> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On Behalf Of Bill, W6WRT
> Sent: Sunday, January 31, 2010 2:47 PM
> To: Amps reflector
> Subject: Re: [Amps] Fw: Good amp to buy /amp notes
>
> ORIGINAL MESSAGE:
>
> On Sun, 31 Jan 2010 12:33:55 -0500, "Gary Schafer"
> <garyschafer@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
Yes that is correct Bill, "IF" you are always tuning up to the same specific
power output!
I was basing it on tuning up for MAXIMUM power output (as most of us do)
from the amp in both pulse tune and carrier tune. In this case the amplifier
is limited in the amount of current that it will draw by the plate voltage
value.
You will always be able to get more power out with pulse tuning because you
will have higher plate voltage AND will be able to draw more plate current.
Now what that ratio actually works out to be will determine the actual plate
load impedance. It could be as I said in my last post (the part that you
left out) the load impedance could actually go the other way. It all depends
on how much sag there is in plate voltage and how much current the tube will
draw at a particular plate voltage.
As to tuning up for maximum power out, that should ALWAYS be done. You don't
want to tune up to only a specific power output! That is inviting splatter.
If you are exceeding the maximum power out that you want when tuning for max
out on the amp then DRIVE level must be reduced first.
73
Gary K4FMX
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