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High Gain Mobile Antenna

alcahuete

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Hi all,

I'm looking for a high gain UHF mobile antenna 450-470/480-ish, or even 403-470. The most important segment is 451-457 MHz, and the 460s after that. I'm looking for the highest gain possible, as use will be mobile-to-mobile and mobile-to-handheld radios at ground level. Don't need to shoot the signal off to repeaters.

Right now, I'm looking at:

Larsen NMO450B
Larsen NMO450CHW

I know the latter is 1/2 wave. Not needed. The NMO450B has slightly (i.e. unnoticeable) gain over the other, and is also 2" shorter, which is a plus.

Anybody have experience with either antenna, or want to add other possibilities ot the mix? The higher gain the better!

Thanks!
 

mmckenna

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I played around with 1/2 wave and 5/8 wave antennas and GMRS and 70CM for a while, and could never tell the difference. If you have a ground plane, use the 5/8 wave and it ~may~ give you a very slight edge on range, but don't expect much.

Other than that, go with a co-linear antenna. https://www.theantennafarm.com/catalog/larsen-nmo450chw-833 that'll give you about 5.5dB of gain. The 5/8 wave will give you 3dB at the most.

Beyond that, if you want more gain, you'd be looking at a base antenna.
 

K4EET

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<snip> I'm looking for the highest gain possible, as use will be mobile-to-mobile and mobile-to-handheld radios at ground level. <snip>
Ask and you shall receive...

Here is one, 450 MHz to 470 MHz with 5 dB of gain and only 8 feet tall. It doesn't come in a NMO mount though so you will have to fabricate some form of an adapter. But that should be no problem.


This should be ideal for those "mobile-to-handheld radios at ground level" comms...



:oops: :ROFLMAO: :oops:
 

alcahuete

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Thanks @mmckenna Yeah, not looking for a base antenna. These are strictly for mobile use with a ground plane (truck roofs) for commercial purposes. The co-linear you listed was my #2 choice above. Tessco lists that antenna as being 5.5 dBi and the 5/8 wave I listed above as 5.6 dBi. I know 0.1 dBi is not going to make a difference, but the 5/8 wave being 2 inches shorter is welcoming.

@K4EET Thank you Sir, but am looking for mobile antennas only.
 

mmckenna

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Tessco lists that antenna as being 5.5 dBi and the 5/8 wave I listed above as 5.6 dBi. I know 0.1 dBi is not going to make a difference, but the 5/8 wave being 2 inches shorter is welcoming.
Ah, I see, two things going on.
You are looking at dBi and I was referring to dBd.
I was also looking at some different antennas.

The non co-linear antennas will have less gain. A straight 1/2 wave will have 2.4dBd of gain with a ground plane under it. The same antenna will have 0dBd of gain without the ground plane.
The non co-linear 5/8 wave antennas will have 3dBd of gain and require the ground plane.

The co-linear designs will give you some additional gain.
For mobile applications, if antenna length isn't an issue, the co-linear antennas will be your better choice. The difference between the two antennas is because of the bottom portion of the element. The lower gain one has a 1/2 wave lower section, so no ground plane required, but more gain with one. The higher gain one has a 5/8 wave lower section, so requires a ground plane, but gives you a touch more gain.
 

alcahuete

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Ah, I see, two things going on.
You are looking at dBi and I was referring to dBd.
I was also looking at some different antennas.

The non co-linear antennas will have less gain. A straight 1/2 wave will have 2.4dBd of gain with a ground plane under it. The same antenna will have 0dBd of gain without the ground plane.
The non co-linear 5/8 wave antennas will have 3dBd of gain and require the ground plane.

The co-linear designs will give you some additional gain.
For mobile applications, if antenna length isn't an issue, the co-linear antennas will be your better choice. The difference between the two antennas is because of the bottom portion of the element. The lower gain one has a 1/2 wave lower section, so no ground plane required, but more gain with one. The higher gain one has a 5/8 wave lower section, so requires a ground plane, but gives you a touch more gain.

Thanks! Yeah, I didn't even catch that we were mixing up our dBs. I just pulled the gain figures straight from Tessco, which put them in dBi. Yeah...I personally don't think the 2" is going to make that big of a difference from a height/usability perspective, so looks like I'll just go with the co-linear.
 

prcguy

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I have a couple of old Motorola UHF colinear NMO antennas that were the highest gain that I have ever found, but I don't remember the model #. The lower part is a SS tube about 3/8" dia, then an enclosed grey coil about the same diameter then a thick whip the same length as the bottom tube. There was a spring inside the bottom tube that allowed the antenna to fold over about an inch above the roof. There was also a removable matching coil inside the NMO base.

I have not seen any of these new in years but I tested them against the biggest Larsen open and closed coil colinear, A/S 5dB rated colinear and everything else available years ago and they worked the best on weak signals. Tomorrow I can post a picture.

