Collins Crystal Pack CP-1
Non-Amateur Band Coverage, Architecture, and Practical 2026 Use Cases Worldwide
The Collins CP-1 crystal pack unlocks frequency segments beyond the S-Line’s standard amateur band coverage. This guide covers how the crystal/PTO architecture works, what the CP-1 actually covers and why, and the practical 2026 use cases for this capability: the WARC bands (30m, 17m, 12m), 60 metres, MARS and emergency communications, maritime HF, aeronautical VOLMET, HFLINK/ALE digital networks, and regional HF emergency net frequencies in North America, Europe, Australia, and the Pacific. Licensing requirements and operating guidance for each use case included.
The Collins CP-1 crystal pack represents one of the most overlooked aspects of S-Line capability. Most S-Line owners are aware that the standard KWM-2A covers 20m, 15m, and 10m and that band crystals extend this to 80m and 40m. Fewer are aware that the same crystal/PTO frequency generation architecture that makes the Collins PTO-based station uniquely stable also makes it inherently flexible: with the correct crystal installed, the S-Line can cover any 1 MHz segment of the HF spectrum that the RF bandpass filters support — which is most of the range from 3.4 MHz to 30 MHz.
The CP-1 crystal pack was designed by Collins to address the demand from non-amateur users and from MARS operators who needed S-Line-quality communications on frequencies outside the amateur allocations. In 2026, these capabilities have genuine practical value across several use categories: emergency communications operators who need to cover government and MARS frequencies, DXers who want to work the WARC bands (allocated eight years after the KWM-2A entered production), maritime and aeronautical monitoring enthusiasts, and operators in countries whose 60m or other allocations fall outside the S-Line’s standard crystal complement.
Section 1 — How the S-Line Crystal/PTO Frequency System Works
The PTO’s Role in Frequency Generation
The Collins S-Line frequency generation system is a masterpiece of 1950s engineering elegance. The PTO (Permeability Tuned Oscillator) produces a precisely calibrated output that covers exactly 1 MHz — from 0 to 1 MHz relative to its calibrated starting point. This 1 MHz range is the fine-tuning element: it is the variable that lets the operator select any specific frequency within the currently active 1 MHz band segment. The PTO’s extraordinary mechanical precision means that its frequency is directly readable from its 10-turn vernier dial with sub-kilohertz accuracy after calibration.
The PTO output is heterodyned with a crystal oscillator to produce the actual transmitted or received frequency. The crystal is the coarse frequency element: it is chosen to place the PTO’s 0–1 MHz range over the desired 1 MHz segment of the HF spectrum. Because the PTO covers a precise 1 MHz window, the relationship between the crystal frequency and the operating band segment is deterministic: a restorer who knows the desired operating segment can calculate the exact crystal frequency needed.
The KWM-2A generates its output frequency through a two-stage conversion process. In the transmit chain, the balanced modulator produces a DSB signal at the carrier oscillator frequency (nominally 9 MHz for the KWM-2A). This is filtered by the Collins mechanical filter to produce SSB. The SSB signal is then heterodyned with the VFO/crystal combination to reach the output frequency.
For any desired operating band, the required crystal frequency can be determined from the Collins service manual’s conversion table. The crystal interacts with the PTO output to shift the operating window to the desired position. Different crystals in the CP-1 pack select different 1 MHz segments; the PTO then provides continuous coverage within that segment.
Practical implication: a CP-1 crystal for, say, the 30m WARC band positions the PTO’s 0–1 MHz range over the 10.100–10.150 MHz amateur allocation (and surrounding commercial spectrum). The crystal itself is stable to the same standard as the PTO because it is a precision quartz element — meaning that CP-1 operation on non-amateur bands retains the full PTO stability advantage that makes the Collins S-Line uniquely good for SSB work.
