First Impressions: Yaesu VL-1000 Quadra & IC-756

This is the text of an e-mail I posted to the Icom and Yaesu reflectors on 8 December 1998.

The following may be of interest to Icom HF radio owners who are contemplating the purchase of a solid-state kilowatt linear:

I got the VL-1000 linear up and running with my IC-756 very easily. First, I reprogrammed it per Yaesu's instructions, to activate 10 and 12m; this 15-minute task in effect reconfigured the amplifier as the "International" model. I then connected it to the 756, via 4 cables: RF, ALC (mandatory), PTT and remote keying. The latter allows the Quadra to key the exciter for tuning when the F SET or TUNE button is pressed.  The remote keying cable is a shielded cable which connects VL-1000 Amplifier Band Data 2 (DB15) to Icom ACC2 (8-pin DIN). Connect Band Data 2, Pin 9 (F SET COMMON) via shield to ACC2 Pin 2 (GND). Connect Band Data 2, Pin 11 (F SET 2) via center conductor to ACC2 Pin 3 (SEND). Click here for detailed information on interfacing the VL-1000 to an Icom exciter.

The final step was ALC calibration; the Quadra's ALC level was set to limit power output to 1 kW, corresponding to approximately 65W of drive. The power output is almost constant across all HF bands. (Note: If the exciter power output can exceed 100W, as is the case for the IC-775, IC-781, IC-7700, IC-7800 or IC-7850/51, the input attenuator ATT should be enabled).

I initially tested the setup at the 500W output level, with the amp powered from 120V mains. Operation is flawless; tuning is smooth, and the fans in the amp and power supply are whisper-quiet! The amplifier RF unit has a small fan (beneath the autotuner), which runs once the interior reaches 40C. It also has two large muffin fans on the rear panel; these run when the amplifier is keyed. Two similar fans on the rear panel of the VP-1000 power supply run as needed, when the interior temperature rises to 40C.

When using the VL-1000 with an Icom radio and the remote keying (Band Data 2) cable, pressing the [F SET] button on the amplifier keys the exciter. The VL-1000 counts the excitation frequency to the nearest 100 kHz, and sets the bandswitching and pre-positions the tuner for the correct band. The tuner is a T-network with two series-arm air-variable capacitors driven by stepper motors, and a shunt-arm inductor with relay-switched taps. It will match loads with a maximum VSWR of 3:1 (impedance range 16.5 to 150 ohms) on HF, and 2:1 (impedance range 25 to 100 ohms) on 6m. The tuner is in th esignal path on receive and transmit, and thus offers some additional receive preselection when enabled.

When setting up the system, a midband frequency is selected in each band, and the [TUNE] button is pressed. This keys the exciter and amplifier, and starts the tuning cycle. An interesting graphic display, with an SWR bargraph and two rotating capacitor images, appears on the LCD screen. When tuning is complete, the display switches to a chart of frequency vs. SWR at the tuner input and output. Tuner set points are memorized, and displayed as a graph of SWR at the tuner input and output against frequency.

Prior to pressing [F SET] or [TUNE], the exciter is set to RTTY or FM mode to transmit a continuous carrier to the VL-1000.

Other selectable displays include peak and average power output, SWR, operating frequency to the nearest 100 kHz, DC input (drain) voltage (Vdd) and current (Idd).

Overall, I am "thrilled to bits"; after getting the 220V mains hooked up, I stayed up very late working the European 80m DX window, then ran the Icom Users' Net on 20m.

Operation is not quite as automated as it was with my old IC-2KL setup; one must press F SET every time one changes bands. This is not a major inconvenience, however. Automatic antenna selection by band does not occur in the frequency-counting mode; it works only if the exciter is a Yaesu transceiver which provides band data to the VL-1000. I can live with that, as I am only running two Cushcraft vertical antennas - an R8 for 40 through 10m, and an AV-80 for 80m.  Excellent reports are received from Europe on 80m, and also on other bands, with the 756/756Pro and the Quadra.

I have been running this station with various Icom exciters for nearly 18 years now; in July 2000, I replaced the IC-756 with an IC-756Pro. The Icom transceiver and the Quadra are performing flawlessly together. My current exciter (since 2008) is an IC-7700.

In conclusion, I can heartily endorse teaming up the Quadra with an Icom HF transceiver. The Quadra is a marvellous piece of equipment; it offers the added bonus that it can be operated with any exciter, and still maintain almost all its automation.

Copyright  1999-2016 A. Farson VA7OJ/AB4OJ. All rights reserved. Last updated 07/28/17