K0UO Antenna Site Number 2 & Stand-Alone Towers
Updated: 6 hours ago
By reading this blog you will learn more about the K0UO antenna site number 2 and the X-Rhombic HF Array with SMART control, how they work, field testing and construction
"An antenna is a device designed mainly to emit or capture electromagnetic energy." this new site is now the category as one of the largest and highest gain HF ham antenna farm in use, with miles of wire, all thanks to a DoD project.
Amateur radio culture values experimentation, but serious R&D work adds a different kind of discipline. Commercial and government projects require clearer documentation, repeatable methods, controlled tests, safety planning, construction standards, and results that other people can inspect.
Commercial and government projects bring discipline to amateur experimentation
As an example: This facility is designed to operate autonomously, featuring EMP protection and backup systems capable of running for several months without relying on the grid. It utilizes on-site natural gas for AC power generation, deep storage batteries, and Starlink for connectivity if the fiber network fails. Additionally, there is an RF link to the K0UO's main site with fail-safe controls. This facility is intended to function independently, EMP protection, equipped with backup systems that can operate for several months off the grid using on-site natural gas for power generation, deep storage batteries, and Starlink in case the fiber network fails, with a RF link back to the K0UO's main site with fail safe controls.
K0UO has set up a second antenna site, (which is much larger than the original site 1), re-engineering nine X-Rombic arrays with a modern design, and positioning them on a hilltop where K0UO once had a 300-foot tower. The tower's top at this location is 500 feet Height-Above-Average-Terrain (HAAT) above the surrounding ranch land, allowing for an extremely low take-off angle. These nine updated X Rhombic arrays have 1200 feet on each leg,or a total of 4800 feet for each array, equating to about 72 wavelengths for the 20-meter ham band.
Providing an array for every 20 degrees of direction with "Smart Control" to ensure global coverage. These arrays also employ "SMART ANTENNA" technology, allowing them to rival genuine HRS Curtain arrays by achieving over 20dB of gain with real-time Smart control phasing and pairing.
This new site significantly surpasses and Dwarfs the main "K0UO Rhombic Farm", while incorporating "Smart Technology" arrays an impressive site overall.
Consider this: each single array spans an area of more than 11.32 acres, which is nearly equivalent to 10 football fields, see the site layout later in this Blog.
Adaptive Phased Array Systems
Smart Antennas: The nine X-Rhombic antennas utilize an adaptive array (as part of a DoD project), commonly referred to as a fully digital or dynamic beam-forming array. This system continuously adjusts both the amplitude and phase of the signal directed to each radiating element in real-time, optimizing the selection of antennas at any given moment.
This technology is currently deployed on certain arrays at the K0UO site 1, with future updates planned for site 2, where AI enhances the automatic control system with its decision-making capabilities. This is likely the first ham station to implement Smart Antenna technology for a massive High Frequency (HF) Array of this scale. Originally initiated as a DoD research project, this endeavor is paving the way for dedicated ham radio DXers, Contesters, and others while also providing benefits to amateur radio enthusiasts in general.
K0UO may host Universities along with STEM groups to this and always at the RSI Corp test range.
OVERVIEW
Fiber Optic Connectivity
Six FlexRadio Remotes with amps
AI Smart technology
Two forms of Backup AC power
Low take off angles, has 500 foot Height-Above-Average-Terrain (HAAT)
Fiber Optic Connectivity
No neighbors or RFI noise
DoD standards with EMP
This site is intended for Commercial, DoD, along with remote ham radio DX and Contest ham radio applications, positioned hundreds of feet above the surrounding ranch land, ensuring an environment free of RFI noise.
Optimizing Terrain & Low-Angle Takeoff: This new site, with its significant height-above-average-terrain (HAAT) provided by the Kansas Red Gyp hilltop, offers an extremely low-angle radiation footprint on HF bands. By customizing the ground counterpoise and radial networks to follow the hill's contours, ground absorption losses are minimized, and the radiation angle is lowered for long-distance DX. The arrangement of wideband X-Rhombics arrays along the ridge line provides exceptional forward gain and directivity compared to flat-land setups.
The X-Rhombic antenna functions electrically like a conventional rhombic, maintaining the same traveling-wave or leaky-wave properties. However, with modern technology, the crossed geometry offers spatial phase reversal, further reducing side lobes and concentrating energy into the main forward beam.
This hilltop's natural physics work to your advantage, providing an elite, ultra-low takeoff angle that is typically unattainable for most backyard radio operators.
This configuration channels a significant amount of RF energy into a razor-thin main lobe at approximately -1° to 5°.
