Low Band Low Profile

[DisasterGuy]

I am looking for some options for small mobile antennas for use on CB as well as a small mobile for use from 39-46MHz. Use of NMO mount would be preferred and I not looking for the best performance since these are limited use / interop use only. I fully understand the physics of RF wavelength but really don't want anything longer than 24". With the exception of a 19" VHF quarter wave, I use phantoms for everything else and vehicles are primarily Tahoe with some Expeditions and Crown Vic's in the mix.


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[popnokick]

Watching this thread to see if someone discovers new laws of physics WRT wavelength, frequency, gain, or propagation....
There's a good reason Laird doesn't make a VHF Lowband version of the Phantom.... it wouldn't work worth a darn. This thread here on RR also discusses "mini" VHF low / CB antennas (and why you don't see them)....
http://forums.radioreference.com/amateur-radio-antennas/261752-6-meter-mobile-covert.html
Now, if you have absolutely no intention of transmitting (which I doubt since you imply you are connecting to a CB radio, and I think by "interop" you mean transmitting).... the Tram 1199 antenna works amazingly well to -RECEIVE- CB on my Uniden BCT15. Transmitting on it is not recommended, both because it would not only not work well, but would present a very mismatched antenna to the CB finals.

 

[prcguy]

In the late 70s there was a CB antenna that had a small tuning box and a wire you placed across a vehicle window and it made car body into a "slot" antenna. They worked surprisingly well and much better than the ultra short CB antennas of that time.

Two companies made them and one was called Intenna but I'm not sure if they were the inventor or the copy. Anyway they are probably still in business and the CB version should easily tune most of the VHF lo band.

In installed a few dozen of these in the 70's and the main goal is to make sure the tuning box and the wire at the other end is well grounded.
prcguy

Watching this thread to see if someone discovers new laws of physics WRT wavelength, frequency, gain, or propagation....
There's a good reason Laird doesn't make a VHF Lowband version of the Phantom.... it wouldn't work worth a darn. This thread here on RR also discusses "mini" VHF low / CB antennas (and why you don't see them)....
http://forums.radioreference.com/amateur-radio-antennas/261752-6-meter-mobile-covert.html
Now, if you have absolutely no intention of transmitting (which I doubt since you imply you are connecting to a CB radio, and I think by "interop" you mean transmitting).... the Tram 1199 antenna works amazingly well to -RECEIVE- CB on my Uniden BCT15. Transmitting on it is not recommended, both because it would not only not work well, but would present a very mismatched antenna to the CB finals.

 

[zz0468]

There is a style of antenna called a "transit antenna", intended for installation on things like buses and railroad locomotives. In the past, several manufacturers made them for VHF low band. They're only inches high, but use a fair amount of real estate on the roof. I don't know if anyone currently makes such a thing for low band, but you could probably make on yourself.

 

[DisasterGuy]

I certainly would expect (or want) a Phantom for low band. I don't even use VHF Phantoms. I'm just hoping to find something compact (ie not 40" long) through the use of loading coils.


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[popnokick]

The Cobra HGA1500 is 36", which meets the 2nd length you mentioned (less than 40") but not the first length you wrote (24" or less). And there are several K40 CB antennas that are 35" long.

 

[captaincab]

laird makes transit style antennas in low band for buses trolleys etc we use to use them when i ran a shop for a cab company that used alot of low band and ran a few english trolley cars on the road i would give one of their local dealers a call.

QUOTE=DisasterGuy;2093949]I certainly would expect (or want) a Phantom for low band. I don't even use VHF Phantoms. I'm just hoping to find something compact (ie not 40" long) through the use of loading coils.


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[RadioDaze]

the Tram 1199 antenna works amazingly well to -RECEIVE- CB on my Uniden BCT15.

Does it have any low band ears as well?

 

[jeepsandradios]

There was a company called Untenna that made low profile antenna's. We used them on a lot of fire trucks and ambulances. I searched online but don't seem to find them. They were in Western NY (Buffalo Area) and they worked great for local communications although trying to get a wide band of frequencies to tune up was challenging. We were 45.88 - 46.46 but could normally get it tuned to the middle.

