[Amps] 6 mtrs:

[Tom Rauch]

> On another note, Carl and I have seen many failed attempts 
> to SB-200
> conversions to 6 meters and we have fixed them.  Some 
> people who can't seem  to get
> it together with an Sb-200 conversion to 6 meters, cop out 
> and say it  can't be
> done or blame the tubes or some other lame excuses.  Then 
> go on to  try and
> convince the masses that it is not a good item to buy.  I 
> am sure  Carl and I
> can come up with hundreds of satisfied customers.  Might I 
> add  W2CQM to the
> list.

It could be you are doing enough wrong that it works, and 
they are doing so much right it doesn't work.

That's what happens when we use a device in a region where 
it is unstable.

The problem comes in when we inflate ourselves and be openly 
critical of others when we really succeeded through luck.

Here is the test.....

Take a pair of 572B's and put them in a near-perfect layout 
with very short grid leads, a very short anode path to the 
tank, and good shielding.

Does it dip in the center of the RF power peak?

Is it unconditionally stable for all tuning conditions?

The answer above about 15MHz with the 572B in a pair is NO. 
As a matter of fact a well shielded design will oscillate if 
lightly loaded at full anode voltage. It will also NEVER 
have the output peak anywhere close to minimum anode 
current.

Now if we go higher, especially in a much less than perfect 
layout, we can find frequency bands of stability. The 
problem is when we credit our accident to great skill and 
ability and heap tons of bad verbiage on others because they 
had what really amounts to bad luck, or we start saying the 
tube manufacturer is wrong.

Rejoice in the fact you have found a good recipe, but let's 
not slam others who very likely could be just as 
knowledgeable or more knowledgeable than you or Carl. They 
just might not be as lucky as you two.

73 Tom