[BC] Are there AM stations still using Tube Rigs?

[Ronald J. Dot'o Sr.]

From: "Cowboy" <curt at spam-o-matic.net>

>Not at all applicable to a directional.

I agree, I should have made myself clearer that I use this method for 
non directionals and leave directional tune ups to someone else 
better qualified than me.

>>  It's important to do the adjustments without modulation so that the
>>  tuning is centered on the carrier frequency.
>>  When you add modulation the sidebands will raise the reflected power
>>  slightly.  So far the sidebands seem centered during our annual proof
>>  for occupied bandwidth with this method.
>
>Without a sweep, you don't know that.
>( but it's a good guess )

If the annual proofs show that the sidebands are equal then I guess 
that I do know that .

>>  In the past I've adjusted the ATU with a bridge to a 50 ohm, 0J match
>>  but the TX didn't like it when I applied power, as I guess things
>>  change under full power, so I adopted this method which doesn't
>>  require the test equipment and works for me.

>No, things don't change.
>You do have a tolerance in bridge calibration, and you *may* have
>some Z rotation in the line if the bridge cal doesn't exactly match the
>manufactured tolerance in the line.
>If things change under power, then something is heating and the whole
>thing should be revisited.

I remember a thread sometime back where it was discussed that some 50 
ohm fixed output TX's want a little "J" with their 50 ohms and 
therefore don't like the 50 ohm, 0 J input of the ATU and need some 
fine tuning.   When I first fire up the TX and get an elevated 
reflected reading things don't have time to warm up so it shouldn't 
be an instability in the load.  Once I achive a good match things 
stay stable from switch on through extended normal operation so I 
would say that the load is stable.

Ron D