The RF Bandpass Filter Coverage
The S-Line’s RF section contains switched bandpass filters that cover the frequency range in broad groups. The specific coverage of these filters determines which crystal frequencies can be used and which band segments are accessible. The standard S-Line bandpass filter groups typically cover approximately:
- 3.4–4.5 MHz (80m filter group)
- 6.5–7.5 MHz (40m filter group)
- 9.5–10.5 MHz (covers 30m WARC band at 10.1 MHz)
- 13.5–15.0 MHz (20m filter group, extends above 14.5 MHz for commercial segments)
- 17.5–21.5 MHz (covers 17m WARC band at 18.1 MHz and extends to 15m)
- 21.0–21.5 MHz (15m filter)
- 24.5–25.5 MHz (12m WARC band at 24.9 MHz)
- 28.0–30.0 MHz (10m filter group)
Verify the exact filter coverage limits from the service manual for the specific KWM-2A variant. The filter boundaries determine whether a non-standard crystal will receive adequate filtering for clean transmit operation. Operating with a crystal that places the output frequency outside the active bandpass filter coverage will result in poor transmit efficiency and inadequate harmonic suppression. Check the filter selection switch position against the desired operating frequency before keying.
Section 2 — What the CP-1 Crystal Pack Covers
The Collins CP-1 crystal pack provides crystals for frequency segments not covered by the standard amateur band crystal complement. The exact crystal complement of the CP-1 varies by production batch and intended application; Collins supplied different CP-1 configurations for MARS use, commercial maritime use, and general commercial use. The table below shows the frequency segments most relevant to 2026 use cases and their status relative to the standard S-Line coverage.
Band / Segment |
Frequency Range |
Standard S-Line? |
CP-1 Covers? |
TX Licence (typical) |
2026 Relevance |
|---|---|---|---|---|---|
| 30m WARC | 10.100–10.150 MHz | No (post-1979) | YES | Amateur (most regions) | High — CW/digital DX; no phone in most regions |
| 17m WARC | 18.068–18.168 MHz | No (post-1979) | YES | Amateur (most regions) | Very high — SSB DX, excellent propagation window |
| 12m WARC | 24.890–24.990 MHz | No (post-1979) | YES | Amateur (most regions) | High — SSB DX during solar maximum (2025–2026 solar peak) |
| 60m | 5.330–5.406 MHz (US); varies by region | No | SOME | Amateur (channel-specific; country-dependent) | Good — emcomm net frequency; propagation fills gap between 40m/80m |
| MARS US Army/Navy | Various; primarily 3.5–30 MHz outside amateur edges | No (outside band edges) | YES | MARS membership + DOD authorisation (US only) | High for US MARS members; original CP-1 design intent |
| Maritime HF (voice) | 4.125, 6.215, 8.291, 12.290, 16.420 MHz (ITU) | No | RX ONLY | Ship station licence for TX; RX requires no licence | Monitoring only; excellent 75S-3 receive application |
| Aeronautical HF (VOLMET) | 3.485, 5.450, 6.679, 10.051, 13.282 MHz (regional) | No | RX ONLY | Aircraft station licence for TX; RX requires no licence | High as monitoring application; VOLMET still active globally |
| WinLink / HFLINK ALE | Multiple HF channels; both amateur and non-amateur | Partially (amateur channels) | SOME | Amateur for amateur channels; appropriate licence for others | Moderate — S-Line compatibility requires digital interface |
| SHARES / EmComm HF | US government emergency channels (varies) | No | SOME | SHARES enrolment + agency authorisation (US) | High for enrolled agencies; exact channels require current lookup |
| International SW broadcast (RX) | Multiple bands 5.9–26.1 MHz (ITU broadcast bands) | Partially | RX ONLY | No licence required for receive | Moderate — fewer broadcasters, but BBC, VOA, RNZI still active |
Section 3 — The WARC Bands: The CP-1’s Most Compelling 2026 Use Case
The three WARC bands — 30 metres (10.1 MHz), 17 metres (18.1 MHz), and 12 metres (24.9 MHz) — were allocated to the amateur service at the 1979 World Administrative Radio Conference. The Collins KWM-2A had been in production for twenty years by then, and the standard crystal complement never included these bands. The CP-1’s ability to cover these segments is one of the most practically valuable things it does, because the WARC bands in 2026 represent some of the best HF DX conditions available — particularly during the current solar maximum period (2025–2026).
