LDG AT-600ProII
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| Frequency | 1.8-54.0 MHz |
| TX power | 600 W (Passes 600 W SSB / 500 W CW / 400 W FT8 / 300 W digital / 250 W on 6 m after matching (Manual Rev C). Tune at 5-125 W only (firmware blocks relay switching above 150 W).) |
| Modes | all |
| Weight | 1.59 kg (3.5 lb) |
| tx in | TX: SO-239 (Teflon), from the radio/amplifier |
| ant out | ANT1 + ANT2: two SO-239 (Teflon) - 2-position antenna switch |
| radio | Radio interface: jack for optional Icom (IC-PAC) / Yaesu (Y-ACC) tune cables |
| ext meter | Ext. Meter jack (for the discontinued M-600 analog meter) |
| dc in | DC coaxial, 11-16 V DC at 1 A max (idle ~7 mA), center positive |
| ground | wing-nut ground terminal |
| power req | 11-16 V DC, 1 A max (idle ~7 mA), center positive (standalone - needs its own supply) |
Estimated (unverified): The ProII-generation introduction year is not documented by LDG; the automatic switched-L line dates to 1995-96 and the current manual is Rev C (2023). Some dealer listings still publish older/incorrect figures (600 W CW, 250 W digital, 6-800 ohm); the current manual's values are used here.
A mid-power automatic tuner for stations running a few hundred watts: after matching it passes 600 W SSB (500 CW, 400 FT8, 300 digital, 250 on 6 m), with set-and-forget operation. A built-in two-position antenna switch and over 4,000 memories handle most station layouts without a separate switch box, and the wide 6-1000 ohm range covers most multiband antennas. Compact (~1.6 kg) with an LED bar-graph wattmeter and an optional analog meter.
The tune cycle must run at 125 W or less (firmware blocks above 150 W), so an amplifier is bypassed during tuning. The relay network clicks while searching, and it needs its own 12 V supply plus an external balun for ladder-line antennas. Several long-standing dealer listings carry incorrect specs (600 W CW, 6-800 ohm). And LDG is a very small company whose continuity has been questioned - confirm warranty support before buying.
A mid-power automatic tuner that brings LDG's set-and-forget tuning to stations up to about 600 watts, with a two-antenna switch and 4,000 memories built in. It does the same job as the kilowatt AT-1000ProII at lower cost and bulk; for QRP or barefoot operating the smaller Z-100Plus covers the same ground. Mind the low-power tune cycle and the usual LDG caveat about confirming current support.
The AT-600ProII is the mid-power member of LDG's automatic-tuner line, sized for stations running up to a 600-watt amplifier. It works exactly like its bigger sibling the AT-1000ProII: a microprocessor-driven switched-L network of relay-selected capacitors and inductors that hunts for a match and remembers it, covering 1.8 to 54 MHz and matching 6 to 1,000 ohms (16 to 150 on 6 meters).
It passes 600 watts on SSB, 500 on CW, 400 on FT8, 300 on the continuous digital modes, and 250 on 6 meters. As with every tuner of this type the tune cycle happens at low power - 5 watts up to around 125, with a 150-watt firmware ceiling on relay switching - so an amplifier is bypassed while it searches, then run at full power once the match is set. A built-in two-position antenna switch with its own SO-239 jacks, more than 4,000 memories across the two ports, and an LED bar-graph wattmeter (60- and 600-watt scales) round it out, with an optional analog meter available.
At about 3.5 pounds it is compact, and it is a standalone tuner with its own 12-volt input rather than a radio-powered unit, though optional cables let it tune from many radios' TUNE buttons. A note on the specs: some long-standing dealer listings still show 600 watts on CW and a 6-to-800-ohm range, but LDG's current manual rates it at 500 watts CW and 6 to 1,000 ohms - the figures used here. As with the rest of the line, LDG is a small company whose continuity has been questioned, so confirm warranty support before buying.
For a station running a few hundred watts into multiband wire or vertical antennas, the AT-600ProII removes manual tuning without the cost or bulk of the kilowatt AT-1000ProII, and its two-antenna switch covers most setups without a separate switch box. Operators who want the same automatic behavior at QRP or barefoot power can look at the smaller Z-100Plus.