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en:e-629 [2019/04/05 21:18]
mb
en:e-629 [2019/04/05 22:04] (aktuell)
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 ===== Technical Principle ===== ===== Technical Principle =====
 {{:​images:​e-629-collins-51j4-block.jpg?​direct&​400|}}\\ ​ {{:​images:​e-629-collins-51j4-block.jpg?​direct&​400|}}\\ ​
-The HF circuit of the 51J-4 is nearly as complicated as the mechanical synchronisation of the preselection using very impressive gears. In the 0,5-1,5 segment, the 51J-4 uses triple conversion, the signal will be converted to 11,5-10,5 MHz in the first mixer and to the usual 3,5-2,5 MHz in the second mixer. In the 1,5-3,5 segments, the receiver is switched as single conversion and the signal directly proceeds to the second mixer. In the other shortwave bands from 3,5-30,5 MHz, the typical double conversion circuit takes action: In the shortwave bands with even MHz counts, the signal is mixed to 1,5-2,5 MHz after having passed the first RF amplification stage, in the bands with uneven MHz counts to 2,5-3,5 MHz. In the second mixer, the signal is converted to the second intermediate frequency of 500 kHz. The signals first has to get passed the switchable crystal filter and the through the bank of mechanical IF filters. After another RF amplification stage, the signal is passed over to the detection stage and into the AF stage.+The HF circuit of the 51J-4 is nearly as complicated as the mechanical synchronisation of the preselection using very impressive gears. ​
  
-==== Valve setup ====+The RF signal from the antenna input first has to pass a tuned circuit and a RF amplifier stage (V101: [[de:​6AK5]]).
  
 +In the  **0.5 - 1.5 MHz** frequency range, which in fact can only be used from 540 kHz up due to the IF of 500 kHz, the 51 J-4 acts as a triple conversion receiver: the RF signal is converted to a 11.5 - 10.5 MHz intermediate frequency in the first mixer (V102: [[de:​6BE6]]) with a 12 MHz quartz oscillator (V105: [[de:​6AK5]]) signal. In a second mixer stage (Band I mixer, V103: [[de:​6BE6]]) it is mixed with an oscillator frequency of 8 MHz to generate the standard IF of 3.5-2.5 MHz. The third conversion is done in V106 ([[de:​6BE6]]) when the signal is mixed with the VFO signal of 2 - 3 MHz (V001: [[de:​6BA6]];​ V002: [[de:​6BA6]]) to generate the third IF of 500 kHz.
 +
 +In the **1.5 - 3.5 MHz** frequency range, the receiver acts as single conversion receiver; the signal is fed directly to V106 ([[de:​6BE6]]),​ thus generating the IF of 500 kHz.
 +
 +In the other shortwave bands from **3.5 up to 30.5 MHz** , the receiver operates as a double conversion superhet: after the first HF amplifier stage (V101: [[de:​6AK5]]),​ in the even frequency bands, the signal is converted to a 2.5 - 1.5 MHz intermediate frequency in the first mixer (V102: [[de:​6BE6]]). In the odd frequency bands the intermediate frequency is 2.5 - 3.5 MHz. In the second mixer (V106: [[de:​6BE6]]),​ the product is also converted to the second IF of 500 kHz by mixing it with the 2 - 3 MHz signal of the highly linear VFO (V001: [[de:​6BA6]];​ V002: [[de:​6BA6]]).
 +
 +After that, the 500 kHz IF signal first has pass through the switchable crystal filter and then the bank of mechanical filters (with two 500 kHz IF amplifiers V301: [[de:6BA6]] and V302: [[de:​6BA6]]),​ after two additional IF amplifier stages (V108: [[de:6BA6]] and V109: [[de:​6BA6]]) it is fed to the detector (one system of the V110: [[de:​12AX7]]) and after the noise limiter (one system of the V112: [[de:​12AX7]]) to the audio frequency preamplifier stage (second system V112: [[de:​12AX7]]). After the AF final stage (V113: [[de:​6AQ5]]),​ the audio signal is converted to the connectors for the 600 ohms and 4 ohm output.
 +
 +The second system of the V110 ([[de:​12AX7]]) acts as the first and the first system of the V111 ([[de:​12AU7]]) as the second AGC amplifier, the other system of the V111 ([[de:​12AU7]]) acts as amplifier for the 500 kHz IF output. Another tube [[de:6BA6]] (V104) is used in the crystal calibrator, ​ a further [[de:6BA6]] (V114) in the BFO, whose signal is fed to the detector for [[CW]] reception.
 +
 +The mains rectifier is a [[de:5V4G]] (V115), a [[de:0A2]] (V116) acts as voltage stabilizer. ​
 +
 +==== Valve setup ====
 +V001 and V002 ([[de:​6BA6]],​ VFO 2-3 MHz );
 +V101 ([[de:​6AK5]],​ RF preamplifier);​ V102 ([[de:​6BE6]],​ 1st mixer to 2.5 → 1.5 MHz ); V103 ([[de:​6BE6]],​ 2nd mixer, Band I); V105 ([[de:​6AK5]],​ 12 MHz oscillator);​ V106 ([[de:​6BE6]],​ 3rd mixer to 500 kHz)
 +V301 ([[de:​6BA6]],​ 1st IF amplifier 500 kHz); V302 ([[de:​6BA6]],​ 2nd IF amplifier 500 kHz); V108 ([[de:​6BA6]],​ 3rd IF amplifier); V109 ([[de:​6BA6]],​ 4th IF amplifier); V110a ([[de:​12AX7]],​ detector); V112b ([[de:​12AX7]],​ Noise Limiter); V112a ([[de:​12AX7]],​ AF preamplifier);​ V113 ([[de:​6AQ5]],​ audio final amplifier)
 +V110a ([[de:​12AX7]],​ 1st AGC amplifier); V111a ([[de:​12AU7]],​ 2nd AGC amplifier; V111b ([[de:​12AU7]],​ amplifier 500 kHz IF output; V104 ([[de:​6BA6]],​ calibrator);​ V114 ([[de:​6BA6]],​ BFO)\\ ​
 +V115 ([[de:​5V4G]],​ mains rectifier), V116 ([[de:​0A2]],​ voltage stabilizer).
  
 ==== Development ==== ==== Development ====
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 ==== Variants ==== ==== Variants ====
  
-{{gallery>:​images?​e-609*.jpg&​0&​80x80&​lightbox&​showtitle&​titlesort}}+{{gallery>:​images?​e-629*.jpg&​0&​80x80&​lightbox&​showtitle&​titlesort}}
 ===== Manuals ===== ===== Manuals =====
   * {{ :​manuals:​e-629-collins-51j4-manual.pdf | 51J-4 Communications Receiver, Instruction Book, Collins Radio Comp.}}   * {{ :​manuals:​e-629-collins-51j4-manual.pdf | 51J-4 Communications Receiver, Instruction Book, Collins Radio Comp.}}
en/e-629.txt · Zuletzt geändert: 2019/04/05 22:04 von mb