Uwe wrote in message ...
With the help of some folks here I did troubleshoot my AC-1 tube transmitter
(using a 6V6) and got it working somehow. Since I passed my code test and
had my first QSO using the transmitter and boy was that exciting.

Congatulations and well done!

But questions remain.

I monitor the output signal on my scope and notice that right after key down
the waveform contract just a bit and the tone changes pitch. I guess this is
called chirp.

That's correct. You won't see it much on a 'scope but you can hear it.

I normally use B+ 200V.
If I increase the voltage lets say to 300V this effect becomes much more
pronounced.
I still use an external bench supply capable of much higher currents and I
don't think it is a power supply weakness. In fact putting a VOM on the
supply line shows no sag in my supply voltage.

How can I minimize this and especially keep it from becoming more severe at
higher outputs.

Several things to check:

1) If the receiver you are using to monitor the signal is overloaded
by the strong local signal, it can make the signal sound like it is
chirping or clicking even if no such chirps or clicks actually exist.
This is particularly true if the receiver isn't really meant for CW
use. What are you using to listen to the transmitter's signal?

2) Besides the power supply, chirp in that sort of rig can be caused
by:

a) the crystal - try a different one if you can

b) the feedback capacitors (the one from the grid to cathode, and the
one from cathode to ground). These control the feedback in the
oscillator, and if there is too much or too little, chirp can result.

c) the 6V6GT tube - try a different one if you can

d) output tuning - maximum output is often not the best setting for
chirp.

Also, the circuit diagram for the tranmitter did not state the coil diameter
of the pi network.

It's 1-1/4 inches.

The pi network still has me scratching my head. Coils
with slight variations in diameter give dramatically different results.

That's to be expected.

A common formula for the inductance of a solenoidal air-core coil is:

L = (a * a * n * n)/ ((9 * a) + (10 * b))

where

L = inductance in uH
a = radius of coil winding in inches
b = length of coil winding in inches
n = number of turns


Also changing the air cap with one of an identical range can have a vast
effect, which surprised me. Is this the "real world components" versus the
theory???

Perhaps - but how do you know the caps are the same value?

73 es hope to CU on 40

Jim, N2EY

Uwe