Collins Mechanical Filters For Sale
2021年4月4日Download here: http://gg.gg/ox72n
*Collins Mechanical Filters For Sale In Ct
*Collins Mechanical Filters For Sale Near Me
*Collins mechanical filter. Cracked, broken cases. Mechanical Filter Fc = 455 kc / BW = 18 kc (COL) 526-9310-009. F455Q3, ’Y’ style filter will fit S-Line. 100k ohm in / out impedance. 3.5 dB BW is 18 kc, 70 dB BW is 70 kc.
*Get the best deals on collins filter when you shop the largest online selection at eBay.com. Collins Mechanical Filter 455 KHz CF, 1,2 or 4 KHz BW.
*Collins SSB / RTTY mechanical filter. 500 KHz IF, 1.4 KHz bandwidth. Fits 51J series collins receivers. Brand new stock that was squirreled away when.Home PageCollins Equipment Assorted Collins Parts Collins rubber feet kit. Kit includes (4) rubber feet, (2) extension feet & (1) set of hardware.
Collins mechanical filters for the 75A-4. Available bandwidths: 6khz and 10 khz AM, 2.5 khz SSB and 500hz CW. $195.95 each plus $7.00 shipping. ($15.00 international). MECHANICAL REQUIREMENTS: CONSTRUCTION: Sealed, Non-Hermetic CASE STYLE: PS MARKING: Rockwell Collins Part Number Date Code TEST CIRCUIT: 2k Ω 2k Ω ± 1% ± 3 pF 30 pF 30 pF ± 1% ±3 pF NOTE: 30 pF Includes any board stray capacitance. ROCKWELL COLLINS FILTER PRODUCTS 14101 MYFORD ROAD, TUSTIN, CA 92780 526-8693-010.(COL) 540-5175-000*** SOLD OUT ***0.01µF or 10,000 pF, Tusonix feedthru. 4kvw, 8kv test, 2-3/8’ long, 7/16’ bushing mount. #8/32 stud runs through center. Ceramic body, silver hardware. Our customers report this may replace your KWS-1 feedthru capacitor.#47 pilot bulb. Bayonet base. T 3-1/4. 6.3v, 0.15 amps. Fits all S-line / KWM2.Two pin microphone connector. Fits vintage Collins, Heath, etc. Made by Cooper Instrument.Operation parts manual for 180S-1, copy. Plug in solid state replacement for vacuum tubes 5R4 & 5U4. Octal base. Rated @ 2800 vdc, 1 amp. 1-3/8’ diameter x 1-1/8’ high. Solid State direct replacement modules are much more efficient than their vacuum tube predecessors. In some case, dropping resistors should be used if the higher output voltages often yielded with these diodes will create an unsafe condition. No heater current is required, saving watts there too. Printed on adhesive backed paper, NOT photocopies
or transfer decals. Instructions included.Part NumberDescriptionPrice EachPrice for 3(COL) DCL-KWS/0Fits older KWS-1 w/15 meter scale starting @ 21.0 MHz. 10.0024.00Add(COL) DCL-KWSFits newer KWS-1 w/15 meter scale starting @ 20.5 MHz.10.0024.00Add(COL) DCL-75A/0Fits older 75A-4 w/15 meter scale starting @ 20.8 MHz.10.0024.00Add(COL) DCL-75AFits newer 75A-4 w/15 meter scale starting @ 20.5 MHz.10.0024.00Add(COL) DCL-75A3Fits 75A-3.-SOLDOUT(COL) DCL-75A2Fits 75A-2.10.0024.00Add(COL) DCL-51JFits all 51J receivers.10.0024.00AddJ-4 PartsPart NumberDescriptionPrice Each(COL) 278-0092-000T102, 500 kc can95.00Add(COL) 278-0093-000T101, 500 kc can95.00Add(COL) 526-9009-00F500B60, 6 kc349.00Add(COL) 526-9030-00F500B14, 1.4 kc295.00Add(COL) 526-9215-009F500F-14, 1.4 kc (See below for more info & picture)249.00Add(COL) 51J451J-4 manual, copy35.00Add(COL) 526-9215-009Collins SSB / RTTY mechanical filter. 500 KHz IF, 1.4 KHz bandwidth. F500F-14. Fits 51J series collins receivers. Brand new stock that was squirreled away when this ’Radio Row’ shop closed in NYC. Brand new in the box!!Part NumberDescriptionPrice Each(COL) 278-0197-00T3, T4 IF can49.00Add(COL) 259-0417-00S5 AVC switch25.00Add(COL) 667-0018-00Collins T5A-4 Hammond Audio Transformer. 2’ c-c mount holes.
