Web-888 with the Collins S-Line
Integrating the Web-888 SDR with the 75S-3 Receiver and 32S-3 Transmitter — Hardware, Station Architecture, and Best-Practice Operation
The Collins S-Line is a complete transmitting station with its own operating discipline: dual PTOs to track, an ALC loop between transmitter and receiver, a console for audio monitoring, and the classic Collins selectivity and spectral purity that defined amateur HF operation from the 1960s onward. The Web-888 adds what the S-Line was never designed to have — a real-time panadapter and on-air transmit quality monitor — without disturbing any of what makes the S-Line exceptional.
The S-Line station is a different integration challenge from the R-390A companion described in the Web-888 remote access guide. The R-390A is a receiver; it does not transmit. The S-Line is a complete HF station: the 75S-3 receiver and 32S-3 transmitter are separate but tightly coupled instruments that share an ALC loop, use matched PTO-derived VFOs that must be manually aligned to the same frequency, and are operated together as a functional pair. Adding a Web-888 SDR to this station introduces three new operational considerations that do not exist in the receiver-only context: T/R switching must protect two devices simultaneously, the Web-888 panadapter must show the frequency that both the 75S-3 and 32S-3 are operating on, and the Web-888 can monitor the quality of the transmitted signal in a way that nothing in the original S-Line design could do.
This guide covers the complete hardware integration, the operating procedures that extract the most value from the Web-888 as an S-Line companion, and the specific best practices that address the S-Line’s unique operating characteristics. The 312B-4 speaker/console is addressed throughout as the standard companion to the 75S-3 and 32S-3; its role and the Web-888’s complementary functions are explicitly distinguished.
Section 1 — The S-Line Station: What Each Unit Does
The 75S-3 is the receive element of the S-Line station. It covers all amateur HF bands using the same PTO architecture as the R-390A: a precision permeability-tuned oscillator provides the variable frequency element; fixed crystals select the band; a Collins mechanical filter at 455 kHz provides selectivity in SSB, CW, and AM modes.
The 75S-3 provides its received audio output to the 312B-4 console speaker. It also provides the ALC (Automatic Level Control) voltage derived from its detected signal to the 32S-3 transmitter for RF power control. The 75S-3’s AGC voltage reflects the incoming signal strength on receive; this same line carries the ALC reference during transmit.
Antenna connector: SO-239 (UHF). IF: 455 kHz (Collins mechanical filter).
The 32S-3 generates the transmitted signal on all amateur HF bands. Like the 75S-3, it uses a PTO for the variable frequency element and band crystals for band selection. In a correctly operating S-Line station, the 32S-3 PTO and the 75S-3 PTO are set to the same frequency, so that the transmit frequency matches the receive frequency.
The 32S-3 receives the ALC voltage from the 75S-3 (via the ALC interconnection cable) to regulate its drive level and maintain clean SSB emission. The 32S-3 also generates the sidetone audio during CW operation. PA output: approximately 100 W PEP SSB into 50 Ω. PA connector: SO-239 (UHF).
The 312B-4 is the station monitor console: it houses the loudspeaker for the 75S-3’s receive audio, the CW sidetone volume control for the 32S-3, the station monitor meter for transmit power and ALC indication, and the microphone connections. It is not a required component for basic operation but is the standard S-Line companion and provides the audio interface between the 75S-3/32S-3 and the operator.
In a Web-888-augmented S-Line station, the 312B-4 continues to serve as the primary audio monitor. The Web-888 does not replace the 312B-4; it adds visual spectrum display and remote monitoring capability that the 312B-4 cannot provide.
The Web-888 adds two capabilities the S-Line does not have: a real-time panadapter (spectrum and waterfall display of the HF band around the operating frequency) and a transmit quality monitor (the Web-888 sees the 32S-3’s transmitted signal on the antenna and can display its frequency, bandwidth, and any spurious products in real time).
The Web-888 connects to the antenna via a passive RF splitter (sharing with the 75S-3). It connects to the shack computer via Ethernet and is accessible via a browser on the same network. Its integration does not require any modification to the 75S-3, 32S-3, or 312B-4.
