Ham Radio's Influence on the Commercial Market

THE INFLUENCE OF AMATEUR RADIO ON THE DEVELOPMENT OF
THE COMMERCIAL MARKET FOR QUARTZ PIEZOELECTRIC
RESONATORS IN THE UNITED STATES

By Patrick R. J. Brown, N7KRG

Hewlett Packard Company, Spokane Division
E. 24001 Mission Blvd., Liberty Lake, WA, USA 99019
E-Mail: Pat_Brown@HP.com or nakhla@ix.netcom.com


Article from the IEEE Proceedings of the 1996 IEEE International Frequency Control Symposium (pp. 58 - 65)
© 1996 Institute of Electrical and Electronics Engineers. This material is posted here with permission of the IEEE and the author.

Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.


CONTENTS

  • Abstract
  • Introduction
  • Historical Time Line
  • Crystal Controlled Transmitter Development
  • Company Histories
  • The Early Crystal Market
  • Summary
  • References

  • Abstract

    In the mid and late 1920s, amateur radio operators were experimenting in great numbers with crystal control of radio transmitters. At the time, most amateurs used home built transmitters made from a combination of purchased and home made parts. The use of quartz crystals by amateurs predated the first U.S. commercial broadcast station to use crystal control. Amateur radio operators were the first sizable commercial market for crystals. Many of the crystal companies of the 1920s and 1930s were founded by amateur radio operators to supply other amateurs.

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    Introduction

    The earliest history of the science of piezoelectrics, that period from 1880 to about 1917, was the era of the pure science contributors such as the Curie brothers, Voigt and Lippmann . The period from about 1917 to about 1924 was the era of the applied scientists like Langevin, Nicolson and Cady. The period from 1924 until about 1934 proved to be the decade of the amateur radio operator's contributions. During that 10 years, literally thousands, possibly tens of thousands of amateur radio operators experimented with making their own resonators and applying resonators in practical, low cost transmitting circuits. During this decade, amateur radio operators comprised the majority of the market for resonators [33]. This is a brief overview of their impact on the modern crystal industry.

    Note: The terms amateur radio operator, ham radio operator, amateur, and ham are all used interchangeably.

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    Historical Time Line

    1880

    The piezoelectric effect was discovered by brothers Pierre and Paul-Jacques Curie at the Laboratory of Mineralogy at the Sorbonne. The brothers were awarded the Plante prize in 1895 for this discovery [1].

    1881

    The Curie brothers demonstrate the converse of the piezoelectric effect. This converse of the piezoelectric effect was not foreseen by the Curies, but rather was predicted by Lippmann [1].

    1880 - 1915

    Piezoelectricity remains a specialized academic subject studied mostly in Germany and France [2].

    1917

    Professor P. Langevin working in France uses X-cut quartz plates to generate and detect compression sound waves in water. This work was directed towards detecting submarines. Along with the simultaneous and independent work of Dr. A. M. Nicolson at Bell Telephone Laboratories (who used Rochelle salts due to their greater piezoelectric sensitivity), this became the basis of SONAR [3][6].

    1918

    The first crystal (Rochelle salt) controlled oscillator is invented by A.M. Nicolson. Even though the crystal was described as a transducer used to modulate the oscillator with audio frequency sound waves, there is reason to believe that the normal resonant mechanical vibrations of the crystal controlled the radio frequency of the circuit. Future litigation pitting Nicolson against Cady was decided in Nicholson's favor, giving him the distinction of being the inventor of the piezoelectric crystal controlled RF oscillator [3].

    1919

    Dr. Cady uses a quartz crystal to control the frequency of an oscillator [6].

    1920

    Dr. Cady submits a patent application for the piezoelectric resonator describing possible applications as a resonator, a filter and as a coupler. Dr. Cady also includes a detailed description of the operation of the resonator, not realizing that Nicolson considered his oscillator to be controlled by the Rochelle salt crystal [3].

    1921

    Dr. Cady publishes a paper describing the first quartz crystal controlled RF oscillator [4].

