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newbie Midland MXT275 antenna placement question


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#1 jharv

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Posted 23 August 2018 - 07:50 PM

hello all,

 

newbie here, so i wanted to introduce myself along with asking a question about antenna placement. i few weeks ago i purchased / installed a midland mxt275 (15w) in my jeep. i also installed midland's -6db gain antenna. i also have a midland handheld.

 

in the past few weeks i've been reading many of the forum posts and doing as much research online as i could find. i've also done some local testing to compare this radio to my old cobra cb. my initial thoughts are that i've very impressed! i love the feel of this mic and the quality is awesome.

 

the one mistake i made was looking at the coverage circles of the repeaters thinking "oh wow, that's great" - not realizing at first that circle is the estimated range of the repeater's transmit... and my being able to reach that repeater is a whole different story! in my testing to the handheld, i got about 2, maybe 2.5 miles, through a suburban type area, with some trees and plenty of houses and buildings along the way. plus, the handheld was in the house, my daughter using it to test with me.

 

in another test from my jeep to a buddy with a midland mxt400 (40w), we got about 3 miles, hearing each other clear as sitting right next to each other. so i'm pretty happy with this - compared to the cb - but i want to make sure i'm getting as good range as a should be (with 15w).

 

here's the shameful part. i mounted my antenna on my jeep's tire carrier, between the tailgate and spare tire. i say "shameful" because i know it's not the best place, but i think (or thought at the time) that it was my best choice. i don't see many posts with pics here, but if anyone wants to see i do have two i can share. i knew mounting the antenna there would be shielded, which is why i went with the -6db loss antenna. it's 27.5" long and reaches up about 2-3" above the top of the jeep. recently i've been reading so many posts from people saying not to do this. my second choice for mounting it was at the base of the windshield, in front of the driver side mirror. i didn't choose that because i take my jeep off-road a lot, and it's going to constantly get whacked by tree branches.

 

i think 2.5 - 3 miles under these conditions is probably what i can expect, but that's just a guess and wanted to ask your opinions. if it's normal, that's ok. but if you think i should easily get 10+ miles then i have a problem. i ordered a uhf swr meter that should be here tomorrow. i'm assuming my ground is good - which is somewhat questionable, since it's mounted to a metal swing-out tire carrier. will test that with a multimeter tomorrow as well. the other problem - i've read recently to not mount an antenna near many vertical surfaces.... my nmo mount is on an L-bracket, screwed into what is basically a 2-3" wide vertical beam. 

 

so my questions are: do you think my range is about what i should expect? and more importantly, if i am getting feedback from the antenna back towards the radio because of the lack of ground plane or all the metal surrounding the base of the antenna, would i see the result of that as a high swr reading? i wanted to ask in case the swr is actually good, i didn't want to assume the mounting location isn't causing a huge performance problem. i've read about non-ground plane antennas and am thinking to try one of those, based on the readings tomorrow and any suggestions you may have.

 

thanks in advance for any advice or comments you may have!



#2 Elkhunter521

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Posted 23 August 2018 - 10:00 PM

Hi, Everything I have read says a ground plane antenna (i belive yours is) requires a conductive surface of 1/4 wave length in diameter. 462.xxx MHz is about 6.35 inches. It would help if you could put a piece of sheet metal under your antenna about this size. Ground it to the chassis.
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#3 WRAA720

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Posted 24 August 2018 - 01:27 PM

The range of a UHF radio will be pretty much limited to line of sight.  If your antenna is 6 feet off the ground, its distance to the horizon is 3 miles.  If the antenna for the other radio is also at about 6 feet, then you have an approximate theoretical range of 6 miles.  Trees, structures, land, antenna gain, RF interference, output power, etc will all have an effect on this range.  If you're currently getting 3 miles simplex between radios, that's pretty good!  You are also correct in that your current antenna placement on the Jeep spare tire is less than ideal.  The best location for a mobile antenna is always the center of the roof - this is the highest point on the vehicle and the surface area of the roof will provide a ground plane.  Is this is the antenna you are currently using?  I * think * this is a 5/8 wave antenna, which will require a ground plane to operate efficiently.  Since you're in a jeep, a fiberglass roof is not a great surface for that ground plane (and you may not even have a roof at times..) so you should look into 1/2 wave antennas, which do not require a ground plane to operate.  The antenna should still ideally be mounted as high on the vehicle as possible.


