nmea interface problem, can you solve it ??

[tome]

What type of cable are you using to interconnect?

 

[jimg]

I am fairly sure you will find that this is the problem....

 

[simonfraser]

5 core shielded, tried earthing it, made no diference
it only runs AH nmea

the power is in a seperate two core cable

 

[tome]

Try earthing the shield ONLY at the end the messages come from, never at the receiving end - leave it floating

 

[Danny]

Simon - just a thought: is the AH actually working at the time you have the problem or do you still get the problem if the AH is connected, powered up, but in standby?

If you only get the problem when the AH is actually doing work (ie steering the boat) then the problem may be a poor connection between your AH and instrumentation and the battery. My reason for saying this is that, if the AH is steering the boat it is continually switching a considerable current on and off. If there's a poor connection, common to the supply to the AH and the supply to the echo sounder, then that will generate noise on the e/s power supply.

Because of this sort of problem it's advisable for the power supply wiring from the battery to the AH to be seperate from your other instrumentation.

Might be worth checking how yours is connected.

The problem with this theory is that you should still get your fault with the NMEA cable to the AH disconnected - just so long as the AH is still steering the boat.

 

[simonfraser]

Hi Danny,

thanks for the power supply sugestion, but, no, it's not related to power usage at all, as long as the AH is connected to power the problem exists, either a helming AH or one on standby

i'm prob wrong, but i would like to fit some ferrites, now what frequency does TT work on ?

 

[Danny]

They say it's close to GSM phone frequencies. I would guess it's about 1800MHz (assuming they mean GSM1800).

 

[simonfraser]

thanks danny, i have e-mailed TT as well