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+ | ====== E-610: National HRO ====== | ||
+ | **E-610**, **National HRO**; developed and produced by the [[National|National Company Inc., Malden, MA]]. | ||
+ | After the sudden outbreak of World War II and the mobilisation of the Swiss Army, it turned out that the Swiss Army had no high quality all wave receivers to intercept foreign shortwave traffic and to monitor foreign news broadcasts of the international broadcasting stations. | ||
+ | |||
+ | So a few men from the newly formed air traffic monitoring command had to acquire a few decent shortwave receivers which were for sale at an amateur radio equipment shop - so the Swiss Army acquired their first [[National]] HRO sets. | ||
+ | |||
+ | Even before this, the [[Autophon|Autophon Radio Company]] located at Solothurn started development of a measuring and control receiver based on National' | ||
+ | |||
+ | {{: | ||
+ | ===== Technical Data ===== | ||
+ | * [[Principle]]: | ||
+ | * [[Modes]]: [[A1]] with BFO, [[A3J|SSB (A3J)]] with BFO, [[A3|AM (A3)]] | ||
+ | * [[Frequency range]]: 1,7 - 30 MHz (with additional coil sets 50-430 and 480-2050 kHz), **plug in coil sets** for band selection | ||
+ | * **Analog dial**, micrometer dial with calibration curves. | ||
+ | * [[Sensitivity]]: | ||
+ | |||
+ | ==== Power Supply ==== | ||
+ | * [[Mains]] with " | ||
+ | * [[Accumulator / Batteries]]: | ||
+ | |||
+ | ==== Dimensions ==== | ||
+ | * 438 x 223 x 300 mm, 14.5 kg | ||
+ | |||
+ | ==== Accessories ==== | ||
+ | * **Headphones** | ||
+ | |||
+ | ---- | ||
+ | |||
+ | {{: | ||
+ | ===== Operation ===== | ||
+ | For the needs of American flight communications, | ||
+ | |||
+ | The revolutionary concept of the high precision tuning condensator PW-4 in conjunction with the " | ||
+ | |||
+ | Bandswitching in the HRO is realised with coil sets, the four main shortwave coil sets can be switched from general coverage to bandspread coverage of the amateur radio frequency bands. There have been five optional coil sets to cover VLF and mediumwave frequencies. | ||
+ | |||
+ | The HRO was one of the earliest receivers featuring not only separate RF and AF gain controls, an automatic gain control (AVC) but also a signal strength meter to determine the signal level of a station and a crystal filter with a control to set the passband or rejection curve. | ||
+ | |||
+ | A separate power supply has been used, which made less problems with noise from the power transformer and heat dissipation: | ||
+ | Over the years, National' | ||
+ | |||
+ | When you look at the outside of the radio, you can clearly recognize it's roots from commercially used receiving equipment. The metal cabinet comes with a hinged lid to access the chassis for changing valves from the top. An important accessory is the mains power supply, usually the " | ||
+ | |||
+ | The frontpanel of this very early sample of commercial receiving equipment is not that clearly structured as found in later receivers: most controls in the earliest sets came without lettering, but the operator simply knew which knob is used for which control: The main tuning knob with the " | ||
+ | The bottom control at the right is the RF gain control. | ||
+ | |||
+ | At the left, you find the signal strength meter, in early HROs, it's activated by a pushbutton, in later variants by a toggle switch. The next control is the AF gain control, the volume control. The switch underneath will turn off the automatic gain control (AVC) when in it's right position, the bottom control activates the BFO for the reception of telegraphy signals. | ||
+ | |||
+ | ===== Technical Principle ===== | ||
+ | {{: | ||
+ | Technically, | ||
+ | |||
+ | The intermediate frequency will pass the crystal or Lamb filter where the bandwidth can be regulated and unwanted interfering signals can be rejected using the rejection tune feature. After two IF amplifier stages ([[de: | ||
+ | |||
+ | In the external power supply 697, you find an [[de:80]] rectifier tube for the B+ / plate voltage of 240 V, this and the 6,3 V heaters voltage will be fed to the radio by means of a four pole power cable. | ||
+ | |||
+ | ==== Valve setup ==== | ||
+ | V1 ([[de: | ||
+ | Gl ([[de:80]], mains rectifier) in the 697 power supply. | ||
+ | |||
+ | ==== Development ==== | ||
+ | |||
+ | ==== Field use ==== | ||
+ | At the beginning of World War II, HRO receivers were purchased in amateur radio stores to build up an air traffic monitoring service. | ||
+ | |||
+ | In a list of receivers, which were used in the Swiss Army, several types of HRO receivers are mentionned. I suppose, that in the earliest time, maybe even single receivers got their own E-xxx designation. As far as i know, the HRO has never been acquired in large numbers. Maybe, we can add more informations about the use of the HRO receivers in Switzerland later. | ||
+ | |||
+ | In a early list, I found: | ||
+ | * **E-606**: HRO No. 1 (later, the number E-606 has been assigned to a troop information / entertainment portable transistor radio | ||
+ | * **E-607**: HRO No. 2 | ||
+ | * **E-610**: HRO Standard | ||
+ | |||
+ | {{gallery>: | ||
+ | ===== Manuals ===== | ||
+ | |||
+ | ==== Additional information ==== | ||
+ | * [[http:// | ||
+ | * [[http:// |
en/e-610.txt · Zuletzt geändert: 2019/03/23 21:31 von 127.0.0.1