RX-888 Mk II with the Collins R-390A/URR
Practical Cascade Integration via the CASCADE-390 IF Tap Kit
The antenna-sharing approach gives you a panadapter that happens to be near your operating frequency. The CASCADE-390 IF tap gives you a panadapter that is your operating frequency — centred automatically on whatever frequency the R-390A’s PTO is tuned to, showing you the spectrum exactly as the receiver’s own RF section and bandpass filters have processed it. This guide covers the CASCADE-390 kit, the RX-888 Mk II USB setup, the 455 kHz IF offset calibration, tap point selection, and the practical operation of the most tightly integrated R-390A/SDR panadapter available without permanently modifying the receiver.
Two SDR integration approaches exist for the R-390A, and they serve different purposes. Antenna sharing — connecting the RX-888 to a passive splitter alongside the R-390A — gives the SDR its own independent view of the HF spectrum centred wherever the SDR software VFO is set. The operator must manually adjust the SDR software frequency to match the R-390A’s PTO reading. The cascade approach, using the CASCADE-390 IF tap kit, is fundamentally different: the RX-888 receives the R-390A’s 455 kHz intermediate frequency output, not the raw RF from the antenna. The panadapter is therefore centred on the R-390A’s exact tuned frequency by design — it moves when the R-390A’s tuning ring moves, at 455 kHz, showing what has already been processed by the R-390A’s front-end bandpass filters. No synchronisation between the SDR software and the R-390A’s PTO is needed.
This is the integration that R-390A operators who want a genuine panadapter — not a nearby-but-separate SDR display — have been building since SDR hardware first became affordable. The CASCADE-390 kit, designed by VK6ADA for the R-390A/URR specifically, provides the buffered high-impedance tap and the rear-panel BNC output that makes the integration reversible and clean. This guide covers the complete integration from kit installation through operating procedure.
Design principles: the CASCADE-390 buffer amplifier uses a high input impedance (
>10 kΩ at 455 kHz) JFET follower stage that presents negligible load to the R-390A’s IF circuit. The R-390A operates identically with the CASCADE-390 installed and connected; the tap is purely additive. The BNC output is terminated at 50 Ω to match the RX-888 and other SDR inputs directly.Kit documentation and availability: full CASCADE-390 kit documentation, PCB layout, schematic, and parts list are available at vk6ada.com.au. Contact via the site for kit availability. All components in the kit are in current production; no obsolete or hard-to-source parts.
Section 1 — Why the IF Tap Approach Outperforms Antenna Sharing for Panadapter Use
The Fundamental Difference: Where in the Signal Chain the SDR Connects
In antenna sharing, the SDR connects at the beginning of the signal chain — at the antenna. The SDR sees everything the antenna receives, in the same raw form the R-390A’s front-end processes. The SDR and the R-390A are two independent receivers sharing the same antenna signal source. Their tuned frequencies are unrelated unless the operator manually synchronises them.
In the cascade approach, the SDR connects in the middle of the signal chain — after the R-390A’s first conversion stage has processed the incoming RF and produced the 455 kHz IF signal. The SDR sees a signal that has already been:
- Amplified by the R-390A’s RF amplifier stage (improving the effective noise figure before the SDR’s own noise figure adds to it)
- Filtered by the R-390A’s switchable bandpass filters (removing signals outside the currently active band segment)
- Frequency-converted by the R-390A’s PTO/crystal combination (meaning the 455 kHz output is centred precisely on the R-390A’s tuned frequency)
Antenna → R-390A RF amp → R-390A bandpass filter → R-390A mixer (PTO + crystal) → 455 kHz IF signal → CASCADE-390 tap↓ (pre-filter tap)
→ [Collins mechanical filter at 455 kHz] → narrowband filtered IF → post-filter tap → R-390A audio stagesWhat this means for the panadapter: the SDR’s display is locked to the R-390A’s PTO. As the R-390A’s tuning knob is rotated, the 455 kHz IF signal remains at 455 kHz (it is always the fixed IF frequency) but its spectral content changes — the signals it contains shift in response to the PTO tuning. The SDR software, displaying the 455 kHz window with a frequency offset applied, shows the spectral content exactly centred on the R-390A’s current dial frequency. Turn the R-390A’s tuning ring; the panadapter display content changes synchronously.
