Negative ground

[NonHyphenated American]

I've upgraded to a Midland MXT575 and Uniden CMX760, to hide them both, and re-did my wiring with positive direct to the battery. Which way is better for the negative? Direct to battery, both to factory chassis ground on the passenger side, or both to a bus bar that uses a 10guage wire to the factory chassis ground?

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[Commodus]

I've upgraded to a Midland MXT575 and Uniden CMX760, to hide them both, and re-did my wiring with positive direct to the battery. Which way is better for the negative? Direct to battery, both to factory chassis ground on the passenger side, or both to a bus bar that uses a 10guage wire to the factory chassis ground?

I always went by the rule when wiring that the least number of connections to a positive or a negative source the better. Less chance for corrosion or connectors coming loose

 

[NonHyphenated American]

I ended up grounding them to their own chassis ground.

 

[sharpsicle]

That's exactly what I would do. Best choice.

 

[Josh00333]

I tried that and had interference, I had to go + and - direct to the battery.

Wish I could have gone to the ign hot from the aux switches but it just wouldn't work.

 

[NonHyphenated American]

I changed it again and went both to battery. My antenna cable was bad on my CB so I couldn't tune the antenna. Before I hooked the MXT575 negative to the battery I was only getting 40 watts max on the higher channels and 4 on the lower power. I hooked up the negative the battery and removed the inline glass fuse and got 44 watts on high channels and sometimes 4.5 watts on lower channels. Highest SWR was 1.3 and that was on the repeater channels. I wanted to see 50 watts.

 

[Jaxmax]

So you have the radio and wiring unfused?....Jack

 

[NonHyphenated American]

So you have the radio and wiring unfused?....Jack

The positive wire coming off the battery has an inline 15amp fuse. I snipped off the extra fuse.

 

[kb5zcr]

I changed it again and went both to battery. My antenna cable was bad on my CB so I couldn't tune the antenna. Before I hooked the MXT575 negative to the battery I was only getting 40 watts max on the higher channels and 4 on the lower power. I hooked up the negative the battery and removed the inline glass fuse and got 44 watts on high channels and sometimes 4.5 watts on lower channels. Highest SWR was 1.3 and that was on the repeater channels. I wanted to see 50 watts.

Try putting a 50 ohm dummy load on it to measure the power. Thats a big difference.

Also, please see page 22 of the owners manual.

IMPORTANT! Channels 1-7 cannot be removed from the Lo transmit
power setting due to power output regulations


https://www.amazon.com/XRDS-RF-PL259-Male-RF-Dummy/dp/B08QR9RQJ3/ref=sr_1_3?crid=26QIHUWUI29AO&dib=eyJ2IjoiMSJ9.291G_kGNksXsGeeQcbvK5f6v5IgBNR3j_-RqwTEiu7hYYtQfm1NuMQaHwpVj4JdXXpCkJYyHyruLeV_0aSY86rreEk3_bX-P4GMwqCLmyACmWmsFYLU2uiBeGf_EqQw_07skuJHonXkQQBZ3BKza2TI3Bx8nt4a27XbMCcMY4WVH9Sg_1z4NzxtJdiX3E6ys0hZDSfq9YsSWSSX9vdaq6Y2NSyAmEy-V-IMd5O77EXc.sskbUBK2OVwbljbAzCh9sJiI0zNOsnTwPR5ENJ2Cka0&dib_tag=se&keywords=dummy+load&qid=1726206072&sprefix=dummy+lo,aps,241&sr=8-3

 

[Radio Guy]

Try putting a 50 ohm dummy load on it to measure the power. Thats a big difference.

Also, please see page 22 of the owners manual.

IMPORTANT! Channels 1-7 cannot be removed from the Lo transmit
power setting due to power output regulations


https://www.amazon.com/XRDS-RF-PL259-Male-RF-Dummy/dp/B08QR9RQJ3/ref=sr_1_3?crid=26QIHUWUI29AO&dib=eyJ2IjoiMSJ9.291G_kGNksXsGeeQcbvK5f6v5IgBNR3j_-RqwTEiu7hYYtQfm1NuMQaHwpVj4JdXXpCkJYyHyruLeV_0aSY86rreEk3_bX-P4GMwqCLmyACmWmsFYLU2uiBeGf_EqQw_07skuJHonXkQQBZ3BKza2TI3Bx8nt4a27XbMCcMY4WVH9Sg_1z4NzxtJdiX3E6ys0hZDSfq9YsSWSSX9vdaq6Y2NSyAmEy-V-IMd5O77EXc.sskbUBK2OVwbljbAzCh9sJiI0zNOsnTwPR5ENJ2Cka0&dib_tag=se&keywords=dummy+load&qid=1726206072&sprefix=dummy+lo,aps,241&sr=8-3

A dummy load and run the radio at 13.8v right at the radio, then it should meet specs. For higher current stuff like 30A or more I usually run the negative right to the battery, otherwise for smaller radios I'll find the nearest legit threaded grounding point in the cab.

In my truck I pulled 4ga wire from the battery, both hot and negative to under the rear seat where I made a distribution box with various aircraft circuit breakers and an adjustable timer with an ignition switch input. The timer allows certain radios to run off the high current feed but will shut them off about 30min after the truck is turned off to save my battery. But I have a lot of radio crap in the truck, a dual band Yaesu FTM400, Icom HF/VHF/UHF and a Harris XG-100M multi band from 30MHz to 870MHz and antennas to match.

 

[NonHyphenated American]

***UPDATE***
I ran a dummy load and was only getting 4-4.3 watts on the low channels and 40-43 on the high channels. I got in contact with Midland and ended up sending the radio in for evaluation. Got the radio back in a week and got a full 5 watts on the lower channels and 50 on the high channels and this was reading off the antenna.

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