en:e-624
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+ | ====== E-624: Hallicrafters SX-27 "Ultra High Frequency Receiver" | ||
+ | **E-624**, **S - 27 "Ultra High Frequency Receiver" | ||
+ | The Ultra High Frequency Receiver [[Hallicrafters]] S-27 is a very early all wave receiver covering the [[VHF]] range up to frequencies in the 2 m band, this frequency range was in those days adressed as "ultra high frequency", | ||
+ | |||
+ | The set was usually used for band monitoring purposes, even when it was developed in the forties, this was still many years ahead of the use of the [[VHF]] range for broadcasting purposes. VHF broadcasting started in the USA in the 6 m band on frequencies around 50 MHz and was later reallocated to the 3 m band up to 100 MHz. Also the aircraft communications were moved to the [[VHF]] range from 118 - 137 MHz not before the end of World War II. | ||
+ | |||
+ | The receiver, which was developed around 1940, covers frequencies of 27 - 145 MHz in three ranges, the B-version **S-27B** the frequency range of 36 - 165 MHz . | ||
+ | |||
+ | {{: | ||
+ | ===== Technical Data ===== | ||
+ | * [[Principle]]: | ||
+ | * [[Modes]]: [[A1|CW (A1)]], [[A3|AM (A3)]], [[F3|FM (F3)]] | ||
+ | * [[Frequency range]]: 28 - 143 MHz in three ranges (27.8 - 47 MHz / 46 - 82 MHz / 82 - 143 MHz ) | ||
+ | * **Analog dial**, nonlinear | ||
+ | * [[Sensitivity]]: | ||
+ | |||
+ | ==== Power Supply ==== | ||
+ | * [[Mains]]: 115 V (version S27U switchable to 220 - 250 V) | ||
+ | * [[Accumulator / Batteries]]: | ||
+ | |||
+ | The standard S-27 UHF receiver is powered by 115 Volts AC, the common mains voltage found in the USA. A part of the receivers shipped to Europe came with an optional " | ||
+ | |||
+ | ==== Dimensions ==== | ||
+ | * 483 x 230 x 256 mm, approx. 20 kg | ||
+ | |||
+ | The receiver has a metal cabinet with a hinged lid, which - as found in many Hallicrafter' | ||
+ | |||
+ | ==== Accessories ==== | ||
+ | * A dipole antenna is recommended as standard antenna. | ||
+ | |||
+ | ---- | ||
+ | {{: | ||
+ | ===== Operation ===== | ||
+ | The S - 27 is a hollow state receiver covering the VHF range. The set developed around 1940 covers the 27 - 145 MHz frequency range, the later S - 27B version covers the 36 - 165 MHz frequency range. | ||
+ | |||
+ | The receiver comes in a rugged metal case with a hinged lid giving you access to the chassis to exchange the valves, it's dimensions are 48,3 x 23 x 25,6 cm and it's weight around 20 kg. | ||
+ | |||
+ | On the left side of the front panel, you find the rotating backlit main frequency dial, in contrast to the metal disc dials on older Hallicrafters models, only a part of the dial is visible behind the dial window. In the left lower corner of the frequency dial, you find the three position bandswitch. This lets you select one of three frequency ranges (27,8 - 47 / 46 - 82 / 82 - 143 MHz). | ||
+ | |||
+ | Just below, you find the R.F. gain control, the antenna trimmer, a bandwidth control (SHARP - BROAD) which also acts as mains switch and the A.F. gain / volume control at the right. | ||
+ | |||
+ | At the right of the main tuning dial, you find the fine tuning dial, which is mechanically coupled to the main tuning and is operated with the the typical Hallicrafters " | ||
+ | |||
+ | At the right, below the signal strength meter, you find the tone control and at the right the Send / Receive switch (to mute the receiver when used in connection to a transmitter) and the headphones jack. A high impedance speaker (5000 Ohms) can be connected at connectors at the rear of the receiver, to drive an 8 Ohms speaker, you need a matching transformer. | ||
+ | |||
+ | When You have managed to apply the correct power to the receiver, it's operation scheme is different in AM and in FM mode. | ||
+ | |||
+ | Use the selectivity control to turn the radio on (yes - that's typical [[Hallicrafters]], | ||
+ | |||
+ | In AM mode, You can try to catch some morse code transmissions or communications in the 10 m ham band above 27 MHz with the BFO turned on, sometimes, You get better results in copying CW or single sideband signals with manual R.F. gain control. There is also some AM communications activity in the Air band in the 118 - 137 MHZ, e.g. airport weather reports around 127 MHz. | ||
+ | |||
+ | In the FM mode, look for some FM broadcast stations in the standard FM broadcast band from 88 - 108 MHz, BFO, AVC and ANL is inactive in this mode, the selectivity has to be set to BROAD for broadcasting stations, and the TONE control can be set to HIGH FIDelity or even BASS BOOST. The reception uses a deemphasis constant of 100 usec., the meter is switched to act as a tuning indicator with optimal tuning when the indicator is in the middle position. In some cases, the antenna has to be tuned to maximum signal strength. Besides FM broadcast transmissions, | ||
+ | |||
+ | ===== Technical Principle ===== | ||
+ | {{: | ||
+ | The signal coming from the antenna is amplified in a RF amplifier stage using a acorn miniature tube (V1, acorn tube [[de:956]]) and is fed to the mixer stage (V2, acorn tube [[de: | ||
+ | An [[de:6C8]] is used in as AF preamplifier and two [[de:6V6]] in a push pull arrangement in the AF output stage. For the BFO, a [[de:6J5]] valve is used. | ||
+ | |||
+ | In the power supply, a [[de:5Z3]] valve is used as full wave rectifier and a [[de: | ||
+ | |||
+ | ==== Valve setup ==== | ||
+ | V1 ([[de: | ||
+ | Gl ([[de: | ||
+ | |||
+ | ==== Development ==== | ||
+ | |||
+ | |||
+ | ==== Field use ==== | ||
+ | {{: | ||
+ | |||
+ | Even after the set was developed in 1940, it took several years, until the VHF band was used for FM broadcasting in the United States, first the 6m band around 50 MHz was assigned to broadcasting, | ||
+ | |||
+ | {{gallery>: | ||
+ | |||
+ | ==== Manuals ==== | ||
+ | |||
+ | ==== Additional information ==== | ||
+ | * [[http:// | ||
+ | * [[http:// |
en/e-624.txt · Zuletzt geändert: 2019/04/04 12:03 von 127.0.0.1