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#4 jharv

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Posted 25 August 2018 - 11:25 AM

Elkhunter521: thanks for the sheet metal suggestion! i may actually have just enough room to fit something like that... will look into it and how to mount it.
 
Matt: yes, that's my antenna. actually, i'm wondering if a no-ground antenna might be a good idea... i think i might just have to try one, and compare the results against my current antenna. it looks like laird makes a no-ground antenna (theantennafarm link) in both a 5/8 and 1/2. they're both slightly longer that what i already have (mine being 27.5", theirs being 31" or 33"). 
 
i'm thinking that slightly longer is a good thing - the top would be a few inches higher than the fiberglass roof.
i like how they just screw on to the NMO mount... if i ever want to swap it out for whatever reason, that's convienient.
 
i'm glad to see you think my results so far have been pretty good (distance-wise). it's good to know i'm in-line with expectations and not just hindering myself for doing something silly (like no ground at all). so my next minor projects will be to try to fabricate a ground plane and/or experiment with a different antenna.
 
i measured my SWR, and it came in a roughly 1.4:1 on the GMRS channels (at 15w, measured 3W on the meter). on some channels it was closer to 1.35:1. on a lower-power FRS channel it was actually 1.2 - and surprisingly with the tailgate opened it measured 1.5 (worse)! i also checked my ground continuity from various points on the antenna base, mount, tire carrier, and tailgate. it seems like i have a pretty decent ground.
i don't think i'm bleeding any RF back into the coax.... if anything, i may just be trapping it (or more like distorting the pattern) between the lower part of the antenna and the tailgate/wheel/carrier. 
 
to be honest, i don't think i really have a "signal problem", i just don't know how this compares to other setups, especially knowing mine is less than ideal.
i'm starting to think my current setup isn't so bad... or at least not as bad as i thought... but i do want to test adding a ground plane or different antenna.
 
thanks again for the suggestions!


#5 PastorGary

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Posted 25 August 2018 - 03:11 PM

Before you make any changes, please review the information provided here.....https://www.jlwrangl...-mounting.7307/


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#6 jharv

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Posted 27 August 2018 - 05:09 AM

Before you make any changes, please review the information provided here.....https://www.jlwrangl...-mounting.7307/

 

PastorGary - thanks for the link, there's a lot of good info there! i feel bad for the person cutting their hood... they quickly abandoned that plan, said it wasn't going so well, and chose another spot. i'm glad i wont be cutting anything at this point.



#7 PastorGary

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Posted 27 August 2018 - 09:59 AM

This one may work out for you.  NO ground plane (1/2 wave).   A colleague has a Jeep with a removable fiberglass top. He has TWO NMO mounts - one on the fiberglass roof and one on an "L" bracket on the roll bar, top center.  When he has the top on, he has this antenna (below) in place with the coax from the roof NMO mount running to the radio.  When he removes the top, the roll bar NMO coax goes to the radio and he just transfers the antenna listed below from the roof mount to the roll bar mount. 

 

https://shopwiscomm....z-P2106563.aspx


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#8 jharv

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Posted 28 August 2018 - 05:28 AM

This one may work out for you.  NO ground plane (1/2 wave).   A colleague has a Jeep with a removable fiberglass top. He has TWO NMO mounts - one on the fiberglass roof and one on an "L" bracket on the roll bar, top center.  When he has the top on, he has this antenna (below) in place with the coax from the roof NMO mount running to the radio.  When he removes the top, the roll bar NMO coax goes to the radio and he just transfers the antenna listed below from the roof mount to the roll bar mount. 

 

https://shopwiscomm....z-P2106563.aspx

 

oh wow, this is great! and it gives me an idea. 

here's what my tire carrier looks like (not mine, but same one): http://image.fourwhe...rrier-check.jpg

my current mount is on the square part at the middle, which is at just about the height of where the tailgate meets the window. it runs 27.5" up, to about 2-3" just above the roof.

my tire carrier has a steel platform that sits just above the tire - maybe about 6" lower than the top of the roof. it's meant to be a mounting location for rear-facing fog lights, which i'll never need. i think i'd be silly to not mount an antenna there! i thought of that when i first installed it, but the challenge was there wasn't enough material to drill through and hold a mount. and at the time, i thought having a longer antenna would be better. i should think about how i can attach a metal platform to the existing platform, raised up just enough to fit the coax between the two. that will get my antenna completely away from being wedged between the tailgate and tire carrier!

