Scott Dorsey wrote:
Chuck Harris wrote:

The Swan design was very competent, but very much driven by cost.
That said, it is sort of odd that they used the fancy, but expensive,
7360 balanced modulator tube.


That's the sheet-beam tube? Those things actually reduced the cost of
a design because they eliminated a whole slew of parts. Later on there
were a bunch of cheap ones designed for chroma detectors in TV sets, but
at first there was only one.
--scott


I've only heard of them being used because of their extremely good
carrier suppression. They provide on the order of 60dB of carrier
suppression, as compared to a typical balanced modulator which gives
only 30dB. When used in conjunction with a crystal, or mechanical
filter, the 7360 can achieve 80dB of carrier suppression.

I can see that they would provide some reduction in parts, they are
capable of oscillating, but Swan didn't use it that way. I think
they could have achieved a greater cost savings using 4 matched
diodes in a ring modulator configuration.

-Chuck