VHF Radio Use

[sww914]

I understand what a duplex channel is but I don't understand what you mean. I know that my VHF has a usa/int button and that one is duplex and the other is not but I don't know which is which. In Mexico we use the USA setting and everything works.

[s/v 'Faith']

While the law requires the radio be on, it makes no mention of where the squelch must be set. If the constant chatter bothers you, try turning the squelch up.

[GrowleyMonster]

Originally Posted by goboatingnow

Just for the " avoidance of doubt ". There are two licenses in a radio setup aboard , the operators license and the ships station license. The callsign/mmsi are assigned with the ships license.

Dave

Quite right, Dave. Ship Station License is separate. Ham license includes ham station license but regular license does not cover the station.

There are third party organizations that can issue an MMSI for domestic use, for programming DSC radios, EPIRB, AIS, and so forth, but only an MMSI issued with the ship station license by the FCC is usable in the waters of most other countries. A lot of confusion arises because of that. Typically such things are not checked but you never know. Could get a citation and fine for not having proper Ship Station License and government issued MMSI.

[Wotname]

Originally Posted by nolandinsight

As for 121.5 it's my understanding that its the frequency that EPIRB and aircraft ELT transmit on for radio location. I wasn't aware that the frequency was acceptable to use for voice traffic of any kind. Perhaps my ignorance is showing... If it is I at least hope it's worthy of viral video status. You know what they say, if your going to do something wrong, do it upside down and on fire!

121.5 MHz is the international emergency air band VHF frequency. It's use is restricted to emergency (mayday) calls only. That can take the form of voice or EPIRB / ELT / PLB transmissions. It's use as calling frequency is unauthorised but I understand such is common in some parts of the world

[Cormorant]

My VHF pet peeve is the garbled delivery of the Coast Guard radio operators. In the areas where I sail, mostly northeast U.S., way too often a pan-pan will come over the airwaves as "PANPANPANPANPANPANadvisepersoninwateratlatitude42 #%&&
longitude7??#!@mumblemumbleallvesselskeeplookout."

What did he (or she) just say? Their delivery seems rushed, unclear, blurted out, like they just want to get the whole thing over with. The lat /long especially need to be delivered slowly if anyone wants to either write them down or even just absorb them properly.

It's not always like that, but it happens so often that it has become a bit of a running joke. I think all CG operators should be given public speaking and enunciation lessons. Lives may depend on it.

[Hudson Force]

Originally Posted by Cormorant

My VHF pet peeve is the garbled delivery of the Coast Guard radio operators. In the areas where I sail, mostly northeast U.S., way too often a pan-pan will come over the airwaves as "PANPANPANPANPANPANadvisepersoninwateratlatitude42 #%&&
longitude7??#!@mumblemumbleallvesselskeeplookout."

What did he (or she) just say? Their delivery seems rushed, unclear, blurted out, like they just want to get the whole thing over with. The lat /long especially need to be delivered slowly if anyone wants to either write them down or even just absorb them properly.

It's not always like that, but it happens so often that it has become a bit of a running joke. I think all CG operators should be given public speaking and enunciation lessons. Lives may depend on it.

I hear this same message from Coast Guard station "S'besoudef%port" in the South! It's disappointing that important information is presented so poorly.

[Jeff W]

Just new to this forum and hope to do some cruising in the future. I'm a very inexperienced sailor but an experienced pilot.

On the question of emergency communications, there is absolutely no reason that the aviation emergency frequency of 121.5 mhz couldn't be used in an emergency situation. Of course the primary means of distress alerting should be through the usual marine VHF/HF frequencies, DSC , EPIRB etc. However, if unable to establish comms on the marine frequencies and you can see an overflying aircraft, you should be able to talk to it on 121.5 using a cheap handheld aviation vhf transceiver. Is it legal, probably not, but if it gets you saved who cares.


The protocol to establish comms would be something like. "Aircraft near position
23 south 155 west this is sailing vessel xxxxxx". Once you established comms with the aircraft then transfer to 123.45 mhz, which is the general chat freq. Any emergency message could be passed to the aircraft, who are in direct comms to air traffic control, who have a direct line to search and rescue agencies.


