Midland MXT275 power output

[NonHyphenated American]

I installed a Midland MXT275 and ran the power through my Voswitch. I did a watt output check with the vehicle running and on ch 1-7 got 5 watts, on ch 15-22 got 11 watts, on ch 15-22 repeaters I got mid to high 7 watts. SWR ON 1-7 is 1.0, on ch 15-22 is 1.01, and 15-22 repeater is 1.1 to 1.5. I thought maybe the Voswitch wasnt allowing maximum output so I wired the radio directly to the battery with an inline 5amp fuse and got the same results. Initially when I installed the radio I didnt pay attention to the gauge of the wiring the radio came with and I ran 14ga from the battery with quick disconnects to the 16ga radio wiring. I snipped off the cigarette lighter plug and inline fuse the unit came with. Would running 14ga to 16ga wiring cause the radio to not get maximum power? Does a repeater have to be active in an area for the radio to put out maximum power? This is all new to me.

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[Radio Guy]

The maximum power you are allowed on ch 1-5 with a GMRS license is 5 watts and on ch 15-22 its 50 watts, so your radio seems to be working close to its spec. Its probably a little low due to voltage drop through the wiring or the calibration of your wattmeter. You can measure the voltage across the radio side fuse holder and radio chassis to see roughly what the radio is getting.

 

[NonHyphenated American]

Like I said I am new. Right now, I have the inline fuse coming off of the battery and routed through a grommet in the firewall and to the radio. Should I switch to 16ga wire coming off the battery and move the inline fuse closer to the radio? How do I test the wattage like you suggested?

 

[Radio Guy]

Like I said I am new. Right now, I have the inline fuse coming off of the battery and routed through a grommet in the firewall and to the radio. Should I switch to 16ga wire coming off the battery and move the inline fuse closer to the radio? How do I test the wattage like you suggested?

I would use something larger than 16ga like at least 12ga. To accurately test the wattage would take a calibrated wattmeter and a 50ohm load. Hobby type meters can be off by quite a bit, especially when used with an antenna instead of a known resistive load.

 

[bd100]

If you have the 275 with USB-C, you can send it in for wide band programming and they also test it and give you test results including power output.

Info about MTX-275 upgrades

They are very quick on the turnaround, and I bet they'd test yours even if it came with wideband.

My unit came back with good power levels, but I don't know whether it was off from the factory and they adjusted it, or it it was fine from the factory.

 

[sarguy1941]

The 275 is only 15 watts on GMRS. Channel 1-7 are low power and 5 watt max. As said your radio is most likely fine.

 

[NonHyphenated American]

The 275 is only 15 watts on GMRS. Channel 1-7 are low power and 5 watt max. As said your radio is most likely fine.

Only 10 watts on the high channels is a bit concerning since I have seen videos on Youtube with people getting up to 13-14 with the cigarette lighter plug and me only getting mid to high 7s on the repeater channels.

 

[sarguy1941]

So what meter are you using ? Also what jumper cable from meter to radio ? I agree it sounds low but most issues end up being the test equipment and not the devise.

 

[NonHyphenated American]

So what meter are you using ? Also what jumper cable from meter to radio ? I agree it sounds low but most issues end up being the test equipment and not the devise.

Surecom SW-102 and a standard foot long jumper coax cable.

 

[sarguy1941]

Id try to find a friend or someone with a radio and verify the meter. I know others that have shown low power with those meters.

 

[Radio Guy]

Surecom SW-102 and a standard foot long jumper coax cable.

That type of meter could easily be off by +/- 10% or more across its advertised frequency range.

 

[rharr]

If you have the 275 with USB-C, you can send it in for wide band programming and they also test it and give you test results including power output.

Info about MTX-275 upgrades

They are very quick on the turnaround, and I bet they'd test yours even if it came with wideband.

My unit came back with good power levels, but I don't know whether it was off from the factory and they adjusted it, or it it was fine from the factory.

Basicaly the 275 with the USB A is only narrow band and there may not be a firmware update to add wide band.

