[HBR] Opps apologies to our moderator I sent this VIA an alternate mailing address

[Walt Hutchens]

William said:

> Anyone do any substitution analyzing of that
> idea of using Octals instead of the miniatures
> called for???

> Think like I said, will stay with the ones called 
> for, but it might be fun to see which ones would
> be subbed out with which Octals?

Obviously this can be done.  The issues are:

1. That's a design change. Most miniature tubes don't have exact octal
replacements so that's not trivial.

Octal tubes were developed and marketed through the mid-1930s with a
few later on. The first miniatures appeared about 1939-40, with a few
more during the war. The war was fought with octals for applications
not requiring compact design and miniatures for the rest.

By about 1950, though the 30's-40's tubes were nearly all obsolescent.
The 6J6 has a niche all to itself, the 1R5-1U4-1S5-3Q4 lineup for the
battery miniature radio (developed for the BC-611 handy-talky) still
owns that department, but the rest are of historic interest only. The
9-pin miniatures started showing up in the 50's (12AU7 may have been
earlier). In the 60's combination miniatures -- triode-pentodes and so
on -- became common.

Furthermore, the individual devices got better, with gains and upper
frequency limits going up steadily.

Taking a 60's design using combination miniatures and turning it into
one based on octal tubes would require both two octal sockets
replacing one 9-pin miniature in those jobs AND perhaps one more IF
stage because the best octal pentodes -- the 6SG7 I think? -- aren't
equal to the 60's miniature pentodes. (I can't remember the exact
gains ... 6SG7 might replace a 6BA6 well enough.) Larger older local
oscillator tubes won't be equally stable because of lower gain and
higher power consumption.

The larger tubes (and having to use a few more of them) will mean a
larger chassis and layout changes.

Doable, probably interesting. Certainly complex receivers WERE built
using octal tubes -- the Collins aircraft transceivers of the end of
the war (ARC-2 transceiver, ARR-15 receiver) were impressive
performers. But I think building one W6TC design pretty much as is
would offer an easier start.

Walt
KJ4KV