When I worked with the Cobweb antenna for a while, I started to miss working the lower bands, 30 to 80 meters. Now it’s not easy having all your antennas on only only 20 square meters of space on te roof. I can’t fit an EndFed, G5RV or a Windom. I can really only go up in the air and then you end up with a vertical antenna.
With some left over aluminum parts
Earlier I had experimented with a vertical of over 13 m (43 ft) long, fed via a CG-3000 autotuner and a bunch of radials of different lengths. It did quite well from 80 to 30 meters. Only I couldn’t place such a tall vertical antenna anymore, it was simply too tall. With some left over aluminum parts, I made a vertical with different lengths of radials and fed that installation through the CG-3000.
A relative favorable radiation patter
With some experimenting I arrived at an ideal length of 7.7 m. With this length, the antenna also appeared to do surprisingly well above 40 meters. Pretty logical, since the electrical lengths at 30, 15, 12 and 10 meters give a relative favorable radiation pattern for DX. On 10 meters, the vertical was sometimes even better in terms of transmitting than my Cobweb antenna.
The so-called Rybakov 806
When I tweeted about this antenna, Erwin PD3E pointed out its similarity to the so-called Rybakov 806. This is an antenna popular with portable users on HF and covers 80 to 6 meters. Often an 8-meter long fishing rod is used, along which a 7.5-8.0 m long wire is stretched (Rybakov is therefore Russian for fisherman). At the feed point, a 4:1 unun and radials of about the same length as the radiator provide an impedance which is well tuneable with a simple tuner, like such as the one in a transceiver.
Behind the aluminium plate sits the CG-3000 autotuner which tunes the antenne from 160 to 10 meters.
I had built the Rybakov vertical
So without knowing it, I had built the Rybakov vertical, the only difference being that the 4:1 unun had been replaced in my case with the CG-3000 autotuner. The latter one allowing it to be tuned from 160 to 10 meters. However the performance on 160 meters is quite poor due to the short length of the radiator.
Bandwidth on each band is pretty good
The nice thing about this antenna is that you can use it on many bands, although you shouldn’t expect good performance on 80 and 6 meters. The bandwidth on each band is pretty good. Once you have tuned in the middle of a particular band you don’t have to tune again when you work near the bands edges.
Very easy to build yourself
Furthermore, the antenna is remarkable easy to build and deploy. Especially if you use a fishing pole as a base. For portable use, this antenna is more than ideal. Lightweight, easy to set up and seriously good to work with from 40 to 10 meters.
The Rybakov vs. the Cobweb
The Rybakov now shows off next to my Cobweb. I was so impressed with its performance that I wondered if I shouldn’t better take the Cobweb down and promote the Rybakov to my main antenna. To answer that, I compared the receive and transmit performance of the Rybakov with the Cobweb in a long duration experiment.