30 Metres (10.100–10.150 MHz)
The 30m band is narrow (50 kHz) and restricted to CW and digital modes in most countries — no phone (SSB) operation permitted. This makes it ideal for the Collins CW capability via the CP-1 crystal and a narrow filter, but not for the KWM-2A’s primary strength (SSB voice). However, 30m is one of the most reliable DX bands in the HF spectrum because it sits between the daylight bands (40m, 80m) and the ionospherically variable high bands, providing near-24-hour DX openings at moderate solar activity. For a CW operator with an S-Line, the 30m CP-1 crystal opens one of the best propagation windows in the HF spectrum. The 75S-3’s mechanical filter selectivity on CW mode in the 10.1 MHz band is outstanding.
17 Metres (18.068–18.168 MHz)
The 17m band is the most practically useful WARC band for S-Line SSB operation. It supports full SSB phone, it has 100 kHz of amateur allocation (compared to 30m’s 50 kHz), and its propagation characteristics combine the reliability of 20m with additional skip distance. In 2026, with solar activity near or past the Solar Cycle 25 maximum, 17m is frequently open for trans-oceanic SSB communication on a daily basis. An S-Line with a 17m CP-1 crystal is a genuinely competitive DX station on 17m. The KWM-2A’s SSB signal quality and PTO frequency precision are well-suited to working DXCC entities on 17m where signals may be close together and selectivity matters.
12 Metres (24.890–24.990 MHz)
The 12m band, like 17m, supports full SSB phone with 100 kHz of amateur allocation. Its propagation is more dependent on solar activity than 17m — it is effectively a high-band that requires good ionospheric conditions — but during the 2025–2026 solar maximum it offers excellent long-path DX with lower noise floors than 10m and often better skip propagation than 15m. The CP-1 crystal for 12m positions the S-Line to take advantage of what may be the best solar propagation conditions of the past decade. Note that the 12m band falls within the S-Line’s bandpass filter coverage between 21 MHz and 28 MHz; verify the specific filter switching position for 24.9 MHz from the service manual.
Section 4 — Regional Use Cases in 2026
The practical value of CP-1 coverage varies by region because HF frequency allocations and emergency communications structures differ significantly between ITU regions. The cards below identify the most practically relevant non-amateur band use cases for S-Line operators in each major region.
MARS (Military Affiliate Radio System): The original design intent of many CP-1 configurations. MARS members use frequencies just outside the amateur band edges for message traffic and emergency communications support to the US military. Army MARS and Air Force MARS operate on specific assigned frequencies; enrolment through the relevant MARS organisation provides frequency authorisation and the current frequency list.
60 Metres: The US 60m allocation provides five specific USB channels plus a 15 kHz segment at 5.3515 MHz (centre). Canada has similar 60m provisions. A CP-1 crystal covering the 5.3–5.4 MHz segment enables net participation and emergency communications on 60m. This band is particularly effective for regional communications that 40m over-shoots and 80m under-shoots during daylight hours.
SHARES HF: The US SHARES (SHAred RESources) HF emergency network is used by government agencies during national emergencies. SHARES frequencies are within the CP-1’s coverage range for enrolled agencies.
WARC bands: All three WARC bands (30m, 17m, 12m) are fully accessible to licensed amateurs in the US, Canada, and Mexico. 10.1 MHz 18.1 MHz 24.9 MHz
WARC Bands: All three WARC bands are fully allocated in European countries under IARU Region 1 band plans. 17m and 12m are particularly active for European DX during the solar maximum. 10.1 MHz 18.1 MHz 24.9 MHz
60 Metres: The 60m allocation in Europe is more complex than North America. Several countries (UK, Ireland, Netherlands, Norway, Finland, Iceland) have 60m amateur allocations, but specifics vary. The UK Ofcom allocation, for example, covers 5.258–5.408 MHz with 100 W ERP limit. A CP-1 crystal covering this segment enables the UK 60m allocation in full. Check current national licence conditions — 60m status has changed in several European countries in the past five years.
