National HRO

Last updated
National HRO receiver, c. 1938 National HRO shortwave communications receiver.png
National HRO receiver, c. 1938

The original National HRO was a 9-tube HF (shortwave) general coverage communications receiver manufactured by the National Radio Company of Malden, Massachusetts, United States.

Contents

History

James Millen (amateur radio call sign W1HRX) in Massachusetts was in charge of the mechanical design. According to several accounts, Herbert Hoover, Jr. (amateur radio call sign W6ZH), son of U.S. President Herbert Hoover, and Howard Morgan (of Western Electric) designed the electronics in Hoover's garage in Pasadena, California. [1] Dana Bacon (W1BZR) was also involved and wrote about the receiver as second author with James Millen. Some of National Radio's tool makers marked their overtime slips with HOR for "Hell Of a Rush." Management decided that a version of that abbreviation should be the name of the new receiver, choosing the slight alteration HRO to make it less objectionable. [2] [3] That was quickly countered by saying that HRO stood for "Helluva Rush Order". [4]

The HRO receiver was announced in QST magazine in October 1934 and shipped in March 1935, incorporating many design features requested by the fledgling airline industry [5] that were also attractive to the amateur radio community. According to the 1935 instruction manual, [6] the HRO price was US$233, the external power supply (to reduce heat in the receiver cabinet and hum) [7] was US$26.50 less tubes, and a 7000 ohm speaker in a rack panel was US$30.00.

The HRO found widespread use during World War II as the preferred receiver of various Allied monitoring services, including Y-Service stations associated with the code-breaking group at Bletchley Park (Station X) in England. [4] An estimated 1,000 standard HROs were initially purchased by Great Britain, and approximately 10,000 total saw use by the British in intercept operation, diplomatic communications, aboard ships and at shore stations as well as for clandestine use. [8] [9]

Features

Plug-in tuning coil set D for the HRO-60 receiver. National HRO-60 coil set D.jpg
Plug-in tuning coil set D for the HRO-60 receiver.

The two most distinctive features of this radio were its use of a micrometer-type dial, and plug-in sets of tuning coils that slid into a full-width opening at the bottom of the front panel. The dial, [10] designed by Willam Graydon Smith, allowed for continuous analog tuning while digitally indicating incremental progress over a range of ten full turns of the large tuning knob that tuned with velvet smoothness. Ten times the circumference of the dial is 12 feet (nearly 4 m), which allowed for great frequency resolution. The four standard sets of coils, A, B, C, and D, covered 14–30, 7–14.4, 3.5–7.3, and 1.7–4 MHz, respectively. Two other sets of coils, E and F, sold separately, covered 960–2,050 kHz and 480–960 kHz, respectively. [6] [11] Before each radio left the factory, a technician custom calibrated a set of A, B, C, and D coils for that particular radio, a process that took nearly 4 hours. [12] Each of the four main sets of coils also had bandspread modes set by moving screws that limited the frequency range to 28–29.7, 14–14.4, 7–7.3, 3.5-4 MHz, respectively, for amateur radio use. [13]

Models

Main HRO models:

There were also several sub-variations on these models. [16]

Production

National HRO-60 receiver (1952-1964) National HRO-60.jpg
National HRO-60 receiver (1952–1964)

The U.S. military told National, "Start building HROs. We'll tell you when to stop." [12] [17] Before, during, and after World War II, the HRO concept of using plug-in coils with micrometer tuning was copied in several countries, including Germany and Japan. The best-known copies are probably two German models widely employed as monitoring receivers by the German services, the KST made by Korting Radio and the R4 made by Siemens. [18]