1.6’ x 1.6’ x 1.9’H. Alt P/N: 11271. NSN: 5950-00-772-8438 Pic139.00Add(COL) 526-9154-00F455J05, 500 Hz750.00Add(COL) 526-9089-00F455J31, 3.1 kc349.00AddPart NumberDescriptionPrice Each(COL) 662-0034-00T1 power inverter transformer replacement made by Ballastran
(BC-3254) for Collins MP-1. (Pictured)125.00Add(COL) 970-2170-00K1 relay for MP1 mobile power supply.65.00Add(COL) 352-0320-00Q1, Q2 DA3F3 for MP1 mobile power supply.SOLDOUT(PUB)(COL) MP1MP-1 Manual copy.15.00AddPM-2 Power SupplyPart NumberDescriptionPrice Each(COL) 183-1054-00C1, C2 20 µF, 450 v electrolytic caps.6.50Add(COL) 183-1009-00C7, 40 µF / 40 µF, 450 v twist lock.SOLDOUT (COL) 353-1661-00CR1-9 Diodes.2.00Add(PUB) COL-PM-2PM-2 Manual, copy.15.00Add75A-3
THE COLLINS 75A-3 RECEIVER
The 75A-3 is a dual-conversion communications receiver covering all amateur bands in the range 160-10 meters. It is the only amateur-band receiver featuring the Collins Mechanical Filter.
The 75A-3 also features excellent stability, sensitivity, and dial accuracy.Collins Mechanical Filters For Sale In Ct
The Collins Mechanical Filter, a new and radically different means of achieving selectivity – in communications receivers, uses mechanically resonant elements to produce a selectivity curve having a flat “nose” for full sideband response and steep, almost vertical skirts for rejection of adjacent- channel interference.
Because the mechanical filter in the 75A-3 has nearly rectangular selectivity curve, the receiver is well suited for single-sideband suppressed-carrier reception. And with the 75A-3 it is possible to use single-sideband techniques on AM signals by tuning one sideband and the carrier to the exclusion of the other sideband. Because of the unusual tuning characteristics of the 75A-3 the owner should familiarize himself with the operational procedures described in Section III of this manual.
The mechanical filter supplied with the 75A-3 has a 3-kc bandpass for optimum performance in AM and single-sideband reception; however, an 800-cycle filter, an accessory unit, may be installed for use under conditions of heavy QRM and QRN. Both filters are plug-in units and mount side by side in the receiver. A two-position switch on the front panel of the receiver is used to select the desired filter.
The direct-reading tuning dial is calibrated in 1-kc divisions on 160, 80, 40, 20 and 15 meters and 2-kc divisions on 11 and 10 meters. A crystal-controlled front end and temperature-compensated, hermetically-sealed variable frequency oscillator contribute to the frequency stability of the 75A-3. Physical shock will not change the VFO frequency unless the shock is so severe that the dial setting is changed.
Free online radio station software download. Included in the 75A-3 are a 4-position crystal filter, a phone noise limiter which automatically adjusts the clipping level according tothe strength of the incoming signal, a separate noise limiter for CW reception, delayed and amplified AVC, and provisions for external standby control and receiver muting. Two plug-in units available for use in the 75A-3 are the 148C-1 NBFM adaptor and the 8R-1 crystal calibrator.
75A-3 SPECIFICATIONS
a. RF CIRCUITS.
(1) SELECTIVITY.
(a) With 3-kc filter ……. approx. 3 kc at 6 db down and 6. 5 kc at 60 db down
(b) With crystal filter …. position 4: approx. 40 cps at 6 db down and 4 kc at 60 db down.
(2) SENSITIVITY …………… 2 uv for signal-to-noise ratio of 6 db.
(3) STABILITY
(a) Mechanical …………. CW beat note will not change if receiver is jarred unless dial
setting is changed.
(b) Electrical …………. stable within a few cycles under normal
operating conditions and after short warm-up period.
(4) IMAGE REJECTION ………. at least 50 db.
(5) AVC …………………. constant audio output within 6 db for r-f input change of 5 uv to 0.5v.
b. TUNING FEATURES.
(1) COVERAGE ……………. 1.5-2.5 mc; 3.2-4.2 mc; 6.8-7.8 mc
14.0-15.0 mc; 20.8-21.8 mc; 26.0-28.0; 28.0-30.0 mc.
(2) BANDSPREAD …………… linear; ten turns of vernier dial covers each range.
(3) DIAL ACCURACY ………… within 1 kc on 160-15 meters and 2 kc on 11 and 10 meters.
(4) “S” METER ……………. S9 corresponds to signal of about 100 uv.
d. POWER SOURCE …… 115 v, 50-60 cps; power consumption approx. 85 w.; 230-volt model
model available on special order or by use of a 230-volt power transformer.
e. ANTENNA INPUT . . . . . accommodates wide range of antenna impedances; designed
for 50-150 ohms terminal impedance; coax connectors provided.
f. AUDIO OUTPUT . . . . . . approx. 2.5 w
g. CABINET DIMENSIONS . . . 21-1/8 in. wide; 12-1/2 in. high; 13-1/16
in. deep; chassis fits standard relay rack; chassis depth 13-5/16 in.
h. FINISH . . . . . . . . . . . dark grey wrinkle.
i. ACCESSORIES.
(1) 800-CYCLE MECH FILTER . mechanical filter with bandpass of approx.
