What in Heaven’s Name is a Rybakov Antenna?

I love to check out interesting, new antenna designs. The Rybakov isn’t actually a new antenna, it has been around for a while; either I just hadn’t come across it before or I had passed it over and forgotten about it. So when I read about it recently I just knew I had to find out more.

Most descriptions of the Rybakov are essentially the same. A non-resonant wire suspended vertically by a pole, fed via a 4:1 unun against a radial field on the ground. I was immediately suspicious and the following fundamental question sprang into my head:

Is the Rybakov really just just a short, vertical random wire antenna?

I was determined to learn more so I built one. I raised my 31ft telescoping fiberglass pole, hooked one end of a 29ft wire to the top and mounted the pole on the trailer hitch of my truck.

Incidentally, the pole started life as a 33ft unit made by MFJ. Several years ago, while I had it mounted on a tripod in my backyard, a strong gust of wind caught it and sent it crashing into the brickwork near the wall of the house. It suffered catastrophic injuries to several sections in the upper part of the pole. Fortunately, I had a 13ft telescoping fiberglass fishing pole that exactly fit to replace the broken sections. My pole had a new lease on life – albeit shorter by two feet.

But, back to my Rybakov build. I couldn’t fathom why a 4:1 unun was recommended. Random wire antennas usually employ a 9:1 unun. The unun turns ratio implies an antenna feedpoint impedance of 200 ohms in the case of a 4:1 ratio and 450 ohms in the case of a 9:1 ratio. Maybe that was what made the Rybakov distinct. Most random wires are erected as a sloper, an inverted-V or maybe even a flat top. Antenna orientation can affect its impedance. Was this the “aha!” moment that I was looking for?

I have both a 4:1 and a 9:1 unun in my radio toy box. I built both myself from scratch for a fraction of the cost of buying commercial units. My 4:1 unun has served me well feeding a delta loop in the past, while my 9:1 has been used with various random wire antennas. I also have an L-match (home built – of course) which is perfect for matching end-fed wires. As I contemplated which of the three I should use, another question danced in my head:

A Random Wire Antenna always requires a tuner (because it is non-resonant on any band) so if a tuner is needed anyway, why bother with an impedance transformer/unun? Why not just use the L-match?

Every account of the Rybakov I have read sticks to the 4:1 unun and radial field format. I tend to be a contrarian thinker who would prefer to figure stuff out for himself so I decided to tinker with a number of options.

Ground, Counterpoise or Radials?

Something has to provide “the other half” of the antenna. Experience has taught me that whether a good solid ground, a counterpoise or a radial field with a gazillion wires (I prefer just 4 for field portable antennas) is used only affects the efficiency – and to a lesser extent – the propagation pattern of an antenna. Whichever is chosen won’t stop you making most QSOs. My shack-in-a-truck winter portable operating quarters employs a counterpoise called … my truck, and it works!

Rapid deployment, field portable antennas should be as simple as possible, so another option is “none-of-the-above”. How about just letting the coax braid act as the counterpoise? My field portable rig includes a line isolator (Common Mode Current Choke, CMCC) at the rig end of the coax. If a coax is long enough, as my regular 29ft coax has proved to be, any common mode current on the outer surface of the braid will be dissipated by the time it reaches the rig, and if it isn’t, the line isolator will clobber it with more than 30dB of attenuation.

Why a 29ft Radiating Element?

The lowest band I usually need to operate on in the field is 40m. A Random Wire Antenna is recommended to be at least a quarter wave on the lowest band of interest, so 29 feet is too short. But wait. Random wires always require a tuner, and the tuner will see a capacitive reactance on the wire. To get a match the tuner only needs to add a modest amount of inductance. Voila!

But, there is another reason I chose 29 feet and it is more pragmatic. My wire was originally 35.5 feet – but my pole is only 31 feet. Do you see the problem?

Rybakov Antenna Trial Take #1

Tinker, tailor, soldier, sailor, rich man, poor man … lots of variables to play with but let’s keep one constant – the radiating element. Twenty-nine feet works on 40m and up. That leaves the choice of two unun turns ratios or the L-match (three variables) and a choice of ground options (four variables). That’s seven variables. Mathematicians tells us there must be 7! (seven factorial) combinations to try. Seven factorial is 5040 combinations – waaaay too many.

