When VHF IS Out Of Range

[Gludy]

There was a recent case with a boat coming from Ireland to France when they simply could contact nobody on VHF... they were adrift in their liferaft for days.

In fact there are occasions in travelling from Wales to Ireland when you are out of VHF contact.

Solution 1:-
SSB radio transceiver but the Arial needs to be about 23 feet long and I am informed reception is often very poor or at least variable. You need to take a 3/4 day course to get the long range certificate.

Option 2:-
Satellite Phone - now costing about £165 plus £14 per month with calls at £1 per minute plus ability to use as normal gsm phone - this seems a viable, at least partial alternative. I am not claiming that it acts as a substitute for SSB but such a phone and an EPIRB would in my view offer a viable safety alternative at a reasonable cost for those of us who are at times out of VHF contact.

Any more solutions? Any better ideas? What do others do when they are out of VHF range?


<hr width=100% size=1>Paul

 

[longjohnsilver]

"What do others do when they are out of VHF range?"

Listen intently for any changes in engine tone and cross my fingers!

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[boatone]

Interesting how dependent we have become on modern day radio communications in such a comparatively short time<A target="_blank" HREF=http://www.mcga.gov.uk/c4mca/mcga-hm_coastguard/mcga-hmcg-history-of-coastguard/mcga-hmcg-communications.htm>coastguard communications</A>

<hr width=100% size=1><A target="_blank" HREF=http://www.boatsontheweb.com/> Website, Photo Gallery, Chat Room, Burgees</A>

 

[boatone]

Interesting how dependent we have become on modern day radio communications in such a comparatively short time .....<A target="_blank" HREF=http://www.mcga.gov.uk/c4mca/mcga-hm_coastguard/mcga-hmcg-history-of-coastguard/mcga-hmcg-communications.htm>coastguard communications</A>

<hr width=100% size=1><A target="_blank" HREF=http://www.boatsontheweb.com/> Website, Photo Gallery, Chat Room, Burgees</A>

 

[kindredspirit]

Yep, when we went from Ireland to the Scillies last year, we were out of VHF coverage for the majority of the time. (142 miles from East Ferry to St. Marys.)

The two extras I wanted were a Thuraya phone and an EPIRB. But as it happened we went without either because a: I wouldn't have had use for the rest of the year for the Thuraya phone, and b; we couldn't get the EPIRB at short notice locally.

However, I did thoroughly check and re-check everything on the boat before setting sail.

<hr width=100% size=1><A target="_blank" HREF=http://www.begleys.com/weather.htm>Useful links for Irish waters.</A>

 

[Talbot]

SSB is really only suitable for chattering to other vessels/radio hams, and getting weather data.

You dont need to have a global sat/iridium miniM etc to call an emergency, just an epirb.

The epirb only solution also happens to be the cheapest!, but if you are going that far off land, it would be a good idea to make sure your epirb will work for +48 hrs.

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[steverow]

Paul,

23 ft length is the standard leisure loaded vertical antenna ie a shakespeare 390
they do come longer than this by some way.
The true length of a wire dipole given that the wavelength for 2182Khz is just a little under 150 metres would be about 72 metres (electrically corrected).
Of course this is totally impractical on any leisure vessel and thus the antennae are "loaded" with one or more coils increasing the "electrical" length of the antenna. As most of these vertical leisure antennae have a tuned resonance around 10Mhz it is essential to use an antenna tuning unit to match the antenna to the transmitter.
Most of these today are fully automatic and come as an accessory to an MF/HF marine SSB radio.
As you know being a ham and a radio geek, I very much favour HF radio as a means of communication when out of VHF range.
Granted there are others, but relying on just an epirb would seem to be folly to me.
What if the thing failed to deploy correctly or the battery was U/S or as has happened, the GPS fails to lock giving an incorrect or no position.
The satellite mobile seems to be a valid alternative, but I think I would only put to sea when out of VHF range with BOTH satphone and epirb on board.
MF/HF DSC radio on the other hand is pretty bullet proof. It's connected to ships power supply,and most of them are now channellised as per VHF radio. Once you know the basics pretty easy to operate.
The other advantage is that given it's much greater range there are more stations
listening on 2182/2187.500(the DSC Freq). Someone is bound to hear the call.
There is a Europe wide MF/HF coordination centre at Lyngby in Norway which has possibly some of the most sensitive HF Rxing gear and antennas in the world, and this sends all distress traffic to Falmouth MRCC for our area which is the main UK HF/MF centre.
As for poor quality, well yes, its not as crisp as VHF and it is more prone to interference and fading, but sat here in the Midlands about as far away from the coast as you can get, on my FT 847 with just a 40ft wire halfway down the garden, in the last hour I have heard Nav warnings from Aberdeen CG, Malin Head Radio in Eire, Scheveningen in Holland and some Spanish and French coast stations, as well as a number of vessels. Most of these were loud and clear and very intelligable.
So dont disregard it, it still has a very valid place in marine communications.

