DSC Question......Not Medals :-)

[pau1gray]

We have two vessels berthed on the same pontoon SS is fitted with Simrad RD68 and MS is fitted with an ICOM M241. I have tested the DSC options on SS using my own set on my boat and that all seems to work OK.
I have programmed the MMSI into the ICOM on MS today and can't seem to get it to make an individual call - I have checked, double checked and even got someone else to check that I've put in the correct number, so I'm happy on that score.

If I try and make an individual call to SS, when I follow the instructions through in the manual i.e I select Individual Call, Select SS from the list or type in the MMSI of SS, select the channel to chop to and push enter it say individual call ready press enter again to transmit the call - it seems as if the radio switches off then switches back on, on Ch70 and is waiting for he acknowledge. SS does not receive the Individual Call ?????

If I try it the other way and get SS to call MS then the DSC is received on MS but the acknowledge is not received on SS (again MS radio goes blank for a second or two when I try and acknowledge the call) The two boats are only 20 m apart.

It would seem that any attempt to get MS to transmit a DSC call request causes the radio to reboot!

Have any experts on here got any clues?

I know that DSC is the bane of some peoples life on here but we want to check it's all working on the two boats in case we need it one day

 

[Doghousekeeper]

Sounds as if you're doing it all right - in which case the it's radio itself that is probably the problem.

 

[Bilgediver]

If I try it the other way and get SS to call MS then the DSC is received on MS but the acknowledge is not received on SS (again MS radio goes blank for a second or two when I try and acknowledge the call) The two boats are only 20 m apart.

It would seem that any attempt to get MS to transmit a DSC call request causes the radio to reboot!

Have any experts on here got any clues?
)

I am wondering if the supply of power to the radio is ok..Did you try making a voice call and if so was there any dimming of the display when transmitting on full power.

It is possible the voltage at the radio drops too low when full power is demanded for the DSC transmission.

 

[Doghousekeeper]

I am wondering if the supply of power to the radio is ok..Did you try making a voice call and if so was there any dimming of the display when transmitting on full power.

It is possible the voltage at the radio drops too low when full power is demanded for the DSC transmission.

I thought DSC transmission used less power than voice?

 

[pau1gray]

Gold star to BilgeDiver - was indeed power problem - I noticed that transmission on Ch16 was causing the same problem i.e radio goes off then on. I also noticed that various other things i.e GPS reset. Never seen the problem before as we only ever speak to plymouth port control on Ch14 (1W) and never bother the CG on 16.

For info the DSC transmission is transmitted on CH70 at high power

 

[PaulGooch]

Gold star to BilgeDiver - was indeed power problem - I noticed that transmission on Ch16 was causing the same problem i.e radio goes off then on. I also noticed that various other things i.e GPS reset. Never seen the problem before as we only ever speak to plymouth port control on Ch14 (1W) and never bother the CG on 16.

For info the DSC transmission is transmitted on CH70 at high power

So what was causing the problem Paul ?

 

[Bilgediver]

So what was causing the problem Paul ?

Sounds like a bad connection in the circuit powering the radio and plotter not allowing full transmit current to flow.


In actual fact digital transmissions really soak up the power so the radio does take full current for that moment.

Digital transmissions are heard over a much greater range and a radio will receive and decode much weaker dsc signals than the human ear can work with in voice mode.

 

[pau1gray]

So what was causing the problem Paul ?

.
The cause of the problem goes all the way back to the original installation on an old boat owned unbelievably by a sparky - there is a real mishmash of 24V / 12V /36V???? wiring all over the place. The problem was caused by a knackered battery - which is probably down to the ancient chargers that are on the boat. The 12V service battery is only ever charged by the charger as the engine runs a 24V alternator to charge the 24V side. We inherited this boat (and it's wiring!) about 6 years ago and we still find the odd surprise in the wiring -but it keeps me on my toes!

 

[PaulGooch]

.
The cause of the problem goes all the way back to the original installation on an old boat owned unbelievably by a sparky - there is a real mishmash of 24V / 12V /36V???? wiring all over the place. The problem was caused by a knackered battery - which is probably down to the ancient chargers that are on the boat. The 12V service battery is only ever charged by the charger as the engine runs a 24V alternator to charge the 24V side. We inherited this boat (and it's wiring!) about 6 years ago and we still find the odd surprise in the wiring -but it keeps me on my toes!

Cheers Paul, was just curious. Would it be worth fitting one of these :

http://www.adverc.co.uk/product/671