" OK, so I just emailed Midland about this. All of the older USB-A model MXT275 are narrow band only. The new USB-C model MXT275 up to until very recently have shipped as narrow band only. It sounds like they well start shipping from Midland with wide band on the repeater channels, but since not all of their inventory has the update, you need to state you want that firmware/config when ordering so they can update the firmware/config before shipping it. If you have already received a USB-C model or buy one from a retail store it will likely be narrow band only, but you can email Midland Support and then mail your radio in for firmware/config update that sets the repeater channels to wide band. " - From the link referenced.

 

[NonHyphenated American]

That type of meter could easily be off by +/- 10% or more across its advertised frequency range.

Im going to start at the basement and start off with a new jumper cable and get a dummy load. I switched back to running the power for the Midland through my Voswitch and have the same results. 1.0 SWR across the board. With the Midland directly wired to the battery I kept hearing the base speaker pop like it was getting power eventhough the unit was off. Switching to the CB side, I installed a President Bill II CB. I had a 2 foot Fire Stick, heavy duty spring, and quick disconnect. Best SWR I could get on ch1 and ch40 was 2.5 and 1.8 on ch20 which is acceptable per the manual. I replaced the coax with a Fire Stick fire ring and 3 foot Fire Fly and used the spring and quick disconnect. The best I could do on ch1 and 40 is 2.2 and 1.1 on ch20. Channels 10 through 30 are in the 1.1 to 1.5 range. Im going to call it and accept those numbers. I saw how you put aluminum tape on the underside of the cowls. Do you think that will help my case any?

 

[Radio Guy]

Im going to start at the basement and start off with a new jumper cable and get a dummy load. I switched back to running the power for the Midland through my Voswitch and have the same results. 1.0 SWR across the board. With the Midland directly wired to the battery I kept hearing the base speaker pop like it was getting power eventhough the unit was off. Switching to the CB side, I installed a President Bill II CB. I had a 2 foot Fire Stick, heavy duty spring, and quick disconnect. Best SWR I could get on ch1 and ch40 was 2.5 and 1.8 on ch20 which is acceptable per the manual. I replaced the coax with a Fire Stick fire ring and 3 foot Fire Fly and used the spring and quick disconnect. The best I could do on ch1 and 40 is 2.2 and 1.1 on ch20. Channels 10 through 30 are in the 1.1 to 1.5 range. Im going to call it and accept those numbers. I saw how you put aluminum tape on the underside of the cowls. Do you think that will help my case any?

If your doubting your meter its best to compare with a known good commercial quality meter and with a resistive load right on the meter. Maybe there are some amateur radio guys in your area that could check your meter out, they usually like to help and show off their test equipment.

As far as the conductive tape under the plastic cowl pieces, it adds to the useable ground plane but I don't have any tangible information on how much it might improve things. The amount of ground plane it added should be noticeable at VHF and UHF with a slightly more omni pattern and antennas should match up closer to factory spec. Probably minimal change at CB.

 

[NonHyphenated American]

If your doubting your meter its best to compare with a known good commercial quality meter and with a resistive load right on the meter. Maybe there are some amateur radio guys in your area that could check your meter out, they usually like to help and show off their test equipment.

As far as the conductive tape under the plastic cowl pieces, it adds to the useable ground plane but I don't have any tangible information on how much it might improve things. The amount of ground plane it added should be noticeable at VHF and UHF with a slightly more omni pattern and antennas should match up closer to factory spec. Probably minimal change at CB.

Turns out my jumper cable was crap and my new one yielded better results. Ch1-7 4 watts and 1.01 SWR, ch15-22 14 watts and 1.03 SWR, ch15-22 repeater 14 watts, 1.1 to 1.3 SWR. I had a noticeable alternator whine when receiving. The only receiving I can do right now is the weather channels, no one active on GMRS in my area. I tried a different ground and the change in the whine was reduced but still there. I had the radio's cradle mounted to my center console support bracket. I removed the cradle from the bracket and the whine was barely noticeable. I used self-tapping screws to mount the cradle to the side of my console. My handheld GMRS radios came in today, so I did a radio test between the two radios. On transmit from the 275 there was a noticeable whine, but it was tolerable. Then I went to change something on the antenna mount and overtightened the piece that tightens and holds the antenna cable to the mount and snapped off the stud. So, I get to order a new antenna cable and hope I get the same good(ish) results. I did the same mounting for my CB. Ch1 and 40 2.2 SWR, ch20 1.1, 15-30 1.1 to 1.5 SWR.

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