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ContinuousWave: Small Boat Electrical
DSC: Position Polling
|Author||Topic: DSC: Position Polling|
posted 09-12-2006 09:01 PM ET (US)
A group of classic Boston Whaler boats were out fishing in Lake Erie last Saturday, exploring the western shore for some perch. We had four boats, GAMBLER, OUTRE, SPOUTER, and HOME ASIDE.
Kingfish and I on OUTRE and Jerry on SPOUTER were catching all the fish, so Dave and Pat decided to go for a boat ride on GAMBLER and HOME ASIDE. We agreed to keep a lookout on a particular radio channel and catch up with each other later.
This was just about the perfect situation for using Digital Selective Calling and the Position Poling feature. If all the boats had been properly equipped, we could have all signaled our position to each other and had it displayed on each others chart plotters. As it turned out, none of us had the feature. We just exchanged position reports on the radio verbally.
I know that Tom (bluewaterpirate) has a DSC radio and chart plotter connected for exchanging positions, but has anyone else advanced to this point in small boat electronics?
I may be there soon, but unless I get someone else to exchange position reports with, I might be talking to myself most of the time!
posted 09-12-2006 10:08 PM ET (US)
I know how you feel. My boat is equipped with a DSC Standard Horizon radio and a Standard Horizon CP 175 chart plotter, both connected. I don't know anyone fully set up like this.
posted 09-12-2006 10:25 PM ET (US)
The number of boaters having boats that are equipped with DSC radios with CP functionality has increased dramatically around the North Carolina Coast. DSC data exchange is becoming an everyday thing.
What's really nice (this specific service began in 06/06), is when I file a Float Plan with Sea Tow before I also test my DSC exchange functioanlity with them. I have 31 other units programed into my ICOM 504 & SH Phantom 1000. We all exchange information on a regular basis while fishing. It's taken about 2 years for DSC to catch on but now its moving out fast.
posted 09-12-2006 11:42 PM ET (US)
Position Polling isn't "signaled our position to each other".
It's initiated by the boat that wants to know the other boat's
position. Whether manual intervention is required on the
boat being polled is a function of the radio and the options
set in it. My SH Spectrum is setup so that anybody who asks
can find out where I am with me doing anything. Kawika's
Icon (M-402 I think) requires manual intervention no matter
what when polled.
Where I think it will come down over time is that radios can
If someone polls, tell them where I am.
As a diver, I don't care who knows where I am. I suspect
posted 09-13-2006 06:20 AM ET (US)
Tom--I am glad to hear that there is a growing interest in DSC Position Polling in your area. It seems like an natural adjunct to friends who want to share fishing information without making a general broadcast of the hot spot data.
Chuck--Are all those options in the current DSC protocol? Give us a citation in the DSC specifications for them--they sound interesting.
posted 09-13-2006 07:50 AM ET (US)
The biggest thing that helped with DSC awareness was the activiation of 2 Rescue 21 facilities. Boaters have a better understanding of the functionality and capabilities not only for everyday data exchange but emergercy data exchange where instaneous information exchange is necessary (not only to the USCG but other nearby boaters).
AIS is starting to catch on too. My Garmin 2206 came AIS ready. Has high speed NMEA data capability and the capability to display the data. Raymarine, Furuno, and I think SH has the capability in there newer CP's.
posted 09-13-2006 09:20 AM ET (US)
I thought the same thing when we were trying to reach GAMBLER and HOME ASIDE. My system is capable, but of no use when the others are not.
posted 09-13-2006 09:29 AM ET (US)
Those options are implemented in the radio firmware and
have nothing to do with the protocol. The radio and/or the
user decides whether or not to answer the postion request
packet. My Standard Horizon Spectrum (now two generations
old) implements the first and third options.
posted 09-13-2006 09:31 AM ET (US)
And BTW, while the position won't display on my chartplotter
(the 162 was about the last chartplotter where Garmin DIDN'T
implement that), the lat/long of the answering boat will
display on my radio.
posted 09-13-2006 09:42 AM ET (US)
I suppose the radio manufacturers could then add:
--send my position to (some MMSI recipient) (even though he didn't ask for it)
posted 09-13-2006 10:46 PM ET (US)
I'm literally on the edge. I almost bought a Standard Horizon PS2000 last weekend. I already have the Standard Horizon CP180i on my 15_Sport. (an upgrade from my CP150 which I ought to mount at the house and connect to a DSC VHF for the wife to be able to "locate" me).
Some questions I have: If you have a VHF which does not have a dedicated receiver for DSC (such as the SH PS1000), what happens when someone attempts to poll you and your VHF misses the first part of the inquiry? (thinking about all the voice VHF conversations you hear where you miss the first word or two of the initial call while the scan is flipping through channels).
Is the "poll" similar to a normal voice hail where the transmitting station calls the receiver's name several times in succession? (I can imagine this concept would waste precious bandwidth for distress calls, which is why I suspect it does not happen).
When a "poll" goes out from a DSC VHF requesting the position of another known receiver, does it go out in low power 1w, or high power (25w)? (trying to judge the effective range of a "poll" request).
posted 09-14-2006 08:08 AM ET (US)
DSC preempts voice on single receiver DSC radio (yes there could be some interference). Treansmit at 25 watts. Line of sight plus 10-15% good rule of thumb.
I use DSC data exchange regularly and have observed 15 miles the average range with other small boats (I've seen less & more depending on sea state & atmospherics). I conducted a DSC test with Sea Tow 2 weeks ago (ST's shore antenna is 500'& my boat antennas are 10)' I was fishing off shore (55 miles) & sucessfully exchanged 2 way DSC data with both my ICOM 504 & SH Phantom 1000. I also had good two voice VHF comms on both radios at this range.
Here's a video I did on DSC functionality. It meets the forum specs.
There are three videos & your welcome to view them all. The video of interest is the 3 minute one.
posted 09-14-2006 02:21 PM ET (US)
Tom--That is an excellent demonstration. Here is a better link to it:
posted 09-14-2006 08:32 PM ET (US)
Jerry--I am very glad to hear you have DSC position polling on your boat. I think this will inspire me to upgrade. Then we can send our positions to each other next time we are out boating!
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