Tech's Filing Cabinet Miscellaneous General Electric RCA Tube Tech Semi Tech Audio Radio

Scanned articles covering radio topics. Unless otherwise noted, these scans were done by John Atwood. Articles marked "*" were extracted from americanradiohistory.com scans. Listed chronologically.

Armstrong 1915 Some Recent Developments in the Audion Receiver - A summary of Armstrong's receiver designs using the audion, as presented in the Proceeding of the I.R.E. It is followed by a "discussion" (by letter) between Armstrong and Lee DeForest. Reading this, it is clear that: a.) DeForest's concept of how the audion works is clouded by misconceptions and random behavior, and b.) Armstrong's conception is crystal-clear and accurate. Scan by Google.

Armstrong 1924 The Superheterodyne - Its Origin, Development and Some Recent Improvements * - Review of the invention of the superheterodyne receiver and efforts to cost-reduce it and commercialize it.

Crosby 1939 Communication by Phase Modulation * - Implementation and performance tests on phase modulation. Not much used at the time, but forms the basis of the phasing system of SSB and the I-Q modulation used in modern communications systems.

Eastman & Woodward 1941 Binaural Transmission on a Single Channel * - Amplitude and phase modulation of the same channel - essentially the I-Q system used in modern communications systems.

Batcher 1945 Thermal Stability in Receiver Oscillators-I and Batcher 1945 Thermal Stability in Receiver Oscillators-II * - A good tutorial on what causes oscillator drift and how to minimize or compensate this effect.

QST RCA 1947 Transmitting Ratings on Receiver Tubes - A table of class-C transmitter ratings for the 6AG7, 6AK6, 6AQ5, 6C4, 6F6, 6L6, 6N7, 6V6GT, and 12AU7. These are only for amateur use, and are not listed in regular tube manuals or data sheets. Gives screen-grid amplification factors and capacitances.

Goodman 1947 How Sensitive is Your Receiver? - Using a diode noise generator for measuring the noise figure of a receiver front-end. This article is based on information directly from the MIT Rad Lab.

QST 1948 A High-Stability Oscillator Circuit - Details on a high-stability VFO circuit first described by Clapp in the Proceedings of the I.R.E.

QST 1948 The Clapp High-Stability Cicuit - Comments from Clapp himself on the differences between his circuit and an early VFO by Seiler (1941).

Tapley 1949 Some Notes on the Clapp Oscillator - Practical design notes on implementing the Clapp oscillator.

Early FM

Armstrong 1936 A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation * - From Proceedings of the IRE (Vol. 24, No. 5, May 1936), a long (52 page) article by Armstrong on his development of FM. Extensive coverage of various tests from 1933 to 1935, including experiments of multiplexing a second channel (either audio or facsimile) above the base-band signal. Very interesting reading!

Roder 1936 Noise in Frequency Modulation * - A theoretical explanation of how FM improves the signal-to-noise ratio.

Electronics 1936 High Power Frequency Modulation * - Report on Armstrong's proposal to set up a 40 KW FM station.

Electronics Fink 1939 Frequency Modulation Demonstrated * - Demonstration of Armstrong's two experimental FM stations: 42.8 MHz in Apine, N.J. and 110 MHz in Yonkers, N.Y. The 400 foot tower in Alpine still stands today and was used to host TV transmitting antennas after the fall of the World Trade Center in 2001.

Day 1939 A Receiver for Frequency Modulation - An article by J.R. Day of the Marcellus Hartley Laboratories, Columbia University (where Armstrong developed FM) on "The first published data for the construction of an f-m receiver". From the June 1939 issue of Electronics.

Electronics Fink 1939 Frequency Modulated Transmitters * - FM broadcasting moves from being a one man (Armstrong) show towards being a commercial reality. Twenty-five stations are either on the air or have construction permits. The two transmitter manufacturers are R.E.L. and General Electric.

Armstrong 1940 Evolution of Frequency Modulation - from the Dec. 1940 issue of Electrical Engineering, the journal of the American Institute of Electrical Engineers (A.I.E.E). A good overview of the growth of FM broadcasting by the inventor himself.

Walter 1940 Design Notes on a Frequency Modulation Receptor - A pre-war FM tuner, available as a kit from Meissner. From May, 1940 issue of Radio News.

Landon 1941 Impulse Noise in FM Reception * - Experiments are done to evaluate the impact of impulse noise in an FM receiver. Takeaways: perfect symmetry is important, the signal must be tuned to the center of the channel, limiters help when symmetry or center tuning are not perfect.

