FlexRadio FLEX-6600 / 6600M
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| Frequency | 160-6 m transmit; TWO SCUs digitize independently at 245.76 Msps |
| TX power | 100 W (100 W) |
| Modes | SSB, CW, AM, FM, DATA |
| Weight | 5.9 kg (13 lb) |
| Connector | SO-239 |
| antenna 1 | SO-239 (ANT1) |
| antenna 2 | SO-239 (ANT2) |
| xvtr 1 | BNC (transverter 1) |
| xvtr 2 | BNC (transverter 2) |
| rx in 1 | BNC (RX antenna input 1) |
| rx in 2 | BNC (RX antenna input 2) |
| mic | 8-pin (rear panel) |
| headphone | 1/4" stereo |
| key | CW key input |
| ethernet | Gigabit Ethernet (primary control) |
| dc power | 13.8 VDC ±15% (2A RX, 23A TX) |
The architecture argument settled in hardware: two independent digitizers turn diversity reception, full duplex, and single-box SO2R from aspirations into checkbox features, and the doubled sampling rate gives the waterfall a 14-MHz horizon. For contest stations and low-band diversity devotees living the network-radio philosophy, this is the line's sweet spot.
The premium over the 6400 is the price of the second SCU - operators who'll never run two antennas at once are buying silicon they won't light - and all the line's software-soul caveats (update culture, licensing history, screen-first operation) apply at double the stake. The M tax for knobs continues.
The Flex that contest results justify: diversity and SO2R in one network appliance, measured publicly, priced accordingly. The 6400 serves the philosophy at entry cost; the 6600 serves the operators who exploit it.
The FLEX-6600 is the 6400's architecture with the limitation deleted: TWO Spectral Capture Units - independent 16-bit digitizers, each sampling at 245.76 megasamples - which transforms the radio's possibilities in a single stroke. Two antennas digitized separately means true diversity reception (the low-band DXer's two-ears advantage), genuine full-duplex operation, and single-box SO2R contesting; four slice receivers carve the doubled spectrum, and the waterfall's maximum breadth doubles to 14 MHz. Ahead of the converters sit SEVENTH-order bandpass filters on the contest bands - better than 50 dB of rejection, against the 6400's third-order set - because the design brief was multi-transmitter weekends where the other station's kilowatt lives 7 MHz away. The internal ATU is standard at this tier.
The network-native soul carries over whole: SmartSDR clients anywhere, MultiFLEX operator-sharing, DAX digital plumbing without interface boxes, and the M variant dressing the server in a display and knob deck for hands that insist. The 6600M took the full ARRL laboratory treatment in February 2020, whose Bottom Line read: 'top-tier performance and, with its built-in seventh-order band-pass filters, is easily capable of operating full duplex on two bands at a time' - the kind of published sentence contest stations build purchase orders around.
The buying logic is unusually clean: every dollar of premium over the 6400 purchases the second SCU and what it enables, so the decision reduces to whether diversity, duplex, or SO2R appear in your operating future. If yes, this is the line's sweet spot; if no, the 6400 is the same philosophy at entry price; and if the philosophy itself chafes, the knobs-first alternative awaits in the other aisle. The 6000 series has since passed the new-radio catalog to the FLEX-8000 and Aurora generations - launch MSRPs of $3,999 and $4,999 (M) anchor today's Certified Pre-Loved and used pricing - but the 6600 still doesn't argue with anyone: it just samples both antennas and lets the results talk.