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Midland 6db gain antenna tuning?


bobthetj03
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Mine was nearly perfect when I received it. Still nearly perfect 9 months later. Checked it again last week to show a friend. Consistently less than 1.2:1 across the entire GMRS band.

 

I have no reason to mess with it. Adjustments of Collinear antennas are not as simple as basic 1/4 and 1/2 wave antennas are to adjust.

 

 

Michael

WRHS965

KE8PLM

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Along this line, the feed line that came with the mag mount [NMO] is six meters long - enough to practically wrap around the car.  I only needed about 3 meters to reach where I needed to go, so the remainder is coiled up on the car floor in the back where the MTX 275 resides.  

 

Would I be wise to cut down the feed line to the needed length and solder on a new connector?  OR - does the excess feed line make any real difference?  

 

First GMRS radio - obviously - I have both the 6db and 3 db NMO antennas from Midland.  

 

Any feedback is appreciated.

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I'm in the same boat and have not installed my Midland as did not know what to do with the extra cable... One person said do not coil it up...

We are standing by for a good and correct answer...

Jack and for Kevin as well.

 

Along this line, the feed line that came with the mag mount [NMO] is six meters long - enough to practically wrap around the car.  I only needed about 3 meters to reach where I needed to go, so the remainder is coiled up on the car floor in the back where the MTX 275 resides.  

 

Would I be wise to cut down the feed line to the needed length and solder on a new connector?  OR - does the excess feed line make any real difference?  

 

First GMRS radio - obviously - I have both the 6db and 3 db NMO antennas from Midland.  

 

Any feedback is appreciated.

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Along this line, the feed line that came with the mag mount [NMO] is six meters long - enough to practically wrap around the car. I only needed about 3 meters to reach where I needed to go, so the remainder is coiled up on the car floor in the back where the MTX 275 resides.

 

Would I be wise to cut down the feed line to the needed length and solder on a new connector? OR - does the excess feed line make any real difference?

 

First GMRS radio - obviously - I have both the 6db and 3 db NMO antennas from Midland.

 

Any feedback is appreciated.

Hello Kevin.

 

I am using the Midland NMO MagMount with their 6dBi antenna. I have operated that combination for nearly 9 months now. I have left the coax at factory length and operate well with a 5 Watt HT. If you are having a problem storing the extra length feel free to shorten it to suit, but do not shorten it with any expectation that you will somehow experience better receive or transmit performance. The small amount of cable removed will make such an insignificant difference that it would take test equipment to know there was a change. You and others will not be able to tell that you made the change not matter how hard you try. Now, if I were making the cable from scratch, I would make it the exact length needed. No more, not less.

 

 

Michael

WRHS965

KE8PLM

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I'm in the same boat and have not installed my Midland as did not know what to do with the extra cable... One person said do not coil it up...

We are standing by for a good and correct answer...

Jack and for Kevin as well.

I just installed my new midland in my TJ with the antenna mounted on my swing out tire carrier. I too was under the impression not to coil the extra cable but was no problem as I was able to route the cable along the Roll Cage to the radio. I do have my radio mounted to the RockHard plate on my roll cage up high and forward.

I am interested in this as I have to install a radio in the wifey's JK and will use the mount that fastens up by the windshield so there will be a lot of extra cable.

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If you have an unbalanced antenna - such as a vertical that works off a ground plane - it really doesn't matter what you do with excess cable.

I would mainly be worried about the loss.  Transmission line is transmission line.

 

With a balanced type antenna (like a dipole or a beam) - coiling the cable can actually be helpful because is works like a balun transformer.

Balanced antennas are not referenced to ground and want a differential drive.

 

I would say nearly 100% of mobile antennas for vehicle are unbalanced or ground referenced antennas.

 

Vince

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Local radio tech commented to me the other day when I suggested cutting my cable to length for my XJ to 36".  "These antennas/radios like some resistance". 

Just his remark FWIW.  I'll probably loop mine around above the headliner when I get around to how/where to mount the radio.

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Local radio tech commented to me the other day when I suggested cutting my cable to length for my XJ to 36". "These antennas/radios like some resistance".

I would like the tech to back up his assertion by demonstrating to you just how much power the antenna radiates when using more feed-line than with less, all else remaining equal.