800 cycles; plugs in socket on receiver chassis.
(2) SPEAKER . . . . . . . . . external 10-in. speaker in matching cabinet;
Speaker cabinet 15 in. wide, 11-1/8 in. high, 9-1/8 in. deep.
(3) HEADPHONES . . . . . . . low-impedance type preferable.
(4) ANTENNA . . . . . . . . see e.
(5) CRYSTAL CALIBRATOR 8R-1. . plugs into a socket on receiver chassis;
provides 100-kc reference signals for calibration.
(6) NBFM ADAPTOR 148C-1 . . . . plugs into socket on receiver; contains
limiter and discriminator.
Under the hood…
75A-3 CIRCUITRY
1. GENERAL.
The 75A-3 circuit consists of a crystal-controlled front end, a variable i-f system, a low-frequency converter stage and a fixed 455-kc i-f system (see block diagram, Fig. 4-1). In the fixed i-f system, a mechanical filter first provides the necessary selectivity-curve shaping. The 455-kc intermediate frequency is then amplified and fed to the detector and audio circuits. A 455-kc signal from the beat-frequency oscillator is injected at the detector stage for CW reception. The audio system uses separate noise limiters for CW and AM; the CW noise limiter is variable, and the clipping level of the AM noise limiter is automatically adjusted according to the strength of the incoming signal. The output stage feeds a 500-ohm load or a 4-ohm speaker.
2. TUNING.
All variable tuned circuits, including the first r-f stage,the variable i-f system and the variable frequency oscillator are operated by the main tuning control. The vernier tuning dial is coupled directly to the shaft of the variable-frequency oscillator. The other variable-tuned circuits, including the r-f stage and the variable i-f stages, are tuned by powdered iron slugs which are attached to a common platform. The platform is moved up and down by means of a cam-driven mechanism which is coupled to the VFO shaft by means of split gears and metal bands. The 75A-3 uses a unique method of band switching in the r-f stage in which only the 80 and 160 meter coils are tuned by means of the main tuning mechanism, and coils for 40-10 meters are connected across the respective 80 meter coils. Varying the inductance of an 80-meter coil varies the total inductance, and therefore the resonant frequency, of the tuned circuit for the band in use.
3. RF CIRCUITS.
A simplified block diagram of the 75A-3 r-f system is shown in Figure 5-5. The first r-f stage feeds the mixer at the carrier frequency of the incoming signal. The coverage for each band is listed below:
160 meters – 1.5 – 2.5 mc
80 meters – 3.2 – 4.2 mc
40 meters – 6.8 – 7.8 mc
20 meters – 14.0 – 15.0 mc
15 meters – 20.8 – 21.8 mc
11 meters – 26.0 – 28.0 mc
10 meters – 28.0 – 30.0 mc
The first converter, consisting of a crystal-controlled oscillator circuit and a mixer tube, converts the incoming signal to the variable i-f frequency of 2.5 – 1.5 mc for 160-15 meters and 5.455 – 3.455 mc for 11 and 10 meters. From the variable i-f system the signal is fed to the second mixer where it is converted to a fixed i-f frequency of 455 kc. This signal is passed through the i-f amplifiers to the detector stage. A discussion of individual circuits in the r-f portion of the receiver follows:
a. RF STAGE. The RF stage uses a 6CB6 pentode. Individual variable slug-tuned coils are switched into the grid circuit on 160 and 80 meters. On 40-10 meters the coil in use is connected across the 80-meter coil, and varying the inductance of the 80-meter coil tunes the coil for the band use. The 80-meter trimmer capacitors are not in the circuit on 40-10 meters.
On 160 meters the output of the r-f amplifier is fed directly to the variable i-f system. On 80-10 meters the r-f plate circuit tuning system is the same as that of the grid circuit.
b. CRYSTAL – CONTROLLED OSCILLATOR AND FIRST MIXER. The high-frequency converter stage employs a 12AT7 in a Butler crystal-oscillator circuit. In this circuit the crystal is connected between the cathodes of a dual triode. Feedback voltage is coupled from the plate circuit of one section, which contains a tank circuit resonant at the crystal frequency, to the grid of the other section. The 180-degree phase shift necessary for oscillation is provided by the second section of the tube, which acts as a cathode follower to couple feedback energy to the crystal. Crystal-oscillator output voltage is coupled to the injection grid of the 6BA7 first mixer. An individual crystal for each band is switched in to the crystal oscillator circuit except on 160 meters, where the high-frequency converter is not used. The crystal- oscillator frequency beat switch the incoming carrier to produce the first, or variable, intermediate frequency. In this stage because the crystal frequency is fixed and the incoming carrier frequency may be anywhere in the range of the band in use, the difference frequency produced in the mixer must be tuned by a variable i-f system. On 160 meters the band coverage corresponds to the lower frequency range of the variable i-f’s.
