New VHF Aerial - suggestions

[samfieldhouse]

The mast is coming down early next year for some work.
Is it sensible to fit a new VHF aerial? I have no evidence to suggest it’s been changed in recent history (10yrs+) do they suffer from UV degradation? Or just generally die?

If so, any suggestions? I have an AIS transponder but gather these can’t share an aerial without buying a box from Digital Yacht (or similar). True?

I’ll also change the aerial cable - I’m going to run it through a swan neck through the deck straight to the VHF - are all cables made equally?

And finally any tips for mousing mast cables?

 

[Gsailor]

Some vhf co-ax is better than others; afraid I cannot remember specifics. For long runs it makes sense to go for quality stuff.

I would fit a new aerial. A metz if they are still available and keep the old one for emergency use (backed up with your dedicated small packed emergency vhf aerial!)

Yes, vhf aerials 'just' cope with the AIS frequency I believe.

 

[savageseadog]

I would routinely replace at that age. Also replace all cable and connectors.

You do need a splitter box for a transponder if you want to use one aerial. I'm not sure a masthead aerial is really necessary for a yacht. I found a pushpit aerial reasonably adequate.

Make sure you use a tin plated copper coax. RG58.

For mousing I stitch through the cable and mouse line with a needle. Taping can pull off.

 

[samfieldhouse]

Terrific thank you!

 

[savageseadog]

I'll wait to be contradicted!

 

[Beelzebub]

I'll wait to be contradicted!

Agree with your post but would point out that if a masthead aerial installation is chosen, an emergency VHF aerial kept in the chart-table or somewhere close-by would be prudent.

Masts do fall down sometimes.

 

[Momac]

Shakespeare V-Tronix Stainless Steel Whip Antenna

 

[st599]

The mast is coming down early next year for some work.
Is it sensible to fit a new VHF aerial? I have no evidence to suggest it’s been changed in recent history (10yrs+) do they suffer from UV degradation? Or just generally die?

If so, any suggestions? I have an AIS transponder but gather these can’t share an aerial without buying a box from Digital Yacht (or similar). True?

I’ll also change the aerial cable - I’m going to run it through a swan neck through the deck straight to the VHF - are all cables made equally?

And finally any tips for mousing mast cables?

1) Yes, sensible to fit a new one. Metz Manta 5 are rated highly.
2) No, you'd put a large proportion of 25W in to a receiver expecting a tiny signal and let the magic smoke out. If you can't just use a second antenna on the push pit (not at the mast head as it will change the radiation pattern of the first antenna), then you need a splitter - but it's a point of failure in a safety critical system, so you need to check how it fails and only use good brands and accept it will reduce the power out of the antenna.
3) cables are not made equally, and the stuff that comes with most marine antennas is the cheapest going - on a 20m mast you'll lose 1/2 your power before the antenna. Look somewhere like Nevada radio for low loss co-ax.

 

[samfieldhouse]

Good advice thanks. I
The AIS currently runs from a different aerial mounted on the goal post, and can be plugged into the VHF in an emergency if needed.
Will check out the Manta.

 

[Rappey]

You can more than double the performance by using a quality coax so not all cables are equal .
Rg58 is the cheapest and probably the worst ,costing as little as 33p/m.
Can't remember the exact figures- 25w transmit is something like 7.5w at the masthead @75 ft of coax using rg58 due to cable loss.
As a comparison Rg400 gives 22w at masthead over 75ft but costs £10 per metre. It's silver plated , has a larger core and double outer braid.
To run a better quality coax you will need an antenna capable of taking a pl259 type plug to allow for the thicker coax.
You could consider rg-8x or rg 213 .
I would say most marine antennas are ok, its the coax that comes with them that lets them down.
I changed from rg58 to rg400 and the amount of extra radio traffic i can now hear is incredible.

 

[William_H]

You can more than double the performance by using a quality coax so not all cables are equal .
Rg58 is the cheapest and probably the worst ,costing as little as 33p/m.
Can't remember the exact figures- 25w transmit is something like 7.5w at the masthead @75 ft of coax using rg58 due to cable loss.
As a comparison Rg400 gives 22w at masthead over 75ft but costs £10 per metre. It's silver plated , has a larger core and double outer braid.
To run a better quality coax you will need an antenna capable of taking a pl259 type plug to allow for the thicker coax.
You could consider rg-8x or rg 213 .
I would say most marine antennas are ok, its the coax that comes with them that lets them down.
I changed from rg58 to rg400 and the amount of extra radio traffic i can now hear is incredible.

