Collins KWM-1 / KWM-1A — Serial Number & Production Guide
VK6ADA Technical Reference · Collins Vintage Amateur Transceivers · March 2026 · Mike Peace VK6ADA
The Collins KWM-1 holds a unique place in amateur radio history as one of the first truly integrated HF SSB transceivers produced for the amateur market — predating the S-Line and establishing the design language that Collins would refine throughout the 1960s. Produced from approximately 1957 through 1963, the KWM-1 covers only the upper HF amateur bands (10m, 15m, and 20m) and is among the rarest surviving Collins amateur instruments today, with an estimated fewer than 100 units known to survive worldwide.[1] This guide consolidates serial number data, sub-variant identification, emblem era information, and restoration reference notes for collectors and restorers.
Overview & Specifications
Manufacturer | Collins Radio Company — Cedar Rapids Division, Cedar Rapids, Iowa |
Model Designations | KWM-1 / KWM-1A (later production variant with revised mode switching) |
Production Period | ~1957 – ~1963 |
Type | SSB/CW HF Transceiver — mobile or fixed station; external power supply required |
Frequency Coverage | 14.0–30.0 MHz only — 20m, 15m, and 10m amateur bands. Does not cover 40m or 80m.[2] |
Band Segments | 10 segments of 100 kHz each, selected by plug-in crystal box; one crystal box supplied per band |
RF Power Input | 175 W PEP SSB |
RF Power Output | ~100 W PEP nominal[2] |
Modes | USB, LSB, CW, VOX |
PA Tubes | 2 × 6146 (parallel pair) |
Tube Complement | 24 tubes total |
Power Supply Options | 115 V AC (Collins 516F-1 or 516E-1) / 12 V DC / 28 V DC |
Station Console | Collins 312B-1 / 312B-2 |
Emblem Era | Winged Emblem only — entire production run predates the Round Emblem transition of Fall 1969 |
Collector Status | Rare — estimated fewer than 100 units surviving worldwide. A significant collector piece. |
The KWM-1 covers 14.0–30.0 MHz only. It does not cover 40m (7 MHz) or 80m (3.5 MHz). Prospective buyers should confirm band coverage before purchase — the KWM-1 is occasionally misrepresented as a full-coverage HF transceiver. The KWM-2 (3.4–30.0 MHz) is the model to seek for full amateur HF band access.[2]
Important Note on Serial Number Sequencing
Collins Radio issued serial numbers for the KWM-1 in randomised (non-sequential) order, consistent with Art Collins’ documented decree for the amateur product line that serial numbers should not convey production date or pricing information.[5] A lower serial number does not necessarily indicate an earlier production date. For KWM-1 dating, the front-panel emblem is a blunt instrument (all units are Winged Emblem), so internal component date codes and mode-switch configuration are the primary sub-variant discriminators.
KWM-1 vs. KWM-1A — Sub-Variant Identification
The KWM-1A designation is less formally documented in factory records than the KWM-2A transition. The key discriminator between early KWM-1 and later KWM-1A production is the mode switch and associated front-panel legend. Early units lack the LOCK TUNE position; later (KWM-1A) units include it. Secondary confirmation can be sought in the logging scale markings.[3]
The primary field-identification method is the front-panel mode switch:
• Early KWM-1 — Mode switch does not include a LOCK TUNE position.
• KWM-1A — Mode switch includes the LOCK TUNE position.
Secondary check: examine the logging scale legend for revision markings. The chassis serial number tag may or may not carry the “A” suffix depending on whether the unit left the factory as a KWM-1A or was field-updated.
| Feature | KWM-1 (Early) | KWM-1A (Later) |
|---|---|---|
| Mode Switch | No LOCK TUNE position | LOCK TUNE position included |
| Logging Scale | Early legend markings | Revised legend markings |
| Chassis Tag | KWM-1 designation | May show KWM-1A; field conversions may vary |
| Emblem | Winged Emblem | Winged Emblem (unchanged) |
| Frequency Coverage | 14.0–30.0 MHz | 14.0–30.0 MHz (unchanged) |
| Circuit | Original design | Minor refinements; overall substantially similar |
Emblem Era
All KWM-1 and KWM-1A production falls within the Winged Emblem era. The stylised winged Collins insignia appears on the upper-left of the front panel throughout the entire production run (~1957–~1963), ending well before the Round Emblem transition of Fall 1969. The emblem therefore confirms pre-1969 manufacture but cannot discriminate between early and late KWM-1 production.
| Emblem Type | Production Period | S/N Coverage | Physical Description | Notes |
|---|---|---|---|---|
| Winged Emblem | ~1957 – ~1963 (entire run) | All known KWM-1/1A serial numbers | Stylised red winged device; “COLLINS” lettering below; upper-left front panel | No other emblem era applies. Confirms pre-1969 manufacture only. |
Serial Number Lookup Tool
Enter a KWM-1 or KWM-1A serial number for an estimated production context. Given the very limited surviving population and random S/N assignment, results are indicative only.