Toombs 1941 The Radio Battle of 1941 FM vs AM * - From Radio News, March 1941. Investigative reporting on the battle between the entrenched AM interests and the new FM upstarts. On the AM side are the existing broadcasters, RCA, and AT&T. On the FM side are the FCC and its chairman, J.L. Fly, a new generation of broadcasters, manufactureres such as GE, Zenith, Stromberg-Carlson, etc, and, of course, Major Armstrong. This article clearly sets up the players and conflicts that will come into play when Paul Porter becomes FCC chairman and the band allocations are changed in late 1944.

Goldman 1941 FM Noise and Interference * - A theoretical treatment of noise, both random and impulsive in an FM receiver.

Wheeler 1942 Common-Channel Interference Between Two Frequency-Modulated Signals - A theoretical analysis of what happens when two different FM signals occupy the same channel. Although this term is not used, Wheeler essentially explains "capture ratio".

Electronics 1942 FM Network * - The cover of Electronics from Feb. 1942. These stations are linked by receiving then retransmitting programs from a distant station. The noise-reduction capabilities of FM permit this. No more expensive and low-fidelity rented lines from AT&T! The stations in Massachusetts and New Hampshire are part of the Yankee Network.

Hund 1942 Reactance Tubes in FM Applications * - Details on how reactance tube circuits are used as modulators in FM transmitters.

Rodgers 1943 Tuning Indicators and Circuits for Frequency-Modulation Receivers - Various ways of using a conventional tuning eye tube to accurately tune an FM receiver. After the war, GE came out with the 6AL7GT designed specifically to indicate FM tuning.

Radio-Craft 1944 FM Expansion Rapid - 44 stations on the air on the old 44-49 Mc. band. These were essentially frozen due to the war-time construction freeze, but it was noted that there were 154 applications pending. All the transmitters, antennas, and listener's receivers would become obsolete with the shift to the 88-108 MHz band in 1945.

Brown 1944 FM and Its Post-War Future * - An optimistic analysis of the expansion of FM broadcasting after the war. Assumptions: existing 42-50 Mc band with possible extentions in frequency, "super-power" stations covering broad areas. The surprise move to 88-108 Mc will nuke this analysis. Note that the author is from Zenith, which fought the move to 88-108 Mc the hardest.

Martin 1944 FM Reciever Design Considerations * - Stromberg-Carlson weighs-in on how to optimize consumer FM radio design. Low-band, of course.

Electronics 1944 RTPB on FM * - The RTPB (Radio Technical Planning Board) generated recommendations to the FCC. They propose expanding the 42-50 Mc band, keeping the 75 Kc deviation, use horizontal polarization. The surprise move to 88-108 Mc ignored this.

Parker 1944 Design of Intermediate-Frequency System for Frequency-Modulated Recievers - The design of an FM IF system using 8.25 mc instead of the then-common 4.3 mc. After the war, when the FM band was moved to 88-108 mc, the FM IF frequency was standardized on 10.7 mc.

Electronics December 1944 A Report on the FCC Frequency Allocation Hearing - (Note: go to page 92 of the magazine, page 96 of the pdf). This is a report on the hearings for docket 6651 - the 10 kc to 30,000 Mc post-war frequency allocations. The relevant part for the history of FM broadcasting is the sudden move of the FM band to 88 Mc. This change was supported by the new FCC chairman, Paul Porter, and the testimony of Dr. K.A. Norton and Dr. L.P. Wheeler who claimed that sporadic E-layer skip and tropospheric bursts would harm FM reception in the low band. This was based on studies of military communications whose data was classified. It later turned-out that this study was bogus - see the De Mars 1945 article below. Also, Paul Kesten, vice president of CBS, pushed for a "single-market plan" to restrict FM coverage to similar commercial markets as AM. This would eliminate the super-power FM stations and crimp the ability to do over-the-air networking.

The implications of this hearing are well-described in chapter 10 of Scott Wooley's recent book The Network (Ecco Press, 2016). This change in frequency allocation obsoleted over 100 million dollars of transmitting and receiving equipment, and, in fact crippled FM up through the late 1950s. There was speculation that this change was orchestrated by the NAB (National Association of Broadcasters) and its AM broadcasters, who viewed FM as potential competition. AT&T also was behind this, since they stood to loose the lucrative leased line business that enabled AM networking. See the March 1941 Radio News article above for more details. Woolley's book also describes other examples of "regulatory capture" of the FCC. The problem is that when these cases go to court, the FCC is considered, by definition, the experts in this technical area.