The ALC Loop: What It Is and Why It Matters for Integration
The ALC (Automatic Level Control) system is the most important internal interconnection in the S-Line station. During transmit, the 32S-3’s exciter output level is regulated by the ALC voltage received from the 75S-3 over a dedicated cable. The 75S-3 generates this voltage from the detected transmit carrier that feeds back from the 32S-3 PA output through the ALC sample path. The ALC voltage automatically reduces the 32S-3’s drive when the transmit signal exceeds a threshold, preventing overdriving and maintaining spectral purity.
The Web-888 does not interact with the ALC loop in any way. The Web-888 connects only at the antenna port via a passive splitter; it has no connection to the ALC cable or the 32S-3’s control circuitry. However, the Web-888’s panadapter provides a visual indication of whether the ALC is functioning correctly: a correctly ALC-limited SSB signal on the 32S-3 occupies approximately 2.5–3 kHz of bandwidth on the panadapter; a signal that appears abnormally wide or that shows splatter products on either side of the carrier indicates ALC malfunction or drive level issues that should be investigated at the 32S-3 before further operating.
Section 2 — Hardware Integration: Antenna Sharing and T/R Switching
The Passive RF Splitter for Receive
During receive, the antenna is shared between the 75S-3 and the Web-888 using a passive RF power splitter — the same ZFRSC-42 or equivalent approach documented in the vk6ada.com.au Web-888 R-390A companion guide and the Hermes Lite 2 companion guide. The splitter is placed between the antenna feedline and both the 75S-3 antenna input and the Web-888 HF antenna input. Both instruments receive the same RF signal simultaneously during the receive period.
The 3.5 dB insertion loss of the splitter affects the 75S-3’s effective noise figure. On the lower bands (80m, 40m) where atmospheric noise is dominant, this loss is inaudible. On the upper bands (20m, 15m, 10m) where the noise floor is lower, the 3.5 dB insertion loss may be marginally detectable on the weakest signals. For the typical S-Line DX operating scenario, this insertion loss is an acceptable trade-off for the panadapter capability the Web-888 provides.
T/R Switching: Protecting Both Receivers Simultaneously
The T/R switching architecture for the S-Line + Web-888 station must protect two inputs (75S-3 and Web-888) simultaneously when the 32S-3 is transmitting. The correct approach uses a cascaded switch arrangement as described in the vk6ada.com.au Tohtsu CX-140D guide:
Common port → antenna feedlinePort 1 (RX position) → passive RF splitter → 75S-3 input AND Web-888 inputPort 2 (TX position) → 32S-3 PA outputWhen PTT is pressed: upstream switch moves to Port 2 (transmit path). The entire splitter and everything downstream of it — both the 75S-3 and the Web-888 — are simultaneously isolated from the antenna by the upstream switch. Both receivers are protected by a single T/R relay action.
When PTT is released: upstream switch returns to Port 1 (receive path). Both the 75S-3 and the Web-888 resume receiving from the antenna via the splitter.
PTT control of the upstream switch: the 32S-3’s PTT output (available at the rear panel accessory socket) drives the CX-140D relay coil through a small transistor driver circuit. Configure the PTT-to-TX software delay in OpenWebRX (if remote-controlled) or the hardware PTT timing (if direct) to ensure the relay completes its transition before the 32S-3 begins generating RF. A
5–10 ms delay is sufficient for the CX-140D relay; verify the timing sequence is correct before transmitting at full power.
The 32S-3 PA Output Connector
The 32S-3 uses an SO-239 connector for the PA output. The CX-140D uses BNC connectors. Use a BNC-to-PL-259 adapter (as documented in the CX-140D station guide at vk6ada.com.au) at the 32S-3’s PA output port and at the 75S-3’s antenna input port. The Web-888’s HF antenna input is typically BNC or SMA; use the appropriate adapter. All adapters should be silver-plated Amphenol or equivalent quality — not no-name generic types.