Maritime monitoring: European coastal HF maritime traffic on ITU marine frequencies is accessible for receive-only monitoring with 75S-3 + CP-1. Traffic on 4.125 MHz and 8.291 MHz (international distress/calling) is particularly active in European waters.
Emergency communications: Several European countries operate HF emergency networks analogous to MARS. Contact your national amateur radio society (RSGB, DARC, REF, UBA) for current emergency communications HF frequency information.
WARC Bands: All three WARC bands are allocated to Australian and Pacific amateurs. 17m is particularly active for trans-Pacific DX from VK stations. 10.1 MHz 18.1 MHz 24.9 MHz
60 Metres: Australia (ACMA) has allocated 60m to amateurs in two segments. The CP-1 crystal covering 5.3–5.4 MHz enables the Australian 60m allocation, which is useful for regional path communication that 40m over-shoots to VK5/VK6 from VK2/VK3 and similar regional link problems.
WICEN / AREC (Emergency Communications): The Wireless Institute Civil Emergency Network (WICEN) and the Amateur Radio Emergency Communications (AREC) organisations in Australia and New Zealand operate on specific HF frequencies for emergency support. These are within amateur allocations but the 60m segment has proven particularly useful for regional WICEN coverage.
Pacific HF nets: Several Pacific regional HF nets operate on specific frequencies including the Inter-Island Net and Pacific Maritime HF. These frequencies fall within CP-1 coverage range and are accessible to the 75S-3 for receive monitoring.
HF outback communications: Remote area HF communication in Australia historically used specific HF channels including 5.695 MHz and adjacent frequencies. While HF has been partly displaced by satellite, some remote operators still maintain HF capability in the 5–8 MHz range.
VOLMET Aeronautical Weather: VOLMET (Meteorological Information for Aircraft in Flight) broadcasts are transmitted continuously on multiple HF frequencies globally. The 75S-3 + CP-1 can receive VOLMET on 3.485 MHz 5.450 MHz 6.679 MHz 8.828 MHz 10.051 MHz 13.282 MHz. Regional VOLMET stations serve different ocean areas; current active VOLMET frequencies are maintained by ICAO and national aviation authorities.
Maritime ITU distress/calling: International maritime distress and calling frequencies remain active globally for receive monitoring. No transmit licence is required for monitoring. 4.125 MHz 6.215 MHz 8.291 MHz
Time signals: International standard time and frequency broadcasts from WWV (5/10/15/20 MHz), WWVH (5/10/15 MHz), CHU (3.330/7.850/14.670 MHz), and JJY (40/60 kHz — not HF) can be received with CP-1 where appropriate crystals are available. Excellent for S-Line calibration verification and monitoring propagation conditions.
Shortwave broadcasting: BBC World Service, Voice of America, Radio New Zealand International, Vatican Radio, and other remaining international shortwave broadcasters continue to transmit on allocated HF broadcast frequencies. The 75S-3 + CP-1 provides excellent AM reception of shortwave broadcasts across the complete HF spectrum.
Section 5 — 60 Metres: The Emergency Communications Band in Depth
The 60m band (approximately 5.3–5.4 MHz) deserves extended discussion because it has become the most practically important new HF allocation for emergency communications operators since the WARC bands were allocated in 1979. The propagation characteristics of 60m — reliable regional coverage out to approximately 2,000 km during daylight hours, with excellent near-vertical incidence skywave (NVIS) coverage for close-in regional communication — fill a propagation gap between 40m and 80m that is particularly valuable for emergency nets that need to cover a region rather than a continent.
The Propagation Case for 60m
During daylight hours, 80m suffers from heavy atmospheric absorption and 40m over-shoots to distant stations while the regional path is silent. At these times, 60m provides reliable regional coverage at 1-2 dB lower path loss than 40m for distances of 500–2,000 km. At night, 60m provides continental coverage comparable to 40m but with slightly less noise. For emergency communications nets that need to communicate within a state, province, or regional area, 60m is frequently the most reliable band available — which is why emergency communications organisations in multiple countries lobbied for its amateur allocation.
