VHF antenna - where?

[sarabande]

If the pushpit mounted aerial is at 3.5m ASL, then the official range to horizon is 6.7km (3.7 nMi) . Then you add the height of decent rescue vessel's aerial, and you get 10, 20, 30km (other distances are available).

I'd rather have a pushpit aerial which was easily checked and maintained, than one which was in a more vulnerable place and which, if it fails, cannot be mended. Mission critical, and all that. The best usage of a mast head aerial is to stop gulls landing on the cap

Nothing to stop the OP having both installed with a high-quality switch sending to EITHER the mast one, OR to the pushpit one . I think the SWR tuning would not be a problem, but Rev Morris will have the answer.

Another possibility is to have the aerial at the stern on a pole which can be extended upwards to says 5.5m AS, giving 4.5nMi.

 

[geem]

Fit one at mast head, then to guard against a dismasting when you will surely need urgent assistance or more mundanely guard against connection failure at mast head at a time or place when ascending the mast is not practical, fit one on the pushpit. Ideally a half or full wave length one as they give a bit more gain and extra height not an issue there - much much better than a handheld with its truncated aerial. Changeover at radio plug easy peasy if mast one not working. I could tell if my mast head connection was playing up by AIS receiver suddenly only showing boats moderately close to hand and weather forecast unusually blurred. If mast has fallen down dont bother with that check

Pushpit one good for at least 5 miles on mine but poor at 15 miles

Our mainmast antenna

If the pushpit mounted aerial is at 3.5m ASL, then the official range to horizon is 6.7km (3.7 nMi) . Then you add the height of decent rescue vessel's aerial, and you get 10, 20, 30km (other metrics are available).

I'd rather have a pushpit aerial which was easily checked and maintained, than one which was in a more vulnerable place and which, if it fails, cannot be mended. Mission critical, and all that. The best usage of a mast head aerial is to stop gulls landing on the cap

Nothing to stop the OP having both installed with a high-quality switch sending to EITHER the mast one, OR to the pushpit one . I think the SWR tuning would not be a problem, but Rev Morris will have the answer.

Another possibility is to have the aerial at the stern on a pole which can be extended upwards to says 5.5m AS, giving 4.5nMi.

I just don't get it. The mast head antenna has superior range. Between the radio and the antenna there is a cable with a single joint at the antenna end. This is the only place a problem can occur. Unless the antenna fails or the joint is bad you won't have a problem. In either location the repair or replacement is easy. Its the same repair. Is the bigger issue here that some people won't climb the mast? I have replaced an antenna at our masthead 60ft up. Also swapped the masthead navigation light and swapped the Raymarine wind instrument over the years. I don't have a fear for heights so I put the antennas where they are out of harms way and where they are most effective as an antenna. That's the masthead

 

[srm]

with a high-quality switch sending to EITHER the mast one, OR to the pushpit one

Added complication and cost, simply unplug the one antenna cable and plug in the other. Much more reliable than a switch that may be unused for a few years.

 

[oldmanofthehills]

Our mainmast antenna

I just don't get it. The mast head antenna has superior range. Between the radio and the antenna there is a cable with a single joint at the antenna end. This is the only place a problem can occur. Unless the antenna fails or the joint is bad you won't have a problem. In either location the repair or replacement is easy. Its the same repair. Is the bigger issue here that some people won't climb the mast? I have replaced an antenna at our masthead 60ft up. Also swapped the masthead navigation light and swapped the Raymarine wind instrument over the years. I don't have a fear for heights so I put the antennas where they are out of harms way and where they are most effective as an antenna. That's the masthead

Bully for you if you can climb 60ft mast in heavy weather when you need to make an urgent call on behalf of yourself or a n other. Indeed bad weather disturbing the connection is a possibility. At my age 73 with permanently damaged arm I greatly dislike going up even when on the hard. And what do you do if dismasted?

The OP said he had two aerials, and even if he had not they are a mere £40 which is trivial in terms of boat costs. So why not ensure your safety and convenience by having a backup aerial the same as any lifeboat, decent fishing boat, and many motorboats?

