Midland 6db gain antenna tuning?

[bobthetj03]

Midland claims the antenna is pre-tuned for Midland radios, but I'm wondering if there is room for improvement, as Midland has a tendency to dumb down the GMRS radios for us newbs. Is it worth buying a SWR meter to find out? 

 

[bobthetj03]

I tested SWR and got a horrible 2.2. Trimmed a tiny bit and can only get it down to 1.94. For testing purposes, I removed the 6db whip and put the magnet one that came with the MXT-275 and get almost perfect at 1.01. I checked my cable for any sharp bends or pinches and can't seem to find anything out of the ordinary for routing a cable in a jeep. With the cable and antenna being the only change I have to assume there is something wrong with either the 6db antenna, or the coax?

[SkylinesSuck]

Just curious, did you trim to get to 1.94 then keep trying and it didn't get better? Where did you mount it? Tail light?

[bobthetj03]

Just curious, did you trim to get to 1.94 then keep trying and it didn't get better? Where did you mount it? Tail light?

 

It's mounted above the driver side tail light via a bracket that is attached to the tub with the tail light housing bolts. I Took a reading prior to trimming and got the 2.20. Trimmed it 3 times in very small amounts to get 1.94. I'm afraid of trimming off too much at this point. I can get 1.01 with the small mag mount antenna setting on the same spot. 

[SkylinesSuck]

Maybe I cut too much, but I just kept trimming until I got to 1.3. I'm playing in the garage right now. Lemme dig up a tape measure and I'll tell you what length it is now.....

 

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[SkylinesSuck]

644mm from where the whip disappears into the mount.

 

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[bobthetj03]

I'm at 650mm currently.

[RIPPER238]

I also have the Midland 6db whip and the Midland Mag mount NMO. Definitely better reception than the little short standard antenna that came with my MXT275, so im happy. If i come across someone with a SWR meter ill certainly test it. But its fine right now.

 

Mag mount is center on my roof and its seems fine at 80mph. Spring and magnet are real solid. 

[SkylinesSuck]

I'm at 650mm currently.

Maybe a little more snip snip?

[n4gix]

Maybe I cut too much, but I just kept trimming until I got to 1.3. I'm playing in the garage right now. Lemme dig up a tape measure and I'll tell you what length it is now.....

 If it's truly at 1.3:1 just leave it alone! Three-tenths of a dB isn't going to make any practical difference! 

[SkylinesSuck]

If it's truly at 1.3:1 just leave it alone! Three-tenths of a dB isn't going to make any practical difference!

I meant for him to keep snippin a bit more to get it down under 1.5 if he could. I'm happy with mine---but my new 1/2 wave antenna arrives tomorrow anyways :-)

 

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[n4gix]

Ah shucks! I got y'all mixed up and replied to the wrong person...  

[Sbsyncro]

Well I finally just got around to testing my Setup with the MXTA26 antenna and I found some interesting results that I don't know enough to be able to explain...  First the results:

 

 

Given than 80% of my usage is on Channel 15 or 16 and the SWR is reading around 1.3, its "good enough" but I suppose it could be improved upon.  Not sure if its worth the effort.

 

What is puzzling to me (probably just due to ignorance) is why the SWR reads a near perfect 1.09 at 462.5625 but on either sides of that frequency (462.5500 and 462.5750) I'm getting an SWR of 1.3.   Is it that GMRS just doesn't behave like a CB when it comes to antenna tuning?  (I remember in the old days one would tune a CB antenna by taking measurements up and down the channel scale and then adjust either longer or shorter based on those readings).  In addition, I'm showing "perfect" 1.00 SWR when on the repeater channels (467.xxx).  I find that suspicious.   I also notice that the radio is dropping down to 40 watts from 50 watts on the repeater channels.  (Trying to remember if that is a legal requirement or not...)

 

Radio is a Wouxun KG-1000G and the test equipment is a Surecom SW-102

 

The mount is a home-made aluminum mount attached to a roof rack cross bar.  I have not tested for ground, but according to Midland, one is not required for this antenna.

 

 

 

[mbrun]

I have the same Midland antenna you do. It has been checked with both the same meter you are using as well as a NanoVNA. My readings showed the antenna tuning optimized for the repeater channels, exactly what I would have hoped.

 

All your readings look good in my book. I would not expend anymore time trying to improve them. Nothing you do is going to get you any more range in practice.

 

Now, with regards to the subtle differences, those can be tough to track down to find out exactly why. It could be a characteristic of your specific piece fo cable. How well you connector mates to the coax or connector to your radio, reflections from a nearby surface, the connection between the antenna and NMO mount and other things.

 

I recently did some tests that necessitated putting an adapter in the antenna line. That adapter caused the SWR to change from a nice smooth curve to a slightly higher one that also exhibited repeating humps in the SWR pattern as displayed on a NanoVNA.

 

Others may have experiences to share also.

 

Well I finally just got around to testing my Setup with the MXTA26 antenna and I found some interesting results that I don't know enough to be able to explain... First the results:

 

 

Given than 80% of my usage is on Channel 15 or 16 and the SWR is reading around 1.3, its "good enough" but I suppose it could be improved upon. Not sure if its worth the effort.

 

What is puzzling to me (probably just due to ignorance) is why the SWR reads a near perfect 1.09 at 462.5625 but on either sides of that frequency (462.5500 and 462.5750) I'm getting an SWR of 1.3. Is it that GMRS just doesn't behave like a CB when it comes to antenna tuning? (I remember in the old days one would tune a CB antenna by taking measurements up and down the channel scale and then adjust either longer or shorter based on those readings). In addition, I'm showing "perfect" 1.00 SWR when on the repeater channels (467.xxx). I find that suspicious. I also notice that the radio is dropping down to 40 watts from 50 watts on the repeater channels. (Trying to remember if that is a legal requirement or not...)

 

Radio is a Wouxun KG-1000G and the test equipment is a Surecom SW-102

 

The mount is a home-made aluminum mount attached to a roof rack cross bar. I have not tested for ground, but according to Midland, one is not required for this antenna.

 

 

 

 

Michael

WRHS965

KE8PLM