[Collins] AOR DDS-2A Revisited

[Dr. Gerald N. Johnson, electrical engineer]

I think Art would have liked the digital radio. In 1963-4, the tale
around the department was that he wanted the next ham rig to be
expensive and to be remote controlled over a digital serial cable. That
way the radio could be in the trunk, basement, or closet while the
operator had a small interface with a simple cable (single coax I don't
know) at his easy chair or driver's position or cockpit. Surely that
radio would have been completely digital for frequency control much like
the 718T that was eventually sold to military and commercial services
including airlines. Though the 718T had a parallel control cable with
many wires.

In 1964, the only practical synthesizer was of the mixer/divider type as
accomplished in the HP5100/5110 set and neither compact nor expensive.
The performance of the set is very good, though it takes a STURDY rack
to hold the total of about 27" of panels that weigh about 100 pounds,
but the cost of the rack was minuscule compared to the $15,000 list
price from HP. I had a chance to use one on a coil measuring project,
but rejected it because the amplitude between adjacent frequencies
varied too much for my instrumentation. Since then I found one missing
the cables (about 30 cables between the units) for much less than
pennies on the dollar and fine that with less critical instrumentation
it works find for measuring crystal Q.

In 1964, integrated circuits families didn't exist, computers and logic
were all still created with discrete components, mostly transistors and
resistors with a few capacitor thrown in. The phase locked loop was
known, and used for the programmable frequency multiplier in the 821A-1
though that simple 1x, 2x, 4x, 8x multiplier with discrete transistor
dividers and phase detector fit a space about the size of a R-390
receiver even though it used 1/8th watt resistors that Bruene didn't
think appropriate in a transmitter of that size.

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.