Note
The HW-20 is the same basic design as the HW-10 except for frequency coverage. The unit is built around 15 tubes. The frequency coverage of the HW-20 is 143.8 to 148.2 MHz.
Supplied with a Turner 350C ceramic microphone, also sold separately as the GH-12.
CRYSTAL FREQUENCY CALCULATION
operating frequency = crystal frequency x 18
Refer to HW-10 for additional discussion and details.
References:
Brief description. Electronics World, Mar 1961, p. 120.
Review. QST. Jan 1962, p. 50.
Review. CQ. Nov 1962, p. 37.
Notes. QST. Aug 1964, p. 64.
Alignment problems. CQ. Oct 1962, p. 98.
Add discriminator and phase modulator. 73 Amateur Radio. Oct 78, p. 104.
Review. Electric Radio. Mar 2006
Receiver
Frequency coverage: 143.8 to 148.2 MHz
IF Frequencies (double conversion):
First IF: 22 to 26 MHz tunable
Second IF: 2 MHz
Noise figure: 8.5 db or less
Sensitivity: 0.5 µV input will produce an output signal better than 10 db above the noise level
Squelch sensitivity: less than 1.0 µV
Selectivity: 15 kHz at 6 db down
Image rejection: better than 70 db (tunable)
IF rejection: 50 db
Input impedance: 50 to 72Ω
Audio power output:
receiver: 3 watts
PA system: 15 watts
Headphone jack: 1/4 inch, low impedance
Public address speaker connection: 8Ω, RCA jack
Transmitter
Frequency coverage: 143.8 to 148.2 MHz (crystal or tunable)
Modulation: 0.01 volts minimum at 1000 Hz = 100%
Power output:
AM: 10 watts
CW: 8 watts
Distortion: 10% or less, with 100% modulation at 1000 Hz
Output impedance: 50 to 72Ω
Low pass filter cut-off: 152 MHz
Crystal type: FT-243
Microphone: high impedance ceramic: PTT
Crystals frequency range: 8.000 to 8.222 MHz
General
Power requirements:
6 VDC at 14.5 amps transmit and 8.5 amps receive
12 VDC at 7.5 amps transmit and 4.5 amps receive
120 VAC at 1 amp transmit and 0.5 amps receive
Tubes: (1) 12AX7, (1) 6AK6, (1) 0B2, (1) 6AN8, (1) 6BH6, (1) 6BS8, (2) 6EA*, (1) 6DZ7, (3) 6BJ6, (2) 6AQ6, (1) 6360
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.