Advice on short or low-profile dualband antenna?

Woody_99 · Post by **Woody_99** » Fri May 26, 2006 9:58 pm

Hey, I have an Astro van going into a low parking garage and need a shorter antenna. Currently it barely fits clanging all the way through they say. Current antenna is a maxrad cell-look antenna about 12" or so.

Question is, is there a decent low-profile UHF/VHF antenna that works?

I figure they're all dummy loads, but he needs something done.

NMO mount, and rooftop location cannot be changed to window or other type. I have to make it work as-is...

thanks!

tvsjr · Post by **tvsjr** » Fri May 26, 2006 10:09 pm

How about drilling a second hole? Run a VHF and a UHF into a diplexer?

wa2zdy · Post by **wa2zdy** » Sat May 27, 2006 5:23 am

What do you mean by "decent?" A 12 inch antenna is already a loss antenna on high band. To merely have unity gain you need 18-19" on high band/2m. Of course a quarter wave on UHF is 6". The best bet for anything resembling decent is a quarter wave on high band which will also work on UHF.

The only glitch to the 3/4 wave on UHF is the angle of radiation will be high but it'll work.

Smaller than 12 inches and you're really limiting your performance.

MTS2000des · Post by **MTS2000des** » Sat May 27, 2006 7:43 am

the Diamond NR-72BNMO comes to mind, it's actually pretty decent. Requires a permanent (non-magnetic mount)

http://www.rfparts.com/diamond/nr72bnmo.html

No, it's not a super gain antenna, but it performs better than a quarterwave on each band. It looks like a cellphone/800 antenna. I think I paid 40 bucks for mine.

Bruce1807 · Post by **Bruce1807** » Sat May 27, 2006 9:56 am

Check tessco.com
They have lots of low profile stuff in most bands

Woody_99 · Post by **Woody_99** » Sat May 27, 2006 10:41 am

Wow... that's a lot at once, thanks!
to quickly answer all, I can't drill or install anything else,
I didn't climb on the roof and measure the antenna, it's a cell-type, quarterwave on both bands with the coiled load in the middle, but it is about 2" too tall for the ceiling. We're in West Virginia so the higher the AOR the better in most cases, and thanks for the links!!
Whew, that was a mouthful.

Maybe I should rephrase....

What is the best NMO low-profile dualband antenna made?

thanks!

wa2zdy · Post by **wa2zdy** » Sat May 27, 2006 12:55 pm

That Diamond antenna lists the gain on both bands as 2.15dBi. dBi is gain over an ideal radiator - no such thing exists. That 2.15dBi translates to ZERO dBd - gain over a dipole, a more realistic measurement.

That antenna could show some marginal gain over a 1/4 wave on UHF but not on high band. If a 1/4 wave is unity gain and is (for the 2m band) 19 inches, how is a 13 inch antenna going to be better?

No way, it ain't happening. If that thing works better than your 19 inch whip, you have issues with the 19 incher.

If that's the best you can do Woody, so be it. Just be realistic in your expecations.

Woody_99 · Post by **Woody_99** » Sat May 27, 2006 4:14 pm

Chris... well, I understand the facts presented, but what I need
is the shortest antenna I can get, and we know performance will suffer.

The issue is antenna height, not performance. We will make due with whatever works, but we have to get the size reduced.

The diamond antenna linked above is an inch longer than the one in use, so obviously it won't help.

I'm looking for the small radome [dummy loads] that are only inches high. Question is, does anyone make such a critter for vhf/uhf or am I stuck? I figure they all suck, but if there is one, who makes the best of the worst?

thanks!

tvsjr · Post by **tvsjr** » Sat May 27, 2006 4:19 pm

I've not seen any of the can-type transit antennas that are dual-band, until you get up into the 850/1.9 type units.

I think the second hole and two antennas combined is going to be your best bet.

Or lose one band.

Woody_99 · Post by **Woody_99** » Sat May 27, 2006 4:24 pm

Yep... I'm beginning to think you're right tv....

It would qualify as a ham antenna I suppose, so probably not a real market for it. I've not found one to date either...
thanks for the advice though!

Post by Pj » Sat May 27, 2006 9:03 pm

I replaced the big brother version of this antenna..with this antenna.

I must say that I am very happy with it running my APRS stuff. I haven't noticed anything better or worse between the two, and using it in a mountainous/valley area.

I bought it last year in Dayton. To me, it looked like I was RX/TXing within the same coverage from OH to NY.

Just my two cents.

Woody_99 · Post by **Woody_99** » Sat May 27, 2006 10:20 pm

Cool.... which antenna? I think ya missed the link.
thanks!

wa2zdy · Post by **wa2zdy** » Sun May 28, 2006 5:37 am

If you go with separate antennas, at least you can do a full quarter wave for UHF.

Post by Pj » Sun May 28, 2006 9:01 am

I had this orginally on the truck (Still have it...going on the Jeep soon)
http://www.rfparts.com/diamond/nr770hbnmo.html

I now have this on the Suburban:
http://www.rfparts.com/diamond/nr72bnmo.html

Like I said, at least for me, I haven't really noticed a difference.

N4DES · Post by **N4DES** » Sun May 28, 2006 9:19 am

I have the Austin Dual Bander that stands 19" tall and works very well on the roof of my Explorer, but after reading the original post it maybe too long for his application.

Just in case anyone is interested here is the url and it's at the bottom of the page:

http://www.austinantenna.net/multiband.htm

Mark

ku4zs1 · Post by **ku4zs1** » Sun May 28, 2006 10:14 am

http://www.hamstick.com/nmo270.htm

I have two of those on the back of my Saturn. Work pretty good, not wonderful, but good enough. I wanted low profile as well.

Woody_99 · Post by **Woody_99** » Sun May 28, 2006 5:35 pm

Well, thanks for all the info guys. I guess tv has the final answer...
only option I see is the diplexer and single band radomes.

I assume it's as simple as another hole and two jumpers?

thanks!

tvsjr · Post by **tvsjr** » Sun May 28, 2006 6:41 pm

Woody_99 wrote:Well, thanks for all the info guys. I guess tv has the final answer...
only option I see is the diplexer and single band radomes.

I assume it's as simple as another hole and two jumpers?

Affirmative on the hole, negative on the jumpers. You need to buy a diplexor (duplexer...) which will direct the VHF components to the VHF antenna alone... ditto the UHF. Such widgets are built by Diamond, Comet, and others.

Woody_99 · Post by **Woody_99** » Sun May 28, 2006 7:06 pm

Ok, cool. I'll check 'em out.
thanks!

GlennD · Post by **GlennD** » Mon May 29, 2006 6:40 am

Comet makes a rubber dual band NMO mount antenna that is around 19 in tall. I put one on my 4Runner after my garage door killed my Diamond antenna.

It works OK for me and has good return loss on my SiteMaster.

Advice on short or low-profile dualband antenna?

Advice on short or low-profile dualband antenna?

bummer...