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+ | ====== E-625: National HRO-7T====== | ||
+ | **E-625**, **National HRO-7T**; developed and produced by the [[National|National Company Inc., Malden, MA]]. | ||
+ | In several lists, you can find informations about receivers that have been acquired in small numbers and got assigned an E-6xx designation of the Swiss Army. One of these sets it the HRO-7T, a successor of the National [[HRO]], of which also a few sets have been bought. | ||
+ | |||
+ | Telefunken Zürich provided a wooden housing with an integrated speaker, which also had space to store the typical HRO " | ||
+ | |||
+ | {{: | ||
+ | ===== Technical Data ===== | ||
+ | * [[Principle]]: | ||
+ | * [[Modes]]: [[A1]] with BFO, [[A3J|SSB (A3J)]] with BFO, [[A3|AM (A3)]] | ||
+ | * [[Frequency range]]: 0.05 - 30 MHz (standard 4 coil sets 1.7 - 4 / 3.4 - 7.2 / 7 - 14 / 13 - 30 MHz, optional coil sets 900 - 2050 kHz, 480 - 960 kHz, 180 - 430 kHz, 100 - 200 kHz and 50 - 100 kHz). | ||
+ | * **Analog dial**, micrometer dial with calibration curves. | ||
+ | * [[Sensitivity]]: | ||
+ | |||
+ | ==== Power Supply ==== | ||
+ | * [[Mains]] with " | ||
+ | * [[Accumulator / Batteries]]: | ||
+ | |||
+ | ==== Dimensions ==== | ||
+ | * 495 x 280 x 260 mm, 29.5 kg | ||
+ | |||
+ | ==== Accessories ==== | ||
+ | * **Headphones** | ||
+ | |||
+ | A vibrator power supply 686S could be used to power the receiver from a 6V DC source. Also the crystal calibrator and the FM product detector were not standard accessories but could be ordered separately and could be plugged in to an accessory socket on the rear of the set.\\ | ||
+ | The HRO-7T has no internal speaker, it needs a high impedance speaker, e.g. National' | ||
+ | |||
+ | ---- | ||
+ | {{: | ||
+ | ===== Operation ===== | ||
+ | The **HRO-7 T** is a single conversion superhet using plug in coil sets for changing bands like found in the classic [[HRO]]. On the coil sets, there is a printed conversion table for micrometer dial reading and frequency, similar but easier to read then the logging charts on the original [[HRO]] dials. You find two frequency reference charts for general coverage use and for bandspread in the amateur bands. | ||
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+ | The main tuning knob with the " | ||
+ | |||
+ | At the left, you find the signal strength meter. The next control is the noise limiter followed by the AF gain control, the volume control. The switch underneath is the tone control to cut off high frequency parts of the audio spectrum, the bottom control activates the BFO for the reception of telegraphy signals. | ||
+ | |||
+ | In the right column of controls, the top button acts als rejection control like a phasing filter, the rotary control below lets you regulate the passband width of the crystal filter. The next switch will turn on B+, the plate voltage: let the B+ switched off when the receiver is in standby, and B+ must be turned off when changing coil sets! | ||
+ | |||
+ | The bottom control at the right is the RF gain control. | ||
+ | |||
+ | {{: | ||
+ | |||
+ | {{: | ||
+ | |||
+ | ===== 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 tuning feature. After two IF amplifier stages (V4/V5: both [[de: | ||
+ | |||
+ | The external power supply 697, in which you find an [[de:80]] rectifier tube for the B+ / plate voltage of 240 V, and which will also deliver the 6,3 V heaters voltage comes in a strange shaped metal cabinet - everyone who has ever seen a " | ||
+ | |||
+ | ==== Valve setup ==== | ||
+ | V1 ([[de: | ||
+ | In the power supply 697: Gl ([[de: | ||
+ | |||
+ | ==== Development ==== | ||
+ | |||
+ | ==== Field use ==== | ||
+ | For the Swiss Army, [[Telefunken Zurich]] made a special wooden rack with space for the the integrated power supply, a switchbox for receiver operation with or without speaker, and a storage rack for the frequency band coils. | ||
+ | |||
+ | {{: | ||
+ | |||
+ | This wooden rack is still missing in my collection, so if you have one for sale, let me know. | ||
+ | |||
+ | {{gallery>: | ||
+ | ===== Manuals ===== | ||
+ | |||
+ | ==== Additional information ==== | ||
+ | * [[http:// | ||
+ | * [[http:// |
en/e-625.txt · Zuletzt geändert: 2019/04/04 13:12 von 127.0.0.1