6146 et al.

[Dave & Debby Anderson]

Dan -

You asked which of the 6146s are best to use. This is not a dumb or
stupid question.
All of us who use them have been through it in some way at one time or
another. I clearly remember asking whether they developed the variations
just to confuse us.

I can usually remember which is more desireable (to me) but not always
the reason why, so I dug out my books, refreshed my memory, and here
'tis.

A brief rundown on the specs of the various 6146s
(all are good to 60Mhz):
Tube         filament     plate
Number        info       dissipation  comments                 (date
introduced)
6146-       6.3V @ 1.25A   20W        plain old ordinary tube
(Jan  1952)
6146W       6.3V @ 1.25A   20W        military ruggedized version    (?)
6146A       6.3V @ 1.25A   20W        mobile version - 'dark' heater
(Sept 1961)
6146B/8298A 6.3V @ 1.125A  27W        uprated version - 'dark'heater
(Nov  1963)

If you are going to operate out of a suitcase or crate, then the 'W' is
the best.
As long as you are planning to run from a fixed base, then I would
recommend the 'B' model. Of course, the radios themselves are designed
around the plain old 6146s, so any of the versions will work.

The standard filament-cathode used in the '-' and 'W' versions is
directly heated and runs at about 700-750 degrees C.
The 'dark heater' is an indirectly heated cathode (actually a tube which
is the cathode with the filament inside it), which operates at a much
lower temperature. This lower operating temperature gratly extends
filament life and increases tube stability and reliability. (According
to RCA, who developed it, anyway.)

The only really important thing to remember, regardless of which
variation you use, is to ALLWAYS use two of the SAME VARIATION. The
internal capacitance of each model is different, and can give you real
headaches if you mix the models.

I won't go into neutralizing the tubes - some folks don't, some do it
quick and get it over with, and some do it with incantations,
sacrifices, and lots of mumbling. (No, I'm NOT talking about sex,
although the same stuff seems to apply)

The same applies for 'matched sets' of tubes, which consist of two tubes
with 'identical' performance. Some folks swear by them, some swear at
them. I personally don't think that they are worth the premium that you
will have to pay for them.

End of sermon.

The facts above are gathered from 'Tube Lore' by Ludwell Sibley, Various
RCA tube manuals, and various (older) ARRL handbooks. All are worth
acquiring for your general edification and to look impressive on the
bookshelf in your shack.
The opinions expressed here are entirely my own, although they are free
for adoption by anyone.

If I haven't confused you enough, please let me know and I'll try again.

Dave Anderson

nnnn
_________________
Daniel Camp wrote:
<snip-snip>
>    My HW-100 uses a pair of 6146 tubes as finals, as do many of the
> Heath rigs of that timeframe.  I am thinking it could be a wise idea to
> have a spare pair about the shack, but I don'k know what "flavor" of
> 6146 I should be looking at...6146, 6146A, 6146B, 6146W or some other
> variety yet undiscovered???
> Tnx es 73--Dan, N0KFY/7

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