 

[popnokick]

RadioDaze: Yes, the Tram 1199 receives 30-50 mHz as well as CB. But only as well as you would expect for a short length, thru the glass antenna. The VHF low band / CB signal has to be fairly strong / nearby. I hear CBers a couple of miles ahead/behind me, and the local power company's 37 mHz mountaintop transmitter (with some trucks). But if you're trying to pick up VHF low weak signals... this isn't your antenna. Personally when I'm mobile I'm most interested in what is in my immediate vicinity.... not in the next county. And the 1199 fills that bill.

 

[SCPD]

shorties

If you don't mind going to a 3/8"-24 mount, you can get some 2' whips.
Like others have said, you're gain won't be the greatest, but you'll get a few miles xmit, and 10-20 rx.
You can get a trunk lip mount for it.

 

[902]

How about one of these?

http://www.wulfsberg.com/PDFs/ProductPagePDFs/Antennas.pdf

 

[wa1nic]

For all practical purposes, a 2' Low Band antenna is going to work like any other 2' Low Band antenna (not all that great).

Laird makes some 4' Low band commercial antennas.

If you want smaller, a 2' Firestik will work about as good or as bad as anything else. You should be able to grab and start pulling out wire from the tip to move it up to work in the VHF low band.

Rick

 

[eportel6607]

We solved this issue byusing a low band "rubber duck" off of a Motorola MT1000 42-50Mhz and fabricated a mount for it and then connected it to a standard antenna mag mount. It worked out great for local (under 4 miles) comms.

 

[chpalmer]

Police Antennas Stico Antenna Manufacturer in Buffalo NY | Sti-Co

 

[eportel6607]

Ahhh well there you have it. Thanks Chpalmer. I don't remember this existing back a few years, but that's the solution. It's about as efficient as transmitting into a soda can with coax made from string but it should do the job for very short range.

 

[DisasterGuy]

Agree, other than Sti-Co's 800 and higher antennas, many are as effective as 50' of RG-58 into a test load.

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[eportel6607]

Ha yeah..that's about right. Well it will do the job...just make sure the SWR is reasonable when using it. A MT1000/P200 MVA (AKA "convert-a-comm") might be a nice tool for this job (for mobile use). It's a lot cheaper than buying mobiles for your purpose and you get the benefit of having portable communications as well from the same system.

 

[KB7MIB]

...I (am) not looking for the best performance since these are limited use / interop use only. I fully understand the physics of RF wavelength...

The OP is well aware that short antennas are a compromise, and will not give him much range. However, it does not appear that he is looking for long range, but on scene/short range interoperability communications.

Communications needs are not always about achieving the greatest possible range, measured in ten's of miles. Sometimes it's only necessary to measure in ten's of yards.

John
Peoria, AZ

 

[PJH]

Really a specifics of use and vehicle and range/application.

Even with "short" antenna's, you are really sacrificing a lot. The phantom style antennas, as much as they may look cool and blend in are generally just printed circuit boards or really really horrible transmitters. They only work decently if you have a really really really good radio system with outstanding coverage. As someone stated earlier in the posts, you cannot avoid electrical and RF theory. Just isn't going to happen. Products are out there that try to bend them, but the results are certainly mixed.

In general, and in practice, if this is going to be used on a command vehicle, chief's vehicle or the stuch, you need to be using at the minumim 1/4 wave antenna's. Not ones that "look cool".

For my command vehicle, I put 1/2 wave on for the wide area systems and 1/4 wave for the local "fireground" radios. So far, the results have been excellent. On my personal vehicle I use 1/4 wave comtelco's and diamond triplexers with great results.

The other thing I just thought of, most (not all, but most) lowband radios are 100 watt radios. Some CDM's I think you could do around 60 watts. Little antennas and lots of power will cause the RF to gate back to about 1 watt, fry the antenna or fry the radio.

You just can't escape how lowband works.

The transit antennas were a few feet long and resembled the (And most likely were) the Sinclair railroad antennas.

Basically, the OP is asking to fit an elephant into a dog's cage. Its just not going to work well, or at all.