    1923

    August E. "Augie" Miller quits the optical business in which he had developed expertise in grinding lenses. He starts a new venture selling quartz crystal blanks to amateur radio operators, becoming one of the first in this new business. Amateur radio operators are the only commercial market for piezoelectric resonators to date [6].

    1923

    The Bell Telephone Laboratory establishes a quartz crystal laboratory for advanced research [6].

    1924

    The General Electric Company establishes a quartz crystal laboratory for advanced research [6].

    1924

    In a four page article in the July 1924 issue of QST magazine [15], H.S. Shaw introduces the amateur radio community at large to quartz crystal control of radio transmitters. Included is a schematic diagram for building a crystal controlled transmitter.

    1925

    In the August 1925 issue of QST, the General Radio Company of Cambridge, Mass, offers quartz crystals finished to a specified frequency for $50.00 each. Unfinished and untested blanks are offered by A. Espositer of New York City for $4.00 each [16].

    1925

    In the November 1925 issue of QST [9], J.M. Clayton gives detailed instructions on cutting plates from a raw quartz crystal, finishing the plates to wavelength, and mounting the finished resonator.

    1926

    WEAF, New York becomes the first commercial broadcast station to use crystal control. The station was operated by the American Telephone and Telegraph Company [5]. Within a few years other commercial broadcast stations follow WEAF's lead [6].

    1934

    F.R. Lack, G.W. Willard, and I.E. Fair announce their results in the Bell System Technical Journal on a zero temperature coefficient cut called the AT-cut.

    1934

    The November 1934 issue of QST announces that Bliley Electric Company of Erie, PA, has made AT cut crystal resonators available to amateur radio operators [17].

    1936

    Amateur radio crystal control of transmitters is described as the rule rather than the exception [8].

    1939

    The U.S. Military decides to convert its radios to crystal control, starting the incredible boom years for the U .S. crystal industry [6].

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    Crystal Controlled Transmitter Development

    Practical development on economical crystal controlled transmitters was largely done by amateur radio operators. There was work going on at labs like the Radio Division of the U.S. Naval Research Laboratory, but it was more specialized.

    Why crystal control of transmitters in particular? And further, why were transmitters first? The typical tank circuits in use by amateurs before crystal control were quite simple. In general, the antenna was part of the tank circuit. When the antenna moved in the wind, the output frequency would change. This made the transmitting station difficult to copy. Typical transmitters were one tube oscillators with the antenna as part of the tank circuit.

    In addition, in a simply constructed LC tank circuit, the frequency changes significantly with temperature. The amateur radio bands were starting to see more crowding in the 1920s, hence there was significant benefit in staying on one frequency. Amateur radio operators generally found the receivers of the day to be quite serviceable and their desire was to improve their transmitters. Crystal control offered the desired improvement. The excitement for the new technique is captured in this quote of the technical editor introducing the July 1924 article in QST about Oscillating Crystals [15]. "Can you imagine a transmitter that never shifts its wave[length] even a hundredth of a meter? Can you imagine making a schedule for 96.38 meters and knowing that you will be right on that wave[length] and knowing that the other man will be tuned right to you? And can you imagine getting from the receiving operator a report during the hours of operation the beat note in the [ear]phones never changed even a particle? These things are possible with the oscillating crystal."

    Amateur radio operators in the teens, twenties and into the 1930s built most of their equipment. They also built a number of the parts they used. Amateur radio operators were motivated by a number of factors, among which was the pride of working in the state of the art where there was no commercial, non-ham business. Amateurs also prided themselves in building for minimum cost. Ready-built equipment was scarce, and if it could be obtained it was well beyond the financial means of all but a few. This desire to build for minimum cost is a major differentiator between the amateur development and the R&D work done in places like the U.S. Naval Research Labs. A practical side to amateur practice of building their own parts was the lack of radio stores in much of the U.S.

    Finished quartz crystal plates were also very expensive. In August of 1925 [16], General Radio Company offered crystals for sale at the price of $35 finished to an approximate frequency and $50 finished to an exact frequency specified by the purchaser. This was indeed a very large amount of money in 1925.