Practical Advantages Over Antenna Sharing
- Automatic frequency tracking. The panadapter follows the R-390A’s tuning without any SDR software adjustment. When you rotate the PTO dial to a new frequency, the signals in the panadapter window shift immediately to reflect the new frequency context.
- No RF splitter insertion loss on the receive path. The CASCADE-390 tap is after the R-390A’s front-end; the R-390A receives its full antenna signal unattenuated. The 3.5 dB insertion loss of the antenna-sharing splitter is completely eliminated.
- Pre-amplification by the R-390A. The R-390A’s RF amplifier stage amplifies the incoming signal before it reaches the tap. The SDR’s effective sensitivity is improved by the R-390A’s front-end gain, partially offsetting the SDR’s own noise figure.
- Bandpass filter protection. The R-390A’s bandpass filters (which switch with the band selector) prevent signals outside the current band from reaching the 455 kHz IF and therefore the SDR. In an antenna-sharing configuration, the SDR sees the entire HF spectrum including strong out-of-band signals that can saturate the SDR’s ADC. In the cascade configuration, only signals within the R-390A’s currently selected band pass through.
- No need for a second antenna run. The CASCADE-390 tap is an internal connection inside the R-390A chassis; the only external cable is the BNC output to the RX-888. No second coax from the antenna is needed.
Section 2 — The RX-888 Mk II: Key Parameters for R-390A Integration
ADC:
16-bit LTC2208 direct-sampling; 130 dB dynamic range specifiedHF frequency coverage (direct sampling):
~1 kHz to ~64 MHzVHF/UHF coverage (mixing): ~64 MHz to 1.7 GHz (separate hardware path)
Maximum sample rate:
64 MSPS (HF direct sampling mode)ADC dynamic range at 455 kHz operation: typically
>100 dB SNRConnection:
USB 3.0 (SuperSpeed; USB 2.0 will not provide sufficient bandwidth at maximum sample rate)Software: SDR# (SDR Sharp), SDR Console v3, HDSDR, GNU Radio, Cubic SDR, others
Antenna input:
SMA female (requires SMA-to-BNC adapter for CASCADE-390 kit output)Driver: CyUSB3 driver under Windows; standard libusb under Linux
Why 455 kHz operation is well-suited to the RX-888 Mk II:
At 455 kHz, the RX-888’s LTC2208 ADC is operating well below its first Nyquist zone (half the sample rate). The SNR at 455 kHz is at its highest because the ADC noise figure is lowest at low frequencies in a direct-sampling architecture. The R-390A’s 455 kHz IF output is therefore an ideal signal for the RX-888 — clean, well-buffered by the CASCADE-390, and within the ADC’s most linear and lowest-noise operating region.
Section 3 — CASCADE-390 Tap Point Selection: Pre-Filter, Post-Filter, and RF
The CASCADE-390 kit provides three selectable tap points within the R-390A signal chain. The correct choice depends on the intended use of the panadapter. Understanding what each tap delivers is essential for configuring the RX-888 and the SDR software correctly.
Position in chain: after the R-390A’s first conversion stage, before the Collins mechanical filter.
What it delivers: the full bandwidth of the R-390A’s first IF strip, typically several hundred kHz wide depending on the first IF bandwidth. Signals within the R-390A’s selected band segment appear at their correct relative positions around the 455 kHz centre. Signals outside the mechanical filter passband are visible; the mechanical filter has not yet acted on the signal.
Best for: panadapter use. The wide view shows band activity on either side of the R-390A’s tuned frequency, providing the DX spotting and band-awareness function that motivates the whole integration. This is the primary tap for everyday panadapter operation.
Bandwidth visible: typically ±100 kHz to ±500 kHz depending on the R-390A’s first IF filter design. A 2 MSPS sample rate on the RX-888 shows ±1 MHz; 8 MSPS shows ±4 MHz.