c. VARIABLE IF. The variable i-f system covers two frequency ranges, 2.5 – 1.5 mc and 5.455 – 3.455 mc. The variable i-f system for the range in use consists of two slug-tuned circuits on the same frequency. The first of these two circuits is capacity coupled to the second, which in turn is coupled to the control grid of the second mixer.Collins Mechanical Filters For Sale Near Me
d. VFO AND SECOND MIXER. A 70E-12 permeability-tuned precision variable frequency oscillator provides the injection voltage to the second mixer, a 6BA7. The frequency range of the variable frequency oscillator is 1.955 – 2.955 mc. On 160-15 meters the 2.5 – 1.5 mc variable i-f frequency is mixed with the oscillator frequency to produce a difference frequency of 455 kc. On 11 and 10 meters the second harmonic of the variable frequency oscillator, 3.910 – 5.910 mc, is mixed with the variable i-f frequency of 5.455 – 3.455 mc to produce the 455-kc fixed intermediate frequency.
e. CRYSTAL FILTER (see Figure 4-2). The output of the second mixer is fed to the crystal filter. A 455-kc crystal, Y-7, acts as a very high Q resonant circuit which will pass only a narrow band of frequencies peaked sharply at 455 kc.
In order to neutralize the effect of the capacity between the crystal holder plates, phasing capacitor C-58 feeds a small out-of-phase voltage to the crystal filter output circuit. The phasing capacitor serves another purpose- If the phasing capacitor is adjusted so that the crystal holder capacity is not quite balanced out, the crystal forms, in addition to its series resonant circuit, a parallel resonant circuit slightly higher or lower in frequency than 455 kc, depending upon the setting of the phasing capacitor. Signals at this parallel resonant frequency are prevented from passing through the crystal circuit. Thus, the phasing control can be used to “notch out” interfering heterodynes close to the operating frequency. C-58 is a two-section capacitor; as the capacity of one section increases,the capacity of the other section decreases. By this means a capacity balance is obtained so that adjusting the phasing capacitor does not detune L-24.
A five-position switch, S-2, inserts various resistances in series with the crystal. The series resistor “de-Q’s” the crystal so that the value of the resistor determines the bandpass of the crystal filter circuit. In position “O” the crystal is shorted so that the input circuit feeds directly to the output circuit. In position “1” the crystal is in series with the parallel resonant i-f coil L-24 so that the crystal looks into a high impedance at 455 kc and is not fully effective. In positions 2 through 4, increasingly lower values of resistance are inserted in series with the crystal to increase the effective Q of the crystal circuit and thus provide greater degrees of selectivity.
f. MECHANICAL FILTER. The functional schematic diagram of the Collins Mechanical Filter is shown in figure 4-3. The mechanical filter uses the principle of magnetostriction to convert oscillating magnetic energy to mechanical vibration. The magnetostriction transducer input coil is resonated at 455 kc. A nickel wire within this coil vibrates mechanically and transmits this mechanical energy to the first of a series of nickel alloy discs. The mechanical vibration of this first disc is coupled to succeeding discs by means of nickel-wire coupling elements . Biasing magnets at either end of the mechanical filter polarize the filter elements to prevent frequency doubling, in much the same manner as biasing magnets in a headphone prevent the headphone diaphragm from bending in the same direction for both halves of an a-c cycle. The mechanical vibration of the last disc is coupled to a magnetostriction transducer element identical to the one used at the input of the filter. By a reverse principle of magnetostriction, the mechanical vibration of the nickel-wire transducer core is converted to electrical impulses.
Each of the discs employed in the mechanical filter has a mechanically resonant Q exceeding 2,000. Six of these discs are over coupled to produce a mechanically-shaped response curve with a flattop and straight,almost vertical sides. Thus, the filter passes a band of frequencies very little wider than the flat top of the selectivity curve. The mechanical filter used in the 75A-3 passes a band of frequencies approximately 3 kc wide and centered on 455 kc, providing an i-f selectivity curve ideal for the reception of AM and single-sideband signals. The 3-kc filter is supplied as part of the 75A-3; however, a mechanical filter having similar selectivity characteristics but having a bandpass of 800 cycles is available for use in CW reception or in phone reception under conditions of extremely heavy QRM or QRN.
g. 455-KC IF. The rest of the i-f system consists of three 6BA6 455-kc i-f amplifiers. The first of these is broad-tuned and is coupled to the two succeeding amplifiers,V-6 and V-7. The output of V-7 is coupled to the detector.
h. BFO. The BFO uses a 6BA6 in an electron-coupled oscillator circuit whose frequency range is approximately 453-457 kc. The BFO is tuned by means of a knob on the front panel.
i. “S” METER (see main schematic, figure 5-6). The “S” meter is connected in a bridge circuit between the screen grids of i-f amplifiers V-5 and V-6 and the cathode of i-f amplifier V-7. A reference voltage is developed at the negative pole of the “S” meter by the cathode current flow of V-7. This reference voltage is adjusted under no:signal conditions to a value equal to that developed on the positive pole of the “S” meter by the two i-f amplifier screen-grid voltages. The presence of a signal in the i-f strip causes an AVC voltage to be developed wh
https://diarynote.indered.space
*Collins Mechanical Filters For Sale In Ct
*Collins Mechanical Filters For Sale Near Me
*Collins mechanical filter. Cracked, broken cases. Mechanical Filter Fc = 455 kc / BW = 18 kc (COL) 526-9310-009. F455Q3, ’Y’ style filter will fit S-Line. 100k ohm in / out impedance. 3.5 dB BW is 18 kc, 70 dB BW is 70 kc.
