radio repeater

[redsky49]

This was mentioned in regard to the cruising couple attacked this week at Union Island:

"Cruisers are recommended to have a radio repeater on VHF Ch 66 at all times whilst cruising these waters and to monitor it overnight."

I am not sure what is being referred to in this statement. Can anyone explain?

[btrayfors]

I'm sure they meant a vhf receiver tuned to the repeater frequency used in those parts, i.e., channel 66.

Bill

[s/v Jedi]

I believe it was Jonathan of Island Water World who set up this marine VHF repeater on a high peak in Grenada. It has been in use since 2003 at least. It can even reach Trinidad and was used for emergency traffic during hurricane Ivan. It is normally used by local fisherman who only carry handhelds.

[btrayfors]

Originally Posted by s/v Jedi

I believe it was Jonathan of Island Water World who set up this marine VHF repeater on a high peak in Grenada. It has been in use since 2003 at least. It can even reach Trinidad and was used for emergency traffic during hurricane Ivan. It is normally used by local fisherman who only carry handhelds.

Jedi,

Do you know the input frequency for that repeater?

Bill

[Dennis.G]

Repeaters work on duplex channels - where transmit and receive are different frequencies. The repeater simply retransmits the "transmit" signal to the "receive" signal. Transmission between two stations requires the repeater to complete the transmission.

This is at least how system I used for years while on ski patrol worked.

[redsky49]

This is a fuller excerpt from the referenced quote:


"VHF Channel 66 Repeater was privately donated to the Grenadian Government and is used by the Grenada Cruisers Net to provide coverage to all Grenadian waters. It can also be received in southern parts of St Vincent and the Grenadines and the northern parts of Trinidad including Chaguaramas Bay. The Grenada Cruisers Net supplies weather, advice, and information on many subjects to help make Cruisers’ stay in Grenada more rewarding. Its broadcast each day at 7:30 AM.
Cruisers are recommended to have a radio repeater on VHF Ch 66 at all times whilst cruising these waters and to monitor it overnight."


And it was taken from this Noonsite thread:


St. Vincent & the Grenadines, Union Island: Violent attack on cruising boat - further information — Noonsite


Is there a way to rebroadcast a VHF signal? Some sort of daisy chain?


In the past I have assisted the Coast Guard in relaying emergency messages for vessels due to the distances involved, but that was merely repeating (manually) information I was receiving.

[ranger58sb]

Originally Posted by redsky49

Is there a way to rebroadcast a VHF signal? Some sort of daisy chain?

In the past I have assisted the Coast Guard in relaying emergency messages for vessels due to the distances involved, but that was merely repeating (manually) information I was receiving.

Our local automated "radio check" capability -- to mitigate traffic on Ch 16 -- uses Ch 27 and it automatically repeats the transmission (radio check request) it just heard. Same receiving and retransmitting frequency. Sponsored by SeaTow, as I understand it.

-Chris

[btrayfors]

I should have checked my VHF frequency list before posting that question to Jedi.

Marine Channel 66 is a duplex channel, under the International scheme. It uses the following two frequencies:

Ship Transmit 156.325 mHz
Ship Receive 160.925 mHz

So, it's automatic. Dial to Channel 66 and you'll be listening to the repeater on 160.925 mHz.

Bill

[MarkJ]

The statement I made "VHF Channel 66 Repeater was privately donated to the Grenadian Government" appears to be wrong and its privately owned.

In Grenada there are two repeaters, one on 66 for Cruisers and one on 84 for Fishermen. Both Duplex channels
The Grenada Cruisers Net uses 66 and also supplies weather to Fishermen daily on 84.

The morning net on 66 receives radio checks from as far north as Union Island in St Vincent and the Grenadines and Chamungas in Trinidad.

Its real coverage is all of Grenada's 3 islands of Grenada, Cariacou and Petite Martinique.
It means we can supply weather information to boats outside Internet range so they may cruise more widely during the Hurricane Season.

The repeater on 66 was instrumental in coordinating the response to the attack in Union Island some 40nms north of us to medical assistance 32nms north of us over the full length and height of mountainous Grenada. Voice reception was excellent.

As DSC works on VHF 70 and reverts to VHF 16 - neither with a repeater - if the red Distress Button was used in that attack no one would have heard, nor any effective response could have been made until we had got everyone back on 66.

Further, neither the Police nor the Coast Guard have DSC equipped radios.

Thats why in this area (ONLY!) do we recommend cruisers mount a 24 hour security watch on 66 as well as 16/68 and to ensure its monitored overnight.

To people in other areas where coms are affected by distance or terrain can I highly recommend passing the hat for a VHF repeater. I dunno what they cost but I would expect the hat may need to be passed twice....


Mark

[ranger58sb]

Originally Posted by ranger42c

Our local automated "radio check" capability -- to mitigate traffic on Ch 16 -- uses Ch 27 and it automatically repeats the transmission (radio check request) it just heard. Same receiving and retransmitting frequency. Sponsored by SeaTow, as I understand it.

-Chris

Ooops, I should have double-checked first, too. Ch 27 in the U.S. is duplex, ship transmit 157.350 MHz, ship receive 161.950.

