haydude
Well-Known Member
I was wondering if a crew member has a PLB and activates it in case of falling overboard, how would we be able to home on the PLB? Can only rescue services receive the homing signal on 121.5MHz?
Receiving PLB homing signal at 121.5MHz
- Thread starter haydude
- Start date
Courageous
Well-Known Member
No, aircraft can receive it too as we monitor this frequency on our second VHF units. WRT to homing in that is not something we are able to do. We can recognise the relative strength of a signal and usually report that to ATC but not much more. Some control towers have directional finding capability but unless they are near the coast then that is of minimal benefit. I think I read somewhere recently that DF kits are commercially available but can't recall where right now sorry.
Gin
Well-Known Member
You can have a handheld 'YAG' aerial on board to locate an activated PLB unit from an overboard crewmember. It's expensive (£600 last time I looked for my ACR brand PLB- it will work with any other brand on the same frequency of course) and bulky to stow but it could help to recover a crewmember quicker than a Mayday call-out
Last edited:
RestlessL
Well-Known Member
Homing devices are available, but expensive (£500 - £1500), and I doubt if many (if any) small boats carry them.
This is why I have just bought a SH HX851 handheld DSC VHF instead of a PLB. Similar price to a PLB, and a bit bulkier, but would give me a fighting chance of alerting the boat best placed to rescue me, rather than watch it disappear over the horizon under the control of the autopilot, with the crew down below.
A second benefit of the DSC handheld is that if knocked unconcious by the fall the crew could, when they realise that you are missing, send out a DSC Position Request to the handheld which would automatically display the MOB's position as a waypoint on the chartplotter.
J
nimbusgb
Well-Known Member
What you need is an old RDF unit with a swivel mounted aerial on top!
Lady Campanula
N/A
Bilgediver
Well-Known Member
And an old navigator mounted underneath...
Wonder which would be easiest to find???
grumpy_o_g
Well-Known Member
I agree with RestlessL, for the same money as a decent RDF unit you could probably buy a few PLB's and HX851's. Unless they've improved dramatically RDF's aren't that easy to use either. More to the point, make it a rule that people clip on when alone in the cockpit, etc. with lines short enough to stop them going overboard.
Robin
Well-Known Member
With our last boat we inherited 2 121.5 units that you carried or wore around your neck on a strap and were activated if you fell in saltwater. There was a receiver at the chart table that would pick up the transmission and sound a loud alarm but it did not offer a direction finding capability. I have to admit that despite putting in new batteries every year we never ever used them..
I thought, but may be wrong, that nobody monitors 121.5 any more so use as a personal beacon other than as a MOB device might be wasted?
I thought, but may be wrong, that nobody monitors 121.5 any more so use as a personal beacon other than as a MOB device might be wasted?
Courageous
Well-Known Member
Well rest assured it IS monitored!
Wonder which would be easiest to find???
The NAV - you'll find him flat out on the floor in the bar having been drunk under the table by the drivers!
Wonder which would be easiest to find???
The NAV - you'll find him flat out on the floor in the bar having been drunk under the table by the drivers!
Bilgediver
Well-Known Member
121.5 is the aviation equivelant of channel 16 and most commercial planes monitor it and refer to it as Guard frequency. You might be lucky for a passing BA or Airfrance to notify someone if heard. Might also be worth advising the coastguard if you activate in coastal waters so they can liase with civil aviation control centres.
Rescue helicopters and aircraft are equiped to home on this frequency.
Courageous
Well-Known Member
Just out of curiousity why BA or Airfrance?
john86uk
New Member
PLB's and 121.5 is still (and will for some time) be a very important part of GMDSS.
As an RNLI crew member i can assure you the 121.5 is still monitored. All RNLI all weather lifeboats carry direction finding radio equipment that can home in on 121.5 as do all SAR (search and rescue) aircraft.
Commercial aircraft also monitor this freq though they can't normally home in on it, but would normally alert the emergency services who have this capability.
DSC is not a suitable replacment for PLB's wether it has position polling or not. We cannot home in on a DSC signal as we require a constant RF transmission. PLB's will take you to the MOB's current position where as DSC will take you to the last transmitted position which could be miles away dependant upon Weather and tides.
PLB's and 121.5 is still (and will for some time) be a very important part of GMDSS.