*Get the best deals on collins filter when you shop the largest online selection at eBay.com. Collins Mechanical Filter 455 KHz CF, 1,2 or 4 KHz BW.
*Collins SSB / RTTY mechanical filter. 500 KHz IF, 1.4 KHz bandwidth. Fits 51J series collins receivers. Brand new stock that was squirreled away when.Home PageCollins Equipment Assorted Collins Parts Collins rubber feet kit. Kit includes (4) rubber feet, (2) extension feet & (1) set of hardware.
Collins mechanical filters for the 75A-4. Available bandwidths: 6khz and 10 khz AM, 2.5 khz SSB and 500hz CW. $195.95 each plus $7.00 shipping. ($15.00 international). MECHANICAL REQUIREMENTS: CONSTRUCTION: Sealed, Non-Hermetic CASE STYLE: PS MARKING: Rockwell Collins Part Number Date Code TEST CIRCUIT: 2k Ω 2k Ω ± 1% ± 3 pF 30 pF 30 pF ± 1% ±3 pF NOTE: 30 pF Includes any board stray capacitance. ROCKWELL COLLINS FILTER PRODUCTS 14101 MYFORD ROAD, TUSTIN, CA 92780 526-8693-010.(COL) 540-5175-000*** SOLD OUT ***0.01µF or 10,000 pF, Tusonix feedthru. 4kvw, 8kv test, 2-3/8’ long, 7/16’ bushing mount. #8/32 stud runs through center. Ceramic body, silver hardware. Our customers report this may replace your KWS-1 feedthru capacitor.#47 pilot bulb. Bayonet base. T 3-1/4. 6.3v, 0.15 amps. Fits all S-line / KWM2.Two pin microphone connector. Fits vintage Collins, Heath, etc. Made by Cooper Instrument.Operation parts manual for 180S-1, copy. Plug in solid state replacement for vacuum tubes 5R4 & 5U4. Octal base. Rated @ 2800 vdc, 1 amp. 1-3/8’ diameter x 1-1/8’ high. Solid State direct replacement modules are much more efficient than their vacuum tube predecessors. In some case, dropping resistors should be used if the higher output voltages often yielded with these diodes will create an unsafe condition. No heater current is required, saving watts there too. Printed on adhesive backed paper, NOT photocopies
or transfer decals. Instructions included.Part NumberDescriptionPrice EachPrice for 3(COL) DCL-KWS/0Fits older KWS-1 w/15 meter scale starting @ 21.0 MHz. 10.0024.00Add(COL) DCL-KWSFits newer KWS-1 w/15 meter scale starting @ 20.5 MHz.10.0024.00Add(COL) DCL-75A/0Fits older 75A-4 w/15 meter scale starting @ 20.8 MHz.10.0024.00Add(COL) DCL-75AFits newer 75A-4 w/15 meter scale starting @ 20.5 MHz.10.0024.00Add(COL) DCL-75A3Fits 75A-3.-SOLDOUT(COL) DCL-75A2Fits 75A-2.10.0024.00Add(COL) DCL-51JFits all 51J receivers.10.0024.00AddJ-4 PartsPart NumberDescriptionPrice Each(COL) 278-0092-000T102, 500 kc can95.00Add(COL) 278-0093-000T101, 500 kc can95.00Add(COL) 526-9009-00F500B60, 6 kc349.00Add(COL) 526-9030-00F500B14, 1.4 kc295.00Add(COL) 526-9215-009F500F-14, 1.4 kc (See below for more info & picture)249.00Add(COL) 51J451J-4 manual, copy35.00Add(COL) 526-9215-009Collins SSB / RTTY mechanical filter. 500 KHz IF, 1.4 KHz bandwidth. F500F-14. Fits 51J series collins receivers. Brand new stock that was squirreled away when this ’Radio Row’ shop closed in NYC. Brand new in the box!!Part NumberDescriptionPrice Each(COL) 278-0197-00T3, T4 IF can49.00Add(COL) 259-0417-00S5 AVC switch25.00Add(COL) 667-0018-00Collins T5A-4 Hammond Audio Transformer. 2’ c-c mount holes.
