Antenna ground on freightliner cascadia mirror mount

[zigzag man]

Problem is I can't seem to get my dozy meter to read a proper SWR on my truck antenna. Checked the meter on my Jeep setup which is perfect 1.5 with my 5000 wilson hooked to a stryker, the meter isn't the problem. I'm thinking it is the antenna, maybe not grounded properly. I'm heading back to truck this morning to take it apart and reinstall with different gear hoping that will solve the swr problem. My meter reads fine in the swr check mode while I adjust the nob to the correct reading. Then when I switch to SWR read mode it just shows the same reading on the meter, all the way up, no change down to the 1 or 2 reading like it is supposed to when the setup is correct.
Is that what the meter would read if the antenna wasn't grounded properly, or if it was just shorting out from inproper mounting??? It is frustrating.
Thanks for reading and helping. Oh and this is Zigzag BTW

[MDYoungblood]

Hello zigzag man,
Welcome back to the forum. Just about all of the new trucks are made of plastic these days getting a good counterpoise (ground plane) for an antenna or antennas is almost impossible. Is the mounts you are using stock or aftermarket? You may need to run a ground from the mount to a good metal frame post like a door hinge etc. When testing use the lowest possible wattage so CMC (common mode current) isn’t a problem with the meter.
Let us know how it turns out.

3’s

Greg

[zigzag man]

Hello MDYoungblood, appreciate your reply and also the advise. I actually replaced the whole assembly except the aluminum mirror support. The problem was the metal and chrome mount on the bottom of the antenna wasn't shielded properly with plastic washers therefore it was shorting out the connection! Oh, and on the 2016 Cascadia freightliner, day cab, the entire door is steal, lol, they hadn't went fully blown plastic yet, so no extra ground was necessary. Now my Dosey works perfect, 1.4 on channel 20 and my little galaxy talks good now. It is nice to have this forum available to get the pros together for help with problems.
David aka, zigzag man

[MDYoungblood]

Cool, you figured out the problem, hope it didn’t effect the radio keying to ground. I would look at the door, the hinges and lock have a teflon bearing surface so the door might not have a good actual ground to the rest of the vehicle, (found this out working in a power substation and kept getting shocked when reaching out the window to hit the keypad to open the gates). I’d add a strap between hinge bolts if needed.

3’s

Greg

[443 Arizona]

there is a radio shop on the west side of Phoenix, Big Rig Radio, that has figured out how to do it on the plastic cab freightshakers