The AM Forum

Here' s an intersting thought.
You have gone through the trouble to tune your linear into a dummy load and keep the interference to the QSO you would like to join to absolute minimum.
The antenna load is not 50 ohms and it's a 3:1 match, there is nothing you can do about the mismatch.  ???
What do you do now?
1.. re-tune the linear for this mismatch? And cause interference?  :P
2.. leave the tuning alone ?  :-\
3..Turn the RF drive up from the exciter to equal the same power when the TX was
      connected to the  dummy??  :o

There may be more combinations of thougths, but I'm trying to avoid rewiring the station to get the 3:1 antenna (the 40M dipole on the Cushcrap tri-bander) to the K1JJ tuner. UNfortunately the upper-end of 40M is this bad mismatch. All other bands are flat where I set them when I built the yagi.
Thanks always.................dam it's cold up  here in Pa!!!!!!!!  :o  THis would be considered bitter cold in Washington DC HA!

Fred

Fred I always try to have the linear tuned to 50 ohms and adjust the antenna tuner to get a match. Yup may get the linear tuning to look better but you may end up with weird voltages on the loading cap that could flash it over.

Fred,

Good to hear you're concerned about unintentional tuning up QRM to the QSO.

The linear Q is low enuff that you can easily go down the band 20kc and find a clear freq to tune up. The peak tuning will be about the same on the QSO freq.

I can QSY -+40kc w/o retuning my linear tank. All depends upon the designed Q, tho a Q of 12 is common and is reasonable.

If you are type A and want to get it perfect after the initial settings down the band, then just tweak the tuning a little while you're talking in the QSO.

I cud never understand why guys will come on freq and say, "stand by while I tune up".  And the next minute is dead air. [then you hear guys trying to talk over the carrier] When we break in we shud be ready to rumble... ;D  caw mawn.

T

I thought you just pulled an "INR" ;)

Yes, glad you brought up that exception to the rule, Bill.  Ham radio tradition.

Just mention those three letters, and you're permitted a full minute of dead air on freq.   ;D

T

OK
I'll try the 10kc down the next time. Tuning on the fly may screw up your modulation and there could be flat topping. I always tweak for peak RF carrier,with the exciter in the CW or FM mode. Flip the exciter to AM then reduce the carrier to "legal limit", or what ever unmodulated carrier that will not exceed the P.E.P. of the linear and then go back and re-tune the PA tune and loading slightly for a nice waveform by humming into the microphonium. That's why I keep it in a dummy load.
I do miss the plate modulation, though.
Those Class E TX's are tempting $$$$$$
Fred

OK Fred-

Well, my point is that you can tune up completely off frequency, including doing the flat top check, loading the amp heavier, etc. - take your time and make it look pretty.  THEN come up freq 20kc to the QSO and everything will still be tuned FB, including loading and flat topping. The only possible touch up wud be a tweak of C1, the tuning cap. This can be done with a dead carrier and completed in 1 second. This will not affect the flat topping or loading, etc.  With a Q of 12 or so like most commercial amps, you won't really have to touch up things anyway.

T