Section 3 — The Dual-PTO Discipline: Keeping 75S-3 and 32S-3 on the Same Frequency
The S-Line’s most important operating discipline — the one that has no equivalent in a transceiver like the KWM-2A — is the requirement to keep the 75S-3 PTO and the 32S-3 PTO tuned to exactly the same frequency. Unlike a transceiver where the transmit and receive frequencies are mechanically linked, the 75S-3 and 32S-3 are independent instruments. An S-Line operator who moves the 75S-3 tuning ring to work a new signal but forgets to update the 32S-3 PTO will transmit on the wrong frequency — potentially interfering with other stations and not being heard by the station they are trying to work.
The Frequency Verification Procedure
Before any transmission, use the following procedure to verify dual-PTO alignment:
-
1
Tune the 75S-3 to the desired operating frequency Set the 75S-3 PTO dial to the frequency of the station you wish to work. Read the frequency from the 75S-3 vernier dial. Note the reading.
-
2
Set the Web-888 panadapter centre frequency In the OpenWebRX browser interface, note the current displayed frequency. The Web-888 should be showing approximately the same frequency as the 75S-3 dial reading (with the offset discussed in Section 4 applied). Verify the signal you tuned to is centred or near-centred in the Web-888 panadapter display.
-
3
Set the 32S-3 PTO to match the 75S-3 reading Rotate the 32S-3 PTO dial to match the frequency shown on the 75S-3 dial. If the 32S-3 has a frequency display or dial scale, set it to the same reading. Both PTOs should now be indicating the same frequency.
-
4
Verify with a brief test carrier on the Web-888 panadapter Key the 32S-3 very briefly (less than 1 second carrier key) and observe the Web-888 panadapter. The transmitted carrier should appear at the same position in the Web-888 display as the signal you tuned to on the 75S-3. If the transmitted signal appears at a different position: the 32S-3 PTO is offset from the 75S-3 PTO. Adjust the 32S-3 PTO until the test carrier aligns with the target frequency on the panadapter. Do not transmit on an occupied frequency during this verification; use a clear segment of the band.
Section 4 — OpenWebRX Configuration for S-Line Band Profiles
The Web-888’s OpenWebRX software must be configured with band profiles that match the S-Line’s operating bands and sideband conventions. This configuration is done once in the OpenWebRX administration panel and persists across sessions. Each profile should be named clearly so the operator can switch bands on the panadapter with a single click.
S-Line Band and Sideband Profile Reference
Band |
S-Line TX/RX Range |
Standard Sideband |
OpenWebRX Centre Frequency |
Recommended Span |
Default Demod |
|---|---|---|---|---|---|
| 80m | 3.500–4.000 MHz | LSB | 3.750 MHz | 500 kHz (shows full 80m phone) | LSB |
| 40m | 7.000–7.300 MHz | LSB | 7.150 MHz | 500 kHz (full 40m band visible) | LSB |
| 20m | 14.000–14.350 MHz | USB | 14.175 MHz | 500 kHz (full 20m band visible) | USB |
| 17m (CP-1) | 18.068–18.168 MHz | USB | 18.118 MHz | 200 kHz (full 17m band visible) | USB |
| 15m | 21.000–21.450 MHz | USB | 21.225 MHz | 500 kHz (full 15m band visible) | USB |
| 12m (CP-1) | 24.890–24.990 MHz | USB | 24.940 MHz | 150 kHz (full 12m band visible) | USB |
| 10m | 28.000–29.700 MHz | USB | 28.500 MHz | 1.5 MHz (shows full 10m band) | USB |
Configuring the Web-888 Frequency Offset for S-Line Band Monitoring
When using the Web-888 panadapter to verify the 32S-3’s transmit frequency (as described in Section 3), the Web-888’s frequency display must be correctly calibrated. The Web-888’s reference oscillator should be calibrated against a known standard (WWV on 10.000 or 15.000 MHz is ideal) following the procedure in the vk6ada.com.au Web-888 R-390A companion guide. Once calibrated, the Web-888’s frequency readout should agree with the 75S-3 and 32S-3 dial readings to within approximately ±500 Hz — sufficient for all SSB and CW operating purposes.
