[Amps] Fw: Good amp to buy /amp notes

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Sun, 31 Jan 2010 12:33:55 -0500, "Gary Schafer"
<garyschafer at comcast.net> wrote:

>
>Maybe, maybe not. Look at some typical load impedances of an amp.
>3000 volts at 1 amp/2 = 1500 ohm plate load. If you tune with a pulse tune
>the plate voltage stays near 3k.
>
>Now tune up with carrier. The plate voltage will probably drop. Let's say it
>drops to 2600 volts at 800 mA. (if tuning for max output the tube will not
>draw as much plate current with lower plate voltage).
>So 2600 at 800 mA/2= 1625 plate load.

REPLY:

I think there is something wrong with your example here.

If you tune up a legal limit amp with a pulser at 50% duty cycle, you
are tuning up at 750 watts average output with a peak of 1500 watts.
Because the HV will not sag as much, the 1500 watt peak output is
achieved with a higher HV and lower current. That is a relatively
higher impedance.

Now when you tune with full carrier, the HV sags more so to make up
for it, you tune for 1500 watts and the current must be a little
higher than with the pulser to make up for the sag. This is a
relatively lower plate impedance. 

Now when you go to SSB after the full carrier tune up you are talking
into a lower impedance, not a higher one. 

Isn't this correct? And isn't it the opposite of your example in the
earlier post?

73, Bill W6WRT