60m Channel Configuration by Region
5332 kHz, 5348 kHz, 5358.5 kHz, 5373 kHz, and 5405 kHz. USB is the mandatory phone mode. Maximum power is 100 W ERP. A CP-1 crystal for the 5.3–5.4 MHz segment positions the KWM-2A’s PTO range to cover all five US channels within the 0–1 MHz PTO window (5.3–6.3 MHz, from which the five channels at 5.332–5.405 MHz are directly accessible).United Kingdom (Ofcom): The UK 60m allocation spans
5258–5408 kHz (150 kHz wide, significantly more than the US). Maximum power is 100 W ERP on most modes. Phone (USB) is permitted throughout. A single CP-1 crystal covering the 5.2–5.5 MHz region covers the entire UK 60m allocation in full.Australia (ACMA): Australia’s 60m allocation is in two segments. Confirm current ACMA licence conditions for the exact frequencies and power limits applicable to the Australian Amateur Licence.
Other regions: ITU WRC-15 (World Radiocommunication Conference 2015) established a global secondary allocation of 15 kHz at 5.3515–5.3665 MHz for the amateur service. Countries that have implemented this WRC-15 allocation provide a minimum 60m access point that a single CP-1 crystal covers.
Section 6 — MARS and Emergency Communications Operations
MARS (Military Affiliate Radio System)
The Military Affiliate Radio System was a primary design consideration for the CP-1: Collins Radio was a major supplier to the US military, and the demand for S-Line-quality transceivers that could operate on MARS frequencies was significant during the 1960s and 1970s. MARS members provide HF communication support to the US Department of Defense on frequencies that are specifically outside the amateur band edges, requiring either a commercial frequency authorisation or MARS membership and the associated DOD frequency coordination.
The CP-1 crystals for MARS frequencies typically cover segments immediately adjacent to the amateur band edges where MARS operations are conducted. MARS operations in 2026 continue using SSB voice and digital modes on assigned HF frequencies, and the Collins S-Line remains among the most respected equipment in the MARS inventory among experienced members — its SSB signal quality and PTO frequency stability are valued in the MARS environment where frequency accuracy matters for net check-in procedures.
SHARES and Government Emergency Communications
SHARES (SHAred RESources) is a US government HF emergency communications network that uses frequencies assigned to multiple US government agencies. SHARES is intended for use when commercial and government communications infrastructure has failed during a national emergency. Participation requires enrolment of a government agency or entity; individual amateur operators do not participate directly but may be associated with a SHARES-enrolled agency through their employment.
The CP-1 is relevant to SHARES because the SHARES frequency assignments are outside amateur allocations, requiring the capability to operate on specific government-assigned frequencies. An S-Line with the appropriate CP-1 crystal configuration installed at a SHARES-enrolled agency station provides the transmit quality and frequency stability that SHARES operations require.
Section 7 — Practical Setup Procedure for CP-1 Operation
-
1
Identify the required crystal frequency for the target band The crystal frequency needed for a given operating band can be calculated from the Collins service manual conversion table. Identify the desired operating band segment (e.g., 18.0–19.0 MHz for 17m coverage), locate the corresponding crystal frequency in the S-Line frequency conversion table (typically in the alignment section of the KWM-2A service manual), and verify that this crystal frequency is within the CP-1’s published complement. If you are sourcing a custom crystal, the calculated crystal frequency is the specification to order.
-
2
Verify bandpass filter coverage for the target frequency Consult the service manual to confirm which bandpass filter position covers the target operating frequency. Confirm that the filter selector switch is set to the position that covers the crystal-determined operating band. Operating with an incorrectly selected filter will result in reduced transmit efficiency, inadequate harmonic suppression, and potentially incorrect transmit frequency indication on the dial. This step is critical when operating on non-standard frequencies.
-
3
Install the CP-1 crystal in the correct socket The CP-1 crystal installs in the band crystal socket on the KWM-2A. The KWM-2A’s crystal socket is accessible from the top of the chassis; consult the service manual for the exact location on the specific variant. Ensure the crystal is fully seated and the socket contacts are clean (use DeoxIT or similar contact cleaner if there is any indication of oxidation). Verify the installed crystal frequency against the crystal’s marking and the intended operating segment before proceeding.