Section 5 — Best-Practice Operating Procedures for the Web-888-Augmented S-Line Station
-
Always Allow Full Warm-Up Before Any Frequency Verification or Transmit Operation
The S-Line requires 15–20 minutes of warm-up before the PTOs are stable enough for reliable frequency alignment. The Web-888 is available immediately after power-on, but the panadapter display will show the S-Line’s transmitted signal drifting during warm-up if verification is attempted too early. Establish a discipline of powering on the S-Line station, setting the Web-888 to the operating band, and then attending to other station tasks while the PTOs stabilise. Use the Web-888 waterfall to observe the PTO stability: if time markers (WWV or another known-frequency signal) are visible on the waterfall, the gradual frequency drift during warm-up is visible as a slight slope in the marker trace. When the slope flattens, the PTO has stabilised.
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Switch the Web-888 Profile Before Changing S-Line Bands
When the S-Line station changes bands (switching band crystals in both the 75S-3 and 32S-3), switch the Web-888 OpenWebRX band profile to the new band before the S-Line band switch. This ensures the panadapter is showing the correct band when the S-Line completes its band change, and avoids confusion from a panadapter showing 20m activity while the S-Line is now on 40m. The Web-888 band profile switch is a single click in the OpenWebRX browser interface; make it part of the band-change procedure rather than an afterthought.
Band change sequence:
Web-888 profile → S-Line band crystals → PA tune → frequency verify (brief test carrier). This sequence ensures the panadapter is ready to verify the transmit frequency immediately after the S-Line completes its PA tune-up for the new band. -
Use the Web-888 Panadapter as the Primary Frequency Identification Tool for DX
The S-Line’s 10-turn vernier PTO dial is extraordinarily precise for frequency-within-a-band tuning. It is less practical for band-awareness DX spotting. When looking for DX, use the Web-888 panadapter to identify signals: scan visually across the waterfall display, spot signal peaks at their labelled frequencies, then tune the 75S-3 PTO to those frequencies. This workflow is faster than audio scanning with the 75S-3 alone because signals are visible on the panadapter even when their audio has dropped below your threshold for recognition during receive.
A practical discipline: when you see a strong signal cluster on the Web-888 panadapter (a pile-up), the frequency of the cluster is visible without tuning through it. Set the 75S-3 to the DX station’s transmit frequency (the lower-rate cluster in a pile-up), listen to confirm, then set the 32S-3 to match and join the pile-up. This approach is faster and more accurate than tuning the S-Line through a pile-up by ear.
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Monitor Every Transmission on the Web-888 Panadapter for Signal Quality
The Web-888 panadapter shows the 32S-3’s transmitted signal in real time. Use it. Every SSB transmission from the 32S-3 should show a clean spectral envelope approximately 2.5–3 kHz wide at the operating frequency, with no significant energy appearing beyond this window. If the Web-888 panadapter shows splatter products (signals appearing at ±5 kHz, ±10 kHz from the carrier), the ALC system may be malfunctioning or the 32S-3 is being overdriven. Address this before continuing to transmit.
During CW operation, the Web-888 panadapter should show a clean, narrow CW carrier with no sidebands beyond the keying-bandwidth envelope. Key clicks (if present) will show as broadened spectral edges on each character boundary. The Web-888 panadapter’s view of your own CW signal is more informative than any other single test for key-click assessment without requiring another operator to listen to your signal.
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Use the Web-888 as an ALC Loop Health Indicator
A correctly operating ALC loop in the S-Line station produces a transmitted SSB signal with consistent amplitude envelopes from syllable to syllable. On the Web-888 panadapter, this appears as a signal whose peak level rises during loud speech and falls during pauses, but whose spectral width remains approximately constant. An ALC system that is not limiting correctly (either not engaging at all or engaging too aggressively) produces characteristic visual patterns on the panadapter: no ALC limiting produces a signal that varies dramatically in both amplitude and apparent bandwidth with speech peaks; excessive ALC compression produces a signal that looks almost constant in amplitude even during speech pauses, which is also incorrect.
