RE: Orbit Radio
ACL Digilog
Bonner Digimite 8 & 4
C&S Digicon II
Controlaire Digital Proportional
Dee Bee Quadruplex CL5
F&M Digital-5
Kraft KP-6
E.K. Logitrol 5 & 7
Micro Avionics
MIN-X Astromite
Orbit 7-14 & 4-8
PCS (Proportional Control Systems)
A list of proportional systems in the 1966 RCM Annual Proportional roundup. There were a few other systems at the time. A period Kraft ad mentions that there were a total of 19 proportional manufacturers at the time.
Of these systems there were several significant designs and developments by different companies.
Bonner was escapements and reed servos from the early 50's to early 60's, so they were very well known. Howard Bonner won the nats in 1956 with the "Smog Hog" using a 5 channel CG Electronics radio. For those who don't know, 5 channel then was left, right, up, down, and throttle change high to low to high, etc. CG Electronics later became C&S (Bill Cannon).
The Bonner Digimite 8 used a slightly odd pulse scheme of double pulses to start and stop the pulse width for each servo. It was also quite bulky since it incorporated "fail safe" which doubled the component count, thus cutting the reliability in half. Remember this was the day before commerical intergrated circuits.
Orbit was quite well know for reed radios, starting around '57 with an 8 channel system. This was in the dark days of tube transmitters and tube receivers with maybe a transistor or two. Bob Dunham won the Nats in '57 with a Smog Hog with ailerons added to the Bonner design, and then in '58 with the new "Astro Hog" which brought on the low wing design to pattern competition. When proportional radio finally arrive, Orbit bought a analog proportional design and released it with their PS-1 servo. This may have been the first plastic cased servo. The analog radio was fading fast, as the Doug Spreng invented digital servo set the standard for the next 40 years. So Orbit came out with the 7-14 and 4-8 digital radios (a reed mindset in nomenclature) with the PS-2 servo that combined both a linear output with a rotary output. This servo set the standard from '65 to '67 with many others using it in their systems. Orbit was also the first radio system to use integrated circuits.
Doug Spreng and Don Mathes developed the first commerical digital proportional system, call the Digicon. It had problems with the receiver due to the pulse scheme, since each channel that was on for a period was followed by a long period that was off, so the receiver was open to noise - either RF or electrical. However about this same time the solution was developed by Frank Hoover of F&M Electronics. What he developed in encoding is still used today, which was a narrow off pulse to the carrier to show the edge of each pulse. With the narrow off pulse, the receiver was more immune to noise, since the AGC circuits had a nearly continuous signal. His Digital-5 radio also had failsafe circuitry.
Mathes, Spreng, and Jerry Pullen worked at various times for Kraft Systems. Phil Kraft was a very talented experimenter that developed RC radios (he wasn't an engineer) from the late 50's. Kraft and Pullen built a large number of digital designs going back as early as '63. But they sold very few because of the high standards of Kraft, possibly to limit exposure and risk. But after Mathes became involved, Kraft release a system without failsafe, both cutting the cost while doubling reliability. Kraft became the gold standard, and by 1968 came to dominate the industry with the famous Kraft Gold Medal radio along with their new KPS-9 and KPS-10 servos. They were also one of the first companies to use 4 cell nicad battery packs. Many of the earlier radios had 7 cell batteries with multiple taps for different voltages required by servo motors and circuity voltage bias. Naturally, some cell were drained faster than others.
E.K. radio was Elliot and Krause. Bob Elliot designed the amplifier for the Bonner Transmite servo, which was important as it started the transistion toward cheap gain circuits in RC equipment and also because it eliminated relays in the reed receivers. Relays were necessary before, because before transistor were cheap and available, amplifier gain was both expensive (took a lot of batteries to operate tube circuits) and bulky. Anyway, E.K. built a very nice radio and soon used the Orbit servo PS-2 mechanics. Significant developments at E.K. was the bridged servo amplifier which eliminated the need for a center tapped battery pack. Anybody that flew center tapped radios knew that if a cell died, or lost power, you might move a servo one direction, but not be able to move it back to center. This usually showed up as a spirl dive. This happen to an Orbit radio of mine in my first RC airplane - a Falcon 56. The other big developement from EK was the dual conversion receiver.
Mathes also started Micro Avionics, which was simular in design to the Kraft and Orbit radios. Started with the Orbit PS-2 servo and control sticks.
Kraft started PCS which was a repackage Kraft with fewer options. Kraft also sold a design to Heathkit for really low bucks, which strangely enough advertised the new Kraft KPS-9 servo before Kraft did. Kraft actually sold some Kraft KP-4 and KP-6 radios (Kraft Custom) with KPS-9 servo replacing the less reliable KPS-7 before the introduction of the Gold Medal series.
Well, that's all that comes to mind right now. 1964-66 was really a turning point in RC radio development. If you already knew all of this, it's a trip down memory lane. If you got one of these radios, I do a little collecting so keep me in mind. For those unfortunate people who expect their radios to work everytime - Welcome newbie.