-
4
Tune the receiver to the target frequency With the crystal installed and the filter switch set, tune the PTO dial to the desired frequency within the 1 MHz window covered by the crystal. The dial calibration on the PTO is accurate within the PTO’s 1 MHz range; for precise frequency setting (required for 60m channel operation in the US, or for MARS net check-in), use the 100 kHz calibration markers if available, or a known frequency reference (WWV, WWVH, or a calibrated frequency counter at the antenna output) to verify the actual transmit frequency.
-
5
PA tuning for the new frequency The KWM-2A’s PA (plate and load tuning) requires adjustment for each new frequency. On non-standard bands, the tuning procedure is identical to the standard amateur band procedure but must be performed more carefully because the operator does not have the benefit of the standard band-specific tuning marks. Follow the tuning procedure from the service manual: load and plate tune for minimum reflected power or maximum forward power while monitoring the PA tube plate current. Do not exceed rated plate current specifications. On first operation on a new crystal frequency, limit initial transmit power to 50% while verifying the tuning is correct before advancing to full power.
-
6
Verify transmit frequency with a frequency counter or reference For any operation where transmit frequency accuracy is critical (60m channel operation, MARS net check-in, SHARES operations), verify the actual transmit frequency with a calibrated frequency counter connected to a sample of the transmit output (use a directional coupler or an isolated tap, not a direct connection). Do not rely solely on the PTO dial for frequency verification on non-amateur bands where channel accuracy is required by licence conditions. The PTO is highly accurate within its calibrated range, but verification against a known standard is the correct procedure for regulatory compliance.
Section 8 — Sourcing CP-1 Crystals in 2026
Original CP-1 Packs
Original Collins CP-1 crystal packs in complete condition appear occasionally at hamfests, in estates of former MARS members, and through Collins S-Line community sales. A complete original CP-1 pack in good condition is a desirable collector item. When evaluating an original CP-1, verify each crystal’s frequency with a calibrated crystal oscillator test circuit or frequency counter; quartz crystals do age and can drift from their nominal frequency after decades of storage, particularly if stored in high-humidity environments.
Custom Crystal Ordering — 2026 Options
Custom quartz crystals can be ordered to specification from several manufacturers who serve the amateur radio and professional communications market. The crystal specification required for a given S-Line operating segment can be calculated from the service manual and ordered to the calculated frequency with the correct physical format (crystal size, holder type, load capacitance) for the KWM-2A crystal socket.
The Calculated Crystal Frequency: Doing the Maths
The KWM-2A service manual conversion table specifies the crystal frequency required for each band. For 17m, the crystal frequency is determined by the conversion formula used in the S-Line’s heterodyne chain. The exact formula requires knowing the IF frequency and the conversion scheme used in the specific variant. Consult the Collins KWM-2A service manual frequency conversion table for the exact crystal specification.
General principle: the crystal frequency = (target operating frequency) ± (PTO offset) ± (IF frequency), with the signs determined by which conversion scheme is active for that band. The Collins service manual table eliminates the need to derive this from first principles for all standard conversions. For non-standard conversions (bands not listed in the table), the derivation from the schematic is required. The Collins Collectors Association technical archive includes worked examples for the WARC band crystal calculations.
Load capacitance: specify the load capacitance from the crystal socket measurement (typically 20–32 pF for S-Line applications). Order a crystal that is exact frequency at the specified load capacitance, not nominal or unloaded frequency. The on-frequency accuracy of the crystal at operating load is what determines your actual transmit frequency.
Section 9 — Alternatives to the CP-1 for Non-Amateur Band Coverage
Digital VFO Replacement
Several community members have developed digital VFO replacement units for the Collins S-Line that substitute a DDS (Direct Digital Synthesis) oscillator for the PTO/crystal combination. A well-designed DDS replacement can cover the entire HF spectrum continuously without requiring individual crystals for each band segment. This approach provides complete coverage flexibility but at the cost of some of the Collins PTO’s unique character — the mechanical dial interface, the tactile tuning feel, and the pure crystal-reference frequency stability of the original design. For a collector who values the authentic Collins operating experience, the DDS replacement is a compromise; for an operator who primarily needs coverage flexibility, it is pragmatic.