-Chris

[redsky49]

Originally Posted by MarkJ

The statement I made "VHF Channel 66 Repeater was privately donated to the Grenadian Government" appears to be wrong and its privately owned.

In Grenada there are two repeaters, one on 66 for Cruisers and one on 84 for Fishermen. Both Duplex channels
The Grenada Cruisers Net uses 66 and also supplies weather to Fishermen daily on 84.

The morning net on 66 receives radio checks from as far north as Union Island in St Vincent and the Grenadines and Chamungas in Trinidad.

Its real coverage is all of Grenada's 3 islands of Grenada, Cariacou and Petite Martinique.
It means we can supply weather information to boats outside Internet range so they may cruise more widely during the Hurricane Season.

The repeater on 66 was instrumental in coordinating the response to the attack in Union Island some 40nms north of us to medical assistance 32nms north of us over the full length and height of mountainous Grenada. Voice reception was excellent.

As DSC works on VHF 70 and reverts to VHF 16 - neither with a repeater - if the red Distress Button was used in that attack no one would have heard, nor any effective response could have been made until we had got everyone back on 66.

Further, neither the Police nor the Coast Guard have DSC equipped radios.

Thats why in this area (ONLY!) do we recommend cruisers mount a 24 hour security watch on 66 as well as 16/68 and to ensure its monitored overnight.

To people in other areas where coms are affected by distance or terrain can I highly recommend passing the hat for a VHF repeater. I dunno what they cost but I would expect the hat may need to be passed twice....


Mark

Thank you for the explanation. Makes things much clearer to me.
A couple of points:

"As DSC works on VHF 70 and reverts to VHF 16 - neither with a repeater - if the red Distress Button was used in that attack no one would have heard, nor any effective response could have been made until we had got everyone back on 66"

This would very likely never have occurred to me. In any panic situation I most likely would have hit the DSC and started motoring to safety, oblivious to the fact that I had inadverdently cut off communications.

Is channel 68 the local cruiser "calling" channel? I am not sure that every boaters radio is capable of three channel monitoring - 16, 66 and 68.

Do active cruisers truly monitor the radio 24 hours? I have never been in an area where I felt that would be required. Are things that tense/dangerous?

[MarkJ]

Originally Posted by redsky49

Do active cruisers truly monitor the radio 24 hours? I have never been in an area where I felt that would be required. Are things that tense/dangerous?

I always monitor 68 and was doing 66 too till some crackle came on it about a week before the SVG attack. Now I have them on scan.

No, not tense/dangerous... but in the 4 months I have been here theres been a boat at 10pm on the rockery; one on fire at dawn; the Union Island attack and a cluster of 3 attemped dinghy thefts on one night night.... all of which required immediate response.

The dinghy theft cluster the first one recovered their dink and didnt warn everyone else.... so 2 others went that night... LOL



24 hour coms are needed for all sorts of incidents, not just attacks! This photo is just after dawn. The fire started about 4:20am if everyone was on 68/66 early we could have had 50 cruisers with 200 fire extinguishers!

[JPA Cate]

It's one of those deals: would you regret the loss of the night's sleep or not helping someone who needed it more? If you'd rather be helping, then monitor the VHF. Most nights you won't be awakened. If you are, someone probably needs help. In addition, who's going to be nearest to respond? Us. Lots of places we're it, there are no professional services. YMMV We don't always monitor, but have done so and will do so again.

[btrayfors]

From the USCG NavCenter website:

"Radio Watchkeeping Regulations

In general, any vessel equipped with a VHF marine radiotelephone (whether voluntarily or required to) must maintain a watch on channel 16 (156.800 MHz) whenever the radiotelephone is not being used to communicate."

http://www.navcen.uscg.gov/?pageName=mtWatch

This is generally interpreted to mean a 24-hour watch, i.e, whenever you're on the boat....sleeping or not.

To be in compliance, if you're going to monitor, e.g., Channel 66 or any other Channel, you should do so using the Dual Watch capability of your VHF radio (so, you'd be monitoring Channel 66 AND Channel 16).


Any DSC-equipped vessel should receive a DSC call OK, no matter what channel it's tuned to, since DSC signalling is on Channel 70 and is always monitored (either continuously as in Class-D DSC radios, or sampled as in earlier DSC radios).


Bill
WA6CCA

[redsky49]

Of course I would pitch in to help fellow cruisers - I have received enough help over the years that I need to pay it back - but I typically turn off the VHF when I turn the anchor light on. I'm just a miser with the amps.

Sleeping in the aft cabin, I am not certain that I would hear the radio located in the salon unless it was turned way up.

Guess I will have to change my ways.

As for DSC, I am not aware of ever receiving a DSC call. When I was involved with a rescue operation in the Bahamas years ago, I called for support on 16 and was surprised that I had such little response. I think most people were at a dock or anchorage, had no radio on or figured that someone else would help. It turned out well in the end, but calling "Mayday" on the radio sure got my adrenalin flowing.

I wonder how widespread DSC has become? Sorry, thread wander...