The range of VHF radios

[s/v Jedi]

Originally Posted by GordMay

Rescue 21 is operational in the following Regions:
[...]

I know, I read that info too. But DSC/GMDSS is just part of the Rescue 21 project, monitoring ch.16 is also part. I could not find a page that lists areas where the VHF DSC distress call is supported, or guarantied to be received. Or just confirmation that it is for the areas listed and shown on that sat-photo. I did find that they listen to ch.16 (continuous watch).

cheers,
Nick.

[Brent Swain]

I was once in La Paz when I heard over the VHF a yacht asking if Cabo Falso light was working. I communicated with him quite clearly around 200 miles away with a range of mountains between us. I once talked from Isla Isabela to Cabo from over 200 miles away, altho I was talking to a restaurant high on a hill in Cabo. Couldn't reach anyone in the anchorage.
Brent

[Cheechako]

I though VHF was 1 watt/5watt? are they 25 watts?

[Cheechako]

I also got VHF transmissions from mainland Mexico to Cabo at night.. 150/200 miles. My understanding is that the dignal "skips"

[s/v Jedi]

Wow, what a responses ;-)

I think the best posts in this thread came from Bill and he put up a list of installation-points that, if followed, will have your GMDSS VHF radio work great for any A1 area in the world, even if it is 50nm from shore. I agree with that now as I always did, I never said "special" stuff is needed for it, I actually said there was nothing special to it. But there are MANY cruisers that have their radio installed incorrectly. Some have 30-year old coax and no wish to replace it because "they can still hear me". If anyone here in the forums indicate/suggest something like "20 nm is enough", these cruisers will think that it doesn't really matter how well their installation is. I even met cruisers who didn't replace their radio because "some boats can hear what I say through the static/hum/noise". These cruisers should be encouraged to make their radio installation right.

All the talk about "secret EU devices" inside radios to make it 50 nm capable are very funny. I would worry more about forgotten secret CIA devices in your radio that make it go BOOM if you talk bad about George! ;-)

It also seems to matter if you're a pro at this and it was even suggested that my technical knowledge on the subject is a joke. I am not a pro, I am retired and wandering around on my boat. But I was a RF engineer long ago and actually worked for INA some time (now Radio Holland) but the job was radar equipment on shore stations and oil/gas platforms in the North Sea. I am also a HAM and have designed, built and operated at least a dozen VHF antenna systems, including 21-element yagi's and stacked dipole configurations. I also designed & built VHF transmitters, to many to remember, stereo coders etc. (yes it all worked perfectly... most of the time) My electronics study was 6 years; switched to micro-electronics after that, leading to later non-RF work (yep, industrial computer-design). I don't think I wrote anything that endangers the life of cruisers like suggested. To the contrary, I tried to make cruisers aware that in some places in the world, you are supposed to be able to contact shore-stations 50 nm away (and no, not kilometers and Europeans are not mistaken the two... in fact, it was Europeans who invented the nautical mile and most of the nautical knowledge as in use today, but that was another funny joke I think, We might start a separate thread for that, I'll list all the Dutch nautical inventions!).

A GMDSS Operators Certificate is NOT like the standard operators certificate (I got that when I was 14 years old) like the one you need to have outside US waters. The General GMDSS certificate requires study and practice, even for long time HAM's. It includes all GMDSS equipment, incl. VHF, SART, EPIRB, SSB and Inmarsat-C satellite. It even includes "nautical English". The exams last a day with theory (incl. nautical English) and demonstration of ability to operate every piece of GMDSS gear using live equipment or some military style (real looking) simulators.
It goes well beyond "being very basic qualifications giving no knowledge at all apart from how to operate some basic items of radio equipment." and I can state that anyone doing it will come out knowing more about nautical communications than before. I am sure Eric will confirm that. I do not hold my maintainer certificates because I only got this the year I retired. I didn't exist before.

