800MHZ antenna to scan.

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rswagerson

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Hello, Currently my chevy colorado has a fender mounted NMO 22" VHF antenna to scan Low band, VHF and UHF. Couldn't be happier with the performance and used the same setup on my last vehicle however, I just installed some Fender mounted offroad lights and my upper hood area is very crammed, I do not want to use a window mount antenna and my fender mount has got to go. I was thinking of drilling a hole in my roof and using something like this instead (http://www.theantennafarm.com/catalog/laird-tech-trab8213-3292.html) . Obviously an 800 MHZ antenna will not work well transmitting the bands that I said but hopefully just scanning wouldn't be too bad. Any input appreciated, and if it matters Im using a Uniden BCT15X

Thanks.
 

mmckenna

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I had a 2005 GMC Canyon (sister truck to yours) and I still have a 2007 Chevy Colorado as my work truck.
Both had/have permanent mount NMO antennas on them. Even did the same thing on my dad's 2005 Canyon.

The antenna you linked to will likely work just fine for 800MHz, but don't expect any reliable RX performance outside the 700MHz-800MHz band. It's pretty easy to take a 1/4 wave 800MHz antenna and hide it in one of those radomes. Not an issue. I actually had those installed on a couple of the garbage trucks at work, and they've worked just fine. Issue with that design comes at the lower frequencies, but that isn't what you were asking…

Anyway, should work just fine. Concern though is that they are not flexible in any way, so anything that might hit it, low branch, etc. will very likely cause damage. A 1/4 wave 800MHz whip will work just as well, be lower profile, more flexible and cheaper. I run a lot of them at work, and haven't had any issues with them. http://www.theantennafarm.com/catalog/laird-tech-qw800-876.html Kind of hard to beat 8 bucks, and they'll perform as well as the low profile. You can even get the whips/bases in black if that suits your taste.

As for the drilling….
I've done a number of installs on these trucks. All have been either crew cab or extended cab. On the extended cab truck I have at work, the VHF antenna mount is right above the dome light. Remove the dome light and you have access under the roof. Routing the coax down the back of the cab, or along the "A" pillar next to the windshield is pretty easy.
I've also put antennas on the rear of the work truck cab. Removing the center mount stop light gives you easy access under the back 6 inches of the cab roof. Easy to pop a hole just in front of the rear stoplight. There is sufficient ground plane under the antenna for 800MHz, if you put it as far forward as you can. Routing the cable is easy, over to the side of the cab, and then down. I've actually installed two 800MHz 1/4 wave whips on the rear of the cab.

As for RX performance, I have an 800MHz radio in my own truck for work use. I have the radio set up to spit out a received signal strength display. Since my radio system is trunked, there is a constant control channel broadcasting. This makes checking signal levels pretty easy. Using that set up, I've played with a few different antenna designs, and honestly don't see much difference. I can maybe see a 1db increase in signal strength between a 3 dB "gain" 800MHz antenna when compared to a 1/4 wave. I occasionally shift back and forth between those antenna, just for kicks. Honestly prefer the lower profile 1/4 wave over the higher gain whip. Performance is nearly identical and it's much lower profile.
 

rswagerson

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Joined
Jan 30, 2014
Messages
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Location
Nassau County, NY
I had a 2005 GMC Canyon (sister truck to yours) and I still have a 2007 Chevy Colorado as my work truck.
Both had/have permanent mount NMO antennas on them. Even did the same thing on my dad's 2005 Canyon.

The antenna you linked to will likely work just fine for 800MHz, but don't expect any reliable RX performance outside the 700MHz-800MHz band. It's pretty easy to take a 1/4 wave 800MHz antenna and hide it in one of those radomes. Not an issue. I actually had those installed on a couple of the garbage trucks at work, and they've worked just fine. Issue with that design comes at the lower frequencies, but that isn't what you were asking…

Anyway, should work just fine. Concern though is that they are not flexible in any way, so anything that might hit it, low branch, etc. will very likely cause damage. A 1/4 wave 800MHz whip will work just as well, be lower profile, more flexible and cheaper. I run a lot of them at work, and haven't had any issues with them. http://www.theantennafarm.com/catalog/laird-tech-qw800-876.html Kind of hard to beat 8 bucks, and they'll perform as well as the low profile. You can even get the whips/bases in black if that suits your taste.

As for the drilling….
I've done a number of installs on these trucks. All have been either crew cab or extended cab. On the extended cab truck I have at work, the VHF antenna mount is right above the dome light. Remove the dome light and you have access under the roof. Routing the coax down the back of the cab, or along the "A" pillar next to the windshield is pretty easy.
I've also put antennas on the rear of the work truck cab. Removing the center mount stop light gives you easy access under the back 6 inches of the cab roof. Easy to pop a hole just in front of the rear stoplight. There is sufficient ground plane under the antenna for 800MHz, if you put it as far forward as you can. Routing the cable is easy, over to the side of the cab, and then down. I've actually installed two 800MHz 1/4 wave whips on the rear of the cab.

As for RX performance, I have an 800MHz radio in my own truck for work use. I have the radio set up to spit out a received signal strength display. Since my radio system is trunked, there is a constant control channel broadcasting. This makes checking signal levels pretty easy. Using that set up, I've played with a few different antenna designs, and honestly don't see much difference. I can maybe see a 1db increase in signal strength between a 3 dB "gain" 800MHz antenna when compared to a 1/4 wave. I occasionally shift back and forth between those antenna, just for kicks. Honestly prefer the lower profile 1/4 wave over the higher gain whip. Performance is nearly identical and it's much lower profile.
First, thanks for responding. I forgot to mention I have a crew cab and it has aftermarket cross bars so I am not worried about it hitting anything on the roof. I am reallllllly trying to avoid any sort of whips on my roof, I was lurking around last night and I saw this, (http://www.amazon.com/OEM-Motorola-RAD4208A-150-168-Profile/dp/B00BUTU8VG) I didnt know the little black antenna was available in VHF. Right now Im using VHF 1/4 wave to scan and its just great. Will this do worse then the whip to receive you think? Thanks
 

mmckenna

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Those low profile antennas are horrible performers on VHF. They are extremely narrow bandwidth, usually 1mHz or less. Limited power handling capability, usually 50 watts or less, unless you want molten antenna innards all over the roof of your truck. Also, the photo on the Amazon page isn't correct. The VHF ones are about the size of a soup can. Everyone that I know that has tried them have gotten rid of them and replaced them with a quarter wave whip.
A VHF quarter wave will outperform it any time/anywhere.

You'd also find that the 800MHz quarter wave will be the same size as the "low profile" antenna. With the smaller whip diameter, compared to the radome, it'll be lower profile.
 
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