Close to coastal areas this method of comms should be used for emergencies only, however when far from land ( mid ocean), you could even call for a general chat or get the aircraft to pass a non emergency message for you. For long haul flights once you are about 250 miles from the coast you are generally transferred from the active VHF ATC frequency and most comms are then carried out by a SATCOM computer datalink system with a HF backup using SELCAL (selective calling, where HF isn't monitored but ATC can call you if required). Pilots will then have 1 VHF set tuned to 121.5 and generally the other tuned to 123.45 ( in the pacific and indian ocean areas).


For long haul oceanic flights there isn't very much to do in cruise, just monitoring aircraft systems and sending position reports every 30 mins (even this is automated now). Around Asia you are generally a lot busier.
Most of the time you're just sitting looking outside at the stars or down at the occasional light on the water far from anywhere wondering who's down there. For a passing aircraft you would have a window of about 20-30mins where the aircraft would be in VHF line of sight range.


A handheld aviation transceiver should be part of your comms gear for a serious cruiser. For info, normal aircraft don't have the ability to transmit on VHF marine freqs, except that aircraft engaged in Search and Rescue would have the ability.


Hope this info is useful.

[Jeff W]

Just as an addition (unable to edit previous message), non emergency voice comms on 121.5 ARE authorised, but should be minimised. Its use is the same as channel 16, establish comms then transfer to a working frequency.

Typically aircaft will use 121.5 to establish comms with a nearby aircraft to discuss traffic, weather, turbulence etc. Also ATC can ask an aircraft to call another aircraft on 121.5 when that aircraft has gone off frequency, ie out of range.

[Dockhead]

Originally Posted by Jeff W

Just new to this forum and hope to do some cruising in the future. I'm a very inexperienced sailor but an experienced pilot.

On the question of emergency communications, there is absolutely no reason that the aviation emergency frequency of 121.5 mhz couldn't be used in an emergency situation. Of course the primary means of distress alerting should be through the usual marine VHF/HF frequencies, DSC , EPIRB etc. However, if unable to establish comms on the marine frequencies and you can see an overflying aircraft, you should be able to talk to it on 121.5 using a cheap handheld aviation vhf transceiver. Is it legal, probably not, but if it gets you saved who cares.


The protocol to establish comms would be something like. "Aircraft near position
23 south 155 west this is sailing vessel xxxxxx". Once you established comms with the aircraft then transfer to 123.45 mhz, which is the general chat freq. Any emergency message could be passed to the aircraft, who are in direct comms to air traffic control, who have a direct line to search and rescue agencies.


Close to coastal areas this method of comms should be used for emergencies only, however when far from land ( mid ocean), you could even call for a general chat or get the aircraft to pass a non emergency message for you. For long haul flights once you are about 250 miles from the coast you are generally transferred from the active VHF ATC frequency and most comms are then carried out by a SATCOM computer datalink system with a HF backup using SELCAL (selective calling, where HF isn't monitored but ATC can call you if required). Pilots will then have 1 VHF set tuned to 121.5 and generally the other tuned to 123.45 ( in the pacific and indian ocean areas).


For long haul oceanic flights there isn't very much to do in cruise, just monitoring aircraft systems and sending position reports every 30 mins (even this is automated now). Around Asia you are generally a lot busier.
Most of the time you're just sitting looking outside at the stars or down at the occasional light on the water far from anywhere wondering who's down there. For a passing aircraft you would have a window of about 20-30mins where the aircraft would be in VHF line of sight range.


A handheld aviation transceiver should be part of your comms gear for a serious cruiser. For info, normal aircraft don't have the ability to transmit on VHF marine freqs, except that aircraft engaged in Search and Rescue would have the ability.


Hope this info is useful.

Very interesting.

You mentioned legality of making a distress call on an aviation frequency -- AFAIK, if you are genuinely in distress, it is legal to use any all frequencies you can, so I believe this would be perfectly legal.

Many radio amateurs have handheld VHF/UHF transceivers which after some minor modifications can transmit on aircraft bands. Do you really think that you can communicate with an aircraft flying at FL 35 with a 5 watt handheld? If so, then it makes sense to take our ham handhelds into the liferaft with us.

[Wotname]

Originally Posted by Dockhead

Very interesting.

You mentioned legality of making a distress call on an aviation frequency -- AFAIK, if you are genuinely in distress, it is legal to use any all frequencies you can, so I believe this would be perfectly legal.

