So, how does one pick antenna system components?

[e9999]

OK, I did a bit of reading on antennae and I have an idea of the basics.

I"ve seen some specific antenna recommendations here, but I don't understand the basic principles of system choice, so what is less clear to me is how you put together the system in practice, so I'm hoping somebody can give me some practical guidance on that so I can just order the dang thing and not worry about it anymore. TIA.

I'm talking single band 2m.


Do you decide how long an antenna you can handle (garage/trees) and where you want to put it first? Length would then tell you whether you go 1/2 or 1/4 wave I guess. [I don't know if the 1/4 must always have a good ground plane, perhaps hood, roof etc, whereas the 1/2 doesn't matter. Is that an issue?]

I guess one should get the highest gain possible for the length?

Do you have to match the antenna connection that your radio has (mine will likely have a coax 50 ohms 259 something plug - thinking Yaesu 1802] for the feedline, or could I use a parallel wire instead with some adapter if that's better?

Do you need to pick the shortest possible feedline and of a specific type / brand to minimize losses? [And how on earth can people label the coax stuff, say, 50 ohms, without specifying the length?]

Seems like there are several different antenna connectors and mounts (259, NMO etc). Are some more desirable than others?

Do you have to buy a Balun separately if you use a coax or are these normally built-in? What about gizmos to reduce SWR?

Yikes!

TIA

 

[Kofoed]

For 4wd use, I would stay away from the high gain models that use the phase inductors (the loading coils on the whip) These can be damaged by trees.

You can get a 3dBd antenna in the 40 inch length range. They have a fold down option for garages, etc. Very durable, works fine. The maunfactured antennae use coax and everything is plug and play.

 

[e9999]

a manufactured antenna is one that doesn't have a separate mount to be connected to the mast, I imagine?

Is there a direct relationship between length and mounting location? Like if you get a 1/4 wave it should be mounted right over a horizontal surface or something like that?

Should I try to stay with 1/4 and 1/2 or are other lengths (5/8 etc) good too?

(not too many trees around here, mostly desert shrubs so length not a major issue, outside of the garage)

 

[Cruiserdrew]

5/8 will be best, but don't buy an antenna until you decide on a radio. If you get a dual band radio, you'll need a dual band antenna. It's very difficult to find a dual band antenna that is 5/8 wave on 2m.

Your mount is important as well.

If you get a single band radio, the Wilson mag mount is cheap and gives very good performance. It is 5/8 wave too.

A good starter set up:

Yaesu FT2800
Wilson 2M Mag mount.

 

[e9999]

I must have misinterpreted what I read, then. I thought a 1/2 gave better results than a 5/8.

Would the 2m side of a 2m / 70cm work as well as a plain 2m?

Also had the impression that people here were not favoring mag mounts for some reason.

 

[ginericLC]

5/8 is better as you are at less of angle on the wave.

You can use a dual band antenna with a 2M antenna provided one of the bands of the dual band antenna is 2m. The disadvantage is the length will be compromised between the two bands, so there will be some sacrifices on both bands of a dual band antenna.

I have a 5/8 wave Wilson 2MTR antenna on my 80. It works well and is quickly removed. I haven't had any issues with it tipping off on the trail yet. but I have had issues tipping it over on the trail. These run about $50 with the mag mount, whip, and coax. I'm actually thinking of getting rid of it as I've gone to a dual band radio. It is tall.

 

[dfmorse]

E9999;

This antenna is not required for ur system, but has a lot of gain.

http://www.rfparts.com/diamond/nr22l.html

This antenna is a 3.4 dbi gain antenna:

http://www.rfparts.com/diamond/m285.html

I will not explain dbi gain, except to say that it more than a standard 1/4 wave antenna. Antenna gain is a function of electromagnetic reference points.

My personal reference antenna is a dual freq (145Mhz & 430Mhz ) antenna; it has gain over the 1/4 wave and is dual purpose. A standard 1/4 wave mobile will hit almost any repeater in the USA. U can throw a coat hanger out the window and hit some repeater.