The key concept: a low-angle ray travels further across the Earth's curved surface before refracting back down from the ionosphere, covering more distance per hop. For long-haul DX, lower angles are generally more advantageous.
Test range: For ISR equipment testing, the range area is expanding 20 miles to the west and north of 4KS Walz Airport for ISR, EME, RFI, and RF K0UO test site number 2, by RSI Corp. This is part of the Vance AFB 1D MOA DAF, the Action will be the new MOA 1E, (which has not been approved and will go in to effect in 2027), to acquire new airspace that provides the 71 FTW and other groups with autonomous scheduling and ensures easy access to airspace needed for low-altitude non-hazardous flight training and equipment testing, such as electro-optical infrared EO/ISR sensors, operator mission stations with FM tactical radios, and data link systems.
Stand-along towers: Ham radio enthusiasts understand that the effectiveness of their antenna setup is crucial for successful long-distance communication.
For those committed to DX (distance) and Contest operations, having access to lease dedicated stand-alone towers provides a significant advantage. RSI Corp and K0UO/R offer a range of stand-alone towers up to 500 feet in height, specifically designed for DX and contest activities, as well as far-field antenna testing. K0UO is also developed a new larger site, number 2. This new site, along with these towers, are located in rural ranching areas, free from other users or interference, making them perfect for ham radio enthusiasts aiming to maximize their communication potential.
Why Height Matters for DX Operations
When it comes to ham radio, antenna height and location are critical. Sites that reach up to 500 feet above the average ground provide significant elevation above the surrounding terrain. This height allows antennas to operate at low takeoff angles, which is essential for long-distance DX signal propagation. Signals sent at low angles travel farther by bouncing off the ionosphere, enabling communication with distant stations across continents.
The rural ranching locations of these towers mean there is minimal Radio Frequency Interference (RFI). Urban areas often have noise from electronics, power lines, and other sources that degrade signal quality. These towers are isolated, with no other antennas mounted on them, ensuring a clean environment for clear, strong signals.
Site Number 2 Planning and Design overview summer of 2026
Height Enhances Antenna Performance
How Tower Height Enhances Antenna Performance
Elevation plays a key role in antenna effectiveness. Here’s why:
Low Takeoff Angles: Signals launched at low angles travel farther by reflecting off the ionosphere, ideal for DX contacts.
Reduced Obstructions: Taller towers clear trees, buildings, and terrain features that can block or weaken signals.
Improved Signal-to-Noise Ratio: Being above local noise sources improves reception clarity.
Better Antenna Patterns: Height allows antennas to achieve their designed radiation patterns without distortion from nearby objects.
For example, a 500-foot tower can elevate a Yagi antenna well above surrounding hills, enabling it to reach stations thousands of miles away with minimal signal loss.
One of K0UO's 300 foot steel towers in the Red Gyp Hill of KS, that he cut down a few years ago, he didn't want to keep the required FAA lights operational moving forward with the low number of commercial users, however still a premier hill top location for the K0UO Site Number Two, which is reusing the existing concrete base and guy anchors points for the new Rohn 65 199 foot tower
K0UO Now Adding Antenna Site Number 2
K0UO has established a second antenna site, (which is considerably larger than the primary site 1), on a prominently elevated hilltop where K0UO previously maintained a 300-foot tower on this 300 foot AGL hill. This site is intended for Commercial, DoD, and ham radio operations, situated hundreds of feet above the surrounding ranch land, offering an RFI noise free environment.
The top of the new tower at site number 2 stands just under 200 feet, with several custom sections added to the tower's top, making the site 500 foot Height-Above-Average-Terrain (HAAT) .
A major HF array construction project is currently in the testing progress, aiming to optimize the an even larger second site on ranch land. This ambitious project is strategically located on a very high hilltop plateau in the Red Gyp Hill, situated a few miles to the west of the main K0UO site. The choice of this elevated location is crucial, as it not only offers stunning panoramic views of the surrounding area but also provides a unique chance to create a space that is both functional and visually appealing.
In terms of design and construction, the project is being executed with great attention to detail and sustainability in mind. The design incorporates eco-friendly and recycled materials, equipment and practices, ensuring that the structures harmonize with the natural environment rather than disrupt it. The use of renewable energy sources and the natural gas and solar, is also being considered to minimize the carbon footprint of the new location.
The planning phase has involved extensive engineering to meet DoD and other commercial EA specifications, we are tasked with creating a layout that maximizes the advantages of this premier hilltop setting.
