ARRL

Secure Site Login

KG4IHO

Joined: Thu, Jun 22nd 2000, 00:00 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
Ground loop between transmitter and tuner? Mar 15th 2016, 01:27 2 490 on 15/3/16

Latest Posts

Topic Author Posted On
Ground loop between transmitter and tuner? KG4IHO on 15/3/16
I am installing my first transmitter, an Icom m802, in a 30 foot sailboat. The instructions say I should ground the transmitter and tuner to each other at the same ground, yet the transmitter and tuner are already connected to one another through the shield of the coax connecting the two. My question is: Why isn't this a ground loop? Why doesn't half of the RF current travel on the shield and half on the ground between the two units? Why doesn't this cause common mode RF radiation from the ground connection and from the coax shield?

Because the negative power, ground terminal and coax shield are connected internally within the transmitter (and within the tuner), there are actually three other potential ground loops:

1) transmitter negative power --- tuner negative power.

2) negative power of the transmitter --- negative power of the VHF radio --- shield of the VHF antenna --- VHF antenna=== sailboat mast --- sailboat ground system --- tuner. (I know I can fix this one by isolating the antenna from the mast, but it is really hard to get to right now.)

3) negative power of transmitter --- the frame of the diesel engine (for the starter and alternator) --- the propeller shaft --- the propeller --- salt water (about 12 ohms here) === sailboat ground plate --- tuner.

I am a computer engineer, but I seem to be missing something here. Is there some magic that keeps the RF energy on the coax? I could use an intuitive explanation here.

Doug

Back to Top