TexasRF@aol.com wrote:
>Hi All, it makes no sense to not peak the tune C as the last step in a
>matching procedure.
>
>The tuning network is fully adjustable, allowing a match from your nominal
>50 ohm load to what ever plate load impedance you want to use. If the tube
>needs 2000 ohms for best efficiency and power output, it is a simple matter
>to provide that. But, the transformed impedance is resistive only when the
>complete network is resonant. The only way that can happen is when the
>plate tune C is adjusted last, for maximum power transfer. The complete
>network includes all sources of reactance, including tube output C and stray
>C as
>well as the effect of the rf choke and tank inductor and tune C.
>
>When you tweak the tune C for maximum output, you are making all of the
>reactance contributors parallel resonant, leaving only a resistive load for
>the tube.
>
>Sure the plate load impedance changes when you tweak the tune C, that is
>what is supposed to happen. Over coupling slightly is just another way to say
> that the plate load impedance is reduced slightly. If you don't end up
>with the desired over coupled value, then the plate load C is not set to the
>required capacity and needs further adjustment.
>
>Operating a tube into a reactive load just doesn't make any sense in my
>mind. It may not be reactive enough to hurt anything but how can it help in
>any way?
>
>Standing by for other view points and arguments.
>
>73,
>Gerald K5GW
>
>
>
>
That is the ticket! Tune for max smoke at the antenna! It works for me.
I can see how you can improve IMD 2 or 3 db by agonizing over the
"proper way to tune" but your probably already at 20 to 30 db IMD to
start with. That 3 db will never be noticed by anyone except the fellow
looking at the lab equipment.
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|