What is the range of hand-held (5W) vhf radio at sea level ?

[Sailingsaves]

Many owners of small craft carry a hand-held VHF radio on board, primarily for emergency use. With the loss of many local Coastguard stations we now depend on VHF relay stations to transfer the call to the nearest main coastguard station.
My nearest relay station is about 8miles away and when I called the Coastguards for a radio check on my hand-held (Icom) at 5watt power with a fully charged battery, I was told that the signal was "very weak".
A better and cheaper option might be to put a mobile phone in a waterproof pack and dial 999 if an emergency occurred. I think that in some coastal areas the mobile phone coverage is possibly better than the VHF coverage.
What does the Forum think?

I think all boats should have a ship's radio, a h/h WITH a cheap adapter /connector that allows the h/h to connect to the pl254 plug from the masthead aerial, (maybe carry an extension cord so can use h/h/ in cockpit connected to masthead aerial?) also carry an emergency aerial with pl254 and the adapter / connector and carry a mobile too. All your bases covered then I think (without getting into SSB).

One mile away I was unreadable with standard horizon h/h (to a coastguard aerial - high up), but with emergency aerial fitted and higher by an oar I was loud and clear.

 

[jdc]

A very significant factor in the range of hand-helds is the height of the antenna. The power received isn't just that from a free-space direct path even if there is line-of-sight: if it was we'd have much larger ranges than actually experienced. The key factor in calculating range (this applies to mobiles as much as to VHF) is the destructive interference from multiple rays, of which by far the most important is the path reflected from the sea surface. See https://en.wikipedia.org/wiki/Two-ray_ground-reflection_model for instance. This shows the the signal is proportional to the square of the height of the antenna, so one at 1.8m say will be result in 100x less received power than one at 18m. The power fall-off with distance is proportional to the distance to the power 4, so 100x in power is equivalent to a factor of 100^(1/4) = 3.16 in range. And if both antennas are hand-helds that will give rise to a factor of 10 range reduction compared to masthead to masthead.

 

[lw395]

A very significant factor in the range of hand-helds is the height of the antenna. The power received isn't just that from a free-space direct path even if there is line-of-sight: if it was we'd have much larger ranges than actually experienced. The key factor in calculating range (this applies to mobiles as much as to VHF) is the destructive interference from multiple rays, of which by far the most important is the path reflected from the sea surface. See https://en.wikipedia.org/wiki/Two-ray_ground-reflection_model for instance. This shows the the signal is proportional to the square of the height of the antenna, so one at 1.8m say will be result in 100x less received power than one at 18m. The power fall-off with distance is proportional to the distance to the power 4, so 100x in power is equivalent to a factor of 100^(1/4) = 3.16 in range. And if both antennas are hand-helds that will give rise to a factor of 10 range reduction compared to masthead to masthead.

I think for that model to be valid, the roughness of the sea needs to be orders of magnitude smaller than the wavelength. Rarely true at VHF and less likely at GSM frequencies.
Propagation over non-smooth surfaces is often a mixture of dark art and high level maths where I fear to tread.

 

[lw395]

....
One mile away I was unreadable with standard horizon h/h (to a coastguard aerial - high up), ......

There's a technical term for that. Broken.

 

[ShinyShoe]

I was unable to get a reply from the coast guards when crossing St Andrews Bay. initially tried the HH then the ship radio but got nothing. I don't know how they expect to cover this. On the approaches to Aberdeen we did manage to raise the harbour authorities, but couldn't even receive the routine weather reports.

Did you consider your radio may be the issue.
Do you have DSC?

I didn't realise how spoilt we were on the South Coast.

Aha... it would seem I have located the reason why there is less pointless radio checking up Norf...

Depending on where you intend to sail, it might be worth being on a different network with the PAYG phone. There are still beaches in Devon with no Vodafone coverage, and coming back across channel, it's a lottery who gets a signal first.

If you are dialing 112/999 it is provider agnostic anyway...

I was doing more or less exactly the reverse of that last week. Committee boat to hand held on shore, worked OK both ways with us about two miles out, provided the bloke on shore was not indoors or something similar. Shore h/h to h/h in the RIB was more hit and miss.

That's the noise on the RIB that's the issue.

There's a technical term for that. Broken.

Aye - and my work iphone had no signal for several hours on Thursday night. I thought I was in a black spot... till i was still in blackspot when I got home and rebooted it... suddenly full bars...

 

[TallBuoy]

Many owners of small craft carry a hand-held VHF radio on board, primarily for emergency use. With the loss of many local Coastguard stations we now depend on VHF relay stations to transfer the call to the nearest main coastguard station.
My nearest relay station is about 8miles away and when I called the Coastguards for a radio check on my hand-held (Icom) at 5watt power with a fully charged battery, I was told that the signal was "very weak".
A better and cheaper option might be to put a mobile phone in a waterproof pack and dial 999 if an emergency occurred. I think that in some coastal areas the mobile phone coverage is possibly better than the VHF coverage.
What does the Forum think?

This should have been covered on your VHF SRC course, whenever that was.

 

[KellysEye]

Our ICOM hand held was 5 miles in a straight line i.e. no obstructions.

 

[SHUG]

This should have been covered on your VHF SRC course, whenever that was.

That's the sort of attitude which can get you into deep trouble.
The value of the Forum is that you can learn from the actual, practical experience of other yachtsmen and combine that with content of theoretical shore-based courses. There is life beyond the classroom!

 

[ShinyShoe]

That's the sort of attitude which can get you into deep trouble.
The value of the Forum is that you can learn from the actual, practical experience of other yachtsmen and combine that with content of theoretical shore-based courses. There is life beyond the classroom!

Is it? It seemed like a reasonable statement of FACT. It should have been covered on the VHF Course. So either @SHUG missed it, didn't believe it, thinks he knows better or... ...and I'm just putting this out there... ...was baiting us all...

So has a single yachtsman come back and said - @SHUG - you know what - you've hit on a stroke of genius there and I'm stripping my VHF off my boat and digging my old Nokia 3210 out?

Nope ? Thought so... ...because the theory taught on the course is CORRECT on this occasion.

 

[GrahamHR]

Off the West Coast of Holy Island (Anglesey) due to the cliffs/ geography there is no VHF contact with coastguard until a few miles offshore , At least on my boat, with the tip of the VHF antenna some 5m in the air. Likewise UK mobile phone coverage and FM radio; Irish mobile phone networks are OK despite being about 60 miles away as are the Irish FM radio stations.

 

[JumbleDuck]

Is it? It seemed like a reasonable statement of FACT. It should have been covered on the VHF Course. So either @SHUG missed it, didn't believe it, thinks he knows better or... ...and I'm just putting this out there... ...was baiting us all...

So has a single yachtsman come back and said - @SHUG - you know what - you've hit on a stroke of genius there and I'm stripping my VHF off my boat and digging my old Nokia 3210 out?

Nope ? Thought so... ...because the theory taught on the course is CORRECT on this occasion.

Leaving the wholly unnecessary bitchiness aside, is use of mobile phones at sea really covered in the VHF SRC?

 

[ShinyShoe]

Was on mine. With all the explanations of the limitations. That was 15 years ago

 

[grumpy_o_g]

DSC makes a difference when sending a mayday - the method it uses can increase the range so the big red button may get through, even if you can't hear the Coastguard but if sea level means in the water bobbing around in your LJ trying to use a handheld then even the Coastguard may struggle if more than couple of miles or so in some conditions and another boat may well need to be within a mile.

For a mobile phone a text message will get through when there's no chance of a voice call - unfortunately texts can also take a while to be received and can get ignored by the recipient until it's convenient. The big problem with cell phones though is that you can't guarantee coverage will be consistent. When you're trying to get a signal some way offshore a mast being down that would be covered by another cell if you were ashore may result in no signal out at sea. That means that coverage that was there yesterday at a particular location may not be there today.

For emergencies would a PLB be an option for you?

 

[maby]

DSC makes a difference when sending a mayday - the method it uses can increase the range so the big red button may get through, even if you can't hear the Coastguard but if sea level means in the water bobbing around in your LJ trying to use a handheld then even the Coastguard may struggle if more than couple of miles or so in some conditions and another boat may well need to be within a mile.

...

My experience of DSC on a handie is not very good, I'm afraid. We have the Standard Horizon version and I have pinged DSC test calls to the coastguard MMSI from various locations around Southampton and the Solent - I seldom get a response. It is working fine - if I ping a test to the Hythe Ferry or any of the big cruise liners in Southampton, I always get a response back.

My wife goes wind surfing and paddle boarding and she takes the SH handie with her in case she gets into trouble. I sometimes track her from the plotter in the boat using the DSC location request - the responses are beginning to become unreliable when she gets just a couple of miles away.

 

[JimC]

For emergencies would a PLB be an option for you?

From what I've read on this thread and on the earlier thread I referenced in Post 3, it seems a PLB is definitely worth having as everything else has serious and potentially lethal limitations.