Obviously a ketch or schooner gives optimum position for the back up, but while cruising and waiting for yard to do the mast climbing bit, our pushpit mounted aerial did ok

 

[Buck Turgidson]

We all carry an emergency antenna with a long cable right?
In the very unlikely case of the mast coming down offshore you are going to jury rig something to get you home and the spare antenna is going on top of that!
For every other case your mast head antenna is the optimum solution.

 

[oldmanofthehills]

We all carry an emergency antenna with a long cable right?
In the very unlikely case of the mast coming down offshore you are going to jury rig something to get you home and the spare antenna is going on top of that!
For every other case your mast head antenna is the optimum solution.

We dont all carry long emergency cable, some of us fit the alternate aerial in a suitable post emergency place just like rescue services and commercial craft do. When you half awash and trying to prevent fallen mast from smashing the hull, the last thing you want to do is feret around for your long cabled item and find somewhere to mount things. Basic Safety

 

[geem]

Bully for you if you can climb 60ft mast in heavy weather when you need to make an urgent call on behalf of yourself or a n other. Indeed bad weather disturbing the connection is a possibility. At my age 73 with permanently damaged arm I greatly dislike going up even when on the hard. And what do you do if dismasted?

The OP said he had two aerials, and even if he had not they are a mere £40 which is trivial in terms of boat costs. So why not ensure your safety and convenience by having a backup aerial the same as any lifeboat, decent fishing boat, and many motorboats?

Obviously a ketch or schooner gives optimum position for the back up, but while cruising and waiting for yard to do the mast climbing bit, our pushpit mounted aerial did ok

Carry a spare antenna that can be plugged in to the radio. The American requirements for installation of the vhf antenna stipulate that a person should not come closer than 1m of the antenna whilst it is in use. This is hard to do when it is installed on the pushpit of a small boat.

 

[oldmanofthehills]

Carry a spare antenna that can be plugged in to the radio. The American requirements for installation of the vhf antenna stipulate that a person should not come closer than 1m of the antenna whilst it is in use. This is hard to do when it is installed on the pushpit of a small boat.

The risks from radiation are small and the any restriction assumes permanent continuous use. Most guidance is 0.305m (1ft) while in use (refering to Federal Communications Commission (FCC) guidelines for 100W unit) so I imagine any 1m rule is product disclaimer in litigatious USA rather than scientific. Leisure VHFs are 25 W so another factor of 4 less radiation.

My pushpit aerial midpoint is about 1m from my tiller position sitting down and masts on top of fishing boats are probably about that far above skippers head. Using my slightly lower power 5W handheld I certainly need it 0.03m (1inch) from ear and my arms cannot get it 1m away.

If I cant get a may day out the risk of close future death is much more significant than minor risk of cancer some 30 years hence - anyway at age 73 trivial cancer risk at 103 seems not to weigh heavily

 

[Wansworth]

If the pushpit mounted aerial is at 3.5m ASL, then the official range to horizon is 6.7km (3.7 nMi) . Then you add the height of decent rescue vessel's aerial, and you get 10, 20, 30km (other distances are available).

I'd rather have a pushpit aerial which was easily checked and maintained, than one which was in a more vulnerable place and which, if it fails, cannot be mended. Mission critical, and all that. The best usage of a mast head aerial is to stop gulls landing on the cap

Nothing to stop the OP having both installed with a high-quality switch sending to EITHER the mast one, OR to the pushpit one . I think the SWR tuning would not be a problem, but Rev Morris will have the answer.

Another possibility is to have the aerial at the stern on a pole which can be extended upwards to says 5.5m AS, giving 4.5nMi.

Yes my extendable apple picker would be serviceable

 

[geem]

The risks from radiation are small and the any restriction assumes permanent continuous use. Most guidance is 0.305m (1ft) while in use (refering to Federal Communications Commission (FCC) guidelines for 100W unit) so I imagine any 1m rule is product disclaimer in litigatious USA rather than scientific. Leisure VHFs are 25 W so another factor of 4 less radiation.

