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Wega24 05-06-2002 06:42 PM

Raytheon Bidata ST 40
I have a bidata ST 40 and have problems with it. It took me almost a year to find out that the silly thing wasnt showing correct speed. I was sooo lucky when the old boat was humming around with almost 4 knots. Than I got a handheld GPS and hold on ... Instantly the boat was almost going 5.5 knots.... lol

So far so good. I get the rather cumbersome description of the Raytheon and find out, that i can actually adjust the speed...

The problem is that the instrument only shows correct speed around 3 knots. Slower and the ST 40 shows less than the GPS if I go faster than 3 knots the ST 40 shows more speed than actual.
Somewhere around this table :

0 1
0.5 2
1.5 2.5
3 3
4.5 4
6 5
7.5 6

roughly like that anyhow... I could make it slower but than it wouldnt show anything up to 3 knots...

I have contacted Raytheon and getting stupid answers.. like interface it with my gps in the sog mode. I dont have a raytheon gps but a handheld !!! Or the other one was to adjust the CAL ... which would mean it would show probably 15 knots when I am going 5..

I do clean the inducer every week. The position is somewhat amidships 10 - 15 inches away from the keel.

Thanks ahead for all your hel

raven041 05-07-2002 08:41 AM

Raytheon Bidata ST 40
Thorsten - I have a similar problem with the unit and have not gotten around to making an adjustment. The precvious owner installed the unit and I have no documentation. One question: have you compensated for currents? (since the GPS measures speed over ground and the instrument measures speed through the water). My delta is approximately GPS = ST40 + 1.5 kts. But, the delta is less at low speeds.
When you figure out how to make the adjustment, I''d appreciate a note.
Mike Smith
S/V Raven

Wega24 05-07-2002 08:49 AM

Raytheon Bidata ST 40
hehe currents would be a GREAT answer to the problem... BUT I am sailing on a inland lake with no current..

well theoretically there is SOME current somewhere, but in this case its NOT even close to register anything ..


gnorbury 05-07-2002 10:03 AM

Raytheon Bidata ST 40
You can download the user manual for the ST40 at raymarine''s website:

Follow the instructions in Chapter 4 are redo the calibration so it agrees with your GPS Speed Over Ground.


Wega24 05-07-2002 04:58 PM

Raytheon Bidata ST 40
Hi Gnorbury

I did ajust the CAL factor up and down to no avail.
The SOG can only be adjusted when you have other raymarine instruments connected with the seatalk cables.

I do not have a raytheon chartplotter or gps or anything else ...

so I think I am only possible to adjust the CAL factor

Correct me if I am wrong though

Thanks Thorsten

shamgod77 05-08-2002 06:55 AM

Raytheon Bidata ST 40
This won''t solve your problem, but firstly if you have the gps why even bother with the knotmeter? If you are like me and will search endlessly for answers I would assume that the placement of the paddle wheel needs to be more forward to avoid disturbed water from the keel. I have an ST30, and located mine forward of the keel and it seems to be fine, BTW these things don''t really work!

gnorbury 05-08-2002 07:19 AM

Raytheon Bidata ST 40
SOG is a completely separate measurement from the speed reading given by the paddle wheel and knotmeter. Usually it comes from the GPS and is fed into the seatalk bus via an NMEA interconnect at the autopilot.

The CAL factor *will* definitely adjust the speed shown by the knotmeter, unless of course something is wrong with the ST40 instrument itself.

The only time you need to revisit paddle wheel placement is if you get significantly different speeds reported one tack vs the other. Provided it is in relatively clean water and turns freely, you should be able to CALibrate it to read accurately.


Wega24 05-08-2002 01:19 PM

Raytheon Bidata ST 40
good thats what I thought with the SOG reading.... doesnt work, as I dont have any seatalk gps instruments to hook up.

Leaves me the cal factor...

as I said I had the unit installed and left it in factory setting for the first year.
I know somewhat that my hull speed is somewhat around 5.5 knos... The first year i never reached more than 3.5 knots... FLYING the old

Today with the handheld GPS I adjsuted the Cal factor up....

so the instrument is fine around 3 knots ( GPS ) below 1... its not showing anything

if I am faster ..lets say 5 knots the Raytheon shows all the way up to 7 knots..

If I reduce the cal factor, than it will not show anything below 2 knots...

now for the position of the paddlewheel.
It doesnt make any difference what side the boat is leaning..... no measurable difference between starboard or port tack in the speed display ...

csilva 06-03-2002 09:18 PM

Raytheon Bidata ST 40
I have an ST 40 Wind Instrument with Rotavecta transducer already installes and plan to install an ST 40 Bidata mainly to connect both so that I can get true wind speed and angle.
Do I also need to buy and install de Sea Talk Interconnection Kit (Part Nš E25028)?

Many thanks,

Wega24 06-04-2002 08:26 AM

Raytheon Bidata ST 40

I have send several emails to raytheon, with 50/50 success rate. They have a silly system answering to those emails you get back...

Anyhow, I called the guys , they told me to send the transducer in. which I did ( UPS 2 day ) I didnt hear nothing for 10 days, so back to the email.....
Than it all of the sudden came back. Note on the No charge invoice says, couldnt find anything which relates to my description. But they did send me a new transducer at no charge ...

This weekend its going to get back into the boat. Lets see if we can make that thing work halfways correct.

I am amused aout the extra "dummy" transducer plug they have send. did they think I have my boat with duct tape ??? lol

I am not really all that amused to learn that those things dont really work so well... These are not exactly cheap. If tey dont work, than dont sell them , otherwise accurancy is expected ... After all a bicycle computer which measures current speed, trip miles, overal miles, average speed, max speed, clock, riding time, comparison between average speed and actual speed, stopwatch, 2 odometer logs for 2 different bikes, total riding time, cadence... all of this in 6 different languages cost $ 28.00

and not 499 or more ...

Thanks for listening to my rant.

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