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SSB
THE SINGLE SIDEBAND
REVOLUTION
By Forest Cummings, W5LQU (ex W0WKW)
A LITTLE HISTORY
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Think back to the early 1950s. No transistors, internet, computers or
transceivers. AM was the voice mode of ham radio along with many
heterodynes, selective fading, and 6 KHz bandwidth. Collins
Amateur radio equipment then was the 32V-3, 75A-3, and the KW-1
But, Collins realized that single sideband was coming. There were
some commercial users, and when I joined Collins in 1953, there was
already a SSB Study in progress. A special group was investigating
the Techniques and Requirements for SSB
SSB had no carrier, required only 3 KHz bandwidth, and provided
about 9 to 12 dB increase in talk power for a given power amplifier
But, SSB required stable frequencies and very good filters.
Collins had both; the PTO and Mechanical Filters
SSB REQUIREMENTS
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Collins studied SSB and reported on Techniques and Requirements needed
for SSB then used Ham Radio for SSB development : the KWS-1 and 75A-4.
Key Factors for SSB were:
Stability of the VFO and Selectivity (PTO and Mechanical Filters)
Balanced Modulators and Product Detectors
System Linearity of mixers and amplifiers
Linear Power Amplifiers and intermodulation distortion
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THE REPORT ON SINGLE
SIDEBAND
SSB AND COMPETITION
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Central Electronics had marketed a 10 watt SSB exciter (10A) and the
sideband slicer using a phasing method of generating the SSB signal. They
called the sidebands 1 and 2. And Hams were using SSB very successfully.
The Military (SAC) needed reliable long range communication for
their operation in the polar regions (Cold War). Their interest in SSB
precipitated several competitive modes to be proposed. Warren and I
spent many hours on the road and at various meetings promoting the
Collins SSB suppressed carrier approach
Double Sideband Suppressed Carrier
Single Sideband Reduced or Pilot Carrier
Clip and restore SSB to utilize AM Transmitters
Collins Single Sideband Suppressed Carrier
“QUA” (I HAVE NEWS OF……)
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“QUA” (I HAVE NEWS OF…...)
HAM HISTORY:
Over the years, the military and the electronics industry have often drawn on the ingenuity of radio amateurs
to improve designs or solve problems. Hams provided the keystone for the development of modern military
communication equipment, for example. In the 1950s, the Air Force needed to convert its long-range
communication from Morse code to voice, and jet bombers had no room for skilled radio operators. At the
time, hams already were experimenting with and discovering the advantages of single sideband (SSB) voice
equipment. With SSB, hams were greatly extending the distances they could transmit.
Air Force Generals Curtis LeMay and Francis ―Butch Griswold, both radio amateurs, hatched an experiment
that used ham radio equipment at the Strategic Air Command headquarters. Using an SSB station in an aircraft
flying around the world, LeMay and Griswold were able to stay in touch with Offutt Air Force Base in Nebraska
from around the globe. The easy modification of this ham radio equipment to meet military requirements saved
the government millions of dollars in research costs.
Brief exerpt from: The ARRL Handbook for Radio Communications, 2011
THE SSB EXPERIMENT
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Use “Ham Radio” (KWS-1 and 75A-4) to test it out
Fly them in a SAC aircraft over the polar and Pacific Ocean regions
and also have them at the SAC base in Omaha
Test communications with Offutt Air Force Base (SAC)
in Omaha and “Hams” all over the world
THIS IS THE PLANE
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A C-97 Aircraft with Collins 618S 100watt AM Transmitters
(A B-29 from WW2 converted for passenger service)
KWS-1 AMATEUR TRANSMITTER
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The KWS-1 in March 1956
THE KWS-1 TRANSMITTER
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KWS-1 RF Unit Po = 600 watts
(same size as the 75A-4)
HV & LV Power Supplies
and Blower (2000v @ 500mA)
Contains 26 vacuum tubes
HERE’S HOW WE DID IT
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The QSL Card
Willie, Butch & Art
THE FLIGHT PLAN
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THE “HAM” INSTALLATION
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A KWS-1
and
2 75A-4s
THE OPERATING POSITION
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THE ANTENNA COUPLER
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A manually tuned
High Power (180L)
Antenna Coupler
THE FINAL ADJUSTMENTS
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Do you recognize this guy
tweaking up the 75A-4?
IN FLIGHT OPERATION
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Arthur Collins
Butch Griswold
Melville Grosvenor
Nat Geographic
THE FLIGHT RESULTS
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The flight was a great success and proved beyond a doubt that SSB was a
superior mode of long range communication, especially in the in the
polar latitudes
1. March 25 – April 3, 1956
71 hours flight time - over 1000 contacts
Omaha - Alaska – Tokyo – Okinawa - Guam – San Francisco - Omaha
2. June 29 - July 7, 1956 42 hours flight time - over 1200 contacts
Omaha - Andrews – Goose Bay – Thule – Alaska – California – Omaha
made contact with National Geophysical Year group at the South Pole
COLLINS SSB EQUIPMENT
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As a result of the SSB experiments, Collins developed many SSB units for
the Military, Hams, and Commercial users
Military: ARC-58, 1 KW aircraft transceiver, 10KW PA, 45KW PA
(Modified KWS-1s and 75A-4s to military frequencies) and large
Billboard Antennas. This was the “Birdcall” project. Collins had a
station at Cedar Rapids called “Liberty”
Ham Rigs: KWS-1,75A-4,KWM-1,KWM-2,
32S-1,75S-1,30L-1,30S-1,KWM 380
Commercial / Military: 618T-1,2,3 400 watt PEP SSB Transceiver was
Very successful and Collins produced over 80,000 of these units over
many years
EPILOGUE
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It was a really fun and interesting time
to be involved in the SSB Revolution !