Coax balun on PVC form
My experience is that PVC works fine as a form for high Q RF coils. I’ve measured Qs of up to 450 on loading coils wound on PVC pipe. I’ve appended a paper I wrote on measurements of coaxial baluns wound on PVC forms.

Having access to a Hewlett-Packard 4193A vector impedance meter at work, I have made measurements on a number of baluns, coaxial and otherwise. For my beams I was particularly interested how many turns and on what diameter are optimum for air core coaxial baluns, and what the effect of bunching the turns was (formless). Using the remote programming capability of the HP4193A along with an instrument controller, I measured the magnitude and phase of each balun’s winding impedance at 1 MHz intervals from 1 to 35 MHz. For comparison, I also made measurements on a commercial balun which consists of a number of ferrite beads slipped over a short length of coax. I’ve appended some of these measurements so you can draw your own conclusions.

PVC pipe was used for coil forms. The 4-1/4 inch diameter baluns were wound on thin-walled PVC labeled “4 inch sewer pipe”. This material makes an excellent balun form. It’s very light weight and easy to work with, and I obtained a 10 foot length at the local Home Depot for about 3 dollars. The 6-5/8 inch diameter forms are 6 inch schedule 40 PVC pipe which is much thicker, heavier, and more expensive.

Each test choke was close-wound on a form as a single-layer solenoid using RG-213 and taped to hold the turns in place. The lengths of cable were cut so there was about 2 inches excess at each end. This allowed just enough wire at the ends for connections to the HP4193A’s probe tip. After data was collected for each single-layer configuration, the PVC form was removed, the turns were bunched together and taped formless, and another set of measurements was taken. I have only included the “bunched” measurements in the table for one of the baluns, but the trend was the same in each case. When compared to the single-layer version of the same diameter and number of turns, the bunched baluns show a large downward shift in parallel self-resonance frequency and poor choking reactance at the higher frequencies.

Interpreting the Measurements
All the baluns start out looking inductive at low frequencies, as indicated by the positive phase angles. As the frequency is increased, a point is reached where the capacitance between the windings forms a parallel resonance with the coil’s inductance. Above this frequency, the winding reactance is reduced by this capacitance. The inter winding capacitance increases with the number of turns and the diameter of the turns, so “more is not always better”.

The effects of a large increase in inter winding capacitance is evident in the measurements on the balun with the bunched turns. This is probably a result of the first and last turns of the coil being much closer together than the single-layer coil. An important requirement of these baluns is that the magnitude of the winding reactance be much greater than the load impedance. In the case of a 50 ohm balanced antenna, the balun’s winding impedance is effectively shunted across one half the 50 ohm load impedance, or 25 ohms. A reasonable criteria for the balun’s winding impedance for negligible common mode current in the shield is that it be at least 20 times this, or 500 ohms. The measurements show, for example, that 6 turns 4-1/4 inches in diameter meet this criteria from 14 to 35 MHz.

The measurement data also reveals the power loss these baluns will exhibit. Each of the measurement points can be transformed from the polar format of the table to a parallel equivalent real and reactive shunt impedance. The power dissipated in the balun is then the square of the voltage across it divided by the real parallel equivalent shunt impedance. While this calculation can be made for each measurement point, an approximate number can be taken directly from the tables at the parallel resonance points. At 0 degrees phase angle the magnitude numbers are pure resistive. I didn’t record the exact resonance points, but it can be seen from the tables that the four single-layer baluns are all above 15K ohms, while the ferrite bead balun read about 1.4K. These baluns see half the load voltage, so at 1500 watts to a 50 ohm load, the power dissipated in the coaxial baluns will be less than 1.3 watts, and the ferrite bead balun will dissipate about 13.4 watts (neglecting possible core saturation and other non-linear effects). These losses are certainly negligible. At 200 ohms load impedance, the losses are under 5 watts for the coaxial baluns and 53.6 watts for the ferrite beads.

Conclusions
– A 1:1 coaxial balun with excellent choking reactance for 10 through 20 meters can be made by winding 6 turns of RG-213 on inexpensive 4 inch PVC sewer pipe.

– For 40 or 30 meters, use 12 turns of RG-213 on 4 inch PVC sewer pipe.

– Don’t bunch the turns together. Wind them as a single layer on a form. Bunching the turns kills the choking effect at higher frequencies.

– Don’t use too many turns. For example, the HyGain manuals for my 10 and 15 meter yagis both recommend 12 turns 6 inches in diameter. At the very least this is about 3 times as much coax as is needed, and these dimensions actually give less than the desired choking impedance on 10 and 15 meters.

Measurements
————
Magnitude in ohms, phase angle in degrees, as a function of frequency in Hz, for various baluns.