About ITU; where IMO creates the criteria, they involve the ITU for all the technical requirements. The IMO doesn't deal with that at all.

simple VHF line of sight paths and I am sure any person with the required knowledge will assure you it is so

Funny that you can simplify while slapping me when I do the same. As I have the required knowledge (as have you I can assume), you know that there are more factors involved. A handheld with it's antenna 4 meter from the water will not do the job, nor will the big radio at low power setting (I tried, from "weak but clear" on high power to "lost in noise but transmission detected" on low power, 42 nm, sailboat-sailboat with antenna's up 65' during normal conditions). In your simplified view, we could do away with 25W or even 1W. It is not even true that VHF is line of sight: it's close enough to do rough estimates, but every RF engineer knows about the slight bend of VHF with the earth's surface.
I am sure that you all will reply that this is not as written by IMO because we have been mis-communicating a lot in this thread... but that doesn't mean it's not true or that I am a loony EU guy spilling nonsense. The info and formula's are all on the net, Google to find them as I have no further wish to convince you or prove it.
Also, the IMO doesn't state what kind of antenna is required. Does that mean we can stick a rubber-duck antenna on top of the mast? Who then came up with the antenna's we use or the power-level of the radio's or the many other technical details? (=ITU)

My whole intend was to say that some A1 area's are 50 nm from shore and that your radio must be in good working order to make contact under those conditions. I am almost sure that by now, after all the whacking and ridiculing I attracted, anyone reading that believes it's nonsense. But I posted the links that show the 50nm A1 coverage map of Europe so you can look that up and see it's true and I think many will understand that you need more than a handheld or lousy VHF installation to be able to do those contacts. (and know how to operate the radio). If that only helps a single cruiser, I am happy.

Also, users of AIS receivers/transponders will find received targets well beyond normal VHF range regular. As it isn't important at all (it way to far away to be of use), I'll just leave it at that.

cheers,
Nick.

[s/v Jedi]

Originally Posted by Cheechako

I also got VHF transmissions from mainland Mexico to Cabo at night.. 150/200 miles. My understanding is that the dignal "skips"

The best conditions for that are during a cold clear night after a sunny, warm/hot clear day. It happens often on VHF, not just once during a lifetime. We have heard it daily for weeks in the Caribbean, could join the Grenada cruisers net from the Testigo's.

A 150-200 nm contact will probably involve ducting. Your signal is caught between two layers before finally escaping and reaching earth's surface again.

cheers,
Nick.

[hellosailor]

Cheechako-
Handhelds of all sorts are generally regulated to a 5w or 6w maximum power. This is because a radio antenna next to your head may fry your eyes or brains after prolonged use. (Fryage varies with the frequency as well as the power.)
Handheld cell phones are limited to 600mW, the early analog bag phones were limited to 6W in the assumption that the bag--and antenna--would still be someplace close to your body.
But marine VHF "base" stations are limited to 25W, in the assumption that they normally will be used with a remotely mounted antenna, so they won't be frying you. The regulatory limit then considers how much power is "too much" and would cause interference with other users, and in the US our FCC figures 25W plus the 3db to 9db gain from the antenna (which makes it 50W to 200W "effective" radiated power, ERP) is enough for the designed use.

There are a lot of lower power (1W) handhelds, designed to be less expensive, with good battery life, for situations like launch-to-boat where 1W is more than adequate for the task, while keeping costs and interference low.

[s/v Jedi]

HelloSailor,

I agree with everything you write, but don't you think the chance that the fcc and every other national agency in the world like fcc, independently came to that same 25W maximum power for the VHF. None came up with 20W, 30W, 24W nor 26W. Logic dictates that it is impossible that a hundred or so organizations came up with the same number without some coordination. It is therefor very likely that an international organization, in concert with all nations participating in that organization, to have lead to the world standard of 25W. That organization must have been ITU, as only they can define the frequencies/channels that may be used and the power-levels used on them. Not just for marine VHF... for all international radio communications in the world. The ITU was founded in Paris, France, but became a UN organization in the 30's I believe.

The ITU was instrumental in developing GMDSS:

With the pivotal assistance and partnership of the International Telecommunication Union (ITU - CCIR) and other international organizations (notably the World Meteorological Organization (WMO), the International Hydrographic Organization (IHO), INMARSAT, COSPAS-SARSAT) the IMO developed and tested the various systems, components and techniques used in the future global maritime distress and safety system (GMDSS). In addition, ITU established the necessary and appropriate regulatory framework for the implementation of the GMDSS in the Radio Regulations.

Source: http://www.itu.int/ITU-R/conferences...s/20-gmdss.doc

p.s. I am intrigued by your avatar: it appears an ensign much like that of the USA but I don't recognize it. Can you enlighten me?

cheers,
Nick.

[Wotname]

I have tried to stay out of this thread but after 5 pages of "stuff" I have gotta wade in, the water looks so inviting .

As I am coming in at the tail end, I won't respond directly to the claims and counter claims, rather I want to state (as a matter of opinion - not necessary fact) that as far as I knew the range of radio progagtion was based on the laws of physics rather than what goverments (and politicans) would like and legislate for.

As for OTH events, Aussie's are leading the way with the Jindalee radar (at least I think we still are but I do have some late breaking news on the URS.

These devices are anchored on the sea floor (max depth of 200 meters) and gently curves VHF radiation towards the center of the earth. When programmed correctly, they will allow for the radiation to remain parallel to the sea surface and so even a 1 watt handheld will give almost 30 nm range (assuming a calm sea state) while a 5 watt transmitter easily covers the 50 nm EU requirements. However 25 watts of Tx power is necessary to ensure the 50 nm coverage in rough to very rough seas. We are currently shipping these items to the EU but places like the USA and NZ don't seem to be so interested in them. Please note, this equipment is not ITU or IMO approved - yet.

For more info, google "Underwater Radiation Sucker" or URS.

[btrayfors]

AFAIK, those suckers only work in the southern hemisphere.

Bring them up here and they're liable to have the opposite effect, i.e., shooting the VHF signals straight up.

That's probably why they're not approved, yet :-)

B.

[hellosailor]

Nick, I have no idea which body wrote the various power specs. Of course in the 1930's radios would have been made in America not Japan, so sometimes the US regulations determined US manufacturing, and the rest of the world had the choice of adopting the same regs and using the same gear--or cobbling together their own versions in imitation of it. (Once upon a time we did lead the world in many things.)

Today things are still similar, in that global radio manufacturers prefer to build one version of a radio and keep everything as standard as possible. In many cases they adapt JP/EU/US models by jumpering something internally...but they try to keep it as simple as possible for cost reasons. Standards bodies are likely to keep to common standards rather than challenge that and raise local prices, especially when there usually is some physics behind the choices. 20, 25, 30 watts would all be immaterial differences, in terms of regulations aimed at health (radio emissions) and performance (power versus physics).

The avatar is our "Bennington Flag". It is a legal historical flag of The United States, flown by Ethan Allen and the "Green Mountain Boys" at the Battle of Bennington (Vermont) which was one of our first victories against Crown troops during our revolutionary war. There are many subtleties to New York, Vermont, seccession, revolution, victory, and independance associated with it. (Vermont, in fact, seceeded from New York after the governor of Massacussetts defrauded settlers, and sold them land which belonged to New York!) It is especially "famous" among flags as being "wrong" because the outer bars are both white, rather than red, because the folks who made it had no idea how to make a flag and no instructions about the right way to do it. Heralds and flagmakers never use a white outer field, because it cannot be distinguished against the sky. Since it appears here as a decoration, rather than an actual flying flag, there's also a decorative gold border, another tradition that predates America and goes back to the Middle Ages. (A lot of ignorant folks who believe in conspiracies think a gold border is some kind of "New World Order" plot.)

Technically it also was and is a battle flag--the purpose for which it was commissioned and flown. The US does not have a generally designated battle flag, or a particular flag for our federal militia (often confused with our National Guard, which is a militia group often seconded to our regular military) although we have a number of historical ones.

A web search will bring up a lot of information about it and them--some of which is still misinformation, the result of there being only one original flag which wasn't always treated kindly over the years. Something like the debates about John Paul Jones and what he might or might not have flown on Serapis.