Have you looked at the RNLI's MOB Guardian system, it is designed more with the single handed fisherman in mind but still very relevant.
http://www.rnli.org.uk/mob_guardian/
As an RNLI crew member i can assure you the 121.5 is still monitored. All RNLI all weather lifeboats carry direction finding radio equipment that can home in on 121.5 as do all SAR (search and rescue) aircraft.
Commercial aircraft also monitor this freq though they can't normally home in on it, but would normally alert the emergency services who have this capability.
DSC is not a suitable replacment for PLB's wether it has position polling or not. We cannot home in on a DSC signal as we require a constant RF transmission. PLB's will take you to the MOB's current position where as DSC will take you to the last transmitted position which could be miles away dependant upon Weather and tides.
PLB's and 121.5 is still (and will for some time) be a very important part of GMDSS.
Have you looked at the RNLI's MOB Guardian system, it is designed more with the single handed fisherman in mind but still very relevant.
http://www.rnli.org.uk/mob_guardian/
Last edited:
Robin
Well-Known Member
I can't think why or where I thought I heard 121.5 was no longer monitored but whatever it was prior to then we kept our little personal ones in the grab bag rather than wore them for the MOB function as I said in an earlier reply. Maybe it was because they are only now for personal (implying local area as in SAR) use rather than like a 406 EPIRB? Buqqer, if 'd known they were still useful I might not have sold them with the boat!
rob2
Well-Known Member
IIRC Hams have hare and hounds events when they use their home-made DF aerials to locate a signal. Do we have any Hams who'd like to knock up a set based on a 121.5 crystal? Receive only, so no licensing problems...
Rob.
Rob.
haydude
Well-Known Member
The reason for my query was because I am considering the purchase of a PLB. PLB will broadcast the emergency call to satellite, but also send an homing signal on 121.5MHz.
It does not really matter if 121.5MHz is remotely monitored, what matters is that if I loose a crew member overboard 100nm from land, and he has a PLB I would like to get to the MOB first and ASAP and an homing signal receiver would be essential.
So how do I get hold of one? That is because a PLB makes lesser sense if the only ones receiving the emergency call are far away emergency services who might not be able to contact me to tell me the MOB position because I am beyond VHF reception range.
Since I understand that in order to receive a PLB homing signal one should have special equipment, it would make more sense if these PLBs also broadcasted their position on DSC or AIS VHF.
It does not really matter if 121.5MHz is remotely monitored, what matters is that if I loose a crew member overboard 100nm from land, and he has a PLB I would like to get to the MOB first and ASAP and an homing signal receiver would be essential.
So how do I get hold of one? That is because a PLB makes lesser sense if the only ones receiving the emergency call are far away emergency services who might not be able to contact me to tell me the MOB position because I am beyond VHF reception range.
Since I understand that in order to receive a PLB homing signal one should have special equipment, it would make more sense if these PLBs also broadcasted their position on DSC or AIS VHF.
john86uk
New Member
Again haydude look at the RNLI's MOB Guardian.
Each crew member wears a PLB which is wirelessly connected to the base unit fitted aboard. Should a crew member fall over the side then the wireless link breaks after a short distance. At this point the base unit will sound an alarm alerting the remaining crew on board. As this happens instantly the crew member should still be within sight.
As well as sounding an alarm the base unit also transmits a distress signal ashore.
More details below.
http://www.rnli.org.uk/mob_guardian/how_it_works
grumpy_o_g
Well-Known Member
True, but neither is the PLB a replacement for a DSC set as the yacht can't get a position fix from the PLB, whereas a couple of DSC transmissions could get a boat quickly back to the location of the MOB if they had a DSC handheld with them that they could transmit regularly from - that could get them back on board within minutes without needing to tie up rescure services. At the moment you really need both to cover all the bases.
RestlessL
Well-Known Member
If you need a constant RF transmission all you need do is ask the casualty to hold down the PTT.
If you want a current position, just ask the casualty to send a new DSC distress call. Or, if you know the MMSI (from an earlier distress call) then send a DSC position request.
DSC Handhelds with GPS (such as the SH HX851 have only been available in the UK for a couple of months, so I suspect that they have not yet reached the RNLI training manuals. However, the ability to seek help from craft in the vicinity should not be dismissed.
Ideally I would carry both a PLC and a DSC Handheld, but I see the VHF as the more useful of the two.
J
st599
Well-Known Member
What does receive only have to do with licensing problems?
If you haven't got a licence for a particular frequency you can't legally monitor either.
