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#1 WRAF233

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Posted 20 December 2019 - 12:29 PM

Looking for an antenna mount that will bolt onto a vertical 2" UTV rollbar.

Wondering if this will work but unsure if it's 2" wide for 'U-bolt"?


WRAF233

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#2 WRAK968

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Posted 20 December 2019 - 02:20 PM

Well, if there was a product link its missing,

But, what you could do is get a 2" exhaust clamp, use the flat side of the bracket on the clamp to rivit a 90 degree NMO bracket in place onto it, then use the clamp to mount the antenna.

Could do the same with any antenna mount that has a 90 degree bracket, but the only ones I've seen are NMO.



#3 RCM

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Posted 20 December 2019 - 06:32 PM

How about something like this?

https://amzn.to/2PJbXLO



#4 BoxCar

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Posted 21 December 2019 - 08:51 AM

You'll need a good ground plane for the antenna, The roll bar should have a good connection to the frame and the mount will also need a good electrical connection to the roll bar. Probably the best mount would use holes drilled and tapped into the bar with  star washer between the mount and bar.


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#5 quarterwave

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Posted 21 December 2019 - 10:43 AM

You could use something like this and some bigger clamps. 

 

 https://www.american...-nmo-connector/

 

or

 

https://afxmotorspor...4IaAqCFEALw_wcB



#6 WRAF233

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Posted 06 January 2020 - 01:45 PM

You'll need a good ground plane for the antenna, The roll bar should have a good connection to the frame and the mount will also need a good electrical connection to the roll bar. Probably the best mount would use holes drilled and tapped into the bar with  star washer between the mount and bar.

The "electrical connection" you're talking about is ground, correct? So I need to get bare metal to bare metal contact either by mount to bar connection or run a wire to a screw on the bar or frame?

 

I'll be using a non-ground plane antenna. I'm considering this: 

https://www.arcanten...-steel-tkg.html

 

mounted to a RotoPax mount similar to what quarterwave posted:

https://afxmotorspor...4IaAqCFEALw_wcB

 

All in combo with this antenna:

https://www.arcanten...ound-plane.html

(or a 12.5" version https://www.arcanten...50-470-mhz.html)

and:

https://www.arcanten...r-included.html

 

I'll probably get the Midland MXT115 (and a couple HH units) unless I find something superior for not a lot of money.  I'm not interested in programming or used equipment and trying to keep size minimal for mounting purposes.  Usage will be 90% rig-rig offroad comm.  There are very few (and far between) repeaters out West where I ride most.

 

Critique welcome and encouraged (with suggestions maybe). 

 

Also just noticed the new radio posted on this site.

https://shop.mygmrs....able-gmrs-radio

Outperform the Midland HH??


WRAF233

NE NV


#7 WRAF233

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Posted 06 January 2020 - 05:12 PM

Copy/Paste from Equipment Reviews thread.  Thought I'd consolidate my endless questions to keep me on track.  Thanks for input and patience.

 

Searched and found a little bit..

 

Application:  Mobile radio for UTV 

 

Had been thinking Midland MTX115 for my side by side but reading here that they're not that highly regarded so while looking online for a used Motorola M1225 (recommended here) I came across Kenwood TK863G here:

https://used-radios....price-ascending

 

The page if FULL of what look to be good radios in the correct 450-490-ish range.

Recommendations?

 

I know I don't want to get stuck on some kind of search for programming, cables, etc.  Just going for offroad use, seldom repeater access.

 

Wow!

 

Edit/Add.  They will program 16 channels free, 6 additional for $25 to total 22.  That cover all the GMRS spectrum correct?


WRAF233

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#8 RCM

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Posted 06 January 2020 - 10:01 PM


 

They will program 16 channels free, 6 additional for $25 to total 22.  That cover all the GMRS spectrum correct?

You actually only need 15. The 467 MHz interstitial channels (GMRS/FRS Channels 7-14) are not legal for the mobile radios, nor do you need them anyway.



#9 WRAF233

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Posted 07 January 2020 - 01:57 PM

Now for the antenna:

 

If a 32" antenna is 1/2 wave (450 - 470 Mhz) does that make a 15" 1/4 wave?

