I have an MFJ-962d tuner and recently found what I believe is a 900 Mhz Yagi. I have been able to tune it to 1.0:1 SWR on 20 meters and even push 75 watts into it. I am wondering how well this might work if at all. Anyone try to use yagi's with tuner's on different bands then designed for, if so what was your results.
If you tuned a 900 MHz Yagi to low SWR on 20 meters, you are either tuning the feedline to resonance due to common mode currents, or the coil in the tuner is accepting all the power. The 900 MHz Yagi won't radiate anything significant at 20 MHz and it won't be low SWR at 20 MHz.
Most likely the feedline is the radiator. This is very common and it is the thing that fools all these people that design very small antennas by trial and error for the HF bands.
Thanks, that is what I was thinking ... so for my next toy I will get an inline RF Current meter so I can see exactly what is going into the antenna.