Boats? Well...AFAIK Bennington has no connection to boats, other than sharing the times and spirit of Jone's flag, and having the advantage of at least being documented without doubt.

[s/v Jedi]

Hellosailor,

I tried to find who build the first marine VHF radio but the info seems lost in time. I do think I once read that the US came up with standard channels for this band, first at 100 kHz spacing. This was adopted worldwide and changed to the current 25 kHz spacing by International consensus.

First marine radio is easy to find: Italian Marconi but done in England after Italy showed no interest in it ;-) (lightship and ferries were the first ships to have it) I am one of those who supports Tesla as the inventor of radio, after reading a very good book about his life and career.

The flag; what does the number 76 stand for? And why did you make it your avatar?
I studied past Dutch influence in the US and found the Dutch flag in the current NYC, Albany and Nassau County flags... and in the uniforms of the New York Mets, New York Knicks and New York Islanders. I am still figuring out if and why the Dutch colors are on all those "Welcome" and "Open" flags ;-)

cheers,
Nick.

[David M]

Originally Posted by s/v Jedi

Hellosailor,

I tried to find who build the first marine VHF radio but the info seems lost in time. I do think I once read that the US came up with standard channels for this band, first at 100 kHz spacing. This was adopted worldwide and changed to the current 25 kHz spacing by International consensus.

First marine radio is easy to find: Italian Marconi but done in England after Italy showed no interest in it ;-) (lightship and ferries were the first ships to have it) I am one of those who supports Tesla as the inventor of radio, after reading a very good book about his life and career.

The flag; what does the number 76 stand for? And why did you make it your avatar?
I studied past Dutch influence in the US and found the Dutch flag in the current NYC, Albany and Nassau County flags... and in the uniforms of the New York Mets, New York Knicks and New York Islanders. I am still figuring out if and why the Dutch colors are on all those "Welcome" and "Open" flags ;-)

cheers,
Nick.

Bennington flag - Wikipedia, the free encyclopedia

[hellosailor]

Nick-
As David links.

Regarding the Dutch and old colors, yes, New York is still very much in touch with its roots, or at least it has been. Immigrants (I call them tourists, because they don't really plan to live here, just to take money, send it home, and retire after it, meanwhile trying to make NYC into the mirror image of what they left and considered inferior, a true paradox) now outnumber the native-born and English is not spoken as a first language in more than half of the homes in several of our boroughs. Boroughs, from the Dutch, not Counties, in local speak. Lousiana has Parishes (and since it was originally a French territory, Napoleanic Law is traditional) and NYC has Boroughs, and since it started as New Amsterdam and later became Nova Eborica (New Eborica, New York, after the English York Town) we've kept a number of reminders of the city roots. The Knicks are more properly/previously known as the Knickerbockers--you can google that too--and the Mets are short for Metropolitans. No relation to the first NYC police department, also known as the Metropolitans, who have the dubious honor of being the first major urban PD to be disbanded by force of arms after major corruption, in the 1860's. While you puzzle over corporate colors (the sports teams are not sports teams, they are corporate franchises that happen to play sports) I suspect they were taken up by a franchise standard, or at least common design practice, of simply adopting local (county) flag color schemes or something similar. As long as they were flashy enough to sell merchandise.(G)

History here is often soon forgotten, there's a Verrazano Bridge tower built obliterating one of the islands that was a harbor defense in the 1800's, and the others are pretty much invisible except from the water. Manhattan Island is about 30% landfill downtown, extending into the rivers tripling the original width. Hell's Gate, a killer of ships, was blown out by mining and what was then the world's largest explosion. There are some 50 islands in NYC proper, some now no longer islands, others just too small to build on. Still, we can't be mistaken for Venice.(G)

Times change--but some of us try to learn from history.

[Wotname]

Originally Posted by btrayfors

AFAIK, those suckers only work in the southern hemisphere.

Bring them up here and they're liable to have the opposite effect, i.e., shooting the VHF signals straight up.

That's probably why they're not approved, yet :-)

B.

Hmm... maybe we have been rumbled and that is why sales are falling off rapidly to the EU , still we milked it for a while .