Note
The VF-2031 replaced Heath’s original HT (the HW-2021) in 1978. The new unit features several significant improvements. First, it has twice the output power—2 watts. Second, it provides switch selection of simplex and ±600 kHz operation. Third, it provides three additional channels for a total of 8.
The VF-2031’s total frequency coverage is from 143.5 to 148.5 MHz, but in practice the 8 crystal frequencies all must fall within a single 2 MHz section of the total range. One crystal is used for both the transmit and receive frequency.
As with its predecessor, Heath cautioned that the VF-2031 was not for beginning kit builders. The VF-2031 uses a 10.7 MHz IF and has a rated sensitivity is 0.5 µV or less for 20 db quieting.
Top mounted controls include volume, squelch, channel selector, and a three position simplex/offset switch. There is also a connector for an optional external microphone (not a speaker-mic).
A tone encoder was offered as an option (VFA-2031-5). When installed, it adds a small circuit board, and a switch to the top panel. Refer to photos. The encoder provides a selection of two audible or sub-audible tones (but not both), and has an option for burst or continuous tone. If burst is chosen, a burst duration must also be chosen. If the burst option was not chosen, those parts on the circuit board will not be installed.
Other optional equipment includes a touch tone pad and a leather case, and a push-to-talk microphone (VFA-2031-6).
The VF-2031 apparently did not incorporate the battery saver circuit employed in the 2021. Still, the 10 AA NiCads (solder lead type) will provide about 10 hours of “normal” operation. The VF-2031 is built into a black plastic case with a liner of metal foil-covered paper and was supplied with a drop-in charger.
The 2031 sold fairly well but suffered from a variety of problems mostly related to difficulty in assembly. Tiny parts in tiny spaces were more than many builders could take on. The VF-2031 requires only a VTVM for alignment.
CRYSTAL CALCULATIONS
Receive crystal frequency = (operating frequency – 10.7) / 9
Note: Transmit frequency is derived from receive frequency and does not require an additional crystal.
Tolerance: 0.002% or better
Load capacity: 47 pF
Equivalent series resistance: 25Ω maximum at 25C
Motional capacitance: 0.023 pF ±10%
Static capacitance: 5 pF ±1 pF at 1 MHz (pin to pin, case unguarded)
Drive level: 0.5 milliwatts or less
Stability: ±40 ppm (–30 to +60C)
Holder: HC-25U
References:
Review. QST. Oct 1979, p. 47.
RECEIVER
Sensitivity: 0.5 µV or less for 20 db quieting
Squelch threshold: 0.24 µV or less
Audio output: 1 watt 10% or less THD
Frequency stability: 0.005% or better
Adjacent channel selectivity: 40 db or greater
IF frequency: 10.7 MHz
Usable bandwidth: ±7 kHz
TRANSMITTER
Power output: 2 watts or more at 12.5 VDC, adjustable internally
Deviation: 5 kHz or less, adjustable internally
Spurious output: –50 db or greater at 2 watts output
Stability: 0.005% or better
Oscillator frequency: approximately 15 MHz
Multiplication factor: x9
Modulation: FM
Transmitter offsets: –600, +600, 0 (simplex) with supplied crystals
GENERAL
Frequency coverage: 143.5 to 148.5 MHz
Operating temperature: +10F to +125F
Operating voltage: 12.5 VDC nominal
Channels: 8
Antenna impedance: 50Ω
Speaker impedance: 8Ω
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