Following World War II came the HRO-7 (1947–1949, 12 tubes, including 2 miniature tubes), HRO-50 (1949–1950, built-in tuning dials and power supply, push-pull audio amplifier, improved styling and performance), HRO-50-1 (1951, increased IF selectivity), and HRO-60 (1952–1964, dual conversion for coils B (7–14.4 MHz) and A (14-30 MHz), heater current regulation for the HF oscillator and mixer tubes). [19] These were followed by two solid-state receivers that did not use plug-in coils: the HRO-500 (October 1964 – 1972, 5 kHz-30 MHz, [20] and HRO-600 (1970-1972?, 16 kHz-30 MHz). Breaking with tradition, the HRO-600 used a frequency counter instead of a micrometer tuning dial. [21] Ironically, the HRO-600 used nixie tubes for its digital frequency display and thus was, technically, no longer "all solid-state" as its predecessor, the HRO-500, had been. [22]

HRO receivers were said to be outstanding and continued to be popular although even better and more expensive general coverage receivers from such companies as Collins Radio became available in the 1950s and later. One can still find HRO receivers dating back to the original model that have been restored by vintage amateur radio enthusiasts and other hobbyists.

See also

Related Research Articles

<span class="mw-page-title-main">Superheterodyne receiver</span> Type of radio receiver

A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. It was invented by French radio engineer and radio manufacturer Lucien Lévy. Virtually all modern radio receivers use the superheterodyne principle.

<span class="mw-page-title-main">Shortwave radio</span> Radio transmissions using wavelengths between 10 m and 100 m

Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.

<span class="mw-page-title-main">Intermediate frequency</span> Frequency to which a carrier wave is shifted during transmission or reception

In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done.

<span class="mw-page-title-main">Crystal radio</span> Simple radio receiver circuit for AM reception

A crystal radio receiver, also called a crystal set, is a simple radio receiver, popular in the early days of radio. It uses only the power of the received radio signal to produce sound, needing no external power. It is named for its most important component, a crystal detector, originally made from a piece of crystalline mineral such as galena. This component is now called a diode.

<span class="mw-page-title-main">Walkie-talkie</span> Hand-held portable two-way communications device

A walkie-talkie, more formally known as a handheld transceiver (HT), is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald Hings, radio engineer Alfred J. Gross, Henryk Magnuski and engineering teams at Motorola. First used for infantry, similar designs were created for field artillery and tank units, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work.

<span class="mw-page-title-main">Radio receiver</span> Device for receiving radio broadcasts

In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.

<span class="mw-page-title-main">Spark-gap transmitter</span> Type of radio transmitter

A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark. Spark-gap transmitters were the first type of radio transmitter, and were the main type used during the wireless telegraphy or "spark" era, the first three decades of radio, from 1887 to the end of World War I. German physicist Heinrich Hertz built the first experimental spark-gap transmitters in 1887, with which he proved the existence of radio waves and studied their properties.

<span class="mw-page-title-main">Hallicrafters</span> Manufacturer of radio equipment, televisions, and phonographs

The Hallicrafters Company manufactured, marketed, and sold radio equipment, and to a lesser extent televisions and phonographs, beginning in 1932. The company was founded by William J. Halligan and based in Chicago, Illinois, United States.

The National Radio Company, headquartered in Malden, Massachusetts, United States, was an American manufacturer of radio equipment from 1914 to 1991.

<span class="mw-page-title-main">AN/ART-13</span>

The AN/ART-13 was a radio transmitter manufactured by Collins Radio that found widespread use during and after World War II in military aircraft.

<span class="mw-page-title-main">BC-348</span>

The BC-348 is an American-made communications receiver, which was mass-produced during World War II for the U.S. Army Air Force. Under the joint Army-Navy nomenclature system, the receiver system became known as the AN/ARR-11.

<span class="mw-page-title-main">Hammarlund Super Pro</span>

The Hammarlund Super Pro was an American-made radio communications receiver.

Swan Electronics was a manufacturer of amateur radio gear located in Oceanside, California, United States.

<span class="mw-page-title-main">R-390A</span>

The R-390A /URR is a general coverage HF radio communications receiver designed by Collins Radio Company for the United States Armed Forces.

<span class="mw-page-title-main">AN/URM-25D signal generator</span>

The AN/URM-25 signal generator was an electronic vacuum-tube radio-frequency (RF) signal generator used during the 1950s and 1960s by the U.S. Military to test electronic equipment.

