[HBR] Center position v. left mount

[Walt Hutchens]

> why not place the oscillator section where Ted wanted it, and set up
> a chain or belt mechanism between the dial and the cap?

> Hello Bill:
> I would avoid the use of those belts and try to stick with the original
> mounting schemes illustrated over the past decades.  I think you would be
> introducing an extra amount of slop and slip that would defeat the use of
> the 898 dial.   Remember, backlash is your enemy, but a good solid direct
> mechanical mounting is your best friend.

These receivers were so well designed that they're tough to improve
on.

In the case of the dial drive, you're tuning up to 500 kcs in less
than half a revolution of the tuning cap. Yet in order to tune in an
SSB signal you need to be within (say) 100 cps or one part in 5000.
You can't do that with the usual 5:1 National dial (MY hand certainly
isn't steady enough ...) but with the 6/36:1 JB or the Eddystone 898,
it's not hard at all.

But that degree of control over cap position depends on having
essentially zero backlash in the tuning setup.  No flex in the chassis
or panel, none in the shaft coupling (meaning very low torque to turn
the cap), no significant play in the dial drive ...

It is possible to rearrange the front end of an HBR but keeping the
dial output shaft perfectly aligned with the cap shaft and having both
the dial and cap mounted rigidly and with no flex between them is
essential. The easiest bet is to stick to one of the various original
layouts and I certainly wouldn't add gears, chains, or other kinds of
transmission stuff between the knob you turn and the shaft of the cap.

Rearrangement must of course also follow the rules for signal flow and
interstage coupling.

Walt
KJ4KV