Is 1/4 wave ideal?  And which affects range most - antenna length or wavelength?

The Kenwood is 25W so a maximum of 3db gain antenna to stay within 50W regulation on mobile radio?

 

in a mobile application (UTV, no ground plane).  Planning to mound on the side of the steel kayak roof rack or possibly on a vertical roll bar.

 

You guys have already been a lot of help.  Thanks for the guidance.


WRAF233

NE NV


#10 SteveC7010

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Posted 07 January 2020 - 04:07 PM

You are mixing apples and oranges. A 32” UHF antenna is almost certainly a high gain antenna and requires a ground plane. A 15” UHF spike would more likely be a half wave, no ground plane antenna with low gain, probably 2.4 db or so. A quarter wave, unity gain spike at GMRS freqs is about 6” and requires a ground plane of about 6” in all directions. You easily find an NMO base adapter with trimmable radials.

Personally, I’d put my first effort into the very low profile quarter wave option due to best survival of tree branches.

Hint: read the full description and specs for each antenna to avoid inappropriate comparisons.
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#11 WRAF233

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Posted 07 January 2020 - 05:35 PM

I have no ground plane available.  Plastic roof on UTV.  Options are vertical rollbar antenna mount or a NMO mounting bracket off the steel kayak rack.

 

Or I'll just get a couple decent HH and call it a day.


WRAF233

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#12 RCM

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Posted 07 January 2020 - 10:40 PM

This looks like a good choice for your application: https://www.theanten...d-muf4502s-8347

 

A 1/4 wave off either the vertical rollbar or kayak rack will be fine, too. If you go that route, just make sure the radiator is not too close to or obstructed by the rollbar. Have you seen Jeeps with CB antennas mounted on the back? They certainly don't have actual ground planes. The equivalent of a 12 inch diameter piece of metal under a GMRS antenna would, on CB, be 17 feet in diameter. Yet those antennas are still usable with 4 watts output and no real ground plane.



#13 RCM

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Posted 07 January 2020 - 10:57 PM

Now for the antenna:

 

If a 32" antenna is 1/2 wave (450 - 470 Mhz) does that make a 15" 1/4 wave?

Is 1/4 wave ideal?  And which affects range most - antenna length or wavelength?

The Kenwood is 25W so a maximum of 3db gain antenna to stay within 50W regulation on mobile radio?

 

in a mobile application (UTV, no ground plane).  Planning to mound on the side of the steel kayak roof rack or possibly on a vertical roll bar.

 

You guys have already been a lot of help.  Thanks for the guidance.

A 32" antenna is 1/2 wave on 175 MHz or 1/4 wave at the bottom of the FM broadcast band, or about 87 MHz. Neither of those will work on 462 MHz GMRS.

 

Wavelength affects whether or not the antenna will work at all on a given frequency. Antenna length is related to wavelength.

Don't worry about gain, especially for offroading. Gain isn't free. To get gain in one direction, you have to give up signal strength in other directions. It's best to just use a 1/4 wave or 1/2 wave antenna. And I would (and usually do) just use a 1/4 wave because it is small (6 inches), works well and is naturally self resonant and therefore dirt simple. Offroad, simple is better.

 

The power limit for a GMRS (not FRS) radio is power to the antenna, not ERP. So even if you do have some gain, even if you brought along a portable high-gain Yagi beam (single-directional) antenna just to see how far you can reach from a mountaintop, you can still legally feed it the full 50 watts.


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#14 berkinet

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Posted 08 January 2020 - 05:03 AM

A couple of notes related to this discussion.

#1 Frequency and wavelength are 2 ways of describing the same phenomena. The frequency (Hertz)

equals the number of waves that pass a given point per second. A wavelength

equals the distance between two successive wave crests or troughs. 

igt2_wvlngthfreq.gif

 

Here is the formula that is used to convert between the two measurements:

 

wavelength-formula.jpg

Freq is the Frequency in cycles per second
C is the velocity factor 299,792,458 meters per second 

    (the speed of light)
λ represents wavelength in meters

 

So, a single wave at 462.725mHz (GMRS Ch 22) is 0.648 meters long, and a 1/4 wave is 0.162 meters or 6.379 inches.