Update: I found a picture but the model # listed does not pan out. Look at the 12th antenna from the left in this picture. http://interceptradio.com/wiki/index.php/Mobile_Antenna_Comparison
 
Last edited:

mmckenna

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Update: I found a picture but the model # listed does not pan out. Look at the 12th antenna from the left in this picture. http://interceptradio.com/wiki/index.php/Mobile_Antenna_Comparison
Back in the 80's and 90's, San Jose Police Department used those on their 460.x UHF system. I remember doing a ride along with my uncle and hearing it smack tree branches. Even on top of the sedans, they were tall antennas.
Forgot all about those. Thanks for posting the photo.
 

alcahuete

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I have a couple of old Motorola UHF colinear NMO antennas that were the highest gain that I have ever found, but I don't remember the model #. The lower part is a SS tube about 3/8" dia, then an enclosed grey coil about the same diameter then a thick whip the same length as the bottom tube. There was a spring inside the bottom tube that allowed the antenna to fold over about an inch above the roof. There was also a removable matching coil inside the NMO base.

I have not seen any of these new in years but I tested them against the biggest Larsen open and closed coil colinear, A/S 5dB rated colinear and everything else available years ago and they worked the best on weak signals. Tomorrow I can post a picture.

Update: I found a picture but the model # listed does not pan out. Look at the 12th antenna from the left in this picture. http://interceptradio.com/wiki/index.php/Mobile_Antenna_Comparison
Ha ha ha! I would run a base antenna on top of the trucks before I would use one of those. Boy are those UGLY! :D :D :D

Great info!
 

prcguy

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Here are some pics of what I believe is the biggest baddest UHF gain mobile antenna. I've had this one since about 1979 but have not used it in the last 20yrs. Its ugly to some but I really like it. The Motorola is on the right in the first picture next to a Maxrad 5dB and a Larsen open coil unknown model.

You can see the fold over feature and some of the matching goodies housed inside the base.

1.JPG2.JPG3.JPG4.JPG
 

petnrdx

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I think that Motorola UHF antenna was not only the best performer, but the most durable also.
We had a fleet of around a thousand cars nearly all using that antenna, and they were pretty much even car wash proof.
The 450 to 470 is a TAE6062B. They called it to be 5 dB.
There is a small plastic wafer in the base with two "coil" disks that you can change the screw location in and change the freq
range.
 

prcguy

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Ooh, I'm overdue for a manicure.

Here are some pics of what I believe is the biggest baddest UHF gain mobile antenna. I've had this one since about 1979 but have not used it in the last 20yrs. Its ugly to some but I really like it. The Motorola is on the right in the first picture next to a Maxrad 5dB and a Larsen open coil unknown model.

You can see the fold over feature and some of the matching goodies housed inside the base.

View attachment 88030
4.JPG
 

alcahuete

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Well...I went with the NMO450CHW to test. Only bought one so far. Performance is horrible. Any secrets to getting these to work?

I haven't put the SWR meter or antenna analyzer on it yet, but in my defense, it's simply replacing a 1/4 wave on an existing system.

Completely flat land with no obstructions, I'm barely getting 1 bar on the XPR5550e at 1/2 mile to a mile. With the 1/4 wave, under the same conditions, I'm at all 4 bars out to 4-5 miles.

I'm totally at a loss here. The center pin is making contact, because I can see the small indentation.
 

prcguy

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That antenna shows up as a no ground plane model, is that what you need? I've used the standard version many years ago for GMRS and it worked well and similar to the 5dB rated Antenna Specialists that was popular in the late 70s and 80s. They only problem I ever encountered was the nickel plated whips would turn a little green over time but they still worked fine.

Well...I went with the NMO450CHW to test. Only bought one so far. Performance is horrible. Any secrets to getting these to work?

I haven't put the SWR meter or antenna analyzer on it yet, but in my defense, it's simply replacing a 1/4 wave on an existing system.

Completely flat land with no obstructions, I'm barely getting 1 bar on the XPR5550e at 1/2 mile to a mile. With the 1/4 wave, under the same conditions, I'm at all 4 bars out to 4-5 miles.

I'm totally at a loss here. The center pin is making contact, because I can see the small indentation.
 

alcahuete

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That antenna shows up as a no ground plane model, is that what you need? I've used the standard version many years ago for GMRS and it worked well and similar to the 5dB rated Antenna Specialists that was popular in the late 70s and 80s. They only problem I ever encountered was the nickel plated whips would turn a little green over time but they still worked fine.
The no ground plane should be fine, since it "should" work with a ground plane as well, no? I did the testing with a ground plane.
 

mmckenna

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The no ground plane should be fine, since it "should" work with a ground plane as well, no? I did the testing with a ground plane.
Yes, it'll work better with a ground plane.
No ground plane = 0dB
With ground plane = ~2.4dB

Make sure the center tab on the coil is making good contact with the center button on the NMO mount.
 

alcahuete

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Make sure the center tab on the coil is making good contact with the center button on the NMO mount.
Thanks! Yep, that was the first thing I checked, since I have some other Larsen antennas. Looks like it is making good contact. In fact, it looked like there was a small indentation from the button on the mount, so that part looks good. I just don't know what's happening here.
 

alcahuete

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So I did a little more testing today, but I didn't have a good multimeter to test for a short on the center pin.

Threw it on the antenna analyzer. 1.0:1 SWR with no return loss across the board. So it obviously is not working. It is basically just picking up the mount. In fact, if I remove the antenna, the reception just using the mount is really no different than with using the antenna.

I tried two different NMO mounts that I have on the vehicle (both Larsen mounts) with the same results. And both mounts work just fine with other antennas.

Is this a bad antenna, or what could the problem be? I'm truly at a loss here.
 
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