Question about an antenna

[swilliams]

I have just currently purchased a Kenwood TM-281a, and a Tram 1230/1255 L bracket mount. I have a Laird Tech B1322N, 55” antenna (Base loaded 1/2 wave no ground plane antenna. High temperature ABS housing, triple plated brass fittings, machined Delrin coil, gold plated contact and quick rod disconnect.). Will this work for transmitting on 2 meters? Or would it be better to have a quarter wave or high gain antenna?

 

[mmckenna]

That'll work just fine.

You will likely need to cut the whip for the center of the 2 meter band, and the antenna should come with measurements for that. This will be true with just about any mobile antenna.

Don't get too hung up on Antenna gain numbers.
A quarter wave with 0 dB of gain works well, I've used them for years without any issues.
A higher gain antenna, like a 5/8 wave will give you some gain, but likely unless you are really on the fringes, you won't notice a difference.

A half wave antenna will have 0dB of gain without a ground plane, or roughly the equivalent gain of a quarter wave with a slightly different radiation pattern.
Put a ground plane under that half wave antenna and you'll get 2.5dB of gain, or pretty close to what the 5/8 wave will give you.

Don't sweat it, do a good job wiring it up and installing the antenna and it will work fine. One of the fun parts of a hobby like radio is getting to play around with things and watch the results. You can ask for input from others, but don't miss out on your own experimentation.

 

[prcguy]

Where did you get your gain figures?
prcguy

That'll work just fine.

You will likely need to cut the whip for the center of the 2 meter band, and the antenna should come with measurements for that. This will be true with just about any mobile antenna.

Don't get too hung up on Antenna gain numbers.
A quarter wave with 0 dB of gain works well, I've used them for years without any issues.
A higher gain antenna, like a 5/8 wave will give you some gain, but likely unless you are really on the fringes, you won't notice a difference.

A half wave antenna will have 0dB of gain without a ground plane, or roughly the equivalent gain of a quarter wave with a slightly different radiation pattern.
Put a ground plane under that half wave antenna and you'll get 2.5dB of gain, or pretty close to what the 5/8 wave will give you.

Don't sweat it, do a good job wiring it up and installing the antenna and it will work fine. One of the fun parts of a hobby like radio is getting to play around with things and watch the results. You can ask for input from others, but don't miss out on your own experimentation.

 

[mmckenna]

Where did you get your gain figures?
prcguy

From the manufacturers website for the model that the OP listed:
Laird B1322N Item # B1322N, Mobile Load Coil Antennas on Laird Technologies
Gain = 2.4dB

And yes, I was off by 0.1dB, ya got me dead to rights.

For reference:

Laird's very own 1/4 wave specification:
Item # B132, Mobile Load Coil Antennas on Laird Technologies
Where "unity" = 0dB.

For the 5/8 wave:
Item # B1443, Mobile Load Coil Antennas on Laird Technologies
Gain = 3dB

 

[mmckenna]

And before we get into antenna theory, the numbers above are "good enough" for reference. I'm not going to engage in an argument about the above numbers. We all know that feed line losses, coil loss, imperfect ground plane and any number of variables is going to throw this off. The truth is in a mobile installation no one will likely notice the few tenths of a dB difference. You'd have to sit down with an antenna analyzer or a scientific calculator and a bunch of paper to map it all out, and I'm just too tired and not really interested in doing that. The OP asked a simple question and deserves a simple answer. There are plenty of other places on this board to tear this apart with people that will actually care. The OP has ONE post so far, lets not try to scare him off. He's has stated he's already ordered the radio and antenna, let's not make him double guess what he has done. The 1/2 wave will work fine for what he is doing. 1/4 wave antennas are cheap and he can buy one later and compare them on his own.

We all know that ham radio operators can beat theory to death, and then continue on for another hour and still not come to an agreement. I don't think the OP needs to get into a discussion like that on his first post. Just let it go and let the guy be happy.

 

[prcguy]

Hey man, why get bent out of shape without knowing what I was questioning? I just don't happen to agree with the statement "Put a ground plane under that half wave antenna and you'll get 2.5dB of gain, or pretty close to what the 5/8 wave will give you." Putting a ground plane under a half wave antenna will not give you 2.5dB more gain. Maybe a wee little bit more with a ground plane but not that much.