Many radio amateurs have handheld VHF/UHF transceivers which after some minor modifications can transmit on aircraft bands. Do you really think that you can communicate with an aircraft flying at FL 35 with a 5 watt handheld? If so, then it makes sense to take our ham handhelds into the liferaft with us.

Yes

[Jeff W]

Yes, legal wasn't the right term, the old 121.5 epirbs were used for vessels in distress to alert aircraft, but I've never heard any discussion about voice alerts by boats on 121.5.

35,000 feet is only 6 nm, so even a small handheld should be able to talk to an aircraft directly overhead. Aviation forums talk about a handheld radio having a Range of about 5nm transmit talking to a ground station using the inbuilt antenna (25nm with an external antenna). However, that is transmitting from inside the cockpit. Standing on deck you should have more range. You probably won't have 20-30 minute window but comms would be possible when close to overhead.

You can also get an adaptor to connect a standard marine vhf antenna connector (pl-259 ?) to a handeld radio BNC connector. This should allow you to connect a VHF aviation handheld to a yacht mast antenna. Although not ideally matched, the frequencies are fairly close and this should increase you range.

I remember doing a practise search and rescue years ago, P3C Orion searching for a liferaft. Were able to talk to the personnel in the raft up to about 15-20nm, they were using a handheld.

As an aside, for search and rescue, the best device to attract the attention of a searching aircraft by day is your signalling mirror. We were able to see flashing of the mirror easily 20 nm away. Its amazing how this stands out.

[Dockhead]

Originally Posted by Jeff W

Yes, legal wasn't the right term, the old 121.5 epirbs were used for vessels in distress to alert aircraft, but I've never heard any discussion about voice alerts by boats on 121.5.

35,000 feet is only 6 nm, so even a small handheld should be able to talk to an aircraft directly overhead. Aviation forums talk about a handheld radio having a Range of about 5nm transmit talking to a ground station using the inbuilt antenna (25nm with an external antenna). However, that is transmitting from inside the cockpit. Standing on deck you should have more range. You probably won't have 20-30 minute window but comms would be possible when close to overhead.

You can also get an adaptor to connect a standard marine vhf antenna connector (pl-259 ?) to a handeld radio BNC connector. This should allow you to connect a VHF aviation handheld to a yacht mast antenna. Although not ideally matched, the frequencies are fairly close and this should increase you range.

I remember doing a practise search and rescue years ago, P3C Orion searching for a liferaft. Were able to talk to the personnel in the raft up to about 15-20nm, they were using a handheld.

As an aside, for search and rescue, the best device to attract the attention of a searching aircraft by day is your signalling mirror. We were able to see flashing of the mirror easily 20 nm away. Its amazing how this stands out.

If my mast is up and I'm still on the mother ship, then I have HF radio with DSC, so that won't be necessary. But the handheld in the liferaft is good.

I actually have a VHF/UHF ham radio antenna on my first spreader, a really good Diamond with its own radials and about 2 meters long (so full wave on 2 meter VHF). With my 5 watt handheld I get a crystal clear signal on a repeater 20 nautical miles away over terrain.

I'm sure talking to aircraft would be child's play with that antenna, but I won't have it in the life raft.

[Jim Cate]

FWIW,

We often hear Australian Customs coastwatch aircraft calling vessels many miles away on ch 16. Since one can safely assume that the aircraft is calling a vessel within their visual range, this implies that DX comms between aircraft and surface yachts on VHF frequencies are indeed easy.

Thanks for the thoughtful posts Jeff.

Cheers,

Jim

[Dockhead]

Originally Posted by Jim Cate

FWIW,

We often hear Australian Customs coastwatch aircraft calling vessels many miles away on ch 16. Since one can safely assume that the aircraft is calling a vessel within their visual range, this implies that DX comms between aircraft and surface yachts on VHF frequencies are indeed easy.

Thanks for the thoughtful posts Jeff.

Cheers,

Jim

Looks like aircraft VHF uses AM modulation! Not SSB, but A3E - like broadcast AM with both sidebands and a carrier! See: Airband - Wikipedia, the free encyclopedia. I was surprised to read this.

If this is true, then we cannot talk to aircraft with our amateur handhelds, which may receive AM, SSB, etc., but can transmit only in FM.

More sophisticated non-handheld ham radios might be able to transmit in AM.

[Kordie]

I have spoken to helicopters on my handheld VHF.