The N4WIS Radio Club Shack preserves and operates a collection of superlative radio equipment, spanning from the World War II era up to the present day – effectively, a museum in a museum.  Visit us and see our shack in action!

• • Present Day
  • Cold War Era (c. 1947 – 1991)
  • World War II Era (c. 1941 – 1945)

Present Day

FlexRadio FLEX-6500 Software-Defined Transceiver
FlexRadio Systems; mid-2010s–2020s HF/50 MHz amateur radio transceiver

The FlexRadio FLEX-6500 is a pioneer software-defined radio (SDR) HF and 6 meter transceiver that brought cutting-edge digital signal processing to the amateur radio club station.  Designed around a direct digital sampling architecture, the FLEX-6500 digitizes incoming RF signals at the antenna, processing them in software rather than via conventional analog circuits; this approach delivers exceptional receiver performance, real-time spectrum displays, and flexible filtering unmatched by traditional rigs of its era.

Covering a broad receive range from roughly 30 kHz to 72 MHz and transmitting up to 100 W on the 160 m through 6 m amateur bands, the FLEX-6500 supports all common modes (SSB, CW, AM, FM, RTTY, and digital) and offers fine 1 Hz tuning resolution with stable frequency control.  Its integrated Ethernet control interface, paired with FlexRadio’s SmartSDR software, turns a connected computer or tablet into a dynamic front panel, with panadapter waterfalls and multiple “slice” receivers that can tune independent signals simultaneously within a single band segment.

At club stations, the FLEX-6500’s SDR architecture and software-driven interface invite collaborative operation, teaching, and experimentation, blending high performance with a modern, network-centric approach to amateur radio communication and digital signal management.

Icom IC‑756PROII HF 50 MHz 100 W All Mode Transceiver
HF/VHF Amateur Radio Transceiver

The Icom IC-756 Pro II is a landmark all-mode HF (shortwave) and 6 meter amateur radio transceiver first introduced in the early 2000s, prized by clubs and serious operators for its blend of performance, versatility, and user-focused design.  It covers all nine HF amateur bands from 1.8 MHz through 28 MHz and includes the 50 MHz (6 m) band, with reception from about 0.03 MHz to 60 MHz, making it useful for listening beyond amateur bands as well.

Built around a 32-bit IF-DSP (digital signal processing) engine, the IC-756 Pro II offers refined filtering, noise reduction, and a real-time spectrum scope displayed on its large color TFT screen, aiding operators in tuning and discerning weak signals in crowded bands.  Its 100 W maximum transmit output (SSB/CW/FM/RTTY) and built-in automatic antenna tuner make it a capable base-station rig for general amateur work including phone, CW, and digital modes.

Technical features such as multiple selectable bandwidths, digital passband tuning (PBT), RIT/XIT, memory channels, and integrated RTTY demodulation/keyer reflect a design focused on flexibility and ergonomic operation.  These qualities made the IC-756 Pro II a popular choice for club stations and experienced hams seeking robust performance across HF and 6 m bands, balancing modern DSP-enhanced reception with reliable analog fundamentals.

Cold War Era (c. 1947 – 1991)

Collins 390A (R-390A/URR) HF Communications Receiver
Collins Radio Company; United States military high-frequency receiver, mid-20th century

The Collins 390A, more formally designated R-390A/URR, is a rugged, general-coverage high-frequency (HF) communications receiver designed under U.S. Army Signal Corps contract by the Collins Radio Company and produced in large numbers for the U.S. military from the mid-1950s onward.  Revered for exceptional performance in amplitude-modulated (AM) and continuous-wave (CW) reception, it became a workhorse receiver across all branches of the U.S. armed forces, including extensive U.S. Navy use aboard ships and shore stations, where its sensitivity, selectivity, and mechanical reliability supported long-distance HF communications and signal monitoring well into the Cold War era.  It remained in service through the 1980s and beyond, with many units retained due to their robustness and resistance to electromagnetic pulse effects.

Technically, the R-390A is a superheterodyne receiver with double-conversion above ~8 MHz and triple-conversion below, covering a continuous frequency range of approximately 0.5 MHz to 32 MHz over 32 switchable bands.  It employs about 26 vacuum tubes in its signal chain and features sophisticated mechanical filters and a mechanically tracked front end to maintain consistent tuning, sensitivity, and selectivity across the HF spectrum.  Operators could select multiple IF bandwidths to suit CW or AM traffic, and the modular design allowed field servicing and rapid replacement of major subassemblies.  Front-panel controls include automatic gain control (AGC), beat-frequency oscillation (BFO), dual audio outputs, and calibrated tuning indications.

In U.S. Navy applications, the R-390A provided reliable reception for long-range HF communications, circuit traffic, and signals intelligence tasks aboard vessels and at fixed naval communications facilities, supporting tactical and strategic coordination across global theaters where ionospheric propagation dominated long-distance links.