The ideal Web-888 panadapter appearance for correctly ALC-limited SSB from the 32S-3 during normal speech:
signal peaks at approximately 6–10 dB above the noise floor during active speech, near noise floor during pauses, consistent spectral width of approximately 2.5–3 kHz throughout. Significant deviations from this pattern warrant investigation at the 32S-3 ALC circuit before further operation. -
VOX Operation: T/R Switching Timing with Web-888 Connected
When using VOX (voice-operated transmit) on the 32S-3, the T/R switching must complete its transition before the first syllable of transmitted audio reaches the PA. This timing requirement exists regardless of the Web-888 connection, but the Web-888’s panadapter provides a useful visual confirmation that the T/R switching is completing correctly: if the first milliseconds of each transmission show the antenna connected to the receive path (not the transmit path), the panadapter will show an anomalous receive-side transient at the start of each transmission. If the T/R switch is operating correctly, the transmission simply appears as a clean signal onset with no preceding transient.
When using VOX with the CX-140D relay for T/R switching, ensure the VOX hold time (the delay before the 32S-3 returns to receive after the last speech sound) is set sufficiently long that the relay has time to complete its release before the 75S-3 is reconnected to the antenna. A hold time of at least 250 ms is recommended with the CX-140D relay to avoid the relay chattering in the gap between syllables during normal speech.
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Web-888 RF Gain Optimisation for the Splitter-Connected S-Line Antenna
With the antenna split between the 75S-3 and the Web-888, the Web-888 receives 3.5 dB less signal than if it had a dedicated antenna. The Web-888’s RF gain must be adjusted upward from the setting appropriate for a dedicated antenna to compensate. The correct Web-888 RF gain for the splitter-connected S-Line antenna is the lowest gain setting that produces a clean panadapter display with visible signal peaks above the noise floor on a moderately active band.
Verify the gain setting is correct on each new band after a band change: what works on 20m (busy band with many strong signals) may cause ADC overload on 40m at night (very high noise floor and strong regional signals). ADC overload on the Web-888 manifests as characteristic mirror images of strong signals and a flat ADC noise plateau replacing the usual Gaussian noise floor. Reduce RF gain until mirror images disappear. Aim for the noise floor to show the expected Gaussian shape rather than a flat plateau.
Section 6 — Enhanced Integration: 75S-3 IF Tap for Automatic Frequency Tracking
The antenna-sharing approach described above provides an independent panadapter that the operator manually aligns to the S-Line’s operating frequency. A tighter integration is possible using the same IF-tap principle as the CASCADE-390 kit for the R-390A: tapping the 75S-3’s 455 kHz IF output and feeding it to the Web-888, so that the panadapter is centred on the 75S-3’s exact tuned frequency automatically.
The 75S-3 uses a 455 kHz IF chain with the Collins mechanical filter — the same architecture as the R-390A. A suitably designed high-impedance IF tap (following the same design principles as the CASCADE-390 kit) can be applied to the 75S-3’s IF strip without modifying the receiver’s operating characteristics. The tapped 455 kHz signal is then fed to the Web-888’s HF input, and the Web-888’s OpenWebRX software is configured with the appropriate IF offset (as described in the RX-888 Mk II cascade integration guide at vk6ada.com.au) to display the correct HF frequency.