    As a result, in the mid-1920s many amateur radio operators cut and finished their own quartz resonators using the instructions in QST magazine. Articles with detailed instructions for cutting and finishing crystal resonators appeared in the November 1925 issue [9], May 1927 issue [10], January 1928 issue [11], April 1930 issue [12], January 1935 issue [13], and the February 1935 issue [14]. These earlier articles described how to cut a plate out of a faceted crystal using carborundum powder on the back of a hacksaw and how to finish it on a piece of plate glass with carborundum powder. The later articles progressed to automated methods using power driven saw blades and motor driven laps with carriers for 8 blanks.

    In the mid and late-1920s, most purchased crystal resonators did not come with holders. Holders could be purchased for an additional cost or could be made at home. Home cut resonators typically went into home made holders. The amateur radio magazines catered to the ham's desire to home build. No less than seven different plans for building your own crystal holder appeared in the pages of QST [7] magazine between 1924 and 1929. In the July 1926 issue of QST, John M. Clayton wrote a detailed article on the subject titled "Quartz Crystal Mountings" [18].

    The first QST article with a schematic for constructing a crystal controlled transmitter was in the July 1924 issue [15]. In 1925, a total of four schematics for crystal controlled transmitters were presented in QST magazine [7]. Nine more schematics were presented in 1926, as well as a further nine in 1927. Clearly, a great deal of development on the subject of crystal control was going on in the amateur radio community.

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    Company Histories

    Amateur radio activities were the genesis of many crystal companies. From the mid-1920s through the mid-1930s amateurs were the largest commercial market for quartz resonators.

    One of the most fertile parts of the United States for quartz crystal and oscillator work today is the area of south central Pennsylvania, around the town of Carlisle. This concentration is due to the work of three amateur radio operators who were students at Dickinson College, their professor, and a plant engineer with a seemingly unrelated hobby.

    In 1930, Dickinson College hired Dr. W.A. Parlin away from John Hopkins University to head the Physics Department. Dr. Parlin stimulated interest in starting an amateur radio station at Dickinson and enlisted students Howard Bair, Charles Fagan, and Edward Minnich. The first amateur radio station at Dickinson College had the call sign of W3YC. The station was a success. In their contact with other radio amateurs, especially with the amateurs at Penn State, they learned of the work going on with quartz crystal plates for frequency control of transmitters. They desired to get a crystal for their transmitter. The cost of finished crystals in 1930 was still quite high, on the order of $5 to $9 dollars each. Their financial means were modest. The situation resolved itself when Edward Minnich's father, C.O. Minnich, helped to buy a crystal for the club station. After the experience of using this crystal and probably also influenced by the articles in QST magazine [7], the students decided to make more crystals rather than buy them [19]. Dr. Parlin taught the students how to orient the raw quartz. Using the available literature and Dr. Parlin's help, the students each produced their first crystal in 1931 or 1932 [20].

    Mr. Grover Hunt was employed as a plant engineer at Dickinson College. Mr. Hunt, with the assistance of his brother-in-law, Mr. P. Reynold Hoffman, designed and set up a muck saw to cut petrified wood into a chess set. Hunt had collected this petrified (agatized) wood on the way back from a vacation in California. Mr. Hunt eventually lost interest in the chess set project, but, he saw the commercial potential in selling quartz resonators. He had the three physics students teach him how to cut resonators. He then started cutting and selling quartz resonators commercially. Soon, through his own studies, he surpassed the knowledge of the three students. Charles Fagan advertised for Grover Hunt in QST magazine [7], probably in 1933 or 1934. Grover Hunt was the first to produce and sell crystals in the Carlisle area.

    Grover Hunt and Linwood Gagne, formerly the chief radio engineer for the Goodyear Blimp Company of Akron, Ohio, formed Standard Piezo in 1935. This was the first crystal company in the Carisle area and the father of the crystal industry around Carisle. The follow-on companies included Oak Frequency Control (formerly McCoy Electronics), Piezo Crystal Company, Reeves-Hoffman, P.R. Hoffman, and many others.

