FlexRadio FLEX-6400M vs Elecraft K4
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FlexRadio FLEX-6400M or Elecraft K4? I put both radios side by side: data from the manufacturers’ data sheets and photos at the same scale. FlexRadio FLEX-6400M comes out better: AM power and transmit current draw; Elecraft K4: weight.
FlexRadioFLEX-6400M
HF · 6 m100 Wtuner4.8 kgdiscontinued
ElecraftK4
HF · 6 m100 Wtuner4.5 kg
Specs side by side
| FlexRadioFLEX-6400M▲ 2 | ElecraftK4▲ 1 | |
|---|---|---|
| Bands and modes | ||
| Transmit bands | HF 1.8–29.7 MHz50–52 MHz | HF 1.8–29.7 MHz50–52 MHz |
| Receive range | 0.03–54 MHz | 0.1–54 MHz |
| Modes | SSBCWAMFMFreeDV | SSBCWAMFMRTTYPSK |
| Transmit power | ||
| HF | 100 W | 100 W |
| 50 MHz (6 m) | 100 W | 100 W |
| AM | 25 W ▲ | no data |
| Receiver | ||
| Construction | SDR, direct RF sampling (1 A/D converter, 122.88 MHz) | SDR, direct RF sampling; modular (upgradeable to K4D / K4HD) |
| Second receiver | yes — 2 receivers (slices) on any bands, shared antenna | dual receive on any bands (shared A/D converter; K4D: separate KRX4 receiver) |
| Spectrum and waterfall | 2 panadapters + waterfall, up to 14 MHz span | dual spectrum + waterfall, mini-pan |
| Features | ||
| Antenna tuner | internal option (ATU version), up to 3:1 SWR | internal KAT4 option, up to SWR 10:1 (160 and 6 m: 5:1) |
| Display | 8″ colour touchscreen, 1920×1200; HDMI output | 7″ colour touchscreen; HDMI output |
| LAN / remote operation | built-in LAN, SmartLink — remote operation (PC, Maestro, iPad) | built-in LAN, remote operation without a PC (K4 ↔ K4, K4/0) |
| USB | 2× USB-A for accessories; CAT and audio over LAN (SmartSDR CAT / DAX) | USB-B: CAT + audio, 3× USB-A (1 on the front) |
| SD card | — | — |
| Antenna connectors | 2× SO-239 + RX A, XVTR (BNC) | 1× SO-239 (3× with KAT4) + RX ANT, XVTR (BNC) |
| Power and case | ||
| Power | 13.8 V DC, external power supply | 13.8 V DC, external power supply |
| Transmit current draw | 23 A ▲ | 25 A |
| Dimensions | 356 × 171 × 337 mmwidth × height × depth | 343 × 114 × 280 mmw × h × d |
| Weight | 4.8 kg | 4.5 kg ▲ |
| Other | ||
| Memory channels | no data | 200 |
| Release | 2018discontinued | 2020 |
Data: manufacturers’ spec sheets and manuals · as of 31.10.2026
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