World War II Era (c. 1941 – 1945)

Collins TCS-12 Transmitter and Receiver
Collins Radio Company (Cedar Rapids, Iowa), U.S. Navy HF Communications Set

The TCS-12 is a matched high-frequency (HF) transmitter and receiver set produced by the Collins Radio Company for the U.S. Navy during World War II.  Engineered for rugged maritime service, the system provided continuous-wave (CW) and amplitude-modulated (voice) operation across three HF bands (1.5–3 MHz, 3–6 MHz, and 6–12 MHz), enabling long-distance ship-to-shore and inter-vessel communications.  The set required an external dynamotor-fed power supply delivering multiple DC voltages for both units.

Deployed extensively aboard landing craft (LSTs), PT boats, smaller naval vessels, and shore installations, the TCS-12 provided reliable tactical and operational HF communications under demanding sea conditions.  Its robust construction and frequency agility exemplified Collins Radio’s commitment to high-quality military radio gear that sustained naval communication networks throughout the war and continued in limited service into the post-war years.

RCA Navy RAL-7 HF Regenerative Receiver
Radio Corporation of America (RCA); U.S. Navy regenerative HF receiver

The RAL-7 is a U.S. Navy high-frequency (HF) regenerative receiver designed and built by the Radio Corporation of America to provide reliable ship- and submarine-board reception across a broad shortwave spectrum during World War II.  As a tuned-radio-frequency (TRF) set with a regenerative detector, it employed a relatively simple but effective vacuum-tube circuit that enhanced sensitivity and selectivity for Morse code (CW) and, when configured appropriately, voice signals.

Covering approximately 0.3 MHz to 23 MHz in nine switchable bands, the RAL-7 spanned critical naval communications and HF broadcast frequencies used for tactical messages, long-range liaison, and signal monitoring in the Atlantic and Pacific theatres.  Its rugged construction and straightforward design made it suitable for installation in radio rooms where space and power were constrained.  The receiver was typically paired with its lower-frequency counterpart (the RAK series) and external control units on surface ships and submarines, contributing to the U.S. fleet’s ability to maintain HF communications and to intercept or guard vital frequencies throughout the conflict.

RCA Navy RAK-7 Very Low Frequency (VLF) Regenerative Receiver
Radio Corporation of America; U.S. Navy regenerative VLF/LF receiver

The RAK-7 is a U.S. Navy very low frequency (VLF) and low frequency (LF) regenerative receiver designed by the Radio Corporation of America to provide dependable shipboard and submarine reception during World War II.  As part of the Navy’s RAK/RAL series, the RAK employed a tuned-radio-frequency (TRF) architecture with a regenerative detector, trading complexity for robustness and high sensitivity in demanding maritime environments.

Covering approximately 15 kHz to 600 kHz in six switchable tuning bands, the RAK-7 was tailored to the VLF/LF portion of the spectrum used for long-range naval communications, nondirectional beacons, and shore-to-ship links, particularly for continuous-wave (CW), interrupted CW (ICW/MCW), and low-rate voice reception where propagation favored low frequencies. Its regenerative detector boosted signal strength while preserving selectivity, and rugged construction suited it for installation in radio rooms where space and stable power were limited.

RAK-7 units were often paired with their higher-frequency companion, the RAL receiver, to expand a vessel’s receive coverage from VLF up through HF. Together they enabled naval operators to monitor tactical and operational frequencies essential to fleet coordination, navigation aids, and coastal station communications throughout the conflict.

Scott Radio Laboratories RBO Receiver (on loan from Nauticus)
H. Scott Radio Laboratories; U.S. Navy shipboard entertainment superheterodyne receiver

The RBO is a cabin-entertainment radio receiver designed by Scott Radio Laboratories (Chicago) and built for U.S. Navy service aboard ships of all types during World War II.  Engineered to meet strict “low-radiation” requirements so as not to leak local-oscillator energy into shipboard antennas or interfere with direction-finding gear, the RBO provided high-quality reception of amplitude-modulated broadcasts for morale-boosting audio listening in crew spaces and other onboard areas.

As a superheterodyne receiver, the RBO covered three bands: the standard medium-wave broadcast band (~540–1600 kHz) and two shortwave bands spanning approximately 5.55–9.55 MHz and 9.20–15.60 MHz.  This enabled reception of domestic AM stations and widely propagated shortwave entertainment and news broadcasts available during the war.  Its audio output—designed primarily for headphones or local loudspeaker systems—was suitable for crew enjoyment rather than long-range tactical communications.

Installed in robust, shock-mounted cabinets on naval vessels, the RBO helped maintain crew morale with music and news from home and around the world while minimizing interference with critical radio and navigation systems amid the operational demands of wartime seagoing service.