    Another early company is the Bliley Electric Company. The company's history is tightly coupled to F. Dawson Bliley's love for amateur radio. Mr. Bliley was first licensed as an amateur radio operator with the station call sign 8AGR in September of 1920, at the age of 14 [21]. While a student at the University of Pittsburgh, he purchased a steel saw, which he used with a carborundum slurry to cut quartz resonators for his own use and the use of his friends. He evidently was quite successful and the word spread that he was proficient at making resonators. He soon had many amateurs asking him to produce crystals for them. This was a bright spot in Mr. Bliley's life as he graduated from the University of Pittsburgh in June 1929. A spot that was not so bright was the stock market crash some four months later. Job prospects for a newly graduated Electrical Engineer, even one as founded in hands-on radio work as Bliley, were bleak. With financing and guidance from his father, Bliley made a part of this radio interests into his living, and in early 1930 founded the Bliley Electric Company. This was a company founded by an amateur radio operator to provide crystals to amateur radio operators.

    The business grew and prospered serving the amateur community. Bliley Electric went on to be very innovative in a number of areas. In 1935, while working for Bliley, John Wolfskill was involved in work to increase the maximum practical frequency quartz resonators beyond the then current 9 or 10 MHz. In the course of this work, Wolfskill discovered the overtone effect in quartz resonators. He submitted a patent application, and after a legal challenge by the Radio Corporation of America, Wolfskill and Bliley's were awarded the patent for the overtone crystal. This work on the overtone crystal meant that amateur radio operators no longer had to use frequency doubler circuits to achieve crystal control on the 20 meter short-wave band. John Wolfskill also developed an 'etch to frequency' process that proved to be much faster and more labor efficient way to finish crystals. The 'etch to frequency' process also greatly reduced the problem of decreased activity and pre-mature frequency aging in crystals stores for many months. This second benefit was to become very important to the U.S. during WWII. The Bliley Electric Company still thrives today serving the commercial and military markets some 66 years after it was founded by an amateur radio operator to serve amateur radio operators. Possibly the earliest person to produce quartz resonators for amateur radio operators was August E. "Augie" Miller. He started making crystals for the amateur radio community in 1923 [6]. He went on to form Miller Laboratories in 1928.

    In 1927, an amateur radio operator named Herbert Blasier started making crystal resonators in a garage in southern California for his fellow amateurs. Herbert Blasier had been an amateur radio operator since 1913. He used his radio skills as a commercial shipboard radioman and served in WWI with the U. S. Signal Corps in France. Herbert Blasier held call sign W6DCE. His son, John W. Blasier just retired as CEO in April 1996 after 40 years of service to the company that the senior Blasier founded, called Monitor Products Company. Inc. [29] [28].

    In 1927, Professor Gerald Fox of the University of Iowa gave a talk to a group of amateur radio operators on the subject of "The Piezoelectric Properties of Quartz" [6]. In attendance were a number of amateur radio operators who were evidently quite inspired by this presentation and went on to form crystal companies of their own. These included Herbert Hollister of Merriam, Kansas who advertised heavily in QST Magazine [7] and served the amateur radio community until the end of WWII. Another attendee was Bill Petersen, who founded the Petersen Radio Company, which still is in business today. Another attendee with a familiar name is E. M. Shideler. His amateur radio call sign was W0IFI. E.M. Shideler founded the Scientific Radio Products Company and made crystals for over 40 years before he retired. Quartz is in the Shideler family as E.M.'s son is Edward Shideler, president and CEO of Colorado Crystal Corp.

    In 1931, another amateur radio operator named Theodore S. Valpey started making "precision ground quartz crystals and holders for amateur and experimental use" to support local hams. This enterprise lives on today as the Valpey-Fisher Corporation, a subsidiary of MATAC Corporation [30].

    Leon Faber of Sandwich, Illinois had been an amateur radio operator since 1913. In 1932, he started making quartz crystal resonators for his fellow amateurs. When the demand for resonator skyrocketed during WWII, he formed a company with James Knights, a local battery dealer, that went on to be one of the world's largest. The company was known as CTS - Knights and is now called CTS [6]. I am confident that many more stories of amateur involvement in today's crystal companies exist and are not captured here.

