Question about Ch 16

boristhebold · 31 August 2011, 15:41

Was out and about on Monday in Poole Bay, I noticed some numpty head had an open mic on channel 16 for a good few hours, sounded like they were chatting away in the background making their dinner. Apparently it was in the christchurch area somewhere.

So my question is what is the impact of an open mic, I know it stops us hearing things but does it also stop the coastguard / rnli etc, does it stop us being able to transmit on that channel. Can anyone explain better to me what happens.

Poly · 31 August 2011, 15:45

My understanding is the strongest signal will overpower all the others. So yes it can potentially wipe out quite a big area for quite some time. A number of radio manufacuturers have systems in place to stop you accidentally locking the mike on for long periods (so say after 10mins of transmit it just stops).

9D280 · 31 August 2011, 15:48

Potentially drown out a Mayday shout....

It's the same reason when you call someone on CH16 the first thing you do is agree what channel you are going to switch to, the second being to switch to a working channel!

It's related to one of the good things about MMSI "direct dial" - it doesn't clog 16.

Anchorhandler · 31 August 2011, 17:12

Sadly we suffered a problem last week on ch12.....for about 1.5 hours all we could hear were dogs barking????

Although Coast Guard and VTS still only transmit at 25w, they generally have some pretty big, high gain, low loss 'sticks' to help broadcast the message.

It would be difficult for a leisure boat vhf set to drown out the CG or VTS, especially if they are close to shore. Offshore and you happen to be on the threshhold for range of a CG broadcast station then somebody nearby with an 'open mic' could very well cause you problems.

I'm always dismayed at how many times we hear children messing about with a VHF set sometimes (but luckily rarely) for hours. Bring back electro-shock therapy!

Simon

boristhebold · 31 August 2011, 17:32

Thanks that makes sense. At the bournemouth airshow I heard some muppets singing a song on channel 16, the coastguard was not amused.

m chappelow · 31 August 2011, 17:58

in some cases the m.c.a (coastguard) will ask a lifeboat if its fitted with D/F (direction finding equipment ) to try locate the vessle or set,

one of our local fishing boats had the skipper squeeze the mike so hard that the switch stuck on transmit ,,unbeknown to him all we could hear for about 2 hours were the sound of a single cylinder diesel engine and the crew slagging all the other local fishing boats off that they came across ,,,bit embaressed when they finally got back to shore and realised what had happened ,,lol

willk · 31 August 2011, 18:04

Quote:

Originally Posted by boristhebold

I heard some muppets singing a song on channel 16, the coastguard was not amused.

Not entirely relevant, but recently I heard Belfast CG calling a test MAYDAY on 16 when they meant to make it on 0. Clyde CG were not amused. P&O Highlander was not amused. Few redners all round....

Ian M · 31 August 2011, 18:30

Many years ago (but not THAT many) we used to have female divers on the club dive boat

One of these beauties decided that it was too hot for her to be wearing a woolly hat, so she stuffed it into a gap in the console, directly above the mike

You guessed it.................. for 10 minutes we were transmitting on 16. Fortunately one of the more intelligent (male) members of the crew spotted it and it was discretely removed. Thankfully nothing had been said that identified us

Oh the shame

SPR · 31 August 2011, 18:53

I believe that DF equipment have been removed from coastguard ststions .. so need to task two resources now:

House of Commons - Transport Committee - Written Evidence

S.

SPR · 31 August 2011, 18:58

Quote:

Originally Posted by 9D280

It's related to one of the good things about MMSI "direct dial" - it doesn't clog 16.

But DSC Distress or Urgency will switch all radios to ch.16 after the Digital message is sent on ch 70

So still pita if somebody is jamming 16 , although they might notice if its DSC Radio bleeping ...

S.

9D280 · 01 September 2011, 10:42

Aye, but it removes all the "boat 1, this is boat 2 - go to channel 72?" type traffic.....

BogMonster · 01 September 2011, 10:54

Best cure for an open mike is one of these retuned to 16, no repeats

AGM-88 HARM - Wikipedia, the free encyclopedia

Courageous · 01 September 2011, 11:26

Will - what on earth is a "test Mayday"? We get practice pans all the time but can anyone tell me what the purpose of a test mayday would be? Any Lifeboat crew here care to elaborate?

willk · 01 September 2011, 14:11

Quote:

Originally Posted by Courageous

Will - what on earth is a "test Mayday"? We get practice pans all the time but can anyone tell me what the purpose of a test mayday would be? Any Lifeboat crew here care to elaborate?

Sry - my bad - it was an exercise Mayday Relay

m chappelow · 01 September 2011, 14:31

when allweather lifeboats were first fitted with D/F it saved literally hours and hours of searching in fog or bad visibility, all thats needed is a call to the casualty asking them to give a count to 10 and you can home in and head straight for them ,,as long as there was nothing in between such as a headland or reef .

jyasaki · 01 September 2011, 16:19

Quote:

Originally Posted by SPR

But DSC Distress or Urgency will switch all radios to ch.16 after the Digital message is sent on ch 70

Problem is that if your VHF has been scanning and locks onto station with a jammed mic, that's all you'll get. The VHF won't switch to another station until the channel it's receiving is idle (at least I think that's what'll happen.) If it's 16, fine, but if it's some other station, you're stuck there.

Quote:

when allweather lifeboats were first fitted with D/F it saved literally hours and hours of searching in fog or bad visibility, all thats needed is a call to the casualty asking them to give a count to 10 and you can home in and head straight for them ,,as long as there was nothing in between such as a headland or reef .

Well, you'll still head straight for them; you just won't quite get there...

jky

SPR · 01 September 2011, 17:24

unless you press scan stop the scanning process and untag the the affected channel... so when you restart scan it skips the jammed channel....VHF's are wonderful bits if kit if you spend some time playing with the features !

Scan, Dual Watch and Tri Watch are useful!

just DONT press the RED button when playing...

captnjack · 01 September 2011, 21:06

Quote:

Originally Posted by SPR

I believe that DF equipment have been removed from coastguard ststions .. so need to task two resources now:

House of Commons - Transport Committee - Written Evidence

S.

Odd, over here they have been upgrading their DF equipment, although our CG only recently got the capacity to hear digital frequencies (70).

We have open mike situations almost every weekend it seems. Sometimes the CG is able to break in and "override" the transmission, and/or provide some rough location of the offending transmitter. Mostly not though and everyone is just stuck waiting for it to cease. Stern messages about checking equipment for proper operation follow.

If I had a mayday or pan-pan while 16 was effectively jammed, I would try hailing our vessel traffic (VTS) and/or on the CG working channel (22a here).

gotchiguy · 01 September 2011, 22:28

Quote:

Originally Posted by BogMonster

Best cure for an open mike is one of these retuned to 16, no repeats

AGM-88 HARM - Wikipedia, the free encyclopedia

Made by Raymarine

ish

jyasaki · 02 September 2011, 01:32

Almost. That would be Raytheon building the missiles.

The Raytheon consumer division was renamed Raymarine after it was spun off about 10 years ago.