GB> Looking for info on beam-deflection tube mixers

[John Kolb]

On Wed, 6 May 1998, Ben Bradley wrote:

> At 12:40 PM 5/6/98 -0700, Chris Trask wrote:
> >On Wed, 6 May 1998, michael silva wrote:
> >
> >> I'm thinking out my next project, a portable CW transceiver, and I'd
> >> like to know what you all know about using beam-deflection tubes (not
> >> the 7360 due to its cost, but I've got some 6ME8s floating around) as
> >
> >        Another envelope is the 6AR8.  These tubes were very susceptible
>
>    I haven't heard of this type of tube (and I'm not a stranger to these
> things, I remember a couple decades ago reading about what was most probably
> the 7360 in an SSB/DSB exciter circuit). Do you have any type numbers? Would
> any be in an RCA Receiving manual, or are these considered 'transmitting'
> types (as I imagine the 7360 is)?

Here's what I wrote elsewhere the last time the topic
came up.

Discussions on the boatanchors mail list last Aug indicated
that the 6JH8 and the 6AR8 might be substitutes for the 7360.
Jack Hill, the listowner, reported that he had substituted the
6JH8 for the 7360 in a HT-32 and it worked even better.

I have a 51J-3, which I added a 7360 product detector to
many, many years ago, replacing the 12AX7 used for AM detection
and IF output isolation. I don't have the schematic of the change
any more, and it's too crowded to trace out, but it doesn't match
any of the 7360 articles I currently have. I recently made a
plug in adapter to plug the 6JH8 tube into the 7360 socket, since
the tubes have a different pin-out. In my circuit the 6JH8 works
as well as the 7360, withoug changing any component values. Pin 5
of the filiment pair must be grounded, since that pin also contains
the internal connection to Grid 2 and an internal shield. If you
ground pin 4 instead, a loud 60 Hz hum will result.

There are a large number of other possible replacements.
In the Aug 59 CQ magazine, an article by my old boss, Lester Earnshaw,
"A New Product Detector" details his experiences with the 6AR8
and 6BU8 as mixers, product detectors and balanced modulators.

The 6AR8 was a beam deflection tube like the 7360 and 6JH8, but the
6BU8 is called a twin pentode, and has a common cathode, G1 and
G2, but seperate G3 and plates.

Looking through the RCA and Sylvania tube manuals, I found
a number of other possible replacements for the $15 7360. These
seem to have all been widely used in TV's as color demodulators.
Check those stocks of old TV tubes.

TYPE  DESCRIPTION       BASE       OTHERS
6GS8  twin pentode       9FG       3GS8, 3BU8, 4GS8
6LE8  twin pentode       9QZ       8LE8, 10LE8, 15LE8
6ME8  beam deflection    9RU
6MK8  twin pentode       9FG       4MK8
7360  beam deflection    9KS
6BU8  twin pentode       9FG       3BU8, 3GS8, 4BU8, 4GS8
6AR8  beam deflection    9DP

And the list is not complete yet. Search those tube manuals.

John   KK6IL  jlkolb at cts.com

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