Electrical Interference

[BrendAn]

When I press my push to talk button the coolant temp needle moves hard over .

How could these 2 be related. 

Would it be a earthing problem.

Icom a200 . Wesberg temp gauge.

[RFguy]

0) Be sure the gauge is connected through its own negative/earth wire back to the engine OR back to a really good common ground/negative bonding point.

0.5) Check the condition of the sense wire over the run, those things are often not well anchored and may rub somewhere. In the presence of high RF, it will act as part of the antenna...

1)  I'd check that the temperature gauge , when the radio is transmitting, is still receiving the 12V it expects.

 2) I'd check the radio antenna VSWR at the middle of the band 126 MHz. If I didnt have a VSWR meter, I'd check the antenna and cable, and remove the BNC RF connector plugged into the radio and visually inspect to ensure the centre pin is still almost flush (common problem) .

3) Do you get 'normal' range from your radio- Can people 10nm away hear your transmissions loud and clear? Or can someone with a handheld aviation radio with the handheld antenna removed hear your transmissions 100m away ?

 

If all those points are OK, its likely to be RF getting directly into the meer circuit due to proximity of the antenna and engine coolant sensor wire.

At the back of the gauge, apply a 0.01uF disc ceramic capacitor across the sensor input and ground. Or change the sense wire to some miniature coaxial teflon cable. ...

 

Edited July 15, 2023 by RFguy

[BrendAn]

Excellent thanks for that. Will go through all those checks.

 

[onetrack]

A dirty earth wire connection somewhere can produce some interesting electrical gremlins.