Section 7 — Complete S-Line + Web-888 Station Architecture
┌──────────────────────────────────────────────────────────────────────────┐
│ COLLINS S-LINE + WEB-888 — COMPLETE STATION ARCHITECTURE │
└──────────────────────────────────────────────────────────────────────────┘
ANTENNA (50 Ω HF antenna — dipole, vertical, or beam)
│
[UPSTREAM CX-140D — T/R switch; PTT controlled from 32S-3 accessory socket]
├── Port 1 (RX): feeds → passive RF splitter (ZFRSC-42)
│ ├── → Collins 75S-3 antenna input (SO-239)
│ └── → Web-888 HF input (BNC/SMA)
│
└── Port 2 (TX): ← Collins 32S-3 PA output (SO-239)
via BNC-to-PL-259 adapter
INTERNAL S-LINE INTERCONNECTIONS (unchanged by Web-888 integration):
┌────────────────────────────────────────────────────────────────────────┐
│ 75S-3 audio output → 312B-4 console loudspeaker │
│ 32S-3 sidetone → 312B-4 console CW sidetone volume │
│ 75S-3 ALC output ←→ 32S-3 ALC input (ALC interconnect cable) │
│ 32S-3 PTT output → CX-140D relay coil driver (new connection) │
└────────────────────────────────────────────────────────────────────────┘
WEB-888 CONNECTION:
Web-888 HF input ← passive RF splitter Port B
Web-888 Ethernet port → shack network switch → computer
Computer browser → http://[Web-888 IP]:8073 → OpenWebRX interface
─────────────────────────────────────────────────────────────────────────
OPERATING FREQUENCY CHAIN — THE DUAL-PTO DISCIPLINE
─────────────────────────────────────────────────────────────────────────
75S-3 PTO dial ─────────────────→ 75S-3 tuned receive frequency
32S-3 PTO dial ─────────────────→ 32S-3 transmit frequency
↑ Must match 75S-3 PTO manually
Web-888 panadapter ────────────→ Shows BOTH:
(1) Signal tuned on 75S-3 (from antenna)
(2) 32S-3 transmitted signal peak
Frequency alignment verified by:
32S-3 test carrier → CX-140D TX position → antenna
→ back through antenna to splitter (adjacent lobe)
→ Web-888 input → panadapter shows TX frequency peak
If 32S-3 peak aligns with 75S-3 tuned signal: ✓ PTOs matched
If 32S-3 peak is offset from 75S-3 signal: adjust 32S-3 PTO to match
─────────────────────────────────────────────────────────────────────────
T/R TIMING SEQUENCE FOR S-LINE + WEB-888
─────────────────────────────────────────────────────────────────────────
PTT pressed (or VOX activates):
t=0: 32S-3 PTT line activates → CX-140D relay coil energises
t=2ms: CX-140D contacts complete: antenna → 32S-3 TX; 75S-3+Web-888 isolated
t=5ms: 32S-3 begins generating RF (delay ensures switch completed)
[TX period: 75S-3 and Web-888 both protected at >60 dB isolation]
PTT released (or VOX hold timer expires):
t=0: 32S-3 PTT line releases → CX-140D relay coil de-energises
t=2ms: CX-140D contacts release: antenna → splitter → 75S-3 and Web-888
[RX period: 75S-3 receiving; Web-888 panadapter showing receive spectrum]
VOX hold time recommendation: ≥250 ms to prevent relay chatter in speech gaps
─────────────────────────────────────────────────────────────────────────
WEB-888 TX QUALITY MONITOR — WHAT TO LOOK FOR
─────────────────────────────────────────────────────────────────────────
CORRECT SSB from 32S-3 (ALC functioning, correct drive level):
┌────────────────────────────────────────────────────────┐
│ Clean spectral envelope, ~2.5–3 kHz wide │
│ Carrier null between sidebands (balanced modulator OK)│
│ No energy beyond ±3 kHz from carrier frequency │
│ Signal peaks with speech, near noise floor on pauses │
└────────────────────────────────────────────────────────┘
PROBLEMS TO INVESTIGATE (visible on Web-888 panadapter):
┌──────────────────────────────────┬─────────────────────────────────────┐
│ Observation │ Likely cause │
│ ─────────────────────────────── │ ────────────────────────────────── │
│ Splatter ±5–10 kHz from carrier │ ALC not limiting; overdrive │
│ Residual carrier in null │ Balanced modulator needs alignment │
│ Signal too wide (>4 kHz) │ Microphone eq or AF overdrive │
│ Signal constant level (no dip) │ ALC over-limiting; too much compr. │
│ Key clicks on CW (wide edges) │ Rise/fall time too fast; RF shaping │
│ Asymmetric SSB (one sideband) │ Filter or carrier null adjustment │
│ Frequency offset from expected │ PTO mismatch; 32S-3 ≠ 75S-3 PTO │
└──────────────────────────────────┴─────────────────────────────────────┘
Collins S-Line + Web-888 complete station architecture. The T/R timing values shown are for the Tohtsu CX-140D relay; verify against the specific relay’s datasheet energise time. The TX quality monitor observations are community-documented typical appearances from Web-888 panadapter monitoring of 32S-3 operation; actual appearance varies with antenna VSWR, operating frequency, and band conditions. All internal S-Line interconnections (ALC cable, console audio, CW sidetone) are unchanged by the Web-888 integration.