1.6’ x 1.6’ x 1.9’H. Alt P/N: 11271. NSN: 5950-00-772-8438 Pic139.00Add(COL) 526-9154-00F455J05, 500 Hz750.00Add(COL) 526-9089-00F455J31, 3.1 kc349.00AddPart NumberDescriptionPrice Each(COL) 662-0034-00T1 power inverter transformer replacement made by Ballastran
(BC-3254) for Collins MP-1. (Pictured)125.00Add(COL) 970-2170-00K1 relay for MP1 mobile power supply.65.00Add(COL) 352-0320-00Q1, Q2 DA3F3 for MP1 mobile power supply.SOLDOUT(PUB)(COL) MP1MP-1 Manual copy.15.00AddPM-2 Power SupplyPart NumberDescriptionPrice Each(COL) 183-1054-00C1, C2 20 µF, 450 v electrolytic caps.6.50Add(COL) 183-1009-00C7, 40 µF / 40 µF, 450 v twist lock.SOLDOUT (COL) 353-1661-00CR1-9 Diodes.2.00Add(PUB) COL-PM-2PM-2 Manual, copy.15.00Add75A-3
THE COLLINS 75A-3 RECEIVER
The 75A-3 is a dual-conversion communications receiver covering all amateur bands in the range 160-10 meters. It is the only amateur-band receiver featuring the Collins Mechanical Filter.
The 75A-3 also features excellent stability, sensitivity, and dial accuracy.Collins Mechanical Filters For Sale In Ct
The Collins Mechanical Filter, a new and radically different means of achieving selectivity – in communications receivers, uses mechanically resonant elements to produce a selectivity curve having a flat “nose” for full sideband response and steep, almost vertical skirts for rejection of adjacent- channel interference.
Because the mechanical filter in the 75A-3 has nearly rectangular selectivity curve, the receiver is well suited for single-sideband suppressed-carrier reception. And with the 75A-3 it is possible to use single-sideband techniques on AM signals by tuning one sideband and the carrier to the exclusion of the other sideband. Because of the unusual tuning characteristics of the 75A-3 the owner should familiarize himself with the operational procedures described in Section III of this manual.
The mechanical filter supplied with the 75A-3 has a 3-kc bandpass for optimum performance in AM and single-sideband reception; however, an 800-cycle filter, an accessory unit, may be installed for use under conditions of heavy QRM and QRN. Both filters are plug-in units and mount side by side in the receiver. A two-position switch on the front panel of the receiver is used to select the desired filter.
The direct-reading tuning dial is calibrated in 1-kc divisions on 160, 80, 40, 20 and 15 meters and 2-kc divisions on 11 and 10 meters. A crystal-controlled front end and temperature-compensated, hermetically-sealed variable frequency oscillator contribute to the frequency stability of the 75A-3. Physical shock will not change the VFO frequency unless the shock is so severe that the dial setting is changed.
Free online radio station software download. Included in the 75A-3 are a 4-position crystal filter, a phone noise limiter which automatically adjusts the clipping level according tothe strength of the incoming signal, a separate noise limiter for CW reception, delayed and amplified AVC, and provisions for external standby control and receiver muting. Two plug-in units available for use in the 75A-3 are the 148C-1 NBFM adaptor and the 8R-1 crystal calibrator.
75A-3 SPECIFICATIONS
a. RF CIRCUITS.
(1) SELECTIVITY.
(a) With 3-kc filter ……. approx. 3 kc at 6 db down and 6. 5 kc at 60 db down
(b) With crystal filter …. position 4: approx. 40 cps at 6 db down and 4 kc at 60 db down.
(2) SENSITIVITY …………… 2 uv for signal-to-noise ratio of 6 db.
(3) STABILITY
(a) Mechanical …………. CW beat note will not change if receiver is jarred unless dial
setting is changed.
(b) Electrical …………. stable within a few cycles under normal
operating conditions and after short warm-up period.
(4) IMAGE REJECTION ………. at least 50 db.
(5) AVC …………………. constant audio output within 6 db for r-f input change of 5 uv to 0.5v.
b. TUNING FEATURES.
(1) COVERAGE ……………. 1.5-2.5 mc; 3.2-4.2 mc; 6.8-7.8 mc
14.0-15.0 mc; 20.8-21.8 mc; 26.0-28.0; 28.0-30.0 mc.
(2) BANDSPREAD …………… linear; ten turns of vernier dial covers each range.
(3) DIAL ACCURACY ………… within 1 kc on 160-15 meters and 2 kc on 11 and 10 meters.
(4) “S” METER ……………. S9 corresponds to signal of about 100 uv.
d. POWER SOURCE …… 115 v, 50-60 cps; power consumption approx. 85 w.; 230-volt model
model available on special order or by use of a 230-volt power transformer.
e. ANTENNA INPUT . . . . . accommodates wide range of antenna impedances; designed
for 50-150 ohms terminal impedance; coax connectors provided.
f. AUDIO OUTPUT . . . . . . approx. 2.5 w
g. CABINET DIMENSIONS . . . 21-1/8 in. wide; 12-1/2 in. high; 13-1/16
in. deep; chassis fits standard relay rack; chassis depth 13-5/16 in.
h. FINISH . . . . . . . . . . . dark grey wrinkle.
i. ACCESSORIES.
(1) 800-CYCLE MECH FILTER . mechanical filter with bandpass of approx.
800 cycles; plugs in socket on receiver chassis.