Documented Serial Numbers
| Serial Number | Model | Emblem | Approx. Year | Notes / Source |
|---|---|---|---|---|
| 42 | KWM-1 | Winged | ~1957–1958 | Documented early example associated with State Department / Moscow Embassy use. One of the lowest confirmed KWM-1 serial numbers on record.[3] |
| Additional S/Ns wanted | KWM-1 / KWM-1A | Winged | — | CCA survey data for the KWM-1 is incomplete. Community-documented serial numbers are actively sought. |
The CCA KWM-1 production survey is one of the least complete in the Rod Blocksome K0DAS series, reflecting the scarcity of surviving units. If you own or have documented a KWM-1 or KWM-1A, contributing your serial number, emblem type, and mode-switch configuration to the CCA survey will help build the definitive production record for this rare instrument.[4] Contact the Collins Collectors Association via collinsradio.org.
Restoration Considerations
| Item | Notes |
|---|---|
| Power / RF connector | The specialised multi-pin power and RF connector is the single most critical missing-component challenge in KWM-1 restoration. Without it the transceiver cannot interface with its power supply or antenna system. Sourcing or fabricating this connector is the first restoration priority for incomplete units.[3] |
| Crystal box | The plug-in crystal box is band-specific and often missing. Each 100 kHz segment requires its own crystal. Complete crystal sets across all three bands (10m, 15m, 20m) are rarely found with surviving units. |
| Power supply | The Collins 516F-1 is the correct heavy-duty AC power supply; the 516E-1 is lighter duty. Both are themselves scarce. DC operation (12 V / 28 V) is documented for mobile and military use and may be a practical path when the AC supply is unavailable. |
| 6146 PA tubes | The original 6146 (not 6146A or 6146B) was specified. Modern 6146B substitution is generally acceptable with appropriate bias adjustment. Match the PA pair for plate current balance. |
| Wax paper capacitors | Full capacitor replacement is standard practice. All wax-coated paper capacitors should be replaced before alignment. Electrolytic capacitors in audio and supply sections warrant replacement on age alone. |
| Rarity assessment | With fewer than 100 estimated surviving units worldwide, cosmetic damage is particularly significant to collector value. Document originality of paint, knobs, escutcheon, and crystal box before any restoration work begins. |
| Documentation | The KWM-1 factory instruction manual is available via BAMA and the CCA Technical Archives. The Antique Radio Forums KWM-1 thread is a useful community resource for restoration discussion and parts sourcing.[3] |
Compatible Accessories & Station Equipment
| Accessory | Collins Model | Notes |
|---|---|---|
| Power Supply (AC heavy duty) | Collins 516F-1 | Primary recommended AC mains supply for KWM-1 fixed-station use |
| Power Supply (AC limited duty) | Collins 516E-1 | Lighter-duty alternative; intermittent operation only |
| Station Console / Speaker | Collins 312B-1 / 312B-2 | Matches KWM-1 cabinet styling; includes phone patch capability |
| Mobile DC Operation | 12 V DC / 28 V DC direct | Documented for vehicle and military mobile installation |
Manual & Documentation History
| Document | Description | Notes |
|---|---|---|
| KWM-1 Instruction Book | Factory manual covering operation, alignment, and parts list | Available via BAMA and CCA Technical Archives; consult for circuit reference before any alignment work |
| Technical Bulletin supplements | Factory TB sheets covering running changes and updates | CCA Technical Archives; check for applicable TBs before restoration |
| CCA Technical Archives | Supplemental articles, restoration notes, CCA Journal back-issues | collinsradio.org |
| Antique Radio Forums — KWM-1 thread | Community restoration discussion; parts sourcing; documented S/Ns | antiqueradios.com[3] |
Historical Notes
The KWM-1 attracted significant attention beyond the amateur market. Its combination of compact size, DC power capability, and SSB performance made it attractive for diplomatic and intelligence community applications. The State Department and related agencies are documented as early purchasers — S/N 42 is specifically associated with Moscow Embassy communications — reflecting the Collins reputation for reliability and security-grade build quality in the late 1950s.[3]
The KWM-1’s limited frequency coverage (upper HF only) was a deliberate design choice reflecting the propagation preferences of the era and the operational requirements of the intended market. For operators requiring 40m and 80m access, Collins developed the KWM-2 — a full-coverage successor introduced in 1959 that would go on to a 20-year production run and become one of the most admired amateur transceivers ever built.
References
- Collins Collectors Association. CCA Historical Archives — KWM-1 Transceiver. collinsradio.org.
- Electronics Notes. Collins KWM-1 Vintage Ham Radio Transceiver. electronics-notes.com.
- Antique Radio Forums. Collins KWM-1 discussion thread (includes S/N 42 documentation and restoration discussion). antiqueradios.com.
- Blocksome, Rod K0DAS. Collins Radio Production Surveys. Collins Collectors Association Technical Archives. collinsradio.org.
- Johnson, Gerald K0CQ. Collins Serial Numbers — Random Assignment Policy (mailing list post, June 2004). QTH.net Collins Reflector. qth.net.
- QTH.net Collins Reflector. Collins Serial Numbers — Randomisation Policy Confirmation (July 2005). qth.net.
- WA3KEY Virtual Collins Radio Museum. Collins equipment reference pages. wa3key.com.
- VK6ADA. Collins Vintage Radio Reference Collection. vk6ada.com.au · r-390a.net.