See: My system lay out.

http://homepage.mac.com/dfmorse/RigProj/page4.html


The length of the 1/4 wave ant in feet = 234/Freq in mhz; i.e., 234/145 = 1.614 feet. [1'-71/2"]. 145 Mhz is ruffly the center of the band.

In ur first post, u exhibit good thinking on setting up a mobile radio station. The first thing u need to know is that impedance matching is really important; and the second thing is simply this, since WWII and the 1950's, all that crap is passé .

When u buy a rig (new, mobile) its output impedance is, by design, 50-52 ohms. The cable connects to the rig thru a PL-259 connector [PL-259 stands for the engineering spec for this devise, RG58, RG59 are also engineering spec] its impedance is ruffly 50 ohms; the same as the cable that is most used . The cable most used is (spec) RG-58C cable.

The antenna is also, by design, 48-55 ohms in impedance. If u buy a commercial antenna (Diamond), it is set to go in the center of the band (145Mhz), and is around 50 ohms impedance. U will probably never have to "trim" these antennas.

I do not recommend buying RS (RadioShack) cable; it is cheap s*** from china or somewhere.



This cable, in most amateur systems, can be RG58C/U.
http://en.wikipedia.org/wiki/RG-58

There is RG58A, B, & C. the C is the best/ but all will work. Ampennol & Belden are best.

U do not need to worry about the length in ur application, it will be around 20 feet or so. However, the length is important if u can NOT get the VSWR below 2 to 1 . In otherwords, don't worry about this, yet! U do not need a balun in a mobile system. The mobile system uses 50 ohm coax throughout the whole system.

RG-58 and RG316 (This is 1/16" cable) cable require high skill in putting connectors on same. I would suggest this org if u need help, I've used them for my system: I had them build me cables just for my rig set up. I am very skilled at this task; it takes me around 30 minutes per connector, yet I still elected to have these guys do the work.

http://www.rfparts.com/index.html




U can tune most antennas to the length reqrd for the freq that u use the most; usually tuned to center of band. Diamond stuff is really high quality; HRO carries this product.
Their web site is:
http://www.hamradio.com/
An amazingly crappy site. Look in the phone book for a dealer near u.

I am quite positive this post will confuse u. If u need to contact me , call 303 584 9174; hope fully my phone system will not dump u.


...


&&&&&&&&&&&
To answer ur first question; go to a locale HRO OUTLET and let them know what ur doing. Almost all these guys are licencsed hams and will give info first hand.

...

&&&&&&&&&&&

 

[e9999]

great post, DF, thanks.


all: I was wondering about the different types of connectors and found a great site:
http://ece-www.colorado.edu/~kuester/Coax/connchart.htm
with photos and description.
(Interestingly, it says that the UHF conns (PL-259) are not suitable over 300 MHz. I thought that is what the 440 antennae and rigs use, though?)

OK, so no issues of impedance, good. Still wondering how come antennas can come with different length of cable and be called 50 ohms regardless of length. Could be a characteristic per length value I guess, but then the actual resistance would look different to the rig... odd... Anybody?


Does seem like the 5/8 is a good compromise. About 50". On the bumper or hood, should not get into trees that much. But yes, a mag mount might be the easiest.

No HRO close by. Found a place online with good prices on the Yaesu 1802, but they don't carry the wilson. The have a dual 2m 5/8 / 6m mag mount (MFJ1728B) though that seems OK for $30, rated 4.6/5 at eham, a bit less than the Wilson. Would that be allright?

Gin, I could help you get rid of the Wilson, perhaps.

 

[Cruiserdrew]

Does seem like the 5/8 is a good compromise. About 50". On the bumper or hood, should not get into trees that much. But yes, a mag mount might be the easiest.

The have a dual 2m 5/8 / 6m mag mount (MFJ1728B) though that seems OK for $30, rated 4.6/5 at eham, a bit less than the Wilson. Would that be allright?

Gin, I could help you get rid of the Wilson, perhaps.