6 Turns 12 Turns 4 Turns 8 Turns 8 Turns Ferrite
4-1/4 in 4-1/4 in 6-5/8 in 6-5/8 in 6-5/8 in beads
sngl layer sngl layer sngl layer sngl layer bunched (Aztec)
———- ———- ———- ———- ———- ———-
Frequency Mag Phase Mag Phase Mag Phase Mag Phase Mag Phase Mag Phase
1.00E+06 26 88.1 65 89.2 26 88.3 74 89.2 94 89.3 416 78.1
2.00E+06 51 88.7 131 89.3 52 88.8 150 89.3 202 89.2 795 56.1
3.00E+06 77 88.9 200 89.4 79 89.1 232 89.3 355 88.9 1046 39.8
4.00E+06 103 89.1 273 89.5 106 89.3 324 89.4 620 88.3 1217 26.6
5.00E+06 131 89.1 356 89.4 136 89.2 436 89.3 1300 86.2 1334 14.7
6.00E+06 160 89.3 451 89.5 167 89.3 576 89.1 8530 59.9 1387 3.6
7.00E+06 190 89.4 561 89.5 201 89.4 759 89.1 2120 -81.9 1404 -5.9
8.00E+06 222 89.4 696 89.6 239 89.4 1033 88.8 1019 -85.7 1369 -15.4
9.00E+06 258 89.4 869 89.5 283 89.4 1514 87.3 681 -86.5 1295 -23.7
1.00E+07 298 89.3 1103 89.3 333 89.2 2300 83.1 518 -86.9 1210 -29.8
1.10E+07 340 89.3 1440 89.1 393 89.2 4700 73.1 418 -87.1 1123 -35.2
1.20E+07 390 89.3 1983 88.7 467 88.9 15840 -5.2 350 -87.2 1043 -39.9
1.30E+07 447 89.2 3010 87.7 556 88.3 4470 -62.6 300 -86.9 954 -42.7
1.40E+07 514 89.3 5850 85.6 675 88.3 2830 -71.6 262 -86.9 901 -45.2
1.50E+07 594 88.9 42000 44.0 834 87.5 1910 -79.9 231 -87.0 847 -48.1
1.60E+07 694 88.8 7210 -81.5 1098 86.9 1375 -84.1 203 -87.2 778 -51.8
1.70E+07 830 88.1 3250 -82.0 1651 81.8 991 -82.4 180 -86.9 684 -54.4
1.80E+07 955 86.0 2720 -76.1 1796 70.3 986 -67.2 164 -84.9 623 -45.9
1.90E+07 1203 85.4 1860 -80.1 3260 44.6 742 -71.0 145 -85.1 568 -51.2
2.00E+07 1419 85.2 1738 -83.8 3710 59.0 1123 -67.7 138 -84.5 654 -34.0
2.10E+07 1955 85.7 1368 -87.2 12940 -31.3 859 -84.3 122 -86.1 696 -49.9
2.20E+07 3010 83.9 1133 -87.8 3620 -77.5 708 -86.1 107 -85.9 631 -54.8
2.30E+07 6380 76.8 955 -88.0 2050 -83.0 613 -86.9 94 -85.5 584 -57.4
2.40E+07 15980 -29.6 807 -86.3 1440 -84.6 535 -86.3 82 -85.0 536 -58.8
2.50E+07 5230 -56.7 754 -82.2 1099 -84.1 466 -84.1 70 -84.3 485 -59.2
2.60E+07 3210 -78.9 682 -86.4 967 -83.4 467 -81.6 60 -82.7 481 -56.2
2.70E+07 2000 -84.4 578 -87.3 809 -86.5 419 -85.5 49 -81.7 463 -60.5
2.80E+07 1426 -85.6 483 -86.5 685 -87.1 364 -86.2 38 -79.6 425 -62.5
2.90E+07 1074 -85.1 383 -84.1 590 -87.3 308 -85.6 28 -75.2 387 -63.8
3.00E+07 840 -83.2 287 -75.0 508 -87.0 244 -82.1 18 -66.3 346 -64.4
3.10E+07 661 -81.7 188 -52.3 442 -85.7 174 -69.9 9 -34.3 305 -64.3
3.20E+07 484 -78.2 258 20.4 385 -83.6 155 -18.0 11 37.2 263 -63.2
3.30E+07 335 -41.4 1162 -13.5 326 -78.2 569 -0.3 21 63.6 212 -58.0
3.40E+07 607 -32.2 839 -45.9 316 -63.4 716 -57.6 32 71.4 183 -40.5
3.50E+07 705 -58.2 564 -56.3 379 -69.5 513 -72.5 46 76.0 235 -29.6

Ed Gilbert, WA2SRQ

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Where Do I Go from Here?
Some thoughts on your first antenna for HF
By Bob Raynor, N4JTE

Okay so you got your ticket and passed the exam as your entry into the world of amateur radio, soooooo are you bored yet? Hope not, because we are finally seeing some sunspots which allow your new voice privileges to be explored on 10 meters as opposed to the two meter stuff that might not be quite what you were hoping for. BUT if you have ventured into the next step and got your General ticket, I would like to give you a basic guideline on your HF antenna possibilities and perhaps answer a few questions along the way.