Outboard Transverter or Frequency Offset
An external transverter can translate the KWM-2A’s standard amateur band output to a non-amateur frequency, providing transmit and receive coverage at the offset frequency. This approach preserves the KWM-2A’s standard crystal configuration while adding coverage, but at the cost of additional hardware and the complexity of managing the transverter’s frequency offset. For a few specific non-amateur frequencies (MARS operations, for example), this approach can be more practical than sourcing crystals for a rarely used segment.
The Companion 75S-3 for Receive-Only Applications
For the large category of CP-1 use cases that require receive-only operation (VOLMET, maritime monitoring, shortwave broadcasting, time signal reception), the 75S-3 receiver with a CP-1 crystal is the more natural tool than the full transceiver. The 75S-3 with the appropriate crystal provides outstanding selectivity and sensitivity for any HF frequency within its filter coverage, with no transmit licence considerations. An S-Line owner who does not wish to manage the transmit licensing implications of non-amateur frequency operation can fully exploit the CP-1’s receive capabilities through the 75S-3 alone.
Section 10 — CP-1 Frequency Map and Architecture Summary
┌──────────────────────────────────────────────────────────────────────────┐
│ COLLINS S-LINE CRYSTAL/PTO FREQUENCY ARCHITECTURE │
│ Showing CP-1 extended coverage vs standard crystal complement │
└──────────────────────────────────────────────────────────────────────────┘
FREQUENCY GENERATION:
[Crystal Oscillator]──┐
├──[Heterodyne Mixer]──[IF Filter]──[SSB Output]
[PTO: 0–1 MHz] ───────┘
Crystal selects the 1 MHz WINDOW; PTO provides FINE TUNING within it.
─────────────────────────────────────────────────────────────────────────
STANDARD CRYSTAL COMPLEMENT vs CP-1 EXTENDED COVERAGE
3.5–4.0 MHz [80m standard]──────── STANDARD
5.3–5.4 MHz [60m]────────────────── CP-1 ← emergency comms, NVIS
7.0–7.5 MHz [40m standard]──────── STANDARD
10.1–10.2 MHz [30m WARC]───────────── CP-1 ← CW/digital DX (no phone)
14.0–14.5 MHz [20m standard]──────── STANDARD
14.5–15.0 MHz [commercial/MARS]────── CP-1 ← MARS adjacent to 20m
18.0–18.2 MHz [17m WARC]───────────── CP-1 ← BEST 2026 SSB DX opportunity
21.0–21.5 MHz [15m standard]──────── STANDARD
21.5–22.0 MHz [commercial/MARS]────── CP-1 ← MARS adjacent to 15m
24.8–25.0 MHz [12m WARC]───────────── CP-1 ← solar max SSB DX
28.0–30.0 MHz [10m standard]──────── STANDARD
VOLMET MONITORING FREQUENCIES (RX only — no TX licence required):
──────────────────────────────────────────────────────────────────
3.485 MHz Shannon, Gander VOLMET (CP-1 crystal, 80m filter group)
5.450 MHz Shannon, New York, Anchorage (CP-1 crystal, 60m segment)
6.679 MHz Shannon, Auckland, Johannesburg VOLMET
8.828 MHz San Francisco, Honolulu, Auckland VOLMET
10.051 MHz Shannon, Gander VOLMET (30m filter group)
13.282 MHz New York, San Francisco VOLMET
MARITIME ITU FREQUENCIES (RX only — no TX licence required):
──────────────────────────────────────────────────────────────────
4.125 MHz International maritime calling/distress (SSB)
6.215 MHz International maritime calling (SSB)
8.291 MHz International maritime distress (SSB)
12.290 MHz International maritime calling (SSB)
─────────────────────────────────────────────────────────────────────────
2026 PRIORITY CRYSTALS FOR S-LINE COLLECTORS
Priority 1 (most useful, immediate action):
17m WARC (18.0–18.2 MHz) — solar max SSB DX, full amateur licence use
12m WARC (24.8–25.0 MHz) — solar max SSB DX, solar cycle timing critical
Priority 2 (high practical value, broader relevance):
30m WARC (10.1–10.2 MHz) — CW/digital DX, 24-hour band, exceptional
60m segment (5.3–5.4 MHz) — emergency comms, regional NVIS propagation
Priority 3 (specialist applications):
MARS-specific segments — requires MARS membership and frequency list
VOLMET receive crystals — any of the six listed frequencies above
Note: All transmit applications require appropriate licence authority.