Steve.






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[Gludy]

So how are you going to fit a 23 foot arial on a boat then - no chance of taking it to a point on the bow as this would interefere with fendering and crew movement.
Raggies must stick them on their masts.

My suggestion was sat phone and epirb.

The sat phone would also be handy for contact whilst in the liferaft!

<hr width=100% size=1>Paul

 

[BrendanS]

You buried the epirb and sensible stuff deep in the post, so most missed or ignored it.

<hr width=100% size=1>Me transmitte sursum, caledoni <P ID="edit"><FONT SIZE=-1>Edited by BrendanS on 22/09/2004 01:47 (server time).</FONT></P>

 

[Ships_Cat]

Would carry a 406 EPIRB as first choice over anything else, even over VHF if that choice ever had to be made. They are more reliable than any other piece of alerting equipment, are in coverage everywhere, and you can take it with you if you abandon ship.

In NAVAREA XIV which is one of the largest in the world and looked after by NZ (where I am) - it extends mid Tasman to halfway to S America, up to the equator and down to Antarctica - most yacht rescues initiated by a 406 EPIRB alert are completed within 24-36 hours at worst and usually much quicker (if within coastal helicopter range obviously within hours at worst). It is infrequent that the boat has had to have been abandoned before the rescuers arrive.

We carry 406 EPIRB, DSC VHF and DSC SSB - but the EPIRB is "the one" (like in The Matrix trilogy).

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Gludy]

What size arial do you have for the DSC SSB?


<hr width=100% size=1>Paul

 

[Ships_Cat]

The DSC receiver on our set (Icom IC-M802) is of high sensitivity (more than 3 times that of the main receiver is in J2B or F1B mode) plus it will watch all HF DSC distress frequencies for a response if an alert is transmitted from the radio so a short antenna will suffice - my understanding is that as long as the foregoing is so then the antenna can be almost anything as long as it is not grounded. On a power boat it can be a whip or on a yacht even the lifelines I have heard used if the boat is frp.

We have a short approx 1.25 m whip to go on the pushpit as our boat is metal so all the rigging, lifelines, etc are grounded. Some suppliers advertise similar antennas for the M802. However, I have not gotten around to mounting ours yet, although the coax is run and the bracket is there, mainly because it is in the way for fishing, handling mooring lines, etc. and the radio is mainly used for amateur band use. Also, everywhere we sail there is a good ssb telephony watch on HF. I also carry a spare wire antenna I can use if necessary for either the transceiver or the watch antenna.

I have thought of making up a short active antenna to see how that would go but I think that because of the high receiver sensitivity that it would likely overload the watch receiver.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Medskipper]

Re: Yes but the cost of epirbs....

Yes I agree, an Epirb is the best solution, however I am sure they don't have to be so expensive! at a cost of around £500. or more most boat owners in England still don't own one and clearly this yacht that just recently sank did not have one on board! so they spent 8 days at sea in a very dangerous situation. I understand it was only by luck they were blown within range of their VHF and were then rescued!

Surely manufacturers of Epirbs are just trying to make vast sums of money from these things? do they really cost that much to produce?

Barry


<hr width=100% size=1>I just want to retire with my boat to the Med!

 

[Gludy]

Thanks, that is very interesting.
I would like to know what SteveRow thinks of such a short antenna!


<hr width=100% size=1>Paul

 

[Gludy]

"As most of these vertical leisure antennae have a tuned resonance around 10Mhz it is essential to use an antenna tuning unit to match the antenna to the transmitter.
Most of these today are fully automatic and come as an accessory to an MF/HF marine SSB radio."

Does this mean that in practice you can get away with a much shorter antenna?

Others seem to use 1.25m so I assume these use coils to increase the effective electrical length?

So with such an antenna tuning unit and say a 1.25m antenna does SSB work in transmit?

Please explain the answer in simple terms assuming no knowledge on my part because that is the only way I will understand it

<hr width=100% size=1>Paul

 

[Ships_Cat]

Perhaps there is a bit of misunderstanding - I took your question to mean the antenna for the radio's DSC receiver and that only need be small if the conditions I outlined are met. That little antenna is only for maintaining the DSC watch. The main transmiting and receiving antenna on the radio is, in our case approximately 30 foot high. As I think Steve inferred, 23 foot is the normal standard whip small vessels would use although some small vessels, yachts especially cos they have things like backstays to use, use longer antennas.

