Beam Antennas

[pkveazey]

What I'm going to mention can be and will be VERY CONTROVERSIAL until you look it up in the Ham Handbook. Years ago, I played around with all sorts of antenna construction and found that some things were very easy to build and actually work and others were almost impossible to build and actually work. When I built HF antennas, I always just built wire antennas so everything that follows will pertain to VHF and UHF. First, I love Yagi antennas but you have to make the matching network just right or they will disappoint you. Second, I found that building a Cubical Quad was easy and worked about the same a 3 element Yagi. Hmm.... Well, that wasn't very controversial. Yea, I know but here comes the part where it gets controversial. If you look at the Yagi charts that show the db gain of Yagi antennas starting with the basic Reflector and Driven element and follow it all the way up to about 16 total elements, you'll get some pretty realistic information about what to expect. Then when you read the associated text, you'll see something regarding Diminishing returns. Once you get to 6 elements you will still get more gain by adding elements but the amount of gain for every additional element will be less and less. I think the chart stops at somewhere around 16 elements. OK, that was the controversial part because some folks think that the more elements the better. Well, it is better but you'd be better off running two 6 element co-phased Yagi's. Now comes the hard part. Getting that phasing harness perfect is really hard to do. Now, lets get to the what have I seen and how did it perform part. I have several Ham friends who run 13 B2 Yagis (13 elements) and they kick butt and are like aiming a rifle. If they are off by a few degrees, they lose the signal. There is an old retired fellow who worked for NASA in Hampton, Va. all his life and he built a set of co-phased 6 element Yagis from scratch and we can talk simplex about 65 miles apart. Until he built that setup and got on the air, I was willing to argue that the 13 B2's were about as good as it gets. I really think that the fellow in Hampton gets better results, not because he can talk farther, but because its not like a rifle shot and trying to thread a needle. As for me, I got tired of constantly working on and replacing rotators so I just started building Cubical Quads for 2 meters and 440 and pointing them at whatever I wanted to reach and locking them into position. At the moment I only have one 440 Cubical Quad pointed straight at the closest DMR digital repeater and run my 5 watt BaoFeng DMR digital Handi-Talkie to it. OK, now, I know all of this is not "I'll punch you in the face" controversial but I do expect some possible pushback on some of this. I'm a big boy and won't get all pissy if anyone disagrees. I guess my main point is More is not always Better. I like beams but I'm one of those people who prefers High Quality Coax and lots and lots of Height. Height and Coax is a whole other subject worth exploring.

[JohnyMac]

Good stuff PKv 

[Jackalope]

    PK, I'll agree with you regarding the gain of cubical antennas.  However, cubical quads do have some disadvantages, which weren't mentioned, and yes I've run cubical quads.  In the north country, and even some places here in the south, cubical quads can have serious problems due to ice loads.  The typical cubical quad isn't overly robust, and they are more complicated to construct.  Cubical quads are also three dimensional versus two dimensional yagis, so they require wider separation and a longer mast, which contributes to rotor failures.

     I've never experienced matching problems with any yagi that I've installed, but the antennas are being used within their designed frequency range.  Cubical quads do indeed cover a wider frequency range.  Constructing a phasing harness isn't that complicated, folks just need to follow the necessary formulas, it's not rocket science, but a person needs basic math skills.  Overall, yagis cost less and are generally stronger than cubical quads.  For example, you don't see too many commercial VHF or UHF cubical quads, though I believe there is at least one, manufactured up in Canada.

     The station here has multiple antennas systems, using both omnidirectional and directional antennas.  One of my favorite antennas is a M Squared VHF eggbeater omnidirectional that can also be used for satellite comms, but it's a wire three dimensional antenna which will probably not survive an ice storm.  I'd buy or make another one, if it gets destroyed.  Amateur radio is frequently full of compromises, and at my location I don't have much tower height, but try to make up for it with lots of power and high gain yagi antennas.   I'm in a location where it's height below average terrain.

[pkveazey]

    PK, I'll agree with you regarding the gain of cubical antennas.  However, cubical quads do have some disadvantages, which weren't mentioned, and yes I've run cubical quads.  In the north country, and even some places here in the south, cubical quads can have serious problems due to ice loads.  The typical cubical quad isn't overly robust, and they are more complicated to construct.  Cubical quads are also three dimensional versus two dimensional yagis, so they require wider separation and a longer mast, which contributes to rotor failures.

     I've never experienced matching problems with any yagi that I've installed, but the antennas are being used within their designed frequency range.  Cubical quads do indeed cover a wider frequency range.  Constructing a phasing harness isn't that complicated, folks just need to follow the necessary formulas, it's not rocket science, but a person needs basic math skills.  Overall, yagis cost less and are generally stronger than cubical quads.  For example, you don't see too many commercial VHF or UHF cubical quads, though I believe there is at least one, manufactured up in Canada.

     The station here has multiple antennas systems, using both omnidirectional and directional antennas.  One of my favorite antennas is a M Squared VHF eggbeater omnidirectional that can also be used for satellite comms, but it's a wire three dimensional antenna which will probably not survive an ice storm.  I'd buy or make another one, if it gets destroyed.  Amateur radio is frequently full of compromises, and at my location I don't have much tower height, but try to make up for it with lots of power and high gain yagi antennas.   I'm in a location where it's height below average terrain.

