From the manual:
|Frequency Coverage||40 meters, 7.0 to 7.2 MHz|
|20 meters, 14.0 to 14.2 MHz|
|15 meters, 21.0 to 21.3 MHz|
|Frequency Stability||less than 100 Hz drift after 10 minutes warmup|
|Power Requirements||13 volts DC, nominal. 35 mA receive mode and 450 mA transmit mode|
|Active Devices||synchrodyne detector, 40673 dual-gate MOSFET|
|audio amplifier, CA3035V1 integrated circuit|
|VFO and buffer, MPF105 JFET|
|doubler/tripler, MPS6521 silicon transistor|
|driver, MPS6521 silicon transistor|
|final amplifier, two MPSU05 silicon transistors|
|sidetone oscillator, 2N3393 silicon transistor and X29A829 silicon transistor|
|break-in keying, 2N3393 silicon transistor and X29A829 silicon transistor|
|transmitter keying, S2091 silicon transistor|
|Dimensions||9-¼" wide x 8-½" deep x 4-¼" high, including knobs and feet|
|Weight||4 lbs. 8 oz.|
|DC Power Input||40 meters -- 3 watts|
|20 meters -- 2.5 watts|
|15 meters -- 2 watts|
|Frequency Control||40 meter crystal or built-in VFO on 40 meters|
|20 meter crystal or built-in VFO on 20 meters|
|15 meter crystal or built-in VFO on 15 meters|
|Output Impedence||50 ohms unbalanced|
|Spurious and |
|at least 25dB down|
|Sensitivity||less than 1 microvolt provides readable signal|
|Selectivity||2 kHz at 6dB down|
|Type of Reception||CW or SSB|
|Audio Output Impedance||1000 ohms nominal|
The HW-7 was the first QRP transceiver offered by Heathkit. It was available from 1972 through 1975. The HW-7 provided coverage of 40, 20, 15 meter bands. The transceiver featured a very simple direct-conversion receiver design and this simple design led to performance problems including sometimes-severe broadcast-band interference, microphonics, and AC hum. According to the January, ARRL review (January, 1973), the original price of the HW-7 was about $70.
I built an HW-7 in the late seventies when I held a Novice license. The kit was purchased on close-out from Heathkit after the introduction of the HW-8. (If memory serves, the close-out price was $40, and my parents paid half.) This rig was a miserable performer and very few contacts were made with it. I had installed a choke to reduce common-mode hum and an MFJ CWF-2 four-stage active audio filter. This HW-7 was lost in the 1989 fire.
My current HW-7 was purchased from NS8O who had significantly improved the receiver's front-end. This rig is a much better performer than my original one was and is pleasant to operate.
The HW-7 is designed for use with high-impedence mono headphones. Before I found a proper set of vintage Trimm Featherweight headphones, I used modern low-impedence stereo headphones with an impedence adapter (image) built around a Radio Shack #273-1380 audio transformer.
I plan to install a Small Wonder Labs Freg-Mite audible frequency counter (link) in my HW-7 at some point. This clever device announces the VFO frequency in morse code at the press of a button and will allow me to know my precise frequency no matter where on the dial I am.
An extremely useful reference on the HW-7 is Michael Bryce's HW-8 Handbook, Second Edition. This book provides circuit descriptions, schematics, board layouts, alignment instructions, Heathkit service bulletins, and modifications for the HW-7, HW-8, and HW-9. It is available at Michael Bryce's The Heathkit Shop, at Kanga, USA, and at QRP ARCI. The older, First Edition, HW-8 Handbook has modifications for the HW-7, HW-8, and HW-9 but lacks the other valuable content.
Attribution: scan of HW-7 manual cover from the Boat Anchor Manual Archive.