My pushpit aerial midpoint is about 1m from my tiller position sitting down and masts on top of fishing boats are probably about that far above skippers head. Using my slightly lower power 5W handheld I certainly need it 0.03m (1inch) from ear and my arms cannot get it 1m away.

If I cant get a may day out the risk of close future death is much more significant than minor risk of cancer some 30 years hence - anyway at age 73 trivial cancer risk at 103 seems not to weigh heavily

I guess it depends how you use your boat. In big seas, a rail mounted antenna will have no line of site. You would need to be on top of a wave to get a signal.
If you are happy with a rail mounted antenna then great. The best range is at thr top of the mast, it's not vulnerable to somebody falling on it. No danger of radiation. I will stick with all three of my antennas at the top of my masts

 

[Buck Turgidson]

We dont all carry long emergency cable, some of us fit the alternate aerial in a suitable post emergency place just like rescue services and commercial craft do. When you half awash and trying to prevent fallen mast from smashing the hull, the last thing you want to do is feret around for your long cabled item and find somewhere to mount things. Basic Safety

exactly how do you know what is a suitable post emergency place beforehand?

 

[jdc]

Why not have both? I have a mast-head antenna and a comms post mounted one. Normal usage is for the VHF to be connected to the mast-head one and the AIS to be connected to the comms post. But it only takes seconds to swap them.
For me it's the best of both worlds, and the antenna at the coms post was cheaper than a spliter.

 

[oldmanofthehills]

I guess it depends how you use your boat. In big seas, a rail mounted antenna will have no line of site. You would need to be on top of a wave to get a signal.
If you are happy with a rail mounted antenna then great. The best range is at thr top of the mast, it's not vulnerable to somebody falling on it. No danger of radiation. I will stick with all three of my antennas at the top of my masts

I keep repeating that mast head is best. No dispute. If you have two masts then you stick an aerial on each of them as risk of double dismasting low unless you have that odd trapeze wire between them (generally avoidable with modern rigs)

I am merely serious addressing OPs original post as he clearly only has one mast, thus the clear safety issue of gaining critical redundancy by having a permanently installed secondary aerial on the sternrail. CDM regulations etc: eliminate hazard by do something else, or minimise hazard by changing its nature then mitigate remaining hazard. Clear safety protocol

 

[Fantasie 19]

Pushpit rail for me - it's easier to get to.. and I sail in the Solent and Chi Harbour, why do I need the additional range..

 

[geem]

Pushpit rail for me - it's easier to get to.. and I sail in the Solent and Chi Harbour, why do I need the additional range..

You don't. You could just shout

 

[Zing]

Yes, I know the preferred position is at the masthead, and I know why. Yet, I've sailed on many boats with non-functioning VHF/RT 'cos of a dicky antenna coupling 'up there somewhere' which will be fixed 'sometime'.....

The other option is mounted on the pushpit rail, or on a stub secured there that lifts the antenna a couple of metres higher. At present, that's my favoured option, principally as it would be readily accessible for 'maintenance'.

I DO have two new good quality antennae and a long length of quality cox, courtesy of our friend and contributor SaltyDog Salty John.
Also, my mast is down ATM.

Arguments pro and contra, please....?

I have tested this question for you. My cable in the mast broke and I can’t change it without pulling the mast, so I stuck a replacement on the cockpit roof 3m above the sea. It worked but very badly. Dangerously badly. Then I moved it to the rear arch 5m above the sea level. It worked OK, but not really well enough. It’s going back up the mast for sure. Nothing else will do.

 

[Fantasie 19]

You don't. You could just shout

...or indeed, just use my mobile phone..

 

[Sandy]

...or indeed, just use my mobile phone..

Or use flag signals

 

[Fantasie 19]

Or use flag signals

To be honest I could probably just wave...

 

[KevinV]

To be honest I could probably just wave...

Pass them a note?