SDR sample rate: 2–8 MSPS recommended
Position in chain: after the Collins mechanical filter (the signal has passed through the filter’s passband).
What it delivers: the narrowband filtered signal — 4 kHz (narrow) or 8 kHz (wide) wide, depending on which mechanical filter bandwidth is selected on the R-390A. The panadapter shows only the signal passing through the mechanical filter, centred at 455 kHz.
Best for: mechanical filter analysis; verifying that the filter is functioning correctly and that its passband shape matches specification. Not useful as a practical panadapter (the passband is too narrow to show useful band context). Also useful for monitoring the IF strip noise floor to diagnose sensitivity issues.
SDR bandwidth required: a 100 kHz sample rate is more than sufficient to capture a 4–8 kHz filtered signal; using the RX-888 at 1 MSPS with heavy digital filtering is the typical configuration for post-filter analysis.
SDR sample rate: 100 kHz–1 MSPS; diagnostic use only
Position in chain: at or near the R-390A’s antenna input, providing a high-impedance sample of the RF signal before any receiver processing.
What it delivers: the raw RF signal from the antenna, equivalent to the antenna-sharing approach described in the HL2 companion guide at vk6ada.com.au. The SDR receives the full HF spectrum as seen by the antenna; none of the R-390A’s filtering or amplification has been applied.
Best for: situations where the operator wants a wideband spectrum view that is independent of the R-390A’s current band selection — for example, monitoring multiple bands simultaneously. This tap reverts to the antenna-sharing model and loses the automatic PTO tracking advantage of the IF tap approach.
When to use instead of pre-filter: if the R-390A is being tuned rapidly through bands and the operator wants the panadapter to show the full HF band rather than the band-filtered window, the RF tap provides this. For fixed-frequency DX work, the pre-filter tap is always preferred.
SDR sample rate: full RX-888 capability; full HF visible
Section 4 — Hardware Installation
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1
Review CASCADE-390 kit documentation for the specific tap point location Download the full CASCADE-390 kit documentation from vk6ada.com.au before beginning installation. The documentation identifies the exact component designator and chassis location of the pre-filter tap point for the specific R-390A contract year (Collins, Motorola, General Dynamics, or Stewart Warner). The tap point location varies slightly between contract manufacturers; using the wrong location installs the tap in an incorrect position that may not provide the intended IF signal. Identify your unit’s contract manufacturer from the nameplate before selecting the tap point diagram to follow.
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2
Install the CASCADE-390 PCB inside the R-390A chassis The CASCADE-390 PCB mounts to the existing chassis hardware inside the R-390A using the mounting method specified in the kit documentation (typically a small standoff bracket attached to an existing screw or chassis post). No new chassis drilling is required for the PCB mounting; the rear-panel BNC output requires a single 15 mm diameter hole in the rear panel at the documented position. All soldering is on the CASCADE-390 PCB; the connection to the R-390A’s IF circuit is made via a short length of RG-174 miniature coax from the tap point to the CASCADE-390 PCB input, terminated at the kit’s input pad. The connection at the R-390A IF tap point is a single solder joint at the specific component lead identified in the documentation.
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3
Route the output BNC cable and mount the rear-panel connector The CASCADE-390’s buffered 50 Ω output connects to a BNC bulkhead connector mounted on the R-390A’s rear panel. The kit documentation specifies a chassis location that does not conflict with existing rear-panel connectors (antenna input, audio output, headphone jacks) or internal components. Drill the 15 mm hole using a stepped drill bit (punch drill) from the outside of the panel to prevent burring. Mount the BNC bulkhead connector from inside the chassis. Route a short BNC-to-BNC cable from the CASCADE-390 PCB output to the bulkhead connector.
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4
Verify CASCADE-390 installation: R-390A receives normally after installation With the chassis reassembled and powered via Variac, verify the R-390A receives normally on all band positions. The CASCADE-390 buffer should be completely transparent to the R-390A’s operation. Tune to a known signal (WWV on 5, 10, or 15 MHz; an amateur net on 20m; a shortwave broadcast). The R-390A audio should be identical to its pre-installation behaviour. If sensitivity is reduced (S-meter reads lower than expected on a known-strength signal), recheck the tap connection — a low-resistance connection at the wrong point can load the IF circuit.