 

As for your ground plane, for a 1/4 wave antenna, it should be a bit longer that 1/4 wave in all directions. The longer the better. But, anything over 1/4 wave is fine. However, for your purposes, if you have the antenna mounted well above you and keep the power low, which you should do anyway, you will do just fine for most communications with the roll-bar as a ground plane all by itself.

 

If you want exact measurements, take a look at this site. Also note that for repeater use there is a 5mHz difference between your transmit and receive frequencies. That translates to around 0.03" for Ch 22. The main point here is, unless you are designing the antenna for a single simplex frequency, there will always be tradeoffs in length.    For more information, take a look at this discussion on RadioReference

 

As to the number of channels. First off, don't confuse the term GMRS Channel, which translates to an FCC designated frequency, with the numbers of channels offered by your radio. With the radios, the term channel refers to an assignment of a frequency and other relevant information to a position in the radio's internal programming list. On simple radios, that is a dial position. On radios with a display, it is usually shown on the display. Some radios even allow you to hide the internal channel number and, instead, assign a name.  

 

While it is true that there really is no such thing as a sub-channel You might consider a specific combination of channel (frequency) and PL/DPL audio management to be like a separate channel. That is, if you call home on ch 14 with a PL of 88.5 and call your friend on the same frequency but with a PL of 131.8, you could either assign one channel on your radio to GMRS Channel 14, and then change PL as needed from the front panel or microphone (if possible), or assign two separate channels on kourradio, one for each combination.  So, that is why some users want radios with more than 22 channels.  See the Wikipedia for more information.

 

 


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#15 WRAF233

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Posted 08 January 2020 - 06:24 PM

This looks like a good choice for your application: https://www.theanten...d-muf4502s-8347

 

A 1/4 wave off either the vertical rollbar or kayak rack will be fine, too. If you go that route, just make sure the radiator is not too close to or obstructed by the rollbar. Have you seen Jeeps with CB antennas mounted on the back? They certainly don't have actual ground planes. The equivalent of a 12 inch diameter piece of metal under a GMRS antenna would, on CB, be 17 feet in diameter. Yet those antennas are still usable with 4 watts output and no real ground plane.

 

Have you seen Jeeps with CB antennas mounted on the back?   Yup, I have a CB antenna mounted just like that on my Jeep. Have it on a quick disco and swap between 4' fiberglass and 1/4 wave whip.  Haven't used it tho' so have no idea the range or quality.. go figure.

 

Thinking this rollbar mount (or similar) suggested by a member.

https://www.amazon.c...78526050&sr=8-1

Might have to drill it out for the NMO, but that's ok to get to bare metal, and an NMO mount for 3/4" thickness.

Maybe I'll figure out a way to get a 12" square of sheet metal integrated under whatever mount I end up with so I will have a ground plane, if it doesn't work as well as I hope with the 12.5" unity antenna.

 

Thanks for the feedback..


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WRAF233

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#16 SteveC7010

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Posted 08 January 2020 - 07:40 PM

You don’t need sheet metal. That ultra-sticky aluminum HVAC tape fastened to the underside of roof works well. Just use an NMO mount that has teeth on the inside mount that will bite into the tape. That will give a decent rf ground through the coax to the body of the radio. You don’t need a complete circle either. Just an X or * of about 13” diameter is fine. We did a lot to fiberglassed roofs on ambulances and RV’s. . You’ll find the tape at any hardware or home improvement store.

Another possibility, if there’s a headliner under the non-conductive roof, is to fasten steel or aluminum window screen or even chicken wire to the underside of the roof.

If I doing a UTV like yours, I’d use a 6” quarter wave UHF antenna with the HVAC tape ground plane. It’s small enough to survive most tree branch problems, can be easily straightened if bent, and $10 each, you can keep a spare or two in your tool box for peace of mind. Add a commercial grade radio like the Motorola M1225 properly installed and shock mounted, and you’ve got a nearly bulletproof rig.
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#17 axorlov

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Posted 08 January 2020 - 08:24 PM

Theoretically, 1/2 wave antenna should not require a ground plane. It will require matching, though. The 5/8 wave antenna should have much less dependency on the size and quality of the ground plane than 1/4 wave.