The antennas performed excellently with the relay box situated at ground level, providing an insightful glimpse into the inner workings of the relay box itself. Upon closer inspection, the wires within the box appear to be haphazardly scattered in all directions, creating a complex web of connections. One might initially suspect an impedance issue due to the chaotic arrangement of the wiring, but upon further examination, it was not evident that any such problems were present. The setup functioned smoothly, demonstrating that the all the wires did not adversely affect performance. The late Roy Callison of Bisbee, AZ, ham call W7YRV/SK had nine X Rhombics arrays, which he developed with remarkable ingenuity and dedication. Each of these arrays was designed to cover a specific direction, with one array dedicated for every 20 degrees of azimuth. This level of precision and planning was a truly remarkable accomplishment for an amateur radio station, showcasing his expertise and passion for radio communication.
The legacy of W7YRV's work continues to inspire current enthusiasts and operators in the field, as this site builds on that foundational knowledge and experience. K0UO is now using much longer elements in the updated their antenna design (based on Far Field Modeling), allowing for enhanced performance and range. Additionally, they have incorporated a re-entrant system that provides an impressive efficiency rating of 90%, with Smart Antenna control. This innovative approach not only improves overall signal quality but also optimizes the antenna's ability to transmit and receive signals effectively. From an electrical standpoint, the antenna behaves similarly to a conventional rhombic antenna, maintaining the same traveling-wave properties characteristic of this design. However, what sets this new system apart is its unique crossed geometry, which introduces spatial phase reversal. This technological advancement plays a crucial role in further suppressing side lobes, which can often interfere with signal clarity and strength. By tightening and concentrating energy into the main forward beam, the antenna achieves a level of directional focus that enhances communication capabilities, making it an exceptional tool for amateur radio operators seeking to optimize their setups. The careful engineering and thoughtful design of these antennas reflect a commitment to excellence in the field of amateur radio.
Unlike a standard horizontal rhombic antenna—which forms a single flat diamond loop—the X-Rhombic splits or crosses its wire elements at the side apexes into an "X" configuration. As the traveling radio frequency (RF) current flows down the wire legs, this geometry forces precise spatial phase adjustments. By crossing the elements, off-axis parasitic sidelobes are driven 180 out of phase, causing destructive phase cancellation. This concentrates nearly all radiated RF power into a tight, exceptionally clean main forward beam.
Height-Independent Low Takeoff Angle Standard planar rhombic antennas rely heavily on exact height above ground to establish their vertical radiation angle. The X-Rhombic uses vertical tapering and sloping planes, drastically reducing sensitivity to height constraints while maintaining low-angle skywave propagation (ideal for long-distance HF/shortwave links).
1. The Core Architecture: Cross-Phased Geometry
A standard planar rhombic consists of two V-shaped long-wire antennas connected to form a flat diamond. The X-Rhombic alters this by crossing or splitting the elements into an X-configuration, forming intersecting spatial loops. This design causes RF current to undergo spatial phase adjustments, enhancing performance.
2. Eliminating the "Height-to-Wavelength" Trap
Standard horizontal rhombics have a vertical takeoff angle tied to their height above ground. The redesined K0UO X-Rhombic employs vertical tapering, allowing different vertical planes and sloping angles. This reduces sensitivity to height constraints, providing stable low takeoff angles across various frequencies without adjusting mast height.
3. Radical Sidelobe Damping
Parasitic sidelobes consume power and introduce vulnerabilities. K0UO's redesigned innovative X-configuration places sidelobes 180° out of phase, leading to destructive phase cancellation for off-axis radiation. This boosts the purity of the main forward beam and enhances directional ratios.
4. Enhancing Tower Efficiency (The Economy of Scale)
Constructing new towers involves significant expenses. The X-Rhombic's interlacing and stacking technique enabled the utilization of existing array footprints with just one tower. By powering the X-array with a SMART control system, a single tower configuration could operate as multiple antennas, effectively sustaining high-gain connections to remote targets.
The X-Rhombic modifies the physical structure of a standard diamond loop by crossing the wire elements at the side corners rather than leaving them as flat angles. This specific, altered layout forces the traveling RF current to undergo spatial phase adjustments as it moves down the wire. Skilled antenna designers employ the X-Rhombic configuration to further reduce unwanted side lobes and concentrate more energy into a narrower, clearer main forward beam compared to what a conventional flat rhombic can achieve. A small-scale model was tested in early summer 2026, exceeding the performance of the models that preceded this project.
AI SMART Controlled self-healing is being used at the site to keep the equipment on the air.
Constructing the 18 support masts was a substantial task. Each of the eighteen support masts for the array elements is using 5 1/2" oilfield drill stem pipe, S-135 range, with yield strength 135,000 psi, each with a length of 18 feet (API R1). These are positioned in 24" diameter holes, 6 feet deep, using a skid loader equipped with an auger. Each drill footer hole is filled with 3/4 of a yard of fiber-reinforced concrete, weighing over 3000 lbs.