E-have you read the material and taken the test yet??? If so, please post your call sign.

Why would you want a dual band antenna that is 2m and 6m? Trust me, if you get a dual band, it will need to be 146/440 (2m/70cm)

If you want to do a permanent install, any of the long antennas will bang into things like trees and rocks. I have a 50 inch SBB25-about as good as it gets for a 2m only antenna. I have to take it down on the trail and use an 18 inch dual band antenna (SBB1) that flexes and is ideal for this job. In camp, I tend to set up my better antenna if I really need range.

I strongly suggest you not mount on your bumper for a variety of reasons. The only good reason to mount there is that it looks cool-Australian poser points. Your rear hatch would be the best compromise if you want a permanent install, and don't want to drill holes in your roof. Investigate "lip mounts".

For a retailer-AES is the place. The guys that answer the phones are knowledgable Hams and will make your life easier if you let them.

If you want us to tell you the real secrets, you will have to post your call.

73

 

[e9999]

Andy, the 2m / 6m is a 5/8 for 2 and also 1/4 for 6 I believe but it's sold primarily as a 2m IIRC. Not that I particularly want that one since I'll never use a 6m likely, but it's what they had at the place I was checking out that seemed like it would work OK for 2m, good reviews and low priced. There was not too much choice. I will likely reconsider.

Yes, the 50" length is an issue, although I don't see many trees myself. I guess it's true that unless you have an emergency, a little guy is probably plenty good for simplex on the trail. And if there is an emergency one could always stop and put the big guy on.

No, no exam yet, another couple of months before the next one here. But I'll buy the rig already.

 

[Cruiserdrew]

Eric-I'm not giving you a hard time even though I'm tempted. It sounds like you want really cheap. If so, the 2800 and wilson mag mount is cheap and good. Any dual band antenna is going to be compromised compared to a monoband of similar quality. If you have decided on 2m only, I would get a 2m only antenna.

If you graduate from a mag mount, you will spend more money on the mount-roughly an extra $100 on the mount, coax and antenna. The Comet SBB25 is a 2m only antenna with excellent gain characteristics, and is not over $50. I don't think you'll find a better mobile antenna under 60 inches for less. It folds at the bottom for going in your garage etc. It's still too long for most trails, even in Moab where things are pretty open.

The mount is the problem, and a long lever arm like an antenna will put tremendous stain on the mount when you whack a tree branch with it. Even the best of the lip mounts, like the Diamond K400 series can't take that kind of stress.

I'm going to go outside and take some pics to illustrate, so check back.

edit-some pics of the SBB25 antenna-you can see the length and the mount. This is great on the open road and in the desert. I included a pic of the hinge where it folds to go inside.

 

[Cruiserdrew]

A few more pics of the short dual band antenna I use on the trail. For a shorty, it works really well for most uses, including accessing repeater coverage and simplex use. I do give up some range.

You can see the flex, and the size comparison with the longer antenna. I carry both of these antennas, and the longer one rides above the grab handles in the 80-out of the way and safe. I can change antennas in about 30 seconds.

A practical use--in Death Valley, we were camped up in echo canyon. I could faintly hear Brett calling me on Simplex from about 40 miles away. I answered with the short antenna on the truck, and my signal (and his) was not so good. I put up the long antenna, and we could communicate CLEARLY, like his truck was 100 feet up the road.

 

[e9999]

thanks Andy.
Well, you're talking about the separate mount approach, which is what I was asking about up there. I was originally thinking about that, and was asking about types of connectors and mounts, and then we got diverted into mag mounts... I had seen that you guys were favoring the lip mount. Not sure why besides keeping the little guy out of the brush. Would it not be easier on the roof rack or front bumper?
So, if I were to go with a separate mount, is there a more preferable connection type or does that not matter as long as the mount and antenna are compatible?

 

[alvarorb]

Eric,

The bumpers, specially the front is are BAD mounting places for antennas. Yes they look very cool, but the grounding plane sucks. On the front bumper you get all the engine noise (high voltage noise), on the rear bumper you get a lot of reflection from the vehicle. So much, that it could damage a radio.