I did not extract and clean-up this article, since the quality of the original scan was below my quality standards, hence the direct link to the AmericanRadioHistory magazine file. If I can find a better quality scan, I will link to it.

Arguimbau 1945 Discriminator Linearity * - How to design the most linear Foster-Seely discriminator.

Electronic Industries 1945 IRE Stages Largest Technical Meeting * - Summary of the Winter Technical Meeting of the Institute of Radio Engineers (IRE) on January 24 to 27, 1945. This was dominated by the controversy of moving the FM broadcast band "upstairs".

Electronic Industries 1945 Allocations Nearer * - More on the FM move "upstairs", as well as proposed television allocations. Includes tables showing units and dollars of installed FM receivers ($76 milliion) and transmitters/antennas ($1.9 million) which would be made obsolete by the move.

Electronics 1945 FCC Places FM in 88-106 Mc Band * - The move to the FM high band is now a fait accompli. 106-108 Mc was allocated to facsimile service, but this never materialized, so it later passed to commercial FM.

Johnson 1945 Interference in FM Receivers * - More theory and experiments on interference reduction in FM broadcasting.

De Mars 1945 Discussion of the Secret FM Hearing - As described in the Dec. 1944 Electronics article above, the justification for moving the FM band from 42-50 mc to 88-106 mc was based on Prof. Norton's claim of excessive F2-layer skywave interference on the lower band. His sources were military classified, so couldn't be discussed at the public meeting. A subsequent closed-door meeting was held on March 12 and 13, 1945 to review the classified information. This quote from the introduction to the article summarizes what happened:

"One of those conclusions was that F2-layer transmission would go twice as high in frequency as had been considered possible by others. Much publicity was given to this finding as a reason for shifting FM broadcasting to 88 to 108 mc. At the Secret Hearing, it was determined that the frequency increase was not 100% but 7%. Nevertheless, the Commission suppressed this information, and continued to offer the erroneous conclusion as a reason for shifting the FM band."

The fix was in - the FCC was clearly complicit in hobbling FM broadcasting.

Meyers 1946 Nonlinearity in Frequency-Modulation Radio Systems Due to Multipath Propagation - A theoretical study of FM multipath distortion. It is worst when the path delay difference is large and the signal strength is similar.

Electronics McKenzie 1947 FM Chain Broadcasting * - The idea of chain broadcsting or over-the-air networking is revived. The Continental Network used both leased lines (8 kc) and radio relays and other possible networks are explored. Good history of pre-war over-the-air networking.

Electronics McKenzie 1948 Fremodyne FM Receivers * - The Fremodyne FM detector is a clever circuit developed by the Hazeltine Labs to be an inexpensive way to add FM to a regular receiver. It uses a single 12AT7 dual triode as both a local oscillator, converter, and superregenerative detector, using an IF frequency of 21.75 mc. This article describes extensive tests of various FM receivers, including two with the Fremodydne circuit. The Freodyne uses slope detection, so tuning for minimum noise maximizes distortion. The superregenerative detection has no "capture" to reject interfering signals. The radiated interference is bad enough that two Fremodyne set 100 feet apart interfere with each other. The only advantage over AM was that ignition and other local noise sources are less. So: simple - yes, decent performance - no.

Radio-Craft 1948 FM Station List - All the commercial FM stations on the air in early 1948 (non-commercial/educational not included). Note that Armstrong's W2XMN in Alpine, N.J. is the only one still on the "low band".

Smith & Fouty 1948 Circular Polarization in FM Broadcasting * - By using a circularly-polarized transmitting antenna, a higher received signal level for a randomly-placed receiving antenna can be obtained. The FCC allows twice the transmitted power level with circular polarization. Circular polarization became important when FM car radios with vertical polarization came into use. Circular polarization is standard today.

Day 1948 Serrasoid FM Modulator * - The phasing method of FM generation, used by Armstrong, Raytheon, GE, and others requires no troublesome phase-locked loops, but the early phase modulators could only generate limited phase shifts without distortion. This required many frequency multiplier stages. The Serrasoid phase modulator used a sawtooth wave and threshold detector to give much higher phase shifts with low distortion. This was developed by R.E.L., but was also used by Gates. A nice endorsment by Armstrong is included.

