New VHF radio and tach malfunction

[Randygh]

Several weeks ago, I removed my Standard Horizon VHF radio and replaced it with a Uniden DSC model. I wired it to the same + & - leads as the SH. This weekend while in Bellingham and LaConner, I noted that when I keyed the mike, the tach RPMs dropped 500. Never did that with the SH. I checked the NMEA lead that connected to my GPS and everything looks good. Why in the world would my tach drop 500 rpm like it had a small dead short? Keying the mike doesn't affect any other gauges or the engine. Thanks for any ideas. :?:

[Go Aweigh2452]

I know certain VHF antennae interfere with GPS systems... Did you change out the antennae also? Any info in the installation guide as to where you should install the radio? Or check on line for your radio for problems. I had a Uniden that would sound an alarm when it detected low voltage. I got rid of it because it was so annoying... I would guess It has to be electrical interference...

[Randygh]

Antennae is the same. It's mounted in the same location as the SH. I'll move the radio away from the dash and then I'll check the troubleshooting section of the owners manual. It's got to be a simple fix, but finding the problem may be a PITA.

[debbie]

I am rapidly learning that troubleshooting anything on a boat is a PITA. But it feels GREAT to solve the problem (even if it can't be fixed, LOL). Good luck!