Your expectations:
I have been doing the ham thing for a lot of years and my addiction to the hobby may not become the same for you, but I think it’s safe to say we all want to be heard well enough to have a qso or at least get a fake 5-9 from a DX contester after yelling back at them in a relatively short time. That said, once on the air for awhile you will make friends and even be able to recognize their voices before hearing their callsigns! This is what keeps old farts like me and others coming back to radio at ridiculous hours, like saying hello to my friend in England G0EVY at 1am or checking in with the HHH net at 4am local to say hello to friends inAustralia andNew Zealand. The excitement of being able to this with some homebrew wire in the trees NEVER gets boring!

It has gotten to the point where I don’t even have to explain these bizarre hours to my xyl, got her trained, so to speak, as long as the garbage is taken out, mortgage paid, the wood chopped for the fireplace and the driveway shoveled so she can get to work; while I put up a wire beam for 80 meters halfway into my neighbors yard, all is fine in my ham world. Yeah right!

Anyway, point of this short article is to try to focus our newly licensed Ham brethren and give you folks some tried and true antenna advice before you get sucked into buying a commercial antenna you can build yourself or more importantly avoid wasting hours and money on some magic internet antenna.

Timing is Everything:
As a newly licensed ham, you have joined us after a pretty long dry spell, propagation wise. Band conditions on the upper bands like 10, 15 and 20 meters are showing some incredible signs of life. What this means is you don’t need a $5000 tower and beam to speak to another ham half way around the world, propagation will do most of the work with the antennas I am going to describe and these conditions should last a few years, and this stuff will cost you less than you might spend for a month of internet service!

What’s your Preference?
So many frequencies and only so much time to play on the radio! Good time to make some choices, are you ultimately trying to see how far away you can be heard, or maybe you’ve got another new ham friend some miles away you want to keep in touch with? Or even maybe you are more technically inclined and want to explore antenna building or perhaps contesting? Time for you to focus a little bit, after a little while on SSB you’ll find a niche of interest, BUT; your antenna is your key element to getting it done. A $2000 radio will become an expensive doorstop without studying, reading and building the best antenna you can fit in your backyard.

My first choice in antennas has always been some configuration made from wire and usually for two bands, 40 meters and 80 meters, my reason being that a monoband antenna is easier to build and easier to match efficiently to your radio, I have designed/ reviewed various multi-band wires, see “ribbon” and “G5RV” in old eham articles under my call, but the need for a multiband antenna is probably a good thing for a new ham to explore so I will present a few. BUT; you new generals will have to take the time to research the actual dimensions and construction, this isn’t a “ how to article,” what I do want to present is what actually works and will give the most bang for the buck and get you reading some antenna theory books as opposed to advertisements. Google is our friend if you need more info on the following antennas or email me at my QRZ page.
Gonna give my choices as based on best to last preference for starter efficient antennas from my own personal experience at my location, your mileage may vary.

Multiband Homebrew Wire antennas:

CENTER FED DOUBLET

1: Put up the longest, highest, flattest center fed wire you can fit in your yard, nothing wrong with the ends hanging down near non conductive end supports to add additional length. This antenna needs to be fed with open feed ladderline and will require a tuner to match efficiently to your 50 ohm radio. If you can get at least 75% of the length of your lowest band wavelength up in the air, this antenna will make your day on a lot of frequencies. My first choice for a new ham who wants to explore a bunch of bands.

FAN DIPOLE

For shape reference only!

This kind of antenna allows the use of direct match to 50 ohm coax and should not need a tuner and will allow operation on mutibands with a little sweat equity on the construction side. Like I said in preamble, read up on this one, might fit your yard and your radio needs.

Not going to spend much more time on multi band antennas because once you have narrowed your focus as a newer ham you’re going to want to be louder than the guys using them, so next, a little time will be devoted to how to double your power out and increase that skip distance thing you memorized on your test!

Oh yeah; I GUARANTEE that either of the above antennas will work as well as or better than anything sold commercially for 10 times the price!

AND; I am aware it is a short list, counting on my antenna gurus reading this to jump in and expand!

But before someone else points out the obvious , let it be known that almost any piece of wire will get you on the air and be heard somewhere, but with a little homework you will enjoy designing something to fit in your backyard that will expand your horizons. During WW2 a little toy called a Slinky, yeah that thing, was used to successfully communicate on the battlefield! And hula hoops became super magnetic loops able to work the world at will, just kidding about that one.

