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Connect GMRS radio to front power outlet?

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W

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2023 Sport Latitude
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Discussion Starter · #1 ·
OK... my first post here.
I just recently got a '23 JL (yay) and am looking to install a mobile GMRS unit in it.
I've already ordered the radio (arrives tomorrow - is a midland mxt575).

The biggest question I have is... how do I power this thing?
I assume I can run a wire through the firewall and attach directly to the battery.
That of course has the danger of draining the battery if I leave the the radio turned on with the vehicle off.
Is there some sort of adaptor/plug I can buy to simply plug it into the front power outlet on the dash?
Or is that a horrible idea and I need to be beaten with a stick for even suggesting it?

Or is there some other way I should be powering this thing?

Thanks much in advance for any replies!
 
StevieTex

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#3 ·
GMRS draws so little power the the lighter plug will be OK ..... But going directly to the battery would be much better. You create less possibility of noise from other onboard electronics, which can happen sometimes.
 
cranbiz

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#5 ·
Depends on the power rating of the radio. The lighter plug in the JL is rated at 20A. So, in theory, a MTX575 will draw 10A and be OK.
Like another said, I would be worried about noise coming in from the lighter plug and would go direct to the battery.
Unfortunately, the MXT575 does not have a power off timer (the MXT400 and MXT500 do) so if you do go to the battery directly, you either have to remember to turn it off or wire in a relay that will turn on and off the power when the ignition switch is operated.
 
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W

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Discussion Starter · #6 ·
OK the radio arrived today.
As I expected, it came with little rings to attach it to a battery on the end of the power cord.
So I ran to the store and picked up a male 12vdc auto port plug.
Some quick work with some snips and I have something I can plug into the power port.
I only did a quick and dirty test to ensure it powers on and can send/receive a signal.. but this crap seems to work!
 
W

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Discussion Starter · #8 ·
Nothing like that...
However I did a test and didnt seem to get anywhere near the range I thought I would out of 50w of power.
I live in a fairly rural area - mostly trees and farms around me with the occasional house.
I got about a mile down the road (as the crow flies) before heavy static was reported on my tx.
Once I hit 1.3 miles... it was all pure static.
 
M

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#9 ·
Wingnut1979 said:
Nothing like that...
However I did a test and didnt seem to get anywhere near the range I thought I would out of 50w of power.
I live in a fairly rural area - mostly trees and farms around me with the occasional house.
I got about a mile down the road (as the crow flies) before heavy static was reported on my tx.
Once I hit 1.3 miles... it was all pure static.
Click to expand...
What are you running for an antenna? I had to try 3 different antennas before I got good results, also several different mounting locations
 
cranbiz

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#12 ·
What did you have at the other location for a radio/antenna? Another mobile or a handheld?
Static on both ends? One end?

While the Midland antenna is a good antenna, I don't believe it's a no ground plane antenna like a Diamond 770. Yes, the Diamond is a dual band ham antenna but it is about the same price, it will work anywhere it's mounted and it's proven.

You might have to experiment with antenna placement and possibly with RF bonding of the antenna.

GMRS is 462 MHZ, UHF. It's a more line of sight transmission and obstacles will affect it's range.
 
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W

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Discussion Starter · #13 ·
So I did some troubleshooting.
I have two different mounts:

1) the mount linked above in previous post
2) a mag mount that came with the radio (with a tiny antenna)

I have two different antennas:

1) the antenna linked above in previous post
2) a tiny (roughly 10 inch) antenna that came with the radio


I set the girlfriend at home with a handheld
I drove to a school that is about 1.3 miles away (as the crow flies) and parked it.
I first tried the big antenna on the side mount - static received on other end (reported via text)
I then tried the tiny antenna on the side mount - static received other end (reported via text)
I then tried the tiny antenna on the mag mount (placed on the fiberglass roof via metal plate & sticky tape) - static received on other end
I then tried the big antenna on the mag mount on the roof - my radio died.
Various gear checking and I discovered that the DC plug I bought (see previous post) contained a 5amp fuse. Radio pulls 10 amps.
Went to store and bought better fuse.
I then tried the big antenna on the mag mount on the roof - static still reported on the other end, but it was intelligible static this time.
I was even able to hear her replying via the radio with her crummy little handset.

So it seems that "antenna" (and/or antenna location) is my issue.

With regards to the Diamond (above) - that's a 2m/70cm antenna.
Which means it's designed for 144 / 440 MHz (by all means correct me if/when I'm wrong here - I'm still VERY much learning on the go)
I'm using ~460 MHz.
That's fairly close to 440 - but not quite there.
Would I then need to tune the antenna?
If so... how? Do I legit slap it on a SWR meter and then start snipping pieces off the end?
 
cranbiz

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#15 ·
Ok, The Larsen is also a good antenna. It should help alot.

On my Jeep, my Diamond has 1.25-1 SWR on 462 mhz so I didn't do anything. If I did have to tune it, you could use either an antenna analyzer or a SWR meter and yes, it would usually need a bit removed if the SWR was high.
 
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StevieTex

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#16 ·
Are you certain your radio is operating at 50 watts? Most GMRS frequencies are limited to much lower wattage and the radio will compensate. Get an SWR meter that also shows output wattage to confirm.
 
W

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Discussion Starter · #17 · (Edited)
StevieTex said:
Are you certain your radio is operating at 50 watts? Most GMRS frequencies are limited to much lower wattage and the radio will compensate. Get an SWR meter that also shows output wattage to confirm.
Click to expand...
I'm specifically using channel 15 which (should) be 50w.
It's a fair point to check it - but I do not (yet) have a meter to verify.
My new antenna just arrived today so I'll be trying it out later tonight.

Edit to add:
It does show "high" power on channel 15
(vs "low" power on channel 4 for example)
Yes that's still ambiguous - but it at least acknowledges the fact that 15 has a higher power allotment.
 
cranbiz

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#20 ·
StevieTex said:
Are you certain your radio is operating at 50 watts? Most GMRS frequencies are limited to much lower wattage and the radio will compensate. Get an SWR meter that also shows output wattage to confirm.
Click to expand...
GMRS Channels 15-22 are authorized 50W and the MTX575 says it's a 50W radio.
 
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Wingnut1979
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