 

 

the concept of running two mounts is a really good idea. i could use one for my on-pavement driving for greater distance, and another for when i'm off-road and need to avoid tree branches but probably won't need the distance (we're usually in a tight group).

 

this is great - thank you very much!



#9 raven1390

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Posted 28 August 2018 - 03:02 PM

Good afternoon, and glad you’re liking the MXT275. I’ve been thinking about pulling the trigger on one also. I have the MXT115, and before I upgraded to the DPD Productions 5.5dbi antenna, I was hitting my closest repeater from Woodbridge, VA all the way to Alexandria, VA with great audio reports..and that was with the supplied antenna. Needless to say you should be getting way more out of that setup. I also concur witht the antenna placement, however Midlands 6dbi antenna is also sold to mount to their L bracket for ATV’s which does not have a few inches of ground plane. I’ve also used repeaters in PA about 10 miles away, with no issues and full signal. Hope that helps.

#10 jharv

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Posted 29 August 2018 - 05:27 AM

raven1390 - thanks for the info, that helps the comparison.

 

about the mxt275: part of me wishes i would have gone with the mxt400 instead (just for the increased power - 40w), but i really like having the controls in the mic, which i have mounted close to the top of my dash. it's very convenient for changing anything (scan/channel/volume), and if i do need to look at it, it only takes a quick glance. i think the feel of the buttons and response is excellent. the only reason i didn't go with the 400 is that i would have had to mount it along side the center console, which would have taken up a small amount of space next to my passenger, but would have also been harder to see the screen or reach the controls (i have a manual transmission and also use the cup holders, especially when off-road).

 

i did perform another test: from my mobile on top of a local hill to a handheld in the house. distance was about 6.2 miles, and we had fairly decent quality both ways. i did have better signal on the mobile as i was driving down the hill, perpendicular to the direction of home - but that could be because the signal was stronger towards the sides, but could also be because i was along the side of the hill as opposed to being about 100' from the edge - the signal being obstructed by the edge of the hill. either way, i'm pretty happy with the results! but that also tells me height (line-of-sight and less obstruction) means everything - which i knew, but actually seeing the results is very interesting (fun).

 

as time permits (probably over the next few weeks), i'm going to do a few more tests, noting how far from home i start to loose signal. then once i get a different antenna, and/or add a second mount higher on the tire carrier, i'll do the same tests from similar locations. i'll be sure to post those results.



#11 PastorGary

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Posted 29 August 2018 - 08:29 AM

Is there room on the tire carrier to mount a pipe flange for 1/2 inch water pipe?  Once mounted, an appropriate length of 1/2 inch galvanized water pipe then becomes a mini-mast.  At the top of the mast, you can adapt to just about any type of antenna and mount.blff050-3.jpg


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#12 jharv

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Posted 30 August 2018 - 05:15 AM

PastorGary - that's great, thank you! when i was thinking of how to mount the antenna to the very top of the tire carrier, i was trying to picture how to do it using some sheet metal and maybe some really thick washers. i never thought of a flange - i think it'll fit perfectly, and is exactly how i was picturing to make it! the top is triangular and the sides measure 4.5" on two sides and 5.5" on the other. even better is that there are already 3 holes through the top, about 7/16". i traced it out on paper yesterday, and will take that to some hardware stores. if i'm lucky enough, i might even find a flange where the holes will line up! 


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#13 Hans

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Posted 30 August 2018 - 08:29 PM

Good afternoon, and glad you’re liking the MXT275. I’ve been thinking about pulling the trigger on one also. I have the MXT115, and before I upgraded to the DPD Productions 5.5dbi antenna, I was hitting my closest repeater from Woodbridge, VA all the way to Alexandria, VA with great audio reports..and that was with the supplied antenna. Needless to say you should be getting way more out of that setup. I also concur witht the antenna placement, however Midlands 6dbi antenna is also sold to mount to their L bracket for ATV’s which does not have a few inches of ground plane. I’ve also used repeaters in PA about 10 miles away, with no issues and full signal. Hope that helps.