 

[ShinyShoe]

For a mobile phone a text message will get through when there's no chance of a voice call - unfortunately texts can also take a while to be received and can get ignored by the recipient until it's convenient.

There is a 999 text service. It is intended for use by people with hearing problems. It requires advance registration (takes 24hrs). http://www.emergencysms.org.uk/ If you were planning on only having a mobile as a means of contact at sea, it would be worth considering registering.

For emergencies would a PLB be an option for you?

Thats what the 4 fishermen on Louisa thought...

My experience of DSC on a handie is not very good, I'm afraid. We have the Standard Horizon version and I have pinged DSC test calls to the coastguard MMSI from various locations around Southampton and the Solent - I seldom get a response. It is working fine - if I ping a test to the Hythe Ferry or any of the big cruise liners in Southampton, I always get a response back.

Does that not demonstrate the value of VHF though? If that was a distress alert, the Hythe Ferry would get it and be able to relay it. If that was a mobile call no-one gets it...

My wife goes wind surfing and paddle boarding and she takes the SH handie with her in case she gets into trouble. I sometimes track her from the plotter in the boat using the DSC location request - the responses are beginning to become unreliable when she gets just a couple of miles away.

A whole host of other variables will be at play there too. Where does she keep the VHF, angle, body shielding antenna, height.

Are you using the LiIon battery? or AA cells?
The short range is surprising, because AIS on a pushpit antenna is often being quoted as being visible at 5-7miles with just 2W transmission. That doesn't seem inconceivable. So why would three times the power be 3 times worse?

Have you tried DSC calling her? Would be interesting to see if her DSC receives the call but can't call back...

From what I've read on this thread and on the earlier thread I referenced in Post 3, it seems a PLB is definitely worth having as everything else has serious and potentially lethal limitations.

And so does the PLB. www.ybw.com/forums/showthread.php?483450-MAIB-Louisa-Report You need a range of options in my opinion.

 

[maby]

.....

A whole host of other variables will be at play there too. Where does she keep the VHF, angle, body shielding antenna, height.

Are you using the LiIon battery? or AA cells?
The short range is surprising, because AIS on a pushpit antenna is often being quoted as being visible at 5-7miles with just 2W transmission. That doesn't seem inconceivable. So why would three times the power be 3 times worse?

Have you tried DSC calling her? Would be interesting to see if her DSC receives the call but can't call back...

.....

.

You are, of course, quite right - in all things radio, many factors contribute - I was really just responding to your suggestion that the DSC function on a handie may have a longer range than voice on the same device - my experience is that, if anything, DSC from a handie has a shorter range than voice on the same handie. That said, I still think that it is worth it - the price difference between DSC and non-DSC is not that great these days - assuming that you are comparing radios of similar quality.

In my wife's case, we are talking close to worst case for radio communications - she's standing on a board at sea level and the radio is tucked into a pocket of her lifejacket. It is running on the lithium battery, but I can start to miss pings from it when she is as little as a mile away. This is to a SH fixed radio installed in the yacht with the antenna a good 15m above water level. I've never failed to get a response from the CG base station on the fixed radio, but very rarely get a response to the handie.

 

[DannyB]

I came across an empty dinghy adrift in the middle of Upper Loch Fyne last weekend. I tried calling the coastguard with the fixed set and the handheld, no response, so I called on the mobile, got through no problem. When I explained that I'd tried calling on the VHF I was told I was in a bad area. They actually tried to call me back on the VHF, but ended up phoning me back on the mobile.

 

[Neil_Y]

I've used water proof phones for navigation on open cats a few times and I fill the connection socket and earphone socket with a PTFE grease. The phones have been fine but salt would have corroded the contacts.
My latest which has a really great screen is a SONY M4 Aqua at about £200 or less.
Hand held could be useful for a heli or rescue boat to home in on your signal ( they use directional antenae) if they can't see you, a mobile can't do that easily.

 

[SHUG]

Having let the dust settle on this one for a few days I have taken all the comments seriouskly and cross-referenced them to the RYA recommendations. I also discussed the problem with the Coastguards (by phone) who confirmed that a continuous watch on Ch16 is no longer kept . They also commented that DSC is not the complete answer since poor reception can compromise the integrity of the positional information.
My conclusion is that the range of a hand held VHF in good atmospheric conditions with an aerial height of about 2metres is between 5 and 8 miles. It also seems that the height of the aerial is more important than transmittor power.
On that basis I am buying a PL259 to SMA adaptor and setting up a masthead aerial to which I can connect the hand held when trying to contact the Coastguards.
Thanks for a lively debate . OVER AND OUT...SHUG