The Arrays Antenna Wire
At HF (3–30 MHz), the skin effect significantly impacts RF currents on large antenna wires. Skin effect causes alternating current to flow mainly on a conductor's surface, especially at higher frequencies like those in the HF band. Consequently, a conductor's effective resistance depends not only on its material properties but also on its surface area, linked to the wire's perimeter. More surface area lowers effective resistance, making geometry and material crucial for RF conductors.
Why do many commercial SW radios use steel wire rope cable instead of copper? Grigory Zakharovich Ayzenberg and Soviet engineers chose steel wire (often bimetallic steel-cored or galvanized steel rope) for traveling-wave rhombic arrays due to its balance of physics, economics, and environmental factors.
While resonant antennas like dipoles need copper for efficiency, terminated traveling-wave antennas function differently.
Traveling-wave antennas suppress the reverse wave, using galvanized steel as a distributed attenuator to absorb reflected energy before it returns along the Rhombic or V beams.
Zinc triple-coated cables are crucial for the performance of these antennas in high-frequency (HF) bands because the zinc coating carries the majority of the RF current due to the reduced skin depth. At lower frequencies, some current penetrates the steel core, but the cable's dimensions and surface area remain vital for effective conductivity.
Rhombic arrays are massive, often requiring leg lengths stretching hundreds of meters suspended on tall towers. This project uses eighteen (18), 1200 feet sloping spans of wire rope cable.
The Problem with Copper: Solid copper is soft, heavy, and highly prone to stretching over time under its own weight. In the extreme climates—enduring heavy ice loading, high winds, and massive temperature swings—copper wires would stretch, sag heavily, and eventually snap.
The Steel Advantage: Steel wire or steel wire rope has immense tensile strength. It can be pulled tightly across vast spans, drastically reducing wire sag and ensuring the geometric symmetry of the rhombic arrays remained perfectly intact, despite severe ice and wind weather.
Key Takeaways for the Project on Ice Loading Planning: Determine the appropriate cable size for the nine antennas. This involves a total of 18 wires, each 1,200 feet long, with an additional 200 feet required for the vertical feeders, totaling 25,200 feet, which is almost 5 miles used in this project.
The 1/4" Line Limits: A 1/4-inch 7x19 strand handles normal days and minor 5-year storms perfectly fine. However, it loses its structural safety margin entirely during a 10-year storm and is highly likely to snap when a major 20-year ice event hits. 1000 feet is 110 lbs
The 5/16" Line Sweet Spot: The Priority is keeping the weight down, the 5/16-inch 7x19 line is a highly practical compromise. It only adds about 60 lbs of total weight over the entire 1,200-foot dry run compared to the 1/4-inch line, but its safety factor jumping to 4.1:1 during a 10-year storm gives you real structural peace of mind for the vast majority of seasons. 1000feet is 177 lbs
The 3/8" Line for Absolute Survival: The 3/8-inch 7x19 line is the only option listed that keeps a protective safety buffer during a true 20-year catastrophic ice storm. The trade-off is the physical dry weight: a 1,200-foot spool of 3/8-inch cable weighs roughly 276 lbs, making it significantly harder to pull up a steep hilltop by hand. But the over all wight of 25,200 feet of 3/8" is just too much even for the Rohn R65 tower. 1000 feet is 243 lbs
X-Rhombic: A full rhombic loop where the side wires cross or split into an "X" configuration. An advanced cross-phased geometry modification of a standard rhombic, not a fraction of one.
An X-Rhombic antenna modifies the usual diamond configuration by crossing the wire elements. This phase-reversal design enhances the main forward beam and reduces side lobes. As a multi-wavelength traveling-wave antenna, it demands significant physical space and robust support structures. A sloping X-Rhombic needs only one tall support mast (such as a utility pole, tower, or tree) set up in an exact diamond shape on level ground.
Traditional rhombic antennas are known for their simplicity and high gain over a wide bandwidth, but they require large physical space due to their long wire elements with lower efficiency. The re-entrant rhombic array addresses this limitation with several unique features:
Improved Bandwidth: The re-entrant structure can support a wider frequency range due to the increased electrical length and better impedance characteristics.
Enhanced Directivity: The shape modification focuses the radiation pattern more tightly, improving directivity and reducing side lobes.
Enhanced Efficiency: The design reduces losses due to reflections and mismatches, resulting in increased radiation efficiency and redirecting the power previously lost in termination back into the array, now up to 90% efficient.
These features differentiate re-entrant rhombic arrays from traditional wire antennas and other directional antennas like Yagi or log-periodic arrays.
