>Swamping Resistor:
The Ameritron circuit has some differences - there are low value
gate loading resistors not in EB104, and the feedback resistance
is lower. This is going to lower the impedance on the transistor
side of the input transformer. I don't know the turns ratio in the
ALS600, but I'd guess that the amp circuit might have an input
impedance lower than 50 ohms so that the 35 ohm series resistor
give 50ish overall as well as attenuating the input.
>Output filter:
>I like the idea of using a diplexer instead of a basic low pass
>filter since you can burn up a lot of the harmonics by sending
it >through a high pass filter and into a 50ohm power resistor.
There's a more subtle reason for doing it this way - at low
frequencies harmonics lie within the passband of the amplifier,
and you can sometimes get some very stange effects if they are
simply reflected back from a filter.
>Power:
For best performance you want a regulated supply. You can play
games with transformer ratings, ripple voltages etc. ahead of the
regulator. Bear in mind that the peak current in the transformer
could be 7-8x dc, and the rms (heating effect) current is
typically 1.7-2.5x dc. You might consider hunting for surplus
switcher supplies - 48V is common in telecomms installations, or a
couple of 24/28V supplies can be stacked.
Steve
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|