Arguimbau & Granlund 1949 Sky-Wave F-M Receiver - The idea of sky-wave FM transmission is investigated. A very high performance receiver for this purpose is described.

Early SSB

Hartley 1923 Relations of Carrier and Side-Bands in Radio Transmission - An article by Hartley of AT&T in the Bell System Technical Journal (Vol. 2, No. 2, April 1923) on the mathematical basis of sidebands in radio communications. This article also appeared in the Feb. 1923 issue of the Proceedings of the IRE.

Carson 1923 Signal-to-Static Interference Ratio in Radio Telephony * - A short article in the Proceedings of the IRE (Vol. 11, No. 3, June 1923) by Carson of AT&T on the signal to noise improvement of SSB vs DSB over and above the bandwidth reduction.

Heising 1924 Production of Single-Sideband for Trans-Atlantic Radio Telephony * - Article from the Proceedings of the IRE on the use of SSB in the first trans-Atlantic telephone links by AT&T with the help of RCA. Long-wavelengths (low frequencies) were used. SSB had been previously been used in carrier telephony to expand the number of voice channels that could be sent over open-wire toll lines. Until the first trans-Atlantic telephone cable (TAT-1) in 1956, all trans-Atlantic calls went over SSB radio.

Reeves 1931 The Single Side-Band System Applied to Short Wavelengths * - IT&T develops an SSB telephone system using a pilot frequency to synchonize the receiver with the transmitter. This was the first system to use short waves for trans-atlantic service. Tests were run from Madrid to Paris and Buenos Aires to Madrid on 15 meters.

Honnell 1945 Single-Sideband Generator * - An SSB generator for an 8 Kc power line voice and telemetry channel. Not a normal voice system, but the earliest example I've found for generating SSB by the phasing system.

Dome 1946 Wideband Phase Shift Networks * - Dome's original article from Electronics on designing constant phase-shift networks, crucial for the implementation of phasing SSB systems.

Goodman 1948 What is Single-Sideband Telephony? - A brief overview of SSB. QST finally gets serious about covering SSB, mainly motivated by reducing crowding on the phone bands.

Villard Jr 1948 Single-Sideband Operating Tests - Instructions on how to receive SSB and then descriptions of the first SSB QSOs from the Stanford University campus.

Nichols 1948 A Single-Sideband Transmitter for Amateur Operation - A rather elaborate SSB transmitter using the filter method. Really low IF: 9 to 11.6 KHz.

Norgaard 1948 What About SSB - Good overview of the implementation and benefits of SSB. Note that QST is still calling SSB "s.s.s.c" - Single Sideband Supressed Carrier.

Norgaard 1948 A New Approach to SSB - Norgaard, from General Electric, introduces the "Phasing" method of generating SSB. Quite a few early SSB transmitters used phasing, but eventually the filter method won.

Villard Jr & Thompson 1948 A Detector for SSB Reception - Using the phasing method for receiving SSB signals. Converters using this technique also work well for CW and AM on older receivers. All modern SDRs (Software-Defined Receivers) and mobile phones use this technique.

Dawley 1948 An SSSC Transmitting Adapter - A complete SSB transmitter using the phasing technique. Four 6L6s as a pair of balanced modulators put out about 25 watts.

Rosentreter 1948 Single-Signal Single-Sideband Adaptor * - An external SSB receiving adaptor using the phasing technique. Includes a locked oscillator for exalted-carrier reception of AM. This unit is also described in GE's Sideband Handbook.

Polkinghorn 1948 Commercial Single Sideband Radiotelephone Systems * - Now that SSB is beginning to see commercial and amateur use, Bell Labs (AT&T) puts out a good article on the history of SSB, centered on AT&T's developments. Sorry for the the poor scan quality, but this is the best I could do with the AmericanRadioHistory.com source.

Goodman 1949 The Basic Phone Exciter - A phasing-type exciter design to put out single sideband (SSB), double sideband (DSB), or phasing modulation (PM).

Reque 1949 Linear RF Amplifiers - Reque, of General Electric, revives the idea of power linear amplifiers, essential for SSB work.

Berry 1949 A Filter Design for the SSB Transmitter - An exciter using the filter method. The filter is hand-made using toroids, with an IF of 17 to 20 KHz.

Darlington 1950 Realization of a Constant Phase Difference - A paper from the Bell System Technical Journal on how to design constant-phase-difference networks, such as used in phasing SSB systems. Quite theoretical.