References and Notes
- Collins Radio Company, 75S-3 / 75S-3A / 75S-3B / 75S-3C Operating and Service Instructions and 32S-3 Operating and Service Instructions. Available through the Collins Collectors Association at collinsradio.org and the Virtual Collins Radio Museum (wa3key.com). The 75S-3 and 32S-3 service manuals are the authoritative references for the ALC interconnection, the PTO frequency dial calibration, the antenna connector specifications, and the PA tune-up procedure referenced in Section 2 of this guide. The specific service manual edition applicable to the unit’s serial number range should be used; variant differences exist between the 75S-3 and its subsequent production versions (75S-3A, 75S-3B, 75S-3C).
- Mike Peace VK6ADA, Web-888 Remote Access Setup for Vintage Receivers, vk6ada.com.au (March 2026). The primary reference for Web-888 hardware overview, OpenWebRX software installation and configuration, network setup (static IP, DDNS, WireGuard VPN), security hardening, and the RF splitter approach for antenna sharing. The present guide focuses on S-Line-specific operational procedures; the hardware and software setup foundation is documented in the Web-888 R-390A companion guide. Readers who have not configured the Web-888 hardware should read that guide before this one.
- Mike Peace VK6ADA, Tohtsu CX-140D Use Cases for Collins S-Line, R-388, R-390, R-390A, Hammarlund SP-600 and HQ-180, vk6ada.com.au (March 2026). The primary reference for T/R switching configuration using the CX-140D, including the cascaded switch architecture (Configuration C) that simultaneously protects both the 75S-3 and the Web-888 during 32S-3 transmit operation. The PTT relay timing sequence and relay driver circuit are documented in that guide.
- Mike Peace VK6ADA, Collins Crystal Pack CP-1 — Non-Amateur Band Coverage and 2026 Use Cases, vk6ada.com.au (March 2026). Reference for the WARC band (17m, 12m, 30m) crystal configuration that enables the 75S-3 and 32S-3 to operate on bands not covered by the standard S-Line crystal complement. The 17m and 12m OpenWebRX band profiles in Section 4 of this guide apply only to S-Line stations fitted with the appropriate CP-1 or equivalent crystal expansion.
- Mike Peace VK6ADA, RX-888 Mk II with the Collins R-390A — Practical Cascade Integration via the CASCADE-390 IF Tap Kit, vk6ada.com.au (March 2026). Reference for the IF tap integration approach described in Section 6. The 75S-3’s 455 kHz IF architecture is functionally identical to the R-390A’s for the purposes of the IF tap; the OpenWebRX IF offset calculation (
75S-3 dial reading − 455 kHz) is the same formula documented for the R-390A cascade integration. The CASCADE-390 kit applicability to the 75S-3 is noted in that guide. - Collins Collectors Association, S-Line Technical Resources and Community Forum, collinsradio.org. Community reference for ALC loop alignment and troubleshooting, balanced modulator null adjustment, and the specific SSB quality standards that a correctly operating 32S-3 should meet. The TX quality monitor observations in Section 7 (the station architecture legend) are consistent with the ALC and modulator performance documentation in the CCA technical forum and reflect community consensus on the spectral appearance of a correctly operating 32S-3. Restorers who observe deviations from these expectations should consult the CCA technical forum for alignment guidance.