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    The Early Crystal Market

    Hams were the commercial market until mid-1926 when WEAF went crystal controlled. Hams continued to be the bulk of the commercial market until the mid-and late-1930s. The United States military did not adopt crystal control for their radios until 1939 [6][32]. The production of crystals in the U.S. in 1939 was estimated to be 100,000 units [6]. The production of crystal resonators in the U.K. in 1938 was estimated to be 10,000 units [4]. These numbers compare to the 30 million units made in the U.S. from 1941 to 1945. [34]. Before the military took an active interest, crystals were produced for amateur radio operators, commercial broadcast stations, a few fixed stations (like maritime ship to shore stations), and other uses. The amateurs greatly outnumbered these other uses. The number of amateur radio operators per year were:

    1924
    approx. 15,900 [22]

    1926
    approx. 15,500 [23]

    1928
    approx. 18,100 [24]

    1929
    16,829 [31]

    1930
    18.994 [31]

    1931
    22,739 [31]

    1932
    30,374 [31]

    1933
    41,555 [31]

    1934
    46,390 [31]

    1935
    45,561 [31]

    1936
    46,850 [31]

    In contrast the number of commercial broadcast stations were:

    1926
    approx. 620 [25]

    1928
    approx. 905 [26]

    1930
    approx. 840 [27]

    There were other markets for crystals but these two were the largest. Broadcast stations were assigned one frequency and were expected to stay there. Consequently, a crystal company could sell only one main crystal and perhaps a spare to each broadcast station. In contrast, amateurs are not assigned fixed frequencies and desired to have more than one crystal. An interesting market study done by the Bliley Electric Company in 1936, showed that of the 298 amateur radio operators surveyed, on average, each ham owned five crystals each and planned to buy one more per year.

    The number of advertisements to amateurs in QST [7] magazine testifies to the volume of business to the amateur community. By month and year the number of advertisements of crystals for sale in QST are as follows:

    Aug 1925 1 Ads
    Dec 1925 1 Ads
    Dec 1926 2 Ads
    Dec 1927 3 Ads
    Dec 1928 4 Ads
    Dec 1929 10 Ads
    Nov 1930 11 Ads
    Nov 1931 23 Ads
    Sep 1932 14 Ads
    Sep 1933 12 Ads
    Nov 1934 12 Ads

    The data speaks for itself. This had become an industry.

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    Summary

    Amateur radio operators helped advance the state of the art of crystal control of radio transmitters. They provided the first commercial market that launched the crystal industry in the 1920s and into the 1930s. Even though the build up during WWII was almost unimaginable, there was an industry to build from. This industry originally formed to serve amateur radio operators. Many of those in the industry were amateur radio operators. Amateur radio helped to pave the way to make crystal control of radio transmitters a common and well tested practice.

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    REFERENCES

    [1] W.G. Cady; Piezoelectricity; McGraw-Hill Book Co. Inc., New York, New York, 1946, pp. 2 - 8

    [2] H. Jaffe "Professor Cady's Work in Crystal Physics"; Proceedings of the 18th Frequency Control Symposium, Ft. Monmouth NJ, 1964.

    [3] J.P. Buchanan; Handbook of Piezoelectric Crystals for Radio Equipment Designers; Wright Air Development Center, National Technical Information Services Springfield Virginia 1956, Pages 2 - 5

    [4] D. Salt; Handbook of Quartz Crystal Devices; Van Nostrand Reinhold (UK) C. Ltd., Berkshire, England. 1987. Pages xiii - xv

    [5] R.A. Heising (Ed); Quartz Crystals for Electrical Circuits; D. Van Nostrand Company Inc, New York, New York 1946, Reprinted by the Electronic Industries Association Washington D.C. 1982. Pages 1 - 6

    [6] V.E. Bottom; "A History of the Quartz Crystal Industry in the USA"; Proceedings of the 35th Frequency Control Symposium. USAERADCOM, Ft. Monmouth NJ, 1981.

    [7] QST Magazine; The monthly publication of the American Radio Relay League and the International Amateur Radio Union. Hartford, Conn. U.S.A.

