mast foot and casually turned on the plotter to experience the the satisfaction of a complicated job, completed, when to my horror, I see:



At this point I considered it a Raymarine conspiracy, so I wired my emergency VHF aerial, purchased off Ebay, up to the AIS. The things connector is rusty, the coax is thin and twisted, the aerial itself, slightly rusty... 1.7 VSWR!! It worked! So it is not the AIS giving a duff reading - the VSWR really is high still.

Meaning one of the following is true:

• I've cocked up the connection to the aerial itself (hard to do, it's a pretty simple fitting process). Also the least fun one, as it means another trip up the mast  .
• I've cocked up the plug on the bottom of the aerial coax.
• The brand new connector I purchased from Amazon (one of these:https://www.amazon.co.uk/gp/product/B082G1HW3L) is funky.
• (The most likely) The wire INSIDE the boat, that runs from the mast foot to the nav station, is where the noise was all along. The big, fat wire, in the controlled, dry environment inside the boat! This one, I guess, will be hard to pull through as there will be many cable ties along its route?

To get that wire replaced, is it just taking down the headlining panels amidships in the saloon I suppose? I will test the theory by plugging my emergency vhf aerial into the connector at the mast foot and confirm the high VSWR is still there. I have replaced the plug at the AIS end of this wire but NOT at the mast foot end, so I'll try that first.

[SorinCT]

Beet way to check is replace the anaconda coaxial from mast step to VHF. If you figure out a nice way to remove or route the new cable through the same space, please share. I still have the wire casualy hangong on to the handrails in the saloon 

[MagicalArmchair]

Beet way to check is replace the anaconda coaxial from mast step to VHF. If you figure out a nice way to remove or route the new cable through the same space, please share. I still have the wire casualy hangong on to the handrails in the saloon 

Yup, I have ordered some pre made up coax to try and weave its way aft. Interesting, why did you replace your coax? Same reason? High VSWR?

If I find a good route, I'll post it up here. I am sailing for a week with the kiddies, so I doubt taking the boat into her component parts when we are on holiday will win me any friends after going up the mast last weekend

[SorinCT]

When i got the boat there were some reported issues from previous owner and i decided to change the whole cable including antenna, for good measure. Mast was already down so not so difficult. The lenght from mast foot to VHF has been kind of hanging in the saloon ever since.
While fiddling with the new electronics and partially redoing some of the wiring, i noticed the route for the old thick cable which was never removed. I might end up installing the radar on the mast and would need to route at least a power cable in the same way. Ideally i would remove the headlining only once because i am sure it will be a nightmare to put back. The area near the mast foot has sighs of previous leaks and is not as esthetic as the rest.

[Mirror45184]

To solve the issue of leaking glands for the deck penetration I used some bicycle inner tube over the gland and to the base of the mast. the outlet end hangs down, so water will not normally flow up it!
Cheers

[MagicalArmchair]

To solve the issue of leaking glands for the deck penetration I used some bicycle inner tube over the gland and to the base of the mast. the outlet end hangs down, so water will not normally flow up it!
Cheers

Thank you, I used the same technique to seal up the glands on Mirage also!

Now the boat is back, I've had a few more hours to look at this. I replaced the PL259 plug on the end of the RG213 cable (the fat cable that runs the VHF cable aft) at the mastfoot inside the boat, and noted that the cable was high quality and uncorroded. I also replaced the union, and presto, the VSWR wasn't great, but it was good enough to make the Raymarine gear stop shouting. The VSWR was now 1:3.9, the upper limit that makes the AIS start shouting is 1:5.0. Important to note that it worked well when we delivered the boat even with the VSWR at 1:7.0 (!!).

What fiasco that was!

[dgmultimedia]

I had a similar problem - multiple small cables going through one compression gland - ITS BOUND TO LEAK - its not where the cables exit the mast at bottom and enter the gland thats to problem - its water that runs down the cables inside the mast from the top and runs through the gaps between the cables even though they are wrapped with self-amalgamating tape.
The trick is to form an upward going loop and leave the cables separate ( not wrapped ) after they exit the mast -  the water can drain on to the deck,  then use ordinary silicon sealant between the cables for an inch or two before and through the gland, you can wrap SA tape over the gland nut and cables for an inch or 2 if required for physical protection...

Re PL259, UHF plugs they are notorious for the inner wire breaking after assembly - you have to be very carful that the CABLE and the PIN section are not twisted during assembly of the screen clamp....causes Very High SWR reading - easily checked with a portable SRW/Power meter at the radio end of the coax.
Usual route for the Coax is behind the Lockers that are just under the deck - there are easily removable thin ply trim panels at the back of all these - new cables can be lead with a mouse line or flat wire cable snake from the port inside the front cabin under the mast down to the side cabinets - the space runs in front of the bulkhead and is reasonably accessible..