Hi Chris,
if you really want to use 100 watts drive on that you might want to consider using a bigger radio drive that amp- Viking-II, DX100 etc.
I have a Viking II that has Timtron's audio mods sitting on a shelf and a suitable receiver as well. It wouldn't be hard to press that system into service. I am running an SDR-1000 right now as an RF exciter and receiver to drive a 20V-3 and my intention is to use the same exciter to drive the Gates.
if you try to drive it with an IPA as big as that Alpha your residual noise and distortion numbers will be really bad. and (Bill Orr) will back me up on this: NEVER drive an amp with a class B or AB2 driver. it just multiplies the distortion.
Trying to drive an amp with an amp can cause unintended problems, I agree. I wouldn't want to push a distorted signal that high and the IPA setup would have to be monitored closely. On the other hand Henry did this when they offered the 3CX3000 amp. In reality a 100 watt Viking II is a series of amps as is the SDR rig.
my take on it would be to just use 25 watts of drive from a really clean exciter. that should be all you need. you have 3000 watts of plate dissapation and a TON of gain available. 25 watts should easily give you a 375 watt carrier (legal limit on AM) out with tons of headroom for audio.
On 160 and 80 the 25 watt exciter works fine. Moving to 40, 20 and 10 meters is a different story. The 4CX3000 wants to see an increasing amount of drive in the higher bands. The Viking II output drops in the higher bands as well.
leave the "Alpha for a driver" stuff to the knuckledraggers like Wally and Richard and the CB kiddkies on 3878 SSB. that's why they are SO wide... the secret to a great signal using linear AM is a low distortion amp with lots of headroom.
The 20V-3 is the first AM rig I have owned that has the ability to Exceed the limits of my license and do it all day long. During the three years restoration and conversion process I thought many times about how much fun it would be to dump a kilowatt on 3.880 and have some fun. Reality is I never did that. As a matter of fact I get more pleasure out of holding the 375 watt line. I could also raise hell with an intruding side bander very easily by messing with the input audio gain. Instead I pay close attention to tilt and overshoot and brick wall my signal to 6KHz. I can't sit in judgment of poor operating practices if I use poor engineering practice myself. If the sideband interference is trouble I'll pull in the filter skirt.
I'll see this through Chris. If it doesn't work right it's back to the drawing board. Life is too short for QRP and 10 meters is the target when conditions require a little more umph. Thanks for the comments.
Mike