    [8] C.B. DeSoto; 200 Meters and Down. The Story of Amateur Radio; The American Radio Relay League, Inc., West Hartford, Connecticut 1936, Reprinted by The American Radio Relay League, Inc., West Hartford, Connecticut 1981, Page 113

    [9] J.M. Clayton; "Crystal Control for Amateur Transmitters"; QST Magazine, Volume XII, Number II; November, 1925; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [10] P. Mueller; "A Method of Grinding Quartz Plates", QST Magazine, Volume XIV. Number 5; May 1927. The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [11] E.G. Watts, (Jr); " The Grinding of Quartz Plates"; QST Magazine, Volume XV. Number 1; January, 1928; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [12] J.J. Lamb; "Crystallizing Crystal Grinding"; QST Magazine; Volume XVII, Number 5; April 1930; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [13] I.H. Louchs; "Cutting Quartz Crystal Plates, The Practical Method and Equipment for X and Y Cuts"; QST Magazine, Volume XXII, Number 1; January, 1935; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [14] I.H. Louchs; "Grinding and Finishing Quartz Crystal Plates; QST Magazine, Volume XXII, Number 2; February, 1935; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [15] H.S. Shaw; "Oscillating Crystals"; QST Magazine, Volume XI, Number 7, July, 1924; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [16] Ed; "Experimenters' Section Report"; QST Magazine, Volume XII, Number 8, August, 1925; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [17] Ed; "AT-Cut Crystals Available"; QST Magazine, Volume XXI, Number 11; November, 1934; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [18] J.M. Clayton; "Quartz Crystal Mountings"; QST Magazine, Volume XIII, Number 7, July, 1926; The monthly publication of the American Radio Relay League and the International Amateur Radio Union, Hartford, Conn. U.S.A.

    [19] P. McCommon; "A History of the Crystal Industry in the Carisle [PA] Area"; History Independent Study Paper presented to Professor Warren Gates, Dickinson College, Carlisle, PA January 21, 1974

    [20] H. Fanus; "Quartz Crystal Industry in Carlisle, Pennsylvania" March 24, 1983 [Note: Harriet Fanus is the Daughter of Grover Hunt]

    [21] C.A. Bliley; The Bliley Electric Company, The Early Years; 1930-1955; Published by the Bliley Electric Company in association with The Antique Wireless Association Inc. Holcomb, New York, 1982. Pages 1-6

    [22] ______; Amateur Radio Stations of the United States; United States Department of Commerce, Bureau of Navigation, Edition of June 30, 1924

    [23] ______; Amateur Radio Stations of the United States; United States Department of Commerce, Bureau of Navigation, Edition of June 30, 1926

    [24] ______; Amateur Radio Stations of the United States; United States Department of Commerce, Bureau of Navigation, Edition of June 30, 1928

    [25] ______; Commercial and Government Radio Stations of the United States; United States Department of Commerce, Bureau of Navigation, Edition of June 30, 1926

    [26] ______; Commercial and Government Radio Stations of the United States; United States Department of Commerce, Bureau of Navigation, Edition of June 30, 1928

    [27] ______; Commercial and Government Radio Stations of the United States; United States Department of Commerce, Bureau of Navigation, Edition of June 30, 1930

    [28] Personal conversation with Edward Shideler president and CEO of Colorado Crystal Corp., son of E.M. Shideler of Scientific Radio Products

    [29] Personal conversation with John W. Blasier of Monitor Products Co. Inc.

    [30] Personal conversation with Jack Ross of Valpey-Fisher Corporation

    [31] ARRL (Ed); Fifty Years of A.R.R.L.; The Amateur Radio Relay League, Inc., Newington, Connecticut, 1965, page 68

    [32] W.L. Doxey; "Quartz Crystals Paved the Way", Proceedings of the 40th Annual IEEE Frequency Control Symposium; The Institute of Electrical and Electronic Engineers, Inc. New York, New York; 1986 Page 9

    [33] Personal conversation with Dr. Virgil E. Bottom

    [34] V.E. Bottom; Introduction to Quartz Crystal Unit Design; Van Nostrand Reinhold Company, New York, New York, 1982 Page 6

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