Coast Guard using US mode on radio

[wedivebc]

Forgive me if this has been discussed before but...
Why does both US and Candian Coast Guard insist on using US mode working channels on VHF? My radio can switch channels from the mike button but if I have to switch to US mode (which CG seems to insist on) I have to go below and change a setting on my radio. Does US mode have greater range or is there something else I'm missing?

[Stu Jackson]

For those channels of concern to you, have you checked the actual frequencies being used?

[wedivebc]

Originally Posted by Stu Jackson

For those channels of concern to you, have you checked the actual frequencies being used?

Not sure what you're getting at. USCG uses 22a and CCG uses 83a as working channels.

[Alan Mighty]

Originally Posted by wedivebc

My radio can switch channels from the mike button but if I have to switch to US mode (which CG seems to insist on) I have to go below and change a setting on my radio. Does US mode have greater range or is there something else I'm missing?

You raise a messy topic, wedivebc. Messy, because the history has not been well documented and so it's very hard to discuss accurately.

One way (not the only way and not guaranteed to 100% accurate) of looking at the situation is:

* in around 1947, by agreement at an international conference held in New Jersey, three chunks of the VHF spectrum were allocated to maritime mobile use for safety. But the bottom line always was that individual jurisdictions (i.e. nation states) had to exert their political will to safeguard the spectrum allocation for maritime mobile.

* in the US, in 1948 the USCG did deals with the US FCC, surrendering some spectrum and getting the 21A thru 24A channels in return.

* in other jurisdictions (i.e. outside the US), different nation-states did slightly different things, but generally three chunks of VHF spectrum were allocated to maritime mobile. In truth, VHF 16 is the minimum that is protected around the world. Some jurisdictions don't like their citizens having access to VHF transceivers at all. Not mentioning any names now.

* in the US, the several railway companies were politically much more powerful than the unorganised users of maritime mobile. So the US ended up with only two of those three chunks of VHF spectrum allocated to maritime mobile. And one of the two chunks was made thinner than elsewhere. Railways and other commercial uses took what in non-US jurisdictions is maritime mobile spectrum.

* back in the 1980s, there was a marine incident. A foreign flagged ship was navigating in US waters. The USCG had broadcast a warning (on 21A or one of those other USA-only channels) that a barge carrying flammable petrochemicals (petrol or gasoline, depending what side of the creek you went to school) was adrift. The foreign flagged ship was, not surprisingly, not monitoring the US channels and so received not that warning broadcast. The captain of the foreign flagged ship was not happy. The eventual result was that the US Houses of Congress legislated that all foreign-flagged ships in US waters must carry a VHF transceiver with a switch that changed from "international mode" to the more restricted (but with the 21A - 24A channels that the USCG had bartered from the US FCC) "US mode". Although not governed by US law, most all of this planet's manufacturers of VHF sets have installed that switch. No one specified that that switch should be easy to use - quite the contrary.

* as I understand it, you're in a jurisdiction that neighbours the US. So you're what everyone calls 'SOL'. You ain't got much choice.

* a side benefit (which we're not allowed to talk about, so please close your eyes now) is that one or two of those channels that the USCG bartered from the US FCC, the 21A to 24A spread, is not much used outside the US. So if you want to have a conversation with another cruiser in, say, (insert the name of a non-N American or Central American country), you can look at the frequency list, identify which of those -A channels is not used "iinternationally" and agree to use it. You can open your eyes now. (of course, in at least one "international" jurisdiction, if that -A channel is overused, the local radio police do their best to track down the mis-users of it. Nudge, nudge, wink, wink. 'Nuff said.)

[Paul L]

If you are in Canada or the US why would not just leave your VHF in US Mode?

[alctel]

Doesn't the CCG use Canada mode? That's what I left mine in while in Canada. I switched it to US mode once in Mexico, as people were using US mode and a channel that I had no access to in Canada mode (63 I think)

[gamayun]

Very interesting maritime history, Alan Mighty. I had never heard of this before.

[Brian.D]

It all boils down to this: each country/region is allocated frequencies to use according to the International Telecommunications Union (ITU). Since VHF is pretty much Line of Sight it has limited range and therefore frequencies can be reused. In the case of the US and Canada, certain frequencies are shared but their use might be different.

As an example, take channel 22 and 22A. Most of the channels assigned in VHF Maritime are duplex frequencies. This means (and I am not talking down to anyone) that the transmit and receive frequencies are different. In the US, the "A" designation, as in 22A, means the channel is a simplex channel where the transmit frequency and receive frequency are the same. Here, I believe the 161.7 MHz frequency (the other half of the channel 22 pair) is used somewhere else.

This holds true for geostationary satellites. There are three different sets of down link frequencies. This because some of the downlink frequencies are used by microwave system throughout the world. The satellite downlink could interfere with the microwave links.

As for the dissertation above, I too have never hear that story. It sounds plausible.

[Stu Jackson]

Originally Posted by wedivebc

Not sure what you're getting at. USCG uses 22a and CCG uses 83a as working channels.

You originally asked about MODE, now you're noting the channels are different. Mode and channel are different.


Leave it on one or the other mode, it will read both channels.


If you check the frequencies of each, you may find they are identical in each mode for each channel.

[stewie]

All maritime VHF channels have the same range.

[wedivebc]

Originally Posted by alctel

Doesn't the CCG use Canada mode? That's what I left mine in while in Canada. I switched it to US mode once in Mexico, as people were using US mode and a channel that I had no access to in Canada mode (63 I think)

CCG requires you to switch to 83a for working channel. If you are dealing with an emergency switching modes is an added task loading step that seems unnessasary

[stormalong]

Originally Posted by Stu Jackson

You originally asked about MODE, now you're noting the channels are different. Mode and channel are different.


Leave it on one or the other mode, it will read both channels.


If you check the frequencies of each, you may find they are identical in each mode for each channel.

No, They are not the same frequencies or the same channels. That is the point of which mode you are in. You cannont talk on the USCG working channels in international mode and the channel designations are suffixed for that reason. Also some trivia - England has at least one channel that is different from both US and international. My British friends used their own private channel.

[redneckrob]

Originally Posted by wedivebc

CCG requires you to switch to 83a for working channel. If you are dealing with an emergency switching modes is an added task loading step that seems unnessasary

If you are in the middle of an emergency where switching to 83a will increase you likelihood of death or injury the Coast Guard will keep you on 16. If they don't, you should call the command you were working with on the phone when everything is resolved and speak to a supervisor, as switching someone in the throes of a genuine emergency is not in keeping with standard operating proceedure.

[requiem]

The temptation would be to leave the set in the US mode unless that locks out any Canadian frequencies that you actually make use of. The US frequencies seem easily searchable, and RBR-2 — Technical Requirements for the Operation of Mobile Stations in the Maritime Service - Spectrum management and telecommunications has a table of the Canadian ones partway down the page. Of course, if you also use channels 23B or 83B and don't have a Canada-specific mode you might be out of luck.

[stormalong]

Originally Posted by requiem

The temptation would be to leave the set in the US mode unless that locks out any Canadian frequencies that you actually make use of. The US frequencies seem easily searchable, and RBR-2 — Technical Requirements for the Operation of Mobile Stations in the Maritime Service - Spectrum management and telecommunications has a table of the Canadian ones partway down the page. Of course, if you also use channels 23B or 83B and don't have a Canada-specific mode you might be out of luck.

Huh??? Just leave it in U.S. mode. Canada uses U.S. mode for it's comms. No need to keep the radio in international mode for Canada.