<span class="mw-page-title-main">Hallicrafters SX-28</span> American shortwave radio receiver

The Hallicrafters SX-28 "Super Skyrider" is an American shortwave communications receiver that was produced between 1940 and 1946 that saw wide use by amateur radio, government and military services.

<span class="mw-page-title-main">BC-342</span> World War II U.S. Army radio equipment

The BC-342 was a World War II U.S. Army Signal Corps high frequency radio receiver. It was used primarily as part of field installations such as the SCR-188A, but could be used with mobile sets such as the 2 1/2 ton mounted SCR-399. First designed at Fort Monmouth, New Jersey by the U.S. Army Signal Corps, it was built by various manufacturers including RCA. Many of the later units that are encountered today were manufactured by the Farnsworth Television and Radio Corporation of Fort Wayne, Indiana. Variants include the low frequency coverage BC-344 receiver, and the battery or dynamotor powered BC-312 receiver.

The AN/PRC-10 is an American VHF portable radio transceiver, introduced in 1951 as a replacement for the wartime SCR-300 set. The AN/PRC-8 and AN/PRC-9 sets are basically the same but cover lower frequency bands. It remained in service with the American military until the mid 1960s when it was replaced by the transistorized AN/PRC-25 set.

References

  1. Williams, Barry. "The Evolution of the National HRO and Its Contribution to Winning World War II". radiomuseum.org. Radio Museum. Retrieved 2 January 2019.
  2. Babcock, Larry. "National". Antique Radio Gazette, Vol. 14, No. 4. Antique Wireless Association. Archived from the original on April 22, 2003. Retrieved January 2, 2019. Alt URL
  3. http://jproc.ca/rrp/sradequ.html Antique Wireless Association
  4. 1 2 http://www.qsl.net/jms/bio_rem/bhnc.html Antique Wireless Association
  5. http://www.qsl.net/jms/bio_rem/national.html National Receivers
  6. 1 2 ftp://bama.sbc.edu/downloads/national/hro1935/ National HRO Manual
  7. http://www.radioblvd.com/National%20HRO.htm Radio Boulevard
  8. McKay, Sinclair (2012). The Secret Listeners. London, UK: Aurum Press Ltd. p. 24. ISBN   978-1-78131-079-3.
  9. http://www.prismnet.com/~nielw/HRO_BarryWilliams/HROArticle.htm The Evolution of the National HRO and Its Contribution to Winning World War II, by Barry Williams, KD5VC
  10. U.S. Patent No. 2,060,537
  11. http://www.prismnet.com/~nielw/HRO_BarryWilliams/HROArticle.htm Barry Williams HRO Article
  12. 1 2 http://www.qsl.net/jms/bio_rem/bhnc.html National Receivers
  13. Instruction manual for the National HRO communication receiver (PDF). Malden, MA: National Company, Inc. 1939. Retrieved 2013-10-31.
  14. http://www.wb4gwa.netfirms.com/pagetwoa.html WB4GWA, National radios
  15. http://www.prismnet.com/~nielw/hro_modl.htm W0VLZ Radio Bay
  16. ftp://bama.sbc.edu/downloads/national/hro/National HRO Manual
  17. http://www.allpgh.com:8080/w3bc.us/ The W3BC Report
  18. http://www.armyradio.com/arsc/customer/pages.php?pageurl=/publish/Articles/Clyne/Clyne_N.htm Army Radio
  19. Ron Pollack, K2RP (September 2018). "Classic Radio: The National HRO Receiver". QST . 102 (9). American Radio Relay League: 81–82. ISSN   0033-4812.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  20. http://www.prismnet.com/~nielw/nat_list/hro500.htm W0VLZ Radio Bay
  21. http://www.prismnet.com/~nielw/nat_list/hro600.htm W0VLZ Radio Bay
  22. "National HRO-600 Receiver". www.miami.muohio.edu. Archived from the original on 2006-08-10.