"Don't underestimate the performance of the Rhombic unless you've personally built and used one. Due to their large size, covering many acres, you realize their true advantage of having thousands of feet of wire in the air. This setup provides receive signal diversity by capturing signals at varying times and angles, significantly reducing fading QSB, and transmitting RF in the same manner. Traveling wave antennas are very unique and unlike many other antennas commonly used."
This X-Rhombic is many wavelengths long at 40 or 20 m, so the main lobe becomes narrow.
The takeoff angle drops to ~5–8°, which is excellent for very long-haul DX.
The front-to-back ratio improves because the termination if used absorbs more of the rearward energy at higher frequencies. (using re-entry system for even higher gain),
Pattern Characteristics on 40 or 20 meters
Very narrow beam — only 20~10° wide, so pointing accuracy matters,. with this system it is instantly switched between fixed azimuths every 20 D, without mechanical rotation.
Extremely low TOA — ideal for intercontinental paths, ~5–8°.
With the hilltop and tower, the Height-Above-Average-Terrain (HAAT) is nearly 500 feet, so takeoff angles of less than 5° are very feasible.
High gain — +18–20 dB means you’re effectively running the equivalent of hundreds of kilowatts ERP with a legal-limit transmitter.
Just think about an antenna using over 25,000 foot of wire!
When arrays function at take-off angles of 5 degrees, K0UO consistently opens first and closes last for Europe, Asia, Africa, Pacific and routes over the poles to Western Asia and the Middle East, while ensuring continuous connectivity to North & South America.
Furthermore, the project is not just about expanding physical structures; it also represents a deeper commitment to preserving the Rhombic’s heritage and attributes. By establishing this second antenna location, the aims to create a legacy that can be enjoyed by future ham generations, offering them a place to connect with the world by remote ham radio, engage in learning and build lasting memories.
The Receive Antennas
The site number 2 is using 8 Beverage receive antennas each 1200 foot long, and they are all two wire bidirectional type, providing 16 directions.
Spectral Subtraction Noise Reduction (SSNR) SMART technology estimates and subtracts noise from audio, reducing fatigue and rumble while enhancing the signal. It is especially useful in amateur radio, where noise varies, such as atmospheric hiss or static. While not a substitute for proper equipment setup, SSNR improves SDR/DSP receiver performance, making challenging signals easier to hear.
SMART Dynamic Phasing Matrices
The pinnacle of smart Beverage technology involves active noise cancellation and adaptive beamforming. Hams use multiple staggered or parallel Beverage lines with an active phasing controller like the DX Engineering NCC-2.
The system combines the RF profiles of two wires simultaneously. By adjusting the phase and balance, operators can digitally "steer" the directional null—eliminating localized noise sources (like a neighbor’s plasma TV) while boosting a weak signal from a different direction.
SMART Dynamic Phasing Matrices in Beverage Antenna Systems
Dynamic phasing matrices are advanced in low-band HF reception, evolving from single-wire selection to active, real-time RF signal combination. This pinnacle of smart Beverage technology features active noise cancellation, adaptive beamforming, and real-time HF band conditions. By routing multiple Beverage lines into an active phasing controller like the DX Engineering NCC-2, operators can significantly improve challenging bands like 160 and 80 meters.
Core Operational Principles
Simultaneous RF Combination: The phasing unit blends RF profiles of multiple Beverage lines simultaneously.
Active Null Steering: Adjusting phase and amplitude allows operators to steer a null toward specific noise vectors, reducing interference while maintaining signal gain.
Enhanced Directivity: Using multiple long-wire runs sharpens the Receiving Directivity Factor (RDF) and improves the Signal-to-Noise Improvement Factor (SNIF).
SMART integrating AI-driven real-time analysis: Utilizes ionosonde data for full-spectrum HF propagation monitoring.
AI‑assisted real-time propagation and antenna optimization tools from private ionosonde or chirpsounder radar systems enhance HF monitoring.
Integration with Advanced Station Architecture
In advanced mega-stations with extensive setups, dynamic phasing enhances selectivity. Combined with real-time ionospheric data, automated software, and DSP noise-reduction tools, operators achieve exceptional readability on weak, long-distance DX signals even in challenging conditions.
We utilize eight 1200-foot two-wire bidirectional Beverage antennas, allowing reception in 16 directions and enhancing signal capture. These antennas, designed for long-distance communication, feature a low-angle radiation pattern and exceptional directivity. They are strategically positioned to maximize coverage and minimize interference. The bidirectional design enables reception from both directions along the wire, crucial for directional signal scenarios. We can also implement SMART beamforming and