Kenwood TS-140 / TS-140S (1987)

A compact 160-10 meter workhorse that Kenwood built on the same board as the TS-680 - and then quietly left the 50 MHz parts off.

Overview

The TS-140S is an HF transceiver covering the amateur bands from 160 through 10 meters, with SSB, CW, AM, and FM modes. A ham in the late 1980s could buy it as a primary station or a second radio. Kenwood claimed output power to 100 W on 10 m (SSB: 110 W PEP), but ARRL Lab dynamic testing measured only 52 W on 10 m. QST reviewed it in June 1988 under the banner "160-10 Meter Transceiver," and the magazine's ARRL Lab tested a unit with serial number 8101427. Kenwood rated receiver coverage at 500 kHz to 30 MHz. On the bench, the Lab found it tuned from 50 kHz all the way to 34.9999 MHz.

Owners describe it in terms that don't oversell. "The TS-140 is not a miracle - it's a workhorse," one long-time user wrote on the QRZ.ru forums. "A very reliable and unpretentious rig." Another called it "a quite acceptable option as a supplementary radio."

The design uses double-conversion for FM transmission and triple-conversion for all other transmission modes and for all modes in receive, with a 40 MHz first IF — an up-conversion scheme that forum contributors note provides "not-bad reception" despite the modest conversion count. The receiver front end uses a pair of 2SK125 junction FETs in the first and second mixers, a detail from the factory manual that explains why the radio holds up better than its price class might suggest. The 100-watt output is the headline number, but the interesting story is underneath the chassis.

Key Features

Shared Motherboard with the TS-680

The TS-140S and the Kenwood TS-680 use the same main board. Owners who have opened both report that the 50 MHz band components are simply not populated on the TS-140 - the solder pads are there, the parts aren't. The ROM differs between the two models, so adding 6 meters to a TS-140 isn't a matter of dropping in a few components. Forum contributors note that it would take redesigning and reprogramming the synthesizer, and they generally recommend a transverter instead. The shared platform also means shared documentation: modification guides, front-panel descriptions, and the service manual itself typically cover both radios together.

40 MHz First IF and Up-Conversion

The receiver converts upward to a 40 MHz first IF before dropping to 455 kHz for the second conversion. Together with the 2SK125 FETs in the mixer stages, that gives the TS-140S a receiver that punches above what its simple two-conversion design might imply. It's not a contest-grade front end - nobody claims it is - but it's clean enough for casual operating.

Filter Options: YG-455 C1 and YK-455 C1

For CW operators, the stock filter is workable but not comfortable. One forum regular put it plainly: "For CW without a narrow filter, working is not very comfortable." The YG-455 C1 CW filter, still in production for newer Kenwood models as of the mid-2000s, fits the TS-140S. The original factory CW filter, the YK-455 C1, is no longer manufactured, so anyone hunting for a period-correct filter is looking at the used market. As of 2004, the YG-455 C1 was selling for around 170 USD equivalent from Moscow dealer "Бермос."

IF-10C Computer Interface Compatibility

The TS-140S accepts the IF-10C interface with RS-232, which was still being sold by Piexx in the US and shipped internationally as of the mid-2000s. It lets the rig work with logging software and digital modes without a homebrew interface.

Control Board Diodes D28–D31

On the control board, diodes D28 through D31 handle band-switching logic. Owners note D31 in particular as the diode that "opens transmission across all bands," which matters for anyone doing the common modification to expand transmit coverage. D29 is present on the TS-140 but not on the TS-680, one of the few board-level differences between the two radios.

Compact Chassis and Recessed Switch Bank

Reviewer Dave Ingram, K4TWJ, described the TS-140S as a "deluxe little gem in an attractive package," and noted the recessed bank of switches along the bottom of the front panel. The compact footprint fits into a crowded operating position without dominating the desk, and many owners kept theirs as a secondary rig long after newer radios arrived.

Historical Context

Kenwood listed the TS-140S in 1987, according to the Radiomuseum collection record, and QST reviewed it in June 1988. The radio was already out of production by February 2004. One forum contributor noted it "hasn't been manufactured for about five years" at that point, which puts the end of production somewhere in the late 1990s. Owners used them well into that decade and beyond. One Swedish operator reported running his TS-140S on the "FreeBand" between roughly 1996 and 1999, and an American ham recalled being impressed by the features available in the early 1990s after contesting in Alaska with a 430S and 440S.

The TS-140S shares its documentation and much of its design with the TS-680, and the two are frequently grouped together in modification guides and service literature. It was a solid mid-range HF rig that Kenwood built well, sold in numbers, and supported with documentation that's still circulating today.

Collectibility & Value

Prices for the TS-140S are all over the map. The radio is common enough to show up regularly, but old enough that condition varies wildly. Recent listings have ranged from $250 for a working unit with minor scratches and a recent rebuild, up to $600 for a new-in-open-box example with original microphone and DC power cord. A 2004 forum post summed up the market at the time: "you can find it for not much money."

Common issues are well-documented. The TX-Power/Mic-Gain potentiometer is prone to oxidation, which one owner identified as the only problem he encountered. A more serious failure mode involves a burned transistor key that shorts the receiver input to ground during transmit, causing weak sensitivity. It's worth checking on any used example. Owners who have modified their radios for expanded transmit coverage report low-frequency breakthrough below 3000 kHz that can draw more than 20 amps, though this appears to come from the modification rather than a stock design flaw. On 160 meters, the factory limited output to 10 watts, reportedly to comply with regional regulations. Modified units that attempt more power on that band have been known to fail.

Service documentation is available. The service manual and user manual are both in circulation, and Kenwood's own website has hosted service bulletins for the model. The mechanical assembly (part X41-3030-00) shows up on the secondary market, which suggests at least some spare parts are still findable.