This week has seen me spending far too much time in front of the radio trying to see if I got my money’s worth with the new tower and antenna.
Force 12′s C3 has a few features that make it unique to my limited knowledge of traditional Yagis – namely its feed method. With 7 elements, it looks to the eye to be a superior antenna to the more common 4-element tribanders that adorn many stations but the fact is it has only two active elements on 15 and 20 meters and three on 10 meters.
With each band having its own dedicated elements, there are no traps, the antenna being designed to act as a monobander on each of those three bands. This trading of an element or two for “monoband-like” performance may seem a poor trade-off but the advantage is more broadband performance than would be possible with a trapped Yagi – and this is the main reason I chose it.
Force 12 mentions that the antenna has reduced (with respect to 10-15-20 meters) performance on 12 and 17 meters. In other words, it has gain and F/B on those bands…just less so than on the other three bands. Good enough for me – my main goal was a rotatable antenna to get into the nulls presented by my dipole on as many bands as possible. Any WARC-band gain is icing on the cake.
Regarding the feed method – only the 20m driven element is directly fed by coax. The driven elements for the other bands have their energy coupled into them via the 20m driven element.
On 10-15-20 meters, SWR is 1.4:1 or less. Without a tuner, it’s 2.2:1 on 12 meters and 2.9:1 on 17 meters. That’s good because the aluminum tubes that make up each element are riveted together with the rivet holes being pre-drilled rather than the more common hose clamps with their continuous adjustability. There are options on the 15m elements to use rivet holes for the phone or CW end of the band but I’m under 1.7:1 up in phone country even though set up for CW.
The past week has been spent doing A/B comparisons of the two antennas on all 5 bands using stations from all parts of this little blue orb we share. If I had it to do over again, I’d buy the same antenna. I’m hearing DX on all bands that I can’t copy on the dipole, even in directions favored by its orientation…and this is a dipole that’s earned its keep and then some.
I was surprised by the noise level compared to the dipole. When I took my first listen on the Yagi, it seemed as if the antenna were disconnected. The dipole at that time had an S4 noise level – switching to the Yagi caused the S-meter to barely even register. Tuning to a station quickly dispelled that worry – unless the antenna is pointed toward the sun, it’s much quieter than the dipole.
Best of all, T6LG was logged for a New One (#296) on Day 4 of having the antenna. I’d never been able to even hear Afghanistan before. Conditions have been excellent lately too.
Here’s how the A/B tests are typically going:
UPDATE: Here’s T6LG just after working him on 15 meters: