Heathkit HD-11 reviews

The Heathkit HD-11 was the last version of Heath's Q-multiplier receiver accessory offered about 1961. Previous versions had to be powered from the receiver's power supply but this version had the power supply built in. It's circuit used one vacuum tube, a 12AX7 and, when wired into to an inexpensive short wave radio's 455 kHz Intermediate Frequency (IF) amplifier stage, was used basically as an extra tunable regenerative stage which increased the receiver's selectivity, allowing the listener to pick out only one Morse code signal where there might be several interfering with each other! An additional function allowed for nulling out interfering carriers when listening to AM radio voice transmissions on a crowded band. The regenerative function would also permit low-end short wave radios without beat detectors (BFOs) to detect Morse Code signals. These inexpensive (around $15) kits could boost the functionality of many of the less expensive radios that beginning ham radio (Novice) operators used in the 1950s and 60s. The HD-11 was my first electronic kit when I was 14 years old and was wired into my new Hallicrafters S-107 receiver. As a beginner, it took some time to learn how to adjust the Q-multiplier for best reception, as it could be critical to tune, but today, at age 74, I still have it and have found it very useful as an add-on for several radios in the last 60 years, including a high-end 60's vintage Collins KWM-2A transceiver! Lately, someone compaired the notion of a Q-multiplier as "Grandpa's DSP!" a fair statement although it was only a fairly simple analog device!

DE WA4A Bob Truitt