Jack Schmidling wrote:
I have read page after page of mods and changes to the Ranger to make it
suitable to drive an am and wonder why I can't just reduce the drive to
get about 15 watts out and be done with it.
What am I missing?
js
The problem is that in a Class C amplifier the grid is driven well
beyond "saturation" (no additional power output with increasing drive).
If this wasn't the case, you would have no increase in output with
increasing plate voltage on positive modulation peaks - so there would
be no positive peaks in your "AM" RF output! Also, reducing drive will
reduce your plate efficiency greatly and you may exceed your plate
dissipation in the 6146 PA tube (in case you wanted to try this for CW).
IMHO the best way to reduce the output from a Ranger to drive an amp is
to use the LV power supply (~300V) for the PA plate supply instead of
the HV plate supply. This can be done right at the accessory plug in
back of the rig, but you'll lose your plate current indication on the
panel meter. You can either rewire the Ranger internally so that it will
read Ip no matter whether you use the LV or HV plate supply (as I have
on mine), or use an external plate current meter wired to the accessory
plug. Of you choose the latter you can leave the Ranger stock and not
even take it out of the cabinet!
You can still use the HV supply on the modulator plates for lots of
audio headroom, but turn the audio gain pot will be way down from where
it is when running the rig at full output.
With this approach you'll get about 12-15W out, perfect for driving a
linear amp.
This is the Timtron-approved way of doing it, and I can vouch for it, as
it has worked well for me.
73/GL,
-Larry/NE1S
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