World Sea Fishing Forums banner

1 - 4 of 4 Posts

·
Registered
Joined
·
328 Posts
Discussion Starter #1
I have been reading the threads on batteries and VHF with interest.
I am just getting to know the intricacies of my boat and want to sort a few things out.

1. I have a little black box connected to the GPS and a seperate VHF aerial with a non DSC radio - is this some sort of DSC add on? It has French writing and various voltage settings. No idea how to use it.

2. I have a twin battery set up attached to a 115 hp Johnson. A simple 1 or 2 or both switch. This then goes into the usual mess of wires behind the console. If the switch is set to 1 then i assume only one battery is charging while running? So i should have both batteries on all the time.

3. I plan to use a shore based VHF at home so i can be in contact with the wife if i am out of mobile range. Is this legal or not ? I used to use a base station at my old yacht club and i believe we had a seperate licence for that. (I am talking about Southern Ireland here)

4. I know it is illegal to import and operate USA non CE marked VHF equipment but these are being sold on Ebay right now. As they are not selling them direct but redirecting the import straight to the buyer are they(allegedly) breaking the law?

If anyone can help me out much appreciated.

Freddy
 

·
Registered
Joined
·
5,557 Posts
1/ Sounds like you may be looking at a DGPS box. (Differential GPS)

Very brief explanation. Originally the GPS system was for military use, it is how cruise missiles find their targets. Pres. Clinton got worried when civilian receivers came on the market that other countries could use the GPS system against the US so an error was introduced which threw your position out randomly by 200 yards, this was called Selective Ability. The military spec sets were immune from this signal and still gave accurate positions. The US Coastguard then came along and put receivers on fixed points, typically lighthouses. These recievers know exactly where they are so when the inacurate GPS signal was recieved it broadcast a correction which is picked up by the DGPS receiver and corrects the position shown on the GPS screen. The rest of the world followed and set up their own DGPS stations. This signal is broadcast on VHF hence the separate aerial.

In 2003 the US had a rethink and turned off the SA signal so all GPS are now accurate to about 5 yards which is more than accurate for normal navigation. The DGPS stations remain and are still transmitting so if you have the receiver it is worth having for that little bit of extra accuracy if you are trying to pinpoint a position on a wreck.

Being a VHF system the DGPS stations all broadcast on a different frequency / bit rate and these have to be input into the set for the area you are sailing in. Full list of them for the UK here in PDF format
http://www.redcar-fish.co.uk/pdfs/ukdgpsfrequencies.pdf

2/ Not a good idea to have both batteries connected, if 1 is on it's way out the other will take up the slack until it too fails, then you have 2 dead ones. Best is to have a system where you use Battery 1 on this trip and Battery 2 on the next. This way both batteries are being used and charged regularly. Any fault will show up and you have the safety of changing over to the other battery. Make up a simple laminated card with a '1' on one side and '2' on the reverse. Hang it over the throttle lever. Before you launch reverse the card and reverse your battery battey switch to correspond, saves you forgetting. Don't move the switch position when the engine is running

3/ You would need a second license for the shore based radio and your wife will need to have done the VHF course to stay within the present regs

4/ Selling or buying is not illegal. Use of the non CE marked equipment is. Also foriegn equipment is often programmed with different frequencies so not all the channels in use here will be available and some of the frequencies can conflict with emergency services dedicated frequencies. Not a good idea.


Hope this helps a bit.
 

·
Registered
Joined
·
328 Posts
Discussion Starter #3
Thanks Chris that all makes sense.

I do not know how to actually input the frequency into the unit, can you give any guidance? As i recall the box had voltages on a dial but no display as such. Do i do it on the GPS or the black box?

Also i was doing some drifts and trying to retrace my track on the GPS to find various bottom features but found it impossible to refind the features again on the fishfinder . Is this because i was potentially 5 meters "out" or because i am rather bad at this aspect of fishing. I reckon i was following the exact track again but no sign of the lumps and bumps?? Very frustrating.

Thanks

Freddy
 

·
Registered
Joined
·
5,557 Posts
Can't tell you how to put the frequencies in, sorry, don't know which set you have or even if it is the sort you have to put them in. Some come preset.

It could be that you are slightly off course. If you look at your position on the normal screen display of your GPS you will appear to be right on a mark, then zoom in to the max and you will see how far out you are.

It could also be that you passed over what appears to be a sharp bump at speed on your sounder. When you go back to look for it you will naturally be going a bit slower and therefore the immage on the screen will be composed from more pings than before so what looked like a sharp bump can actually appear as a long reef at slow speed.

It is all down to you interpreting the info on the sounder screen. When I get a new sounder I like to go over an area that will uncover at low tide. I try to find a bit of rock, sand, mud etc and see what it looks like on the screen. Then I go back at low water and see if the bottom actually look as I had immagined from the screen. It will give you a totally different picture at 5knots compared to 20 knots. For instance an isolated boulder on the bottom will show up at 5 knots but at 20 knots may well be missing alltogether. Best way I know to learn how to interpret the screen picture and IMHO time well spent.
 
1 - 4 of 4 Posts
Top