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5
Connect the CASCADE-390 output to the RX-888 Mk II HF input Connect a BNC coax cable from the R-390A’s newly installed CASCADE-390 BNC output connector to the RX-888 Mk II’s HF antenna input. The RX-888 HF input is typically an SMA connector; use a BNC-female to SMA-male adapter, or a short cable with BNC and SMA plugs. Keep this cable short (under 1 m); miniature RG-174 or equivalent is adequate since the signal level at 455 kHz from the CASCADE-390 output is clean and well-buffered. At 455 kHz, cable attenuation is entirely negligible for any reasonable cable length.
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6
Connect the RX-888 Mk II to the computer via USB 3.0 Connect the RX-888 Mk II to a USB 3.0 port on the computer using the supplied USB 3.0 cable. USB 3.0 is identified by the blue-coloured connector inside the port. If the computer does not have USB 3.0 ports, install a USB 3.0 PCI-e expansion card. Do not use USB hubs — connect directly to the motherboard or expansion card USB 3.0 port. Install the CyUSB3 driver for Windows (available from the RX-888 manufacturer or from the ExtIO plugin community); verify the RX-888 is recognized in Device Manager before launching SDR software.
Section 5 — Software Setup and the Critical IF Offset Calibration
The most important software configuration step for the cascade approach is the IF offset. When the RX-888 is receiving the R-390A’s 455 kHz IF output, the SDR software sees signals centred at 455 kHz. But the operator needs to see frequencies in terms of the actual HF frequency being received by the R-390A, not the 455 kHz IF frequency. The offset configuration tells the SDR software: “the signal you are seeing at 455 kHz actually corresponds to [R-390A dial frequency]; adjust your frequency display accordingly.”
The R-390A converts incoming RF to 455 kHz by heterodyning:
RF frequency − LO frequency = 455 kHz, or LO frequency = RF frequency − 455 kHz.When the R-390A is tuned to
14.200 MHz: a signal at 14.200 MHz appears at 455 kHz in the IF. A signal 10 kHz above (14.210 MHz) appears at 465 kHz. A signal 10 kHz below (14.190 MHz) appears at 445 kHz.The IF offset to apply in SDR software:
offset = R-390A dial reading − 455 kHz. With the R-390A on 14.200 MHz: offset = 14,200 kHz − 455 kHz = 13,745 kHz (13.745 MHz).Applied correctly, the SDR display shows
14.200 MHz at the centre of the panadapter window, with signals on either side displayed at their correct HF frequencies. The offset must be updated when the R-390A’s band crystal changes the conversion scheme (each band has its own crystal; the 455 kHz IF relationship holds for all bands on the R-390A/URR in the standard single-conversion design).
Configuring the IF Offset in Major Software Packages
Open SDR# and select the RX-888 (ExtIO plugin or SoapySDR driver). Set the centre frequency to 455 kHz. In SDR#’s configuration, locate the Frequency Shift or Offset setting (available in the Radio panel or via Plug-ins depending on the SDR# version). Enter the offset value calculated from the R-390A’s current dial reading: R-390A frequency (Hz) − 455,000 Hz. The SDR# frequency display will now show the correct HF frequencies centred on the R-390A’s operating frequency. Update this offset whenever the R-390A is retuned to a significantly different frequency or when switching bands (the offset changes proportionally to the R-390A’s new frequency).
Setting: Radio → Frequency Shift (Hz)
In SDR Console v3, open the device definition for the RX-888. In the Calibration or Correction settings, apply an LO offset equal to the R-390A’s current dial frequency minus 455 kHz in Hz. Alternatively, set the SDR Console VFO to 455 kHz and apply the offset in the Frequency Translate field. The result should be a panadapter display centred on the R-390A’s dial frequency. SDR Console’s large and configurable spectrum display makes it particularly useful for the pre-filter tap panadapter: the wide display shows a clean, calibrated view of the band segment the R-390A is working in.