So a testing compromise is called for. Let’s settle on one ground option, thereby reducing the number of possible test combinations to just 3! (three factorial) which is just 6. Perfect. Test number one: a 4:1 unun at the base of the radiating element with the L-match tuner at the rig end of the coax and a 22ft wire laid on the ground. Result – would not tune on the two bands of primary interest, 20m and 40m. That’s interesting; other people recommend a 4:1 unun, maybe an L-match is the wrong tuner for this application.

Rybakov Antenna Trial Take #2

I replaced the 4:1 unun with a 9:1 unun and left everything else the same. Result – yes, as expected, the antenna tuned perfectly on 20m and 40m; no other band was tested. My suspicion that the Rybakov is just an exotic name for a short random wire antenna was gaining momentum. Now let’s try something else along the lines of KISS – Keep It Sweet and Simple.

Rybakov Antenna Trial Take #3

Going back to my question “if a tuner is needed anyway, why bother with an impedance transformer/unun? Why not just use the L-match?“. Both ununs were set aside and the L-match was connected at the base of the radiating element. Again, everything else was left undisturbed. Result – easy tuning on 20m and 40m with an SWR of around 1.7:1. I did have to set my L-match to its low impedance setting. That suggests the antenna was presenting an impedance somewhere between 200 and 450 ohms.

But: problem. My winter portable shack-in-a-truck has the radio inside the truck cab, but the tuner is at the back of the truck. The only way to see both is to move the radio to the back of the truck for tuning, then carry it back inside the truck to operate. Maybe in the summer, when I am operating outside with a ground-mounted pole, that won’t be a problem. But when it’s very cold outside that is not a very desirable arrangement. I scratched my head, stroked my chin and came up with another turkey-brain idea.

Rybakov Antenna Trial Take #4

Suppose I move the L-match back inside the truck and simply connect the radiating element and counterpoise directly to the far end of the coax sans unun? Yes, there is going to be an impedance mismatch between the antenna (maybe a couple hundred or more ohms) and the 50 ohm coax, but will that be a problem? Other antennas like the G5RV do similar things. Result – well I already said it was a turkey-brain idea!

Rybakov Antenna Trial Take #5

One last thing to try. Is that counterpoise wire doing anything useful, or can I get rid of it? The coax braid provides a conductive path along 29 feet of coax back to the rig where, as I said, it hits an RF brick wall in the form of a line isolator choke. So, there is a “counterpoise” of sorts already. There is always the danger of introducing RF into the shack when using a coax braid as a counterpoise, but at QRP levels the risk is vanishingly small.

So, without hesitation, I pulled the counterpoise wire out of the L-match and re-checked the SWR. Yes, the wire was having an impact, but the wrong kind. Without the counterpoise wire my SWR dropped another couple of decimal points. Bingo, simple works!

Am I going to use my Rybakov in the field?

That’s the sixty-four kilo-dollar question. I keep a big box of field antennas in the truck when I go camping or on POTA expeditions. Yes, I’ll throw my Rybakov into the antenna box, but will I ever use it? On that I am not so sure. My goto bands are 20m and 40m and I have an End-Fed Half-Wave antenna that covers them perfectly. An EFHW will only work on its fundamental frequency plus harmonics, but a random wire will tune multiple bands. I also use a coil-loaded vertical whip that will tune multiple bands so is there still an advantage to taking the Rybakov along for the trip?

A coil-loaded vertical whip has a shorter radiating element than a Rybakov so it may be less efficient. If I were using a QRP radio that could possibly be important. But, my main portable operations radio is a Yaesu FT-891 that is capable of 100 watts. If conditions are bad I can always boost power. Since the new solar cycle began I have been reducing power. Five watts is usually quite adequate for a POTA activation but it’s nice to have some extra horsepower available when needed.

Time will tell; who knows which antenna will see daylight when the warmer weather arrives. In any case it was a fun exercise and that is what ham radio is all about.