[Boatanchors] new on list with old gear
Robert Nickels
ranickel at comcast.net
Wed Sep 5 20:11:55 EDT 2018
On 9/5/2018 6:28 PM, Ron VE8RT wrote:
> With respect to the Central Electronics 20A, my suspicion is that
> this was a kit that could be built without phone capability. The
> components and controls for phone operation are missing.
Rich,
The 20A is one of the first commercial SSB transmitters from the 1950s,
and played a major role in popularizing SSB. It's a classic and
deserves restoration and hopefully use on the air, where it will rival
the audio quality of any rig.
But you should begin by reading the manual so you understand what you
have and how it works. You can download it here:
http://bama.edebris.com/manuals/ce/
Basically, the 20A is a heterodyne exciter that requires an external
VFO or signal source, or a crystal for a specific frequency. Since it
generates SSB (or AM or PM) on 9 MHz, the frequency of the external VFO
must be able to mix with that to produce the desired output frequency.
The easiest solution is to use a VFO that tune in the 5 MHz range which
will cover 80 meters (9 minus 5) and 20 meters (9 plus 5). This is why
you'll see that a Command Set transmitter which was available cheaply on
the surplus market at the time was commonly used, and Central sold a kit
that added circuitry to cover the other amateur bands. Those VFOs were
quite good but not perfect, but nowadays a digital synthesizer with the
required output level can be used for stability on par with any modern rig.
The output of the 20A is typically 15-20 watts, which is plenty to drive
a linear, as it was intended to do. But I've made lots of contacts
with a"barefoot" 20A. Properly adjusted they will make very
good-sounding AM as well as SSB.
You're right in that the 20A was sold both as a kit and factory wired,
but everything required for AM, PM, and SSB phone operation was
included. If you noticed an empty octal socket in the middle of the
chassis, that's for the QT-1 which was an optional anti-trip unit for
VOX operation with a loudspeaker. Be sure the other plug-in module
that's halfway back on the left-hand side which is labelled "PS-1" is
present, because the transmitter won't work without it.
Hope this helps, as you can probably guess I love the 20A! There's a
separate list just for Central Electronics gear and lots of help
available if you need it.
73, Bob W9RAN
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