Looks like Laird is using dBi as a reference which places their 1/2 wave antenna at about .26dBd gain and a 5/8 at .86dBd gain which is believable. As always, an antenna gain rating without a reference like dBi or dBd should cause somebody question it.

For the OP, when I switch from a 1/4 wave whip to a 5/8 (Larsen) it makes a very noticeable improvement in fringe areas and the Laird B1322N should be a similar improvement.
prcguy

 

[LtDoc]

It's all frame of reference, what you use as the 'standard' to base those gain figures on. Sometimes manufacturers don't use the 'industry standard' as a reference point. That has to do with 'sales' and advertising and the buyer not understanding that a negative gain figure isn't always bad. That "dB>d<" and "dB>i<" point is a very good indication of how much belief I place in those gain figures posted by manufacturers.
- 'Doc

(Dang near like listening to politicians, ain't it? Honestly don't mean to insult most manufacturers.)

 

[kayn1n32008]

Wirelessly posted (Mozilla/5.0 (BlackBerry; U; BlackBerry 9780; en-US) AppleWebKit/534.8+ (KHTML, like Gecko) Version/6.0.0.600 Mobile Safari/534.8+)

The laird 1/2 wave antenna will work just fine for amatuer radio purposes. Not sure why one would buy the 1/2 wave over the 5/8 wave, unless height is an issue or NGP is required. I use a half wave for my company radio, my only issue is that due to the wide diameter whip being on a mag mount it tips over EASY when on over grown roads, other than that it works very well. For fender mount only being used for amateur radio, I would use a 5/8 wave myself as bandwidth is not so critical.

 

[mmckenna]

Not bent out of shape, I just get weary of the arguments I see on this site about mundane semantics, terminology, etc.
Yes, I understand the difference between dBd and dBi. What I've found over the years is that while people will argue about the meaning, the honesty of vendors and manufacturers and the like, I very rarely see people that back up these discussions with actual first hand experience. I'm not claiming to be the only one here with experience here, just tired of seeing a post where someone new asks a simple question and then that gets followed by 40 something posts where people argue out the details.

Like I said, the OP asked a simple question and deserved a straightforward and simple answer. I've tried quarter waves, 5/8 wave, 1/2 wave and just about any other "wave" you want to talk about, and unless I'm on the fringes, I've really never noticed a difference, and even then it was minimal. What often matters more is focusing on sound installation practices and not cutting corners.

 

[prcguy]

What matters to me is some bad information can send people off thinking if they put a ground plane under their 1/2 wave antenna they will get 2.5dB of free gain.

Someone else nailed it when they compared antenna gain figures to politicians. With that in mind I say Democrats are using dBi where Republicans use dBd. Lets see where that goes....
prcguy


QUOTE=mmckenna;1814002]Not bent out of shape, I just get weary of the arguments I see on this site about mundane semantics, terminology, etc.
Yes, I understand the difference between dBd and dBi. What I've found over the years is that while people will argue about the meaning, the honesty of vendors and manufacturers and the like, I very rarely see people that back up these discussions with actual first hand experience. I'm not claiming to be the only one here with experience here, just tired of seeing a post where someone new asks a simple question and then that gets followed by 40 something posts where people argue out the details.

Like I said, the OP asked a simple question and deserved a straightforward and simple answer. I've tried quarter waves, 5/8 wave, 1/2 wave and just about any other "wave" you want to talk about, and unless I'm on the fringes, I've really never noticed a difference, and even then it was minimal. What often matters more is focusing on sound installation practices and not cutting corners.[/QUOTE]

 

[mmckenna]

Someone else nailed it when they compared antenna gain figures to politicians. With that in mind I say Democrats are using dBi where Republicans use dBd. Lets see where that goes....
prcguy

I hear you, and I understand what you are saying, no hard feelings towards you or anyone else. It's all radio and for guys like us it's a job and a hobby that we are lucky enough to get to enjoy. No matter our exact beliefs or disagreements, we can all get along and enjoy this. One thing that most of us seem to have in common is to help others, and there is nothing wrong with that.

 

[kb2vxa]

"The OP asked a simple question and deserves a simple answer."

'Scuse me while I sit here laughing my (insert body part here) off. This on line forum is FAMOUS for one asking the time and the rest telling him how to build a clock. Looks like we're the only ones who know KISS was around long before Gene Simmonds stuck out his tongue.