I would disagree with the quote "double the performance" If you consider "performance " as range then no. The range if it is line of sight is a function of square of the power. So while Rappey is correct about power loss in cable it does not result in commensurate loss of range. Plus of course range is more often limited by horizon so height of mast head and receiving antenna. So for shorter runs (small boats) RG58 is most common and OK. Tall mast better cable (lower loss) is preferred.
Re changing the antenna. Most problems will be in the cable and cable connection at the antenna. OP should decide himself on close examination of antenna fitted.
As said do not go for splitter for AIS just go for additional antenna on pushpit. ol'will

 

[savageseadog]

I've just re-read my post. It doesn't read as intended.
My suggestion that a masthead aerial i
Wasn't necessary was meant to meant to mean not necessary for AIS. A masthead aerial for VHF radio is recommended. We used a pushpit mounted aerial for our AIS transponder for a few years but RORC rules were changed to specify that the AIS aerial had to be 5m above the waterline. We now have a splitter, I don't like the extra equipment and complexity but that's the rules.

 

[PetiteFleur]

My story - I fitted a Metz aerial a few yrs ago when the mast was down for new rigging. And new better cable but my vhf stopped working 2yrs ago when returning from Holland(whip had disappeared) When I sorted it four weeks ago(using a cherry picker at local marina) I discovered that the whole unit had been loose in the bracket and had been 'wobbling' about for some time. I had already bought a Sirio replacement aerial so fitted it. The Metz does not have an integral cable so the cable is just screwed on to the base. The cable went down the mast, through an Index deck gland then a cable connector below deck. The original Metz has been refurbished and is now a spare.

 

[Rappey]

I would disagree with the quote "double the performance"

I chose my word carefully ! It's the reception that is hugely increased. Im clearly hearing transmissions that boats around me are not.
In the far Eastern end of the Solent I've often heard Falmouth coastguard, Dover coastguard and a lot of french traffic. I'm not sure how. Atmospheric skip ?
I tried to find antenna "shootouts" but its virtually impossible to find any comparisons and many have claims of performance that can't be verified..
I went with a Shakespeare squatty body 5215-d vhf antenna and a 5215-ais . There is around 29mm difference in length.

 

[Poignard]

My Glomex RA106 VHF aerial was fitted in 2003 and was still working OK in September this year when I called up a marina 100 metres away to request a catway.

 

[Bilgediver]

My Glomex RA106 VHF aerial was fitted in 2003 and was still working OK in September this year when I called up a marina 100 metres away to request a catway.

Might have even managed with a piece of wet string

 

[Poignard]

Perhaps I exaggerated, it was probably nearer 50 metres.

 

[Refueler]

My story - I fitted a Metz aerial a few yrs ago when the mast was down for new rigging. And new better cable but my vhf stopped working 2yrs ago when returning from Holland(whip had disappeared) When I sorted it four weeks ago(using a cherry picker at local marina) I discovered that the whole unit had been loose in the bracket and had been 'wobbling' about for some time. I had already bought a Sirio replacement aerial so fitted it. The Metz does not have an integral cable so the cable is just screwed on to the base. The cable went down the mast, through an Index deck gland then a cable connector below deck. The original Metz has been refurbished and is now a spare.

I had similar problem with the Metz ... I bought to replace my VTronix ... which had permanent cable and it had chafed near base of mast.

The Metz was fine for a few years - then it was poor in reception ... others reported back to me that Tx was intermittent.

When I lowered mast ...... the 'whip' literally fell out of the base ......

Repaired and back in service ........... but TBH ? Not impressed.

That old VTronix I took down ? That sits on pushpit as my emergency antenna ... was my AIS until I fitted a splitter ......... Apart from the short cable - its still showing good SWR .......... better than the Metz I have up top !!

 

[savageseadog]

I had two brand new Banten marine VHF aerials bought in a job lot. I used both of them but the quality of them was atrocious. Both bases corroded away in less than two years. The whip of the one on our masthead broke off and flew away when we hit a big wave. I later looked at the construction which was of mixed metals, they were a total mess

 

[Bilgediver]

The mast is coming down early next year for some work.
Is it sensible to fit a new VHF aerial? I have no evidence to suggest it’s been changed in recent history (10yrs+) do they suffer from UV degradation? Or just generally die?

If so, any suggestions? I have an AIS transponder but gather these can’t share an aerial without buying a box from Digital Yacht (or similar). True?

I’ll also change the aerial cable - I’m going to run it through a swan neck through the deck straight to the VHF - are all cables made equally?

And finally any tips for mousing mast cables?

Antennas can suffer from many things sitting up there exposed to the wind and weather and possibly resulting in rain penetration of the antenna connection and moisture travelling down the coax. This may often be detected by an increasing lack of expected performance. Pay good attention to the masthead connection so that further unnecessary trips to the masthead are avoided.

I would avoid connecting an AIS transponder (transmitter) to the same antenna as the main VHF as although theoretically possible they would be fighting each other for access to the antenna possibly at times VHF where the radio was in use for a conversation. The AIS will work perfectly well using its own antenna at another location on the boat.

No not all cables are made equally and some are of very doubtful quality. Tinned copper coax is the better choice however beware as some of the cheaper brands may be totally unsuitable for such an exposed location regarding both the cover material and the material used for the conductors.