Note
The VL-2280 is a 75 watt two-meter all-mode base station amplifier. It got rave reviews and worked extremely well, but Heath discontinued the amp in 1984 as part of a long-term decision to phase out its amateur product line.
Heath also sold a mobile version of this amplifier, the VL-1180.
The VL-2280 covers 144-148 MHz and requires from 1 to 10 watts of drive. It will operate FM, SSB, and CW providing a nominal 75 watts out with 10 watts in—and will do so from one end of the band to the other without retuning. One watt of drive will yield nearly 20 watts of output. Refer to Figure 5.
The 2280 has a well regulated power supply and is built on three PC boards that surround its large power transformer. Refer to Figure 1. Heatsinks on the left side cool the amplifier, while heatsinks on the right side cool the power supply. The RF board uses a single MRF247 power transistor and incorporates “strip-line” construction as well as air-wound inductors.The large heat sinks allow the amp to run with a 50 percent duty cycle—10 minutes on, 10 minutes off. These same heat sinks eliminate the need for SWR protection circuits. The unit will withstand a 30:1 SWR at full power.
The illuminated front panel meter reads drive power, power output, and DC voltage. Front panel controls include main power, mode, standby, and meter function. The mode switch selects between SSB and FM and simply adds a TR relay drop-out delay to prevent relay chatter in the SSB mode. Three front panel LEDs indicate “power on” and “amplifier on” status, as well as an over-temp condition.
Rear panel connections include two SO-239 RF connectors, a connector for supplying 12 VDC at up to 4 amps to an external device (a transceiver, for example), and an accessory socket for remote keying of the amp. There are also two standard cartridge fuse holders on the rear panel. One of these is for the 120 VAC input and the other for the 12 VDC supply.
The amp may be keyed remotely or by RF sensing and has a built-in TR relay. RF is bypassed around the amp when it is off or in the standby mode. Insertion loss is about 0.6 db.
Tune-up requires only an exciter and a wattmeter. The VL-2280 was a very popular amp and sold well.
Caution: Do not exceed drive or duty cycle specifications.
References:
Review. QST. Jun 1982, p. 48.
Frequency range: 144 to 148 MHz, aligned to 146 MHz
Power output: 75 watts nominal (at 13.8 VDC) with 10 watts drive
Power input:
1 to 10 watts (maximum) CW, SSB, FM 50% duty cycle, 10 minutes on, 10 minutes off
10 to 15 watts (maximum) CW, FM 50% duty cycle, 2 minutes on (maximum), 2 minutes off
Mode: SSB, FM, CW, RTTY
Input/output impedance: 50Ω, SWR 2:1 maximum
Conducted spurious and harmonics: –60 db or better
Third order distortion: –24 db referenced to one of two tones, or –30 sb reference to CW power
Operating temperature range: –4 to +104F
Power requirements: 120/240 VAC, 50/60 Hz, 7/3.5 amps
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.