The best place to put an antenna is on the center of the roof. That works fine if you only have the antenna up there when on the trail. In my case, I wanted to have the antenna permanently mounted. I like to use my radio on a day to day basis.

I needed to place the antenna somewhere where it would allow me to get in and out of my garage. This is why I have a 18" antenna with a lip mount on the rear hatch of my 80. Prior to this I had a Wilson mag mount. It's the best antenna you can get for the money. But I had to take it down every time I wanted to get in my garage.

My current setup works really well in town and on bushy trails, such as the ones in the Sierra. The antenna flexes well and it's out harms way. In the future I'm thinking about a longer antenna for desert trips.

Regards

Alvaro

 

[Cruiserdrew]

thanks Andy.
Would it not be easier on the roof rack or front bumper?
So, if I were to go with a separate mount, is there a more preferable connection type or does that not matter as long as the mount and antenna are compatible?

It is much harder to ground properly on a roof rack or bumper-read up on RF grounding. The lip mount gives you a fairly high, reasonably well grounded spot, but it's still a compromise. By far, the best place would be in the center of the roof on an NMO mount, but if you ever run a roof rack, then it's a problem.

Whether you use an SO 239 connector, or NMO connector, is up to you. On a lip mount, I see no real difference.

One other thing to consider-if you don't have a regular group of wheeling friends who also have Ham radios, I'm not sure you need to bother unless you are just interested generally in radio (which is cool too).


In the best tradition of Ham radio, I recently did a bunch of experiments with antennas and my FJ40. I mounted a magmount all over, including on fuel cans, the fenders, on top of my fridge(worked great here) and on top of an inverted hi-lift jack (worked well there too). I made a mount yesterday from some steel, and welded to the roll bar. The mount components are standard stuff. If I get ambitious, I'll run the coax inside the rollbar to protect it better, but this looks pretty good.

I could hit the local repeaters no problem, but did not check the SWR or anything like that.

 

[e9999]

thanks, Alvaro and Andy, good points.

OK, so roof or top (only) of rear hatch is it, then, eh...?


mmm....


oh, and why the big deal about the grounding? Isn't the coax sufficient?

 

[Kofoed]

I disagree with the Wilson antenna being a good performer. The 5/8 wave length does have a good angle of radiation (gain). But, the whip is super flexible and will bend backward at speed, and all over the place in the dirt. This kills the gain effect. Also, it screws up the polarization when the whip is flopping around. Spend money on an antenna, you will not be disappointed.

Re-read post #12 again. Spend the money on the antenna.

 

[Cruiserdrew]

Kofoed-I hate to disagree, but the Wilson mag mount works great. We have used it on numerous trips, in every imaginable scenerio, and it works really, really well, for a $40 antenna. In our local group, there are 4-5 of these antennas, and everyone has had the same experience-good performance, minimal set up time. It is flexible in the sense I have used it on all 3 of my Land Cruisers with better than average results. On 2m, the SBB25 is marginally better, but it's made to be better and with the mount is at least twice the price. The Wilson works better for distance than the SBB1 I run on the trail.

I totally agree, that like CB. the place to spend money is the antenna, not the radio. Unfortunately, we live in a non-ideal world, and everything is a compromise between price, performance and utility.

 

[e9999]

well, the whip being very flexible seems to be more a plus to me, if it will bend and flex when hitting low branches.
(I don't plan on putting in a lot of time on the radio when going high speed on the freeway, anyway. I'm getting this rig in more for emergency when stuck some place by my lonesome...)

can the mast be taken off easily from the mag base with the Wilson?

 

[Kofoed]

In saying that the Wilson is not a good performer, I was implying distance. At a close range it is fine. Which antenna is not?

What I am getting at is that at the margins, when a couple extra dB's in signal strength mean a big diference, is when it will be noticed.

I think that post #12 is an example of what I am talking about.