Yep, I should have made myself a bit more clear on Yagi tuning. Factory Yagis just need little or no tweeking. I was talking about home brew Yagis. The largest Cubical Quad I ever built was for 10 meters and it ending up being pretty flimsy. It worked great but fell apart after one year. The one's I built for 2 meters and 440 were made of PVC tubing and real heavy gauge solid copper wire. I even made the center support out of heavy PVC so as to keep metal from being between the two loops. Now, as to the Phasing harness for co-phasing two antennas together. That damn Ham Manual says to make it out of 1/2 wave of 75 Ohm Coax. Well, golly gee, thanks for not telling me whether it needs to be a physical 1/2 wave or an electrical 1/2 wave. Hell, it took me 10 years to find someone who actually knew which one it was. It turned out to be an Electrical 1/2 wave of 75 Ohm coax and the you have to know the velocity factor of that particular coax in order to do the calculation. I'm still in the dark as to whether you tap the 50 Ohm coax into the Center of the 1/2 wave or whether you use a 1/2 wave from the center to each antenna. I've never co-phased 2 antennas together for that reason alone. If I were to try it, I'd use an electrical 1/2 wave to each antenna from the 50 ohm center tap. My friend in Hampton said he used oversized Hard line as a Cavity Resonator to co-phase his. I told him to stop right there, I didn't want to know how he managed to measure when and how it was resonant. The one thing I'm sure of is that he didn't just measure and cut it to length. Rotators are really handy but I've gone through 2 TV rotators for small antennas and one heavy duty Ham Rotator for large antennas and lord only know how much rotator control wire. I think they make that controller wire so it only last a couple of months. I don't recall ever having a rotator control box crap out on me. I wonder why that is?

[Jackalope]

   I've designed and constructed 11 element 2-meter yagis, and then used them in a 2-element phased array.  If I remember correctly. a gamma match was used on the yagis, but I honestly don't remember because it was over two decades ago.  Modern antenna analyzers make constructing antennas much easier, and antenna modeling software helps immensely.

    I suggest consulting the ARRL Antenna Book for more concrete information regarding phasing antennas.  The Antenna Book is well worth the money, and in the latest copy that I have (24th Edition), there's an entire chapter on both the theory and the practical application of antenna phasing.

    So, two of the best investments an amateur radio operator can make is a recent edition of the ARRL Antenna Book, and purchase or even borrow an antenna analyzer.  A decent antenna analyzer can evaluate your antenna performance, some of them can also point to issues with coax or connectors.  As PK inferred, buy the best coax that you can afford.

    I believe Wireman sells some decent rotor wire, but you will pay a higher price for quality wire.  I would suggest not using the wire that comes with all the wires flat next to one another like bowling lanes(Radio Shack use to sell it), but get the wire that has all the individual wires bundled in a PVC jacket, that particular wire will last decades without issue.

    I've never had a rotor crap out, but I've had the control boxes go, usually because a motor start capacitor goes, which is a relatively easy repair.  Norm's Rotor Repair often has refurbished rotors available.  I also suggest using lightning protectors on your rotor wire too.

     I wish I still had the array that I constructed, as it had remarkable performance, and it was made out of mostly old TV antennas.  Unfortunately, an ex-wife decided to send it to the local dump without my knowledge.

[FeedingFreedom]

I posted the below a while ago, these antennas are not the sturdiest but can be bent back to shape numerous times before the aluminum wire work-hardens and breaks. The one I have left has been folded up and thrown in the truck numerous times, hasn't broken yet. Plus they cost a couple dollars at most, so having spares on hand is easy.

I bought a NanoVNA last year just to try it. Screen is very tiny and hard to read in sunlight, but you can bring it back in the house, hook it up to the computer, and download all the data and look at it on a bigger screen. It's a great tool, much easier to calibrate than the ones from MFJ.

Quality coax is hugely important, especially for VHF and up. All my 2-meter antennas are fed with 1/2" Heliax, I have a bunch of 7/8" but not a lot of connectors, and they're really spendy. Plus, 7/8" hardline is not the easiest stuff to work with on home antennas. My HF antennas are fed with good RG-8x, although I keep a 250' length of RG-214 for field use. And lightning protection on everything! I've been in a 911 center when it was hit by lightning, not a pleasant experience and definitely something I don't ever want to repeat!

I'm not big into VHF, but my elmer (whose callsign I have) was, and he had 2 26-element yagis on a tower for 2 meters, and a homebuilt amp we used to call "Godzilla". Because he lived a little bit down in a valley, he would bounce his signal off the opposite ridge and talk to his friend that lived about 155 miles away. No regard to openings, just wanted to ragchew with his buddy halfway across the state!

For a directional antenna, I'm a huge fan of WA4VJB's "Cheap Yagis". I'm down to the last one I made 10 years ago, and I need to make more soon. Probably make a short video to describe my own method of building them. Huge performance for a couple dollars and a little time. I've even made a phasing harness to stack 2 of them, did really well in a couple VHF contests with them. Here is some more information about them:

http://fredspinner.com/W0FMS/CheapYagi/vjbcy.html

http://www.repeater-builder.com/antenna/pdf/cheap-yagis.pdf

This is my current go-to field VHF antenna: http://arrowantennas.com/arrowii/146-4ii.html. Definitely not the cheapest option, but I got mine new in the package at a hamfest for $25. I painted mine OD green (like most things I own!) and I also picked up the mast clamp for it. I keep it in a bag with some coax that can be put in the car or strapped to the side of my pack.