 

 

Michael

WRHS965

KE8PLM

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Along this line, the feed line that came with the mag mount [NMO] is six meters long - enough to practically wrap around the car.  I only needed about 3 meters to reach where I needed to go, so the remainder is coiled up on the car floor in the back where the MTX 275 resides.

 

Would I be wise to cut down the feed line to the needed length and solder on a new connector?  OR - does the excess feed line make any real difference?  

 

First GMRS radio - obviously - I have both the 6db and 3 db NMO antennas from Midland.  

 

Any feedback is appreciated.

 

 

I too have the Midland mag mount. Found out the cable that comes with the mount (RG58/a/u) is a high loss cable.  I used a coax loss calculator (link below) and my Midland MXT275 15 watt radio is now only a 7 watt radio using the mag mount cable's 9 meter length.  By cutting it down to 8 feet it becomes a 12.2 watt radio.  I will be cutting mine as soon as I have the time. My 6 DB Midland antenna only has a 1.10 or so RWS. The higher that number gets the more loss is incurred....

 

Link to the calculator:

 

https://www.qsl.net/co8tw/Coax_Calculator.htm

 

Best,

 

JAS

WRKP245

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Yeah, I didn't pursue the topic.  Sounds kinda bass-ackwards.

 

I would like the tech to back up his assertion by demonstrating to you just how much power the antenna radiates when using more feed-line than with less, all else remaining equal.


Michael
WRHS965
KE8PLM

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Instead of starting a new thread, I'll add this issue I'm having with this antenna. It has happened twice now, and it's when I'm on the freeway and it's windy or inclement weather. The antenna starts whipping violently, hitting my hard top. I have to come to a complete stop, and that is not fun on the interstate. It's like the spring is too weak. This used to happen with my 3' Firestick, but I cured that by installing a stiffer spring. Anyone running this antenna experience this issue?

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The reference is for the exhaust tuning of the internal combustion engines. This is not only similar physics behind it (and fallacies) but exactly the same. The same wave theory applied to processes inside exhaust pipes and antenna feeders. The point is to match the impedance and reduce the amplitude of reflected waves to not waste energy on pushing exhaust gases through the pipes, and the current through the feeder line and antenna. Two-stroke engines are especially sensitive to exhaust tuning, because they relay great deal on the wave processes inside the pipes (SWR, if you wish) to ventilate out the wasted gases and fill the combustion chamber with the fresh fuel/air mixture. Four-stroke are less sensitive to exhaust tuning (but still are!) but more sensitive to intake tuning for the very same reasons - wave behavior in the transmission lines (intake and exhaust manifolds and pipes). So, the nature of the phenomena is different, but the physics behind it the same, so are misunderstandings.

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Instead of starting a new thread, I'll add this issue I'm having with this antenna. It has happened twice now, and it's when I'm on the freeway and it's windy or inclement weather. The antenna starts whipping violently, hitting my hard top. I have to come to a complete stop, and that is not fun on the interstate. It's like the spring is too weak. This used to happen with my 3' Firestick, but I cured that by installing a stiffer spring. Anyone running this antenna experience this issue?

I cannot see what the antenna is doing while I am driving. The only time I hear noise from the antenna is when I hit a tree branch or forget to remove it before pulling into the garage. I know I have traveled a lot at 70MPH and have not heard anything unusual.

 

 

Michael

WRHS965

KE8PLM

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i have the Midland 6db whip and the Midland Mag mount NMO. Mag mount is center on my roof and I kept clipping the antenna on local overhangs. I now have the Browning BR-176-S 3db, 14" tall mini-whip. I'll switch back to teh Midland for highway/travel or camp/local/simplex.

Both have had great SWR out of the package, no need to trim. But remember that your SWR is based on your install and ground plane. every one with have a different SWR.

The Midland 3bd can antenna had really bad SWR and I returned it.

 

Anyone serious about the hobby should get a good SWR meter, you have trouble shoot soo many things with one.

loose connectors, pinched wires, mis-tuned radios. I found that I had typo'ed the TX on a memory using my metter.

I have several meters, but my go to is the Surecom SW-102S

 

 

WRJT952

Larry

73

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