I do not have a personal experience with 1/2 or 5/8 without ground plane or with limited ground plane. I do run BR-178, which is 5/8 antenna, but it is mounted on the big flat roof of SUV.


- Alex


#18 WRAF233

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Posted 08 January 2020 - 10:03 PM

Looking through Antenna Farm and find options for Custom cable to go with the 1/2 wave antenna suggested.  

 

7' of Belden 8219 Standard RG58 coax

2 Amphenol 082-5375-RFX (N Male) RG-259

Shrink wrapped.

PCTEL Maxrad MUF4502S

 

All for $63 and change.

 

Would combo this with a reman Kenwood TK83G from used-radios.com.

Programmed CH. 1 - 6 and 15 - 22

 

Right track?

 

Maaannnn... I'm a pest!  But, if I get it right the first time..

 

All good food for thought.


WRAF233

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#19 WRAF233

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Posted 08 January 2020 - 10:09 PM

You don’t need sheet metal. That ultra-sticky aluminum HVAC tape fastened to the underside of roof works well. Just use an NMO mount that has teeth on the inside mount that will bite into the tape. That will give a decent rf ground through the coax to the body of the radio. You don’t need a complete circle either. Just an X or * of about 13” diameter is fine. We did a lot to fiberglassed roofs on ambulances and RV’s. . You’ll find the tape at any hardware or home improvement store.

Another possibility, if there’s a headliner under the non-conductive roof, is to fasten steel or aluminum window screen or even chicken wire to the underside of the roof.

If I doing a UTV like yours, I’d use a 6” quarter wave UHF antenna with the HVAC tape ground plane. It’s small enough to survive most tree branch problems, can be easily straightened if bent, and $10 each, you can keep a spare or two in your tool box for peace of mind. Add a commercial grade radio like the Motorola M1225 properly installed and shock mounted, and you’ve got a nearly bulletproof rig.

 

 

It's a double layer plastic roof with a gap in between.  Need the antenna off to one side to stay away from the kayak when loaded.


WRAF233

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#20 RCM

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Posted 08 January 2020 - 11:00 PM

Looking through Antenna Farm and find options for Custom cable to go with the 1/2 wave antenna suggested.  

 

7' of Belden 8219 Standard RG58 coax

2 Amphenol 082-5375-RFX (N Male) RG-259

Shrink wrapped.

PCTEL Maxrad MUF4502S

 

All for $63 and change.

 

Would combo this with a reman Kenwood TK83G from used-radios.com.

Programmed CH. 1 - 6 and 15 - 22

 

Right track?

 

Maaannnn... I'm a pest!  But, if I get it right the first time..

 

All good food for thought.

Here's the connector (with cable) you need for the clamp you linked: https://www.theanten...rad-bmatm3-1155

In the drop-down menu, select the option for PL-259 connector because that's what the TK-863G has. It doesn't have an N connector.

 

Steve has some good ideas for improving the ground. I don't think you will have any problem. But, I have another idea for your consideration. Get about a 15 inch piece of solid copper wire, like one conductor out of a piece of house wiring. Bend and crimp with pliers a small loop in each end (so it doesn't scratch anything/one), then bend and crimp a short (1 inch or so) stub in the middle. Now when you attach the clamp to the rollbar, capture the center stub between the clamp and the rollbar so you have 6+ inches of wire sticking out both forward and aft. Might be good to rough up the inside of the clamp at the pinch point, for better electrical contact. Now if you can, use zipties or tape to secure the ends of the wire so they don't catch on anything.

 

I don't think you will have to do any of that, though. In a offroad vehicle, unity gain is good. Look at it this way. Say your group is headed up a mountain trail, and you are near the top. An antenna with some gain will probably give you a stronger signal into a repeater that is 50 miles away on the horizon, sure. But, it does so by taking away signal from other members of your group who are farther down the mountain and at a different elevation. So your signal to them will be weaker or maybe nonexistent, where an antenna with no gain might work pretty well.






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