Setting: Device → Calibration → IF Offset
HDSDR (High Definition Software Defined Radio) has native IF operation support and is particularly well-suited to the cascade approach. In HDSDR, set the device centre frequency to 455 kHz. Then in Options → Miscellaneous → Lo/Tune Frequency Offset, enter the R-390A’s dial frequency. HDSDR then displays all frequencies offset from the 455 kHz IF centre by the LO value, showing the correct HF frequencies directly. HDSDR’s IF display mode is a mature feature designed exactly for IF-tap panadapter applications; it is the most straightforward configuration path for the cascade approach.
Setting: Options → IF Frequency → Lo/Tune offset
Section 6 — Sample Rate and Bandwidth Selection for the IF Tap
The RX-888 Mk II’s maximum sample rate (64 MSPS) is far more than needed for the 455 kHz IF tap application. Using the maximum sample rate when receiving the IF output is wasteful of USB bandwidth, CPU processing power, and screen real estate, and can produce a panadapter display where the useful signal content occupies only a tiny fraction of the visible spectrum. The correct sample rate is one that shows a useful bandwidth of activity around the R-390A’s operating frequency without including so much spectrum that individual signals are tiny on the display.
Sample Rate |
Visible Bandwidth |
Practical Use |
|---|---|---|
| 500 kHz | ±250 kHz around tuned frequency | DX operating: shows the full 20m or 15m SSB sub-band segment. Signals are large and clearly readable on the display. Minimum CPU load. |
| 1 MSPS | ±500 kHz — approximately half of a 1 MHz PTO segment | Recommended for most panadapter use. Shows the full amateur band segment on 20m, 15m, and most other HF bands. Manageable CPU load at typical display update rates. |
| 2 MSPS | ±1 MHz — the full R-390A PTO window | Useful when the pre-filter tap bandwidth supports 2 MSPS of useful content. Shows the entire 1 MHz band segment the R-390A is currently covering. Moderate CPU load. |
| 8 MSPS | ±4 MHz | Wide view showing multiple adjacent band segments. Most of the visible bandwidth will be below the pre-filter noise floor; signals only appear near the R-390A’s current operating frequency. High CPU load; lower display refresh rate needed. |
Section 7 — Operating the Integrated Station
The Normal Operating Workflow
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1
Power on the R-390A and allow 15 minutes warm-up The R-390A’s PTO frequency stabilises after 15 minutes of operation. Do not use the panadapter for precision frequency identification during the warm-up period — the PTO will be drifting and the IF offset calibration will reflect a moving target. After warm-up, the PTO is stable to within ±500 Hz per hour and the panadapter display is reliable for signal identification.
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2
Launch SDR software and set sample rate and centre frequency Set the SDR centre frequency to
455 kHz. Set the sample rate to the chosen value (1 MSPS recommended for most applications). Verify the RX-888 shows in the device list. The panadapter display should show a noise floor with possibly a central peak at 455 kHz (the DC component; addressable in software with the DC removal filter if needed). -
3
Set the IF offset to match the R-390A’s current dial reading Read the R-390A’s PTO dial and band crystal combination to determine the current operating frequency. Calculate the IF offset:
R-390A frequency − 455 kHz. Enter this offset in the SDR software as described in Section 5. The panadapter display should now show the centre frequency as the R-390A’s operating frequency, with signals visible as peaks in the noise floor. -
4
Tune the R-390A — observe the panadapter responding Rotate the R-390A’s tuning ring slowly and watch the SDR panadapter display. Signals should shift across the display as the PTO changes frequency — a signal that was to the right of centre moves toward centre and then off to the left as you tune through it. This visual confirmation that the panadapter is responding to R-390A tuning changes is the definitive test that the CASCADE-390 connection is correct and the IF offset is properly set. If signals do not shift, the tap connection is not delivering IF signal to the RX-888.
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5
Use the panadapter to identify signals, tune R-390A to them Identify a signal peak on the SDR panadapter display. Read its frequency from the SDR display (which now shows the correct HF frequency due to the IF offset). Tune the R-390A’s PTO dial until the signal is centred in the R-390A’s passband — confirmed by maximum audio from the R-390A’s audio output and the signal peak centred on the 455 kHz centre in the SDR display. Use the R-390A’s audio as the primary receive source; the SDR display is the band-awareness and frequency-identification tool.