(2) SPEAKER . . . . . . . . . external 10-in. speaker in matching cabinet;
Speaker cabinet 15 in. wide, 11-1/8 in. high, 9-1/8 in. deep.
(3) HEADPHONES . . . . . . . low-impedance type preferable.
(4) ANTENNA . . . . . . . . see e.
(5) CRYSTAL CALIBRATOR 8R-1. . plugs into a socket on receiver chassis;
provides 100-kc reference signals for calibration.
(6) NBFM ADAPTOR 148C-1 . . . . plugs into socket on receiver; contains
limiter and discriminator.
Under the hood…
75A-3 CIRCUITRY
1. GENERAL.
The 75A-3 circuit consists of a crystal-controlled front end, a variable i-f system, a low-frequency converter stage and a fixed 455-kc i-f system (see block diagram, Fig. 4-1). In the fixed i-f system, a mechanical filter first provides the necessary selectivity-curve shaping. The 455-kc intermediate frequency is then amplified and fed to the detector and audio circuits. A 455-kc signal from the beat-frequency oscillator is injected at the detector stage for CW reception. The audio system uses separate noise limiters for CW and AM; the CW noise limiter is variable, and the clipping level of the AM noise limiter is automatically adjusted according to the strength of the incoming signal. The output stage feeds a 500-ohm load or a 4-ohm speaker.
2. TUNING.
All variable tuned circuits, including the first r-f stage,the variable i-f system and the variable frequency oscillator are operated by the main tuning control. The vernier tuning dial is coupled directly to the shaft of the variable-frequency oscillator. The other variable-tuned circuits, including the r-f stage and the variable i-f stages, are tuned by powdered iron slugs which are attached to a common platform. The platform is moved up and down by means of a cam-driven mechanism which is coupled to the VFO shaft by means of split gears and metal bands. The 75A-3 uses a unique method of band switching in the r-f stage in which only the 80 and 160 meter coils are tuned by means of the main tuning mechanism, and coils for 40-10 meters are connected across the respective 80 meter coils. Varying the inductance of an 80-meter coil varies the total inductance, and therefore the resonant frequency, of the tuned circuit for the band in use.
3. RF CIRCUITS.
A simplified block diagram of the 75A-3 r-f system is shown in Figure 5-5. The first r-f stage feeds the mixer at the carrier frequency of the incoming signal. The coverage for each band is listed below:
160 meters – 1.5 – 2.5 mc
80 meters – 3.2 – 4.2 mc
40 meters – 6.8 – 7.8 mc
20 meters – 14.0 – 15.0 mc
15 meters – 20.8 – 21.8 mc
11 meters – 26.0 – 28.0 mc
10 meters – 28.0 – 30.0 mc
The first converter, consisting of a crystal-controlled oscillator circuit and a mixer tube, converts the incoming signal to the variable i-f frequency of 2.5 – 1.5 mc for 160-15 meters and 5.455 – 3.455 mc for 11 and 10 meters. From the variable i-f system the signal is fed to the second mixer where it is converted to a fixed i-f frequency of 455 kc. This signal is passed through the i-f amplifiers to the detector stage. A discussion of individual circuits in the r-f portion of the receiver follows:
a. RF STAGE. The RF stage uses a 6CB6 pentode. Individual variable slug-tuned coils are switched into the grid circuit on 160 and 80 meters. On 40-10 meters the coil in use is connected across the 80-meter coil, and varying the inductance of the 80-meter coil tunes the coil for the band use. The 80-meter trimmer capacitors are not in the circuit on 40-10 meters.
On 160 meters the output of the r-f amplifier is fed directly to the variable i-f system. On 80-10 meters the r-f plate circuit tuning system is the same as that of the grid circuit.
b. CRYSTAL – CONTROLLED OSCILLATOR AND FIRST MIXER. The high-frequency converter stage employs a 12AT7 in a Butler crystal-oscillator circuit. In this circuit the crystal is connected between the cathodes of a dual triode. Feedback voltage is coupled from the plate circuit of one section, which contains a tank circuit resonant at the crystal frequency, to the grid of the other section. The 180-degree phase shift necessary for oscillation is provided by the second section of the tube, which acts as a cathode follower to couple feedback energy to the crystal. Crystal-oscillator output voltage is coupled to the injection grid of the 6BA7 first mixer. An individual crystal for each band is switched in to the crystal oscillator circuit except on 160 meters, where the high-frequency converter is not used. The crystal- oscillator frequency beat switch the incoming carrier to produce the first, or variable, intermediate frequency. In this stage because the crystal frequency is fixed and the incoming carrier frequency may be anywhere in the range of the band in use, the difference frequency produced in the mixer must be tuned by a variable i-f system. On 160 meters the band coverage corresponds to the lower frequency range of the variable i-f’s.