Shorter whips are available for pleasure boats but normally only down to around 18-19 foot and at these lengths MF and low end of HF efficency starts to really suffer. Even our 30 foot one is not great compared to a quarter wave vertical (which would be about 3.5x times as high - about 106 foot)

Approx 10 m would be common on a ship, although they may carry a longer or top loaded antenna as well for MF and low end of HF.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Gludy]

Well that clears things up a bit!

So, in practice fitting an SSB transceiver is a bit of a problem on even a 60 foot power boat. 23 foot antenna's are a real problem!

How do people overcome this?

At the moment when out of VHF range my security plan is based on a sat phone and a gps epirb. I also have a very wide range receiver and and SSB reciving antenna used for the SSB receiving.

I would like to consider an SSB set like yours but the anntenna problem seems daunting!



<hr width=100% size=1>Paul

 

[steverow]

It all depends on the frequency Paul.
MF/HF ranges from 1.6 MHz to 30MHz that is a wavelength of 180metres approx, down to 10 metres...quite a huge variation.
There are marine bands at 2, 4, 6,8,12,16,18,22 and 25 MHz.
Different sea areas tend to use predominantly different bands, and because of the distances involved in communication, choose the bands most suited to the propogation given the time of day and distances involved.
In the Pacific for instance it is common to use 16 to 25MHz because that suits the conditions better. It is to do with the skip or "hop distance" as the signal bounces off the D layer of the ionosphere, as there is rarely a direct path or groundwave.
So for that area, because of the higher frequencies involved, the antenna can be shorter, something probably not too different from a mobile CB antenna, maybe about 2 metres in length with a loading coil could be used with a reasonable efficiency.
In europe because of the distances involved, MF frequencies in the range 1.6 to 2.5MHz are used giving a satisfactory daytime direct groundwave coverage of about 150 miles doubling to 300 at night.
Fishing vessels operating in the North atlantic will also use 4.125MHz 6.215 or 8.291 as their distress frequencies because of the distances involved.
Unfortunately for most CG radio stations in the south of the country or Ireland ie our area, you will not find them listening on anything other than 2182Khz MF so it is essential to be equipped with this.
Whereas a short antenna for higher frequencies will load efficiently, unfortunately the efficiency of such an antenna at the low end of the band working at 2182 will be pretty abysmal. At that length it would almost have to be all loading coil. Remember you are going to have to make up that electrical length of a quarter wave vertical with turns round a former to compensate.
So the 23 foot Shakespeare antenna is a compromise, with a natural resonance on about 10MHz. An ATU will be able to tune this adequately both up and down the band.
For amateur use there are some compromise antennas using wires with a series of "traps", which are resonant coils, but these are band specific, although sometimes quite short. I might look at seeing if I can scale one of the 7Mhz types up to work at MF.
Basically with a wide ATU you can get anything to look as if it's loaded, but it's efficiency as a radiator will be extremely poor.
The most efficient radiator is a half wave dipole or a quarter wave vertical that uses the ground to "image" the other quarter wave. Unfortunately at 2182 Khz half wave is a 75metre wire and quarter wave 37.5 metres.
There are really no shortcuts to an efficient antenna. Everything else is a compromise that reduces radiation efficiency


Steve


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[Ships_Cat]

Typically, even on smaller MoBos's, the antenna is side mounted on the outside of the flybridge superstructure with the bottom of the antenna about level with the flybridge deck (but not like this on metal boats, of course). So, I guess, around 18-19 foot stick up above the side of the flybridge, assuming it is open, and 15-16 foot if it is enclosed. On a game fishing boat, for example, they are not much different to the height of the outriggers when erect.

I can see the difficulty from both an aethetics and a practical point of view doing that with the Squadron, however.

Whatever, it needs to be kept as far as practically possible from instrumentation and their cabling in order to avoid radio interference to them (autopilots, in particular, are likely to be a problem). Clamp type ferrites and toroids on instrumentation cabling are frequently required to suppress that.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[steverow]

Some more info for you Paul,

see here:

<A target="_blank" HREF=http://www.usenet.com/newsgroups/rec.boats.electronics/msg01366.html>http://www.usenet.com/newsgroups/rec.boats.electronics/msg01366.html</A>
<P ID="edit"><FONT SIZE=-1>Edited by steverow on 23/09/2004 10:25 (server time).</FONT></P>