Elecraft K3S
$$$$$
| Frequency | 160-6 m transmit; general-coverage receive |
| TX power | 100 W (sold in two configurations - K3S/10 (10 W) and K3S/100 (100 W) - with the KPA3A internal module upgrading a 10 into a 100: the Elecraft way runs upward) |
| Modes | SSB, CW, AM, FM, DATA |
| Weight | 3.8 kg (8.4 lb) |
| Connector | SO-239 (ANT1 and ANT2, NOT BNC) |
| antenna 1 | SO-239 (ANT1, main antenna) |
| antenna 2 | SO-239 (ANT2, second antenna via optional KAT3A ATU) |
| aux rf | SO-239 (AUX RF for sub-receiver) |
| rx ant | BNC (RX antenna in/out on KXV3B module) |
| transverter | BNC (transverter in/out on KXV3B module) |
| mic front | 8-pin front mic jack (NOT 3.5mm TRRS, that is the KX2/KX3) |
| headphone front | 1/4" stereo (front) |
| headphone rear | 1/8" stereo (rear) |
| speaker | stereo speaker jack |
| usb | USB-B (CAT control + isolated audio in/out on same cable) |
| rs232 | RJ45 (with supplied RJ45 to DE9 adapter cable) |
| key | 1/4" stereo KEY jack + 1/4" stereo PADDLE jack + PTT In + KEY Out |
| acc | accessory jack |
| band data | band information output |
| dc power | DC input jack (13.8V, circuit breaker on 100W model) |
| power req | 13.8 VDC. No internal battery option (the K3S is a base station radio; the KX2 and KX3 have batteries, not the K3S). |
A receiver that out-measured radios at triple the price for a decade, in a package light enough for a backpack and modular enough to service by mail: the K3S is what happens when contest-grade RF engineering refuses to weigh anything. The identical-subreceiver diversity option remains genuinely rare, and the option ecosystem means every used unit is a different (upgradeable) radio.
The interface is knobs-and-menus austere by current touchscreen standards (no waterfall without the companion panadapter), the options system means 'a K3S' is really a configuration to audit before buying used, and discontinuation puts parts on the secondary market's clock - though the maker's legendary service continues.
Still the thinking operator's used buy: contest-reference receive performance at half its successor's price, with the audit-the-options caveat. Buyers wanting waterfalls and modern UX shop the K4 line this radio begat.
The K3S was the radio that proved a garage-scale California company could out-engineer the Japanese majors where it counted: the receiver. Its second-generation down-conversion superhet architecture - crystal roofing filters as narrow as 200 Hz guarding a high-dynamic-range chain - parked at or near the top of the independent receiver rankings for the better part of a decade, which made the 8.4-pound, eleven-inch package a standing rebuke to radios three times its weight and price. Contest stations bought them in pairs; DXpeditions flew them in carry-ons; the phrase 'K3 numbers' became shorthand for the performance tier.
The architecture's famous option is the subreceiver: not a junior monitor but an IDENTICAL second receiver, enabling true diversity reception - two antennas, two ears, one brain - the low-band DXer's edge that few radios at any price have matched. The rest is the company's signature modularity: options installing with a screwdriver, boards swapping by mail, the radio sold as a 10-watt K3S/10 or 100-watt K3S/100 with an internal module bridging the two, USB and RS-232 both aboard, and firmware that kept improving the radio for years after purchase. 'Kit heritage' undersells it; the K3S is less a product than a chassis of decisions.
Production ended when the K4 generation arrived with direct sampling and the waterfall the K3S never had, which converted clean K3S units into the used market's blue-chip holding: contest-reference receive at half the successor's price, pending an options audit (no two used K3S radios are the same radio). Its natural companions remain the matched amplifier line and tuner built to its scale - the K-line desk that defined small-footprint excellence.