SO YOU WANT TO BE LOUD WAY OUT THERE?

Well that’s going to take a little work if you are willing to play with some wire.

On the upper bands pretty much everyone has a commercial, expensive beam on some sort, on a tower, not to worry, the same can be done at nominal cost with wire. On 40 and below a wire gain antenna is the way to go and not hard to do. And once you get a little more into phased reversible wire arrays you will be truly competitive with most of the tower/ commercial store bought beam guys on ANY band.

1: YE GOOD OLD DIPOLE!

The most efficient, easy to build mono band antenna out there. Unless you are getting creamed in some contest with the big guns firing up their $20,000 stations, you will be heard, HOW?; because by hook or crook you figured out a way to get that sucker up in the air at around ½ WL on the band of your choice! If DX is your new found interest then broadside it to the NE/SW

If tight for room or lack of supports an inverted vee up as high as possible will give good results also.

Build your own and you will be amazed on any band with a dipole, especially with the emerging sunspots. The secret to DX is the lowering of your take off angle into the ionosphere and getting that first skip into the, direction/ area you’re chasing, a good high dipole can do it, other designs do it better however.

2: WIRE GAIN ANTENNAS:

It is beyond the scope of this article to explain the intricacies of multi element beam antennas like the one way up there on your neighbor’s tower.
Wire beams are relatively simple to build and extremely cheap! Commercial aluminum beams for any band are based on the property of the dipole.
By adding some correct length and spaced wires in front of, or behind, or both, of a dipole you have now focused the antenna in a narrower direction, another way to define gain.
Think of a flashlight as opposed to a candle and you will get the jist of focused energy in a specific direction.

Simple Two Element Wire Beam:

For shape reference only.

The addition of one wire 5% longer behind a dipole in the same plain will give you 3dbd of gain, in other words double your ERP; effective radiated power.
So that new 400 watt amp you saved up for will now have 800 watts going into the ionosphere. Oh yeah the extra power out works on receive also, adding an additional S unit and better signal to noise ratio for your hearing pleasure! You are focusing your transmitted signal in a smaller slice of the compass, helping diminish annoying signals off the side and the back.
This concept is applicable for every band from 2 meters to 160 meters; the spacing and between the two elements is subject to many variables and worth studying as is the possible shapes, quads, yagi, quagi etc.
The usual spacing between the wires for most gain is around .15WL.
If you have successfully built a dipole and remember the formula of 468/freq to achieve your ½ wl wire you are well on your way to using a little high school algebra to build your first beam antenna.

This process of free gain will open up an incredible arena of potential projects that will only be limited by your imagination and your commitment to studying the immutable laws of physics often contrary to a good portion of the advertisements we are all bombarded with everywhere.

Another worthy wire design is called a MOXON antenna with folded in elements that will fit where some wire beams will not. The moxon is a fun antenna and worth some serious study if you are plagued by loud stations behind you as it has very good front to back, meaning you will have an easier time hearing the station you are looking at.

Single Wire Gain Antennas:

About the only true single wire antenna that has 3db gain over a dipole is an EDZ, extended double zepp. These can be really long but if you have the room and tall enough supports this antenna will give you the same gain as a two element beam in two opposite directions. Mine has been up for years and has proven itself as the best narrow beam width single wire I have tried. Collinear antennas are a little shorter but have less gain so I stick with the EDZ.
Point being, as a new amateur either one might fit your needs so it’s worth the homework.

Getting Up In The Air:

The higher the band the smaller the antenna, nice little piece of physical law. Consider a 2 meter or a 10 meter wire beam built on the principals described above. Small enough to build and hang from any available tree and leave a string hanging from one corner to change directions, remember you built a directional beam, primitive maybe but mucho times better than the stub on your 2 meter hand held.

NO TREES ? Try something like below:

For an inverted vee or center of a dipole an easy to get 40 ft in the air pole for $50 is pictured. I use these things all the time in beam and vertical experiments They are 25ft extended and attached to a 2×4 and then to post holed 4×4, no concrete or help needed to install alone. Check fiberglass flag poles or Spider poles.

SUMMARY:

I suggest the best thing for a newly licensed ham to do is to get on the air and start chatting with people. You can ask them what antenna they are using and make your own deductions. Join a WAS net, like CCN or OMISS and see what you like or dislike about your present antenna. Determine if you have a favorite band that fits your interest and maybe upgrade to a mono band wire beam.

This article is a very cursory look at starter antennas and methods that will work great without killing your checkbook. Once you start down the road of designing and building your own antennas you will be addicted to this very important facet of our hobby and who knows, maybe you will writing a better article in the near future!

Tnx for reading,
N4JTE

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