 

Not to go far off topic... Our local Midland Micromibile users have experienced a problem with multiple tones on repeaters. They cannot find a way to set the Midlands to carrier squelch when using a tone to access repeaters. Since our repeaters, and almost all of the other repeaters I've used, have multiple access tones programmed, they are missing traffic transmitted with other tones and unintentionally talking over traffic using other tones. They have resorted to keeping another radio with them to monitor the repeater output with carrier squelch to make sure they don't talk over someone else and that they hear all traffic. AFAIK, Midland hasn't addressed this issue yet. I personally wouldn't buy one for repeater usage until that issue is resolved.


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#14 raven1390

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Posted 31 August 2018 - 08:40 AM

Hans, that’s interesting. Unfortunately the Midlands are essentially tone squelch, when you choose your tone it sets that tone for Tx and Rx. I’ve seen where some people have been frustrated that you can’t set different tones for Tx and Rx also, for those that have repeaters with different tones in and out. I haven’t come across this yet. I’ve used repeaters in VA, PA, WV, NC, SC, and it’s worked really well. I guess I’m surprised that repeaters have split tones for GMRS, especially as the Midlands become more popular. Hopefully some adjustments will be made in the future. I’ve seen that also listed on some reviews on Midlands website.

#15 Hans

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Posted 31 August 2018 - 03:51 PM

The repeaters around here don't have a different tone in and out. There is a tone squelch on the repeater receiver and no tone put out by the repeater transmitter; except that which is already in the user's signal. The repeaters have multiple tones for access. If tone 2 is used to access, tone 2 is passed through the output with the signal. As such, Midland users receiving with tone 1 will not hear traffic from a non-Midland users transmitting with tone 2, tone 3, etc. Of course, the rest of us have our radios set to carrier squelch so we hear all traffic regardless of what tone is used to access.

 

Repeaters can be configured like this and a user would likely never know that they were missing traffic unless someone told them or they were scanning with another receiver at the same time. I have seen many repeaters with multiple access tones but only one listed publicly... Everyone else being unaware there are alternate tones. Our people using Midlands had no clue until we started talking at a meeting. They just thought that the repeaters were really quiet most of the time and one sided conversations heard were due to reception.

 

Midland needs to make a setting where carrier squelch is an option when choosing a transmit tone, even on simplex. I, too, hope they fix the issue soon because we very much like that line of mobile radios.



#16 raven1390

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Posted 31 August 2018 - 04:37 PM

Oh, ok. Thanks for the explanation, Hans.
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#17 jharv

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Posted 02 September 2018 - 10:19 AM

Hans - yes, thanks for the info. i came across that before, but didn't think much of it since i've yet to find a repeater within my transmit range. but i would like the ability to set a PL tone on transmit only and carrier squelch on receive, so that i could use a repeater and still receive local simplex (if the time comes where i can find/reach a repeater). i wonder if or how Midland could ever address this, other than forcing people to purchase a new radio with that capability, if they ever release one. as far as i know, there's no way to program or upgrade the units, at least the mxt275, other than what's available in the menu. 



#18 berkinet

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Posted 02 September 2018 - 12:37 PM

CAVEAT: I know almost nothing about Midland radios. But, often it is possible to program features and settings with the programming software that cannot be performed through the radio controls.  Unfortunately, a quick glance at the mxt275 manual does not suggest it can be programmed externally and there is no CHIRP support for Midland products. However, the radio does have a USB port. While ostensibly for charging, it may have other hidden functionality. Try looking on some of the radio forums and some intense googling. Good luck.

 

Fiollow-up:  I have looked further and it doesn't look like there is any way to program this radio externally.  :( 


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#19 n4gix

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Posted 02 September 2018 - 03:50 PM

Tones that are received by the repeater are normally stripped out (that is removed entirely) before being sent to the transmitter's modulation circuit.



#20 berkinet

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Posted 02 September 2018 - 03:58 PM

Tones that are received by the repeater are normally stripped out (that is removed entirely) before being sent to the transmitter's modulation circuit.

At least in my GR1225, that is an option. I believe tones that are reinserted by the repeater are about 3db louder than times that are passed through.

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