[1000mp] Key clicks and amps

[Tom Rauch]

> Kinda funny but there seem to be many more manufacturers of amps than
> of transceivers.  Yaesu, Icom, Kenwood (in Japan), and Ten-Tec
> manufacture amps as do a bunch of specialists like Acom, Alpha,
> Emtron, QRO Technologies, Commander, Ameritron, Henry...  Except for
> the Yaecomwood solid state amps they are all much more alike than
> different.  Looking inside the boxes you can't tell one from another,
> from a distance anyway. 

The big Ameritron amps are old designs, I did them back in the 80's. 
Here is my opinion as an amp designer for Industrial, communications, 
and medical amps.

First, solid state is now starting to be cost-effective enough to be 
competitive in fixed station operation. I expect soon, with the 
increasing trouble finding reliable sources for tubes and increased 
costs related to tubes, solid state full limit amps with *clean* 
outputs will be available.

I looked at some of the less expensive high voltage FET's designed 
for class C or D ISM applications, but so far the IM performance 
stops me from thinking they are suitable for home high-power 
amplifiers. The only real choice is the MRF150 dies, in whatever 
package they offer. The bad part is Motorola is dumping 
semiconductors like crazy, and the MRF-150 may be next. Fortunately 
other manufacturers are picking up most of the old part designs from 
Motorola.

I've always stayed away from 4CX1600's and such because they were no 
longer being manufactured, and all the tubes floating around were 
surplus. As far as I know, that is why Pat Stein at Command stayed 
away from the same tubes. Before buying any tube amp, check on tube 
history and reliability.
 
I favor the 3CX1200 series of tubes, because they combine the 
reliability of a thoriated tungsten filament with the envelope life 
of a ceramic tube. They are really a 3-1000Z style grid and heater 
inside a ceramic envelope. While they have less gain than a 8877, 
they last many many times longer and are virtually immune to damage 
from overdriving or excessive grid current.  

If you buy an amp with a MOx (metal oxide) cathode tube, make SURE it 
has fast-acting grid current protection systems in place. A 
fuse won't do. You can tell a tube is a MOx cathode because it will 
require some warm-up time, and will have a separate cathode with 
a lower current heater than an equivalent-power directly-heated 
(thoriated tungsten) tube. MOx cathode tubes use gold plated grids, 
and the cathode is easily damaged if you do anything to strip the 
electron cloud away from the cathode during operation. That would 
include low heater voltage, excessive grid or plate current, 
excessive high voltage, or operation while the cathode is not at full 
working temperature.

Myself, I like simple amps that work real well. I've been using the 
same AL1200's with the original tubes since 1984, and I don't treat 
them well. In contrast I go through an 8877 in about four years on 
average.

73, Tom W8JI
W8JI@contesting.com