c. VARIABLE IF. The variable i-f system covers two frequency ranges, 2.5 – 1.5 mc and 5.455 – 3.455 mc. The variable i-f system for the range in use consists of two slug-tuned circuits on the same frequency. The first of these two circuits is capacity coupled to the second, which in turn is coupled to the control grid of the second mixer.Collins Mechanical Filters For Sale Near Me
d. VFO AND SECOND MIXER. A 70E-12 permeability-tuned precision variable frequency oscillator provides the injection voltage to the second mixer, a 6BA7. The frequency range of the variable frequency oscillator is 1.955 – 2.955 mc. On 160-15 meters the 2.5 – 1.5 mc variable i-f frequency is mixed with the oscillator frequency to produce a difference frequency of 455 kc. On 11 and 10 meters the second harmonic of the variable frequency oscillator, 3.910 – 5.910 mc, is mixed with the variable i-f frequency of 5.455 – 3.455 mc to produce the 455-kc fixed intermediate frequency.
e. CRYSTAL FILTER (see Figure 4-2). The output of the second mixer is fed to the crystal filter. A 455-kc crystal, Y-7, acts as a very high Q resonant circuit which will pass only a narrow band of frequencies peaked sharply at 455 kc.
In order to neutralize the effect of the capacity between the crystal holder plates, phasing capacitor C-58 feeds a small out-of-phase voltage to the crystal filter output circuit. The phasing capacitor serves another purpose- If the phasing capacitor is adjusted so that the crystal holder capacity is not quite balanced out, the crystal forms, in addition to its series resonant circuit, a parallel resonant circuit slightly higher or lower in frequency than 455 kc, depending upon the setting of the phasing capacitor. Signals at this parallel resonant frequency are prevented from passing through the crystal circuit. Thus, the phasing control can be used to “notch out” interfering heterodynes close to the operating frequency. C-58 is a two-section capacitor; as the capacity of one section increases,the capacity of the other section decreases. By this means a capacity balance is obtained so that adjusting the phasing capacitor does not detune L-24.
A five-position switch, S-2, inserts various resistances in series with the crystal. The series resistor “de-Q’s” the crystal so that the value of the resistor determines the bandpass of the crystal filter circuit. In position “O” the crystal is shorted so that the input circuit feeds directly to the output circuit. In position “1” the crystal is in series with the parallel resonant i-f coil L-24 so that the crystal looks into a high impedance at 455 kc and is not fully effective. In positions 2 through 4, increasingly lower values of resistance are inserted in series with the crystal to increase the effective Q of the crystal circuit and thus provide greater degrees of selectivity.
f. MECHANICAL FILTER. The functional schematic diagram of the Collins Mechanical Filter is shown in figure 4-3. The mechanical filter uses the principle of magnetostriction to convert oscillating magnetic energy to mechanical vibration. The magnetostriction transducer input coil is resonated at 455 kc. A nickel wire within this coil vibrates mechanically and transmits this mechanical energy to the first of a series of nickel alloy discs. The mechanical vibration of this first disc is coupled to succeeding discs by means of nickel-wire coupling elements . Biasing magnets at either end of the mechanical filter polarize the filter elements to prevent frequency doubling, in much the same manner as biasing magnets in a headphone prevent the headphone diaphragm from bending in the same direction for both halves of an a-c cycle. The mechanical vibration of the last disc is coupled to a magnetostriction transducer element identical to the one used at the input of the filter. By a reverse principle of magnetostriction, the mechanical vibration of the nickel-wire transducer core is converted to electrical impulses.
Each of the discs employed in the mechanical filter has a mechanically resonant Q exceeding 2,000. Six of these discs are over coupled to produce a mechanically-shaped response curve with a flattop and straight,almost vertical sides. Thus, the filter passes a band of frequencies very little wider than the flat top of the selectivity curve. The mechanical filter used in the 75A-3 passes a band of frequencies approximately 3 kc wide and centered on 455 kc, providing an i-f selectivity curve ideal for the reception of AM and single-sideband signals. The 3-kc filter is supplied as part of the 75A-3; however, a mechanical filter having similar selectivity characteristics but having a bandpass of 800 cycles is available for use in CW reception or in phone reception under conditions of extremely heavy QRM or QRN.
g. 455-KC IF. The rest of the i-f system consists of three 6BA6 455-kc i-f amplifiers. The first of these is broad-tuned and is coupled to the two succeeding amplifiers,V-6 and V-7. The output of V-7 is coupled to the detector.
h. BFO. The BFO uses a 6BA6 in an electron-coupled oscillator circuit whose frequency range is approximately 453-457 kc. The BFO is tuned by means of a knob on the front panel.
i. “S” METER (see main schematic, figure 5-6). The “S” meter is connected in a bridge circuit between the screen grids of i-f amplifiers V-5 and V-6 and the cathode of i-f amplifier V-7. A reference voltage is developed at the negative pole of the “S” meter by the cathode current flow of V-7. This reference voltage is adjusted under no:signal conditions to a value equal to that developed on the positive pole of the “S” meter by the two i-f amplifier screen-grid voltages. The presence of a signal in the i-f strip causes an AVC voltage to be developed wh
https://diarynote.indered.space
コメント