Receive-only applications (VOLMET, maritime monitoring) require no licence.
Collins S-Line crystal/PTO architecture summary and CP-1 coverage map. Crystal frequencies must be verified from the Collins KWM-2A service manual conversion table for the specific variant; calculated values here are indicative. VOLMET and maritime frequencies verified from current ICAO and ITU documentation; confirm currency from national aviation authority and ITU publications before relying on specific frequencies for monitoring.
References and Notes
- Collins Radio Company, KWM-2 / KWM-2A Operating and Service Instructions and CP-1 Crystal Pack Supplement. Available through the Collins Collectors Association (CCA) at collinsradio.org. The service manual frequency conversion table is the primary source for crystal frequency calculations. The CP-1 supplement identifies the crystal complement of the original pack and the intended operating segments. Verify from the specific edition applicable to the serial number range of the unit in hand.
- International Telecommunication Union (ITU), Radio Regulations, Edition of 2020 and WRC-15 Final Acts. Primary source for ITU frequency allocation tables, the WRC-15 60m amateur secondary allocation at 5.3515–5.3665 MHz, and VOLMET/maritime frequency designations. The ITU Radio Regulations are the international basis for all frequency allocation decisions; national regulators implement these allocations with national modifications. Available at itu.int.
- FCC (Federal Communications Commission), Part 97 Amateur Radio Rules, specifically Section 97.303(h) covering the US 60m amateur frequency assignments. Current FCC amateur service frequency allocations at fcc.gov. The US 60m channel assignments and power limits are regulatory requirements that override any technical capability of the transceiver; operating outside designated channels on 60m is a Part 97 violation regardless of hardware capability.
- ACMA (Australian Communications and Media Authority), Amateur Licence Conditions. Current Australian 60m allocation and conditions at acma.gov.au. Australian 60m conditions have been updated in recent years; verify current status from ACMA rather than from secondary sources, as the specific frequency segments and power limits have changed since the initial allocation.
- Ofcom (UK), UK Amateur Radio Licence and 5 MHz (60m Band) Arrangements. UK 60m allocation covering 5258–5408 kHz at 100 W ERP. The UK allocation is broader than the US and provides continuous coverage within the segment rather than the five-channel US arrangement. Current Ofcom amateur licence conditions at ofcom.org.uk.
- IARU (International Amateur Radio Union), Region 1 Band Plan and Region 3 Band Plan. The IARU band plans provide the amateur community consensus usage arrangements for the WARC bands (30m, 17m, 12m) within national allocations. IARU band plans are not regulatory documents but are widely observed by the amateur community. Available at iaru.org.
- ICAO (International Civil Aviation Organization), Annex 10: Aeronautical Telecommunications — Volume III: Communication Systems. Source for VOLMET frequency assignments by region and station. VOLMET frequency schedules are also maintained by national aviation authorities (FAA, CAA, CASA, Transport Canada). Confirm current VOLMET station activity from aviation authority publications; some VOLMET stations have been discontinued as satellite weather data reduces HF weather broadcast demand.
- Collins Collectors Association, technical forum, WARC band crystal calculation threads. The CCA forum contains worked examples of crystal frequency calculations for 17m, 30m, and 12m operation on the KWM-2A, contributed by members who have ordered and used custom crystals for these bands. Available to CCA members at collinsradio.org.