SWR

[WRQH230]

I recently installed a midland mxt275 with their whip antenna. 
 

The antenna is installed onto a bare steel tab I mounted onto the top of my aluminum roof rack. 
 

The radio is wired directly to battery power and ground with a 5A fuse at the battery. 

Using a surecom sw102 meter, I get 1.01 on channel 16 low power, about 5.6w out. Engine off. 
 

With the engine on, SWR jumps to 2.5ish on channel 16 low power, 6w out. 

Am I missing something?

[FrostyFruits]

Try disconnecting negative from battery and put it to a bolt on the chassis or even a seat bolt. You could be getting noise or feed back from the alternator or some other electronics. 

I have a DC filter coming because I can hear an alternator whine through cb channels. 

https://www.gigaparts.com/kenwood-pg-3b.html?gclid=Cj0KCQjw1N2TBhCOARIsAGVHQc7XAMe6GAia8Z32Osig50r03P8O1MgaEGAMk1NHe_DItXB3MU2UA54aApqZEALw_wcB

[PACNWComms]

6 hours ago, FrostyFruits said:

DC filter

Those have really gone up in price, have used many of them for Icom A110/120 aviation radios, as that connector is also used by that series of mobile radio, with electrical noise being a huge problem with AM radio. Great filter, and does work well. I also add chokes to power cables, a practice that came from Motorola shipping cases of these when doing large projects, such as P25 installations at Public Safety Answering Points (911 Call Centers). That filter should work well to curb much of that noise heard. 

Back when you could still go to Radio Shack, they had a version that was sold for use with CB (AM 23-40 channel) and stereo equipment too, which was larger, cylindrical and comes up in many auction sites, for about the third of the price of the Kenwood version, it works too. Bought many on clearance years ago and used them all over the place.

[WRQH230]

I moved the ground off of the battery to the chassis near by, started the truck and I’m getting 1.18 on 16 in low power mode, 5.6w, and 1.48 in high power mode, 14.2w. Pretty consistent across the channels and on the repeater channels I’m seeing 1.00 same wattages. 
 

Thanks for the tip. Simple fix! I also tested my antenna mount for ground for giggles, it’s fine.
 

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