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Cyrus Safdari · 26-07-2012, 08:35

So I'm reading an account written in a magazine in one of those "Lessons Learned" type articles of a sailor whose 45ft boat slipped anchor & was lifted onto a reef because "clocking winds and rising tide" and whose spouse was blown out to sea in a rubber dinghy when he tried to kedge the boat, because the dingy's motor was not working and he also had no decent paddles.

There's plenty enough for a face-palm or two right there, but I understand that hindsight is 20/20 etc.

But this is where it gets interesting: she sends out a mayday using VHF and SSB, but somehow it is only picked up (garbled) by a Coast Guard station clear across the country, in Alaska. (She was in the Bahamas) The Coast Guard eventually manages to identify the boat and track down the location. etc etc and everything worked out in the end

WTF? How did the Mayday bounce to Alaska? The author of the article thanks the Coast Guard and everyone else involved without explaining.

Now, it seems to me THAT is the real question that needed an answer!

**David M** · 26-07-2012, 08:39

The ionosphere can bounce signals significant distances sometimes.

Target9000 · 26-07-2012, 08:39

SSB on the right frequencies would bounce there, wouldn't it?

**noelex 77** · 26-07-2012, 08:44

VHF is normally line of sight (or a tiny bit more) but on some occasions it can behave more like SSB.
A few years ago I was calling the coast guard On VHF and an operator near where I lived recognised the boat name and voice and responded. We had a great conversation, but I was 1200nm away.

SSB can travel great distances, but depending on the frequency may not be heard by much closer stations.

belizesailor · 26-07-2012, 08:44

No problem for an SSB signal. Practically impossible for VHF, but I have heard of some very strange bounces for VHF too.

mbianka · 26-07-2012, 08:57

I've heard VHF Coast Guard broadcasts from places like North Carolina when conditions are right on Long Island Sound.

Sailing Mermaid · 26-07-2012, 09:19

Cyprus Safdari,

Which magazine has this article? We know this couple and were thankful and distressed (for them, us and others in our area) upon learning of the incident as they relayed it to us soon thereafter. At least "someone" heard them and did assist..... all ending well in the end.

Thanks,
Sailing Mermaid

Cyrus Safdari · 26-07-2012, 09:22

Well I understand that the SSB skipped over the entire country and ended up in Alaska but the VHF? THe author references another boat in the same area, and friends about 20 miles away -- none of whom apparently responded to the distress signal.

Sending a mayday and not getting a response is pretty terrifying.

storyinframes · 26-07-2012, 10:35

the phenomenon associated with VHF travelling beyond the line of sight distance is called - "Anamolous Propogation" and this happens because of temperature inversion as altitude increases. i.e. ideally temp is supposed to drop at a certain rate as altitude increases but sometimes there can an abrupt change. instead of decreasing it might increase. this forms a trapped layer which acts as an 'optical-fiber-cable' for the VHF communication. it can travel long distance.
PM me to give you an example.

**btrayfors** · 26-07-2012, 10:54

Nothing curious here, especially if the SSB call was at night and on a frequency above, say, 8mHz.

VHF? No way, Jose. Atmospheric ducting of VHF signals is a fairly frequent occurrence (I used to work Portugese stations regularly on 2 meters direct from my station in Rabat, Morocco), but there's no way it's gonna travel from the Bahamas to Alaska.

IMHO,

Bill
WA6CCA

Capt Phil · 26-07-2012, 11:41

I'm with you btrayfors... as a graduate of Gordon Wests' School of Instant Radio Operation, I recall him going into some detail years ago about propagation and 'skips' of VHF vs SSB and HAM signals. Quite common with SSB and HAM, VHF? not so much. There was one cruiser I got to know well who helped out with the Sonrisa net in the Sea of Cortez who became good friends with the Shaw of Iran who was a big HAM radio fan. He even had a card aboard his boat from the Shaw memorializing their radio friendship. Capt Phil

tbodine88 · 26-07-2012, 11:58

I was sailing up to Green Island off Antigua, when I spotted a catamaran stuck on the reef. I turned on the VHF and heard him hollering for help on channel 16. There was no answer, so I pulled out my Cable and Wireless Cell phone and called the local police. Once I got them, I called the catamaran on the VHF and told him what I'd done. Half an hour later the Antiguan Coast guard was there to pull him off.

I'd always thought they just weren't listening. Now I think maybe the island was blocking transmission since the Coasties were either in English Harbor or St Johns.

**btrayfors** · 26-07-2012, 12:08

Quote:

Originally Posted by Capt Phil

I'm with you btrayfors... as a graduate of Gordon Wests' School of Instant Radio Operation, I recall him going into some detail years ago about propagation and 'skips' of VHF vs SSB and HAM signals. Quite common with SSB and HAM, VHF? not so much. There was one cruiser I got to know well who helped out with the Sonrisa net in the Sea of Cortez who became good friends with the Shaw of Iran who was a big HAM radio fan. He even had a card aboard his boat from the Shaw memorializing their radio friendship. Capt Phil

Yep. Lotta celebrities on ham radio.

While in Morocco (CN8CW) I talked with JY1 (King Hussein of Jordan) and with EA0JC, King Juan Carlos of Spain. And, of course, Barry Goldwater was an active ham (K7UGA).

Bill
WA6CCA

Cyrus Safdari · 26-07-2012, 14:54

I understand that the SSB can bounce but the VHF didn't bounce -- according to this story (in Cruising World Jun '12 edition) a nearby cruise ship responded to the distress signal -- I'm assuming to the VHF since the SSB was going to Alaska? -- but no one else did (the cruise ship was too large to get close) The same story mentions other boaters nearby... that apparently did not respond. (She had to alert one with her searchlights)

How does that happen? The article doesnt explain.

I guess that maybe some of the other boats were not monitoring their radios -- but all of them? This is the Bahamas too! Normally everyone is listening in to everyone's communications on VHF!