RX-888 Gain Optimisation for IF Tap Operation
When receiving the CASCADE-390’s buffered output, the RX-888’s RF gain setting interacts with the IF signal level differently than in direct antenna connection. The CASCADE-390 buffer provides a fixed-gain output; the R-390A’s IF signal level increases with signal strength and with the R-390A’s RF GAIN control setting. The correct RX-888 RF gain is the lowest setting that produces a clean panadapter display — visible signal peaks above the noise floor, no ADC overload on strong signals. ADC overload appears as symmetric spurious signals or a flat ADC noise floor that replaces the normal Gaussian noise baseline; reduce RX-888 gain if these artefacts appear.
Section 8 — Troubleshooting the Cascade Integration
Section 9 — Complete CASCADE-390 Architecture
┌──────────────────────────────────────────────────────────────────────────┐
│ CASCADE-390 / RX-888 Mk II INTEGRATION — COMPLETE SIGNAL PATH │
└──────────────────────────────────────────────────────────────────────────┘
ANTENNA (50 Ω)
│
│ (Full antenna signal; no splitter loss)
▼
┌────────────────────────────────────────────────────────────────────────┐
│ COLLINS R-390A/URR CHASSIS │
│ │
│ [Antenna input SO-239] │
│ │ │
│ [RF Amplifier, V501 6DC6] │
│ │ │
│ [Bandpass filter — band-switched with band crystal] │
│ │ │
│ [First mixer — PTO output + crystal oscillator] │
│ │ converts RF to 455 kHz │
│ ▼ │
│ [455 kHz First IF strip] ─────────► PRE-FILTER TAP │
│ │ (cascade panadapter; recommended) │
│ [Collins mechanical filter FL-26/FL-44 at 455 kHz] │
│ │ POST-FILTER TAP │
│ [Second IF amplifier stages] ──────► (filter analysis; diagnostic) │
│ │ │
│ [Detector — envelope or product] │
│ │ │
│ [Audio amplifier → Audio output] │
└────────────────────────────────────────────────────────────────────────┘
│ │ (high-Z tap; minimal loading)
│ │
▼ ▼
[Headphones/Speaker] [CASCADE-390 PCB]
Primary receive audio Buffer amplifier: high-Z in, 50 Ω out
Power from R-390A B+ via dropping resistor
│
│ BNC output (rear panel)
│ SMA or BNC cable, <1 m
▼
[RX-888 Mk II HF SMA input]
USB 3.0 to computer
│
[SDR SOFTWARE]
Centre frequency: 455 kHz
IF offset: (R-390A freq) − 455 kHz
Sample rate: 1–2 MSPS recommended
│
[PANADAPTER DISPLAY]
Centred on R-390A tuned frequency
Follows R-390A PTO automatically
Signals shift as R-390A tunes
─────────────────────────────────────────────────────────────────────────
IF OFFSET QUICK-REFERENCE (pre-filter tap, all bands)
─────────────────────────────────────────────────────────────────────────
The IF offset for any R-390A frequency:
Offset (Hz) = R-390A dial reading (Hz) − 455,000 Hz
Examples:
14.200 MHz → Offset = 14,200,000 − 455,000 = 13,745,000 Hz (13.745 MHz)
21.300 MHz → Offset = 21,300,000 − 455,000 = 20,845,000 Hz (20.845 MHz)
7.150 MHz → Offset = 7,150,000 − 455,000 = 6,695,000 Hz (6.695 MHz)
3.750 MHz → Offset = 3,750,000 − 455,000 = 3,295,000 Hz (3.295 MHz)
10.120 MHz → Offset = 10,120,000 − 455,000 = 9,665,000 Hz (9.665 MHz)
Update offset whenever: changing bands (band crystal change)
Same offset throughout: tuning within a 1 MHz PTO segment on one crystal
─────────────────────────────────────────────────────────────────────────
CASCADE vs ANTENNA-SHARING: WHEN TO USE EACH
─────────────────────────────────────────────────────────────────────────
┌────────────────────────────────┬──────────────────────────────────────┐
│ Criterion │ Choose this approach │
│ ───────────────────────────── │ ────────────────────────────────── │
│ Panadapter follows R-390A │ CASCADE-390 (IF tap) │
│ tuning automatically │ │
│ Multi-band scanning with SDR │ Antenna sharing (HL2 or Web-888) │
│ independent of R-390A │ │
│ R-390A sensitivity maximised │ CASCADE-390 (no splitter loss) │
│ Seeing full HF band at once │ Antenna sharing (full spectrum) │
│ No chassis work on R-390A │ Antenna sharing (no modification) │
│ DX operating on single band │ CASCADE-390 (automatic tracking) │
│ Remote access via Web-888 │ Antenna sharing (Web-888 guide) │
│ IF filter analysis │ CASCADE-390 post-filter tap │
└────────────────────────────────┴──────────────────────────────────────┘
CASCADE-390 / RX-888 Mk II signal path and configuration reference. The pre-filter tap is the recommended connection for panadapter use. IF offset must be updated when changing R-390A band crystals but is constant within a band. For CASCADE-390 kit documentation, PCB layout, schematic, and parts list: vk6ada.com.au.
References and Notes
- Mike Peace VK6ADA, CASCADE-390 Kit Documentation, vk6ada.com.au. The definitive reference for CASCADE-390 kit installation, including contract year-specific tap point locations, PCB mounting instructions, rear-panel BNC drilling template, power wiring to the R-390A’s B+ supply, and buffer amplifier schematic. All CASCADE-390 installation steps in this guide are summarised from the full kit documentation; consult the kit documentation for the specific diagrams and measurements required for installation in your unit’s contract year variant.
- US Army Technical Manual TM-11-5820-357-34&P, Radio Receiver R-390A/URR. Primary reference for the R-390A IF circuit architecture, the 455 kHz IF frequency specification, and the contract year-specific component designators referenced in the CASCADE-390 kit documentation. The IF tap point location is identified in the TM-11 schematic by the component designator used in the CASCADE-390 documentation.
- RX-888 Mk II community documentation, GitHub repositories, and manufacturer documentation. The RX-888 Mk II hardware specifications (16-bit LTC2208 ADC, 64 MSPS maximum sample rate, USB 3.0 connection requirement, SMA antenna input) are documented in the manufacturer’s product page and in community wikis. Driver installation procedures (CyUSB3 for Windows, libusb for Linux) are documented in the ExtIO plugin community resources. Verify the current driver requirements from the manufacturer’s current documentation; driver versions are updated periodically.
- Simon Brown G4ELI, SDR Console v3, sdr-radio.com. Reference for the IF offset calibration configuration in SDR Console v3, including the LO offset field in device calibration settings. SDR Console’s RX-888 support via SoapySDR or ExtIO plugin; confirm current plugin availability from the SDR Console download page.
- HDSDR, High Definition Software Defined Radio, hdsdr.de. Reference for HDSDR’s native IF display mode and LO/Tune offset configuration. HDSDR is the most mature software package for the IF tap cascade approach due to its native IF offset display feature, which was implemented specifically for transverter and IF-tap applications. The HDSDR documentation covers the offset entry procedure and the IF display mode configuration in detail.
- Mike Peace VK6ADA, Hermes Lite 2 as R-390A Companion, vk6ada.com.au (March 2026). Companion guide covering the antenna-sharing approach to R-390A SDR integration. The comparison table in Section 9 of the present guide is consistent with the antenna-sharing documentation in that post. Operators who want both the cascade panadapter (CASCADE-390 + RX-888) and a transmit-capable SDR (HL2) can install both simultaneously, connecting them through the CX-140D station switching infrastructure documented in the vk6ada.com.au CX-140D guide.
- Mike Peace VK6ADA, R-390A/URR Bleeder Resistor Network, vk6ada.com.au. Safety reference for the B+ discharge procedure required before any R-390A chassis work including CASCADE-390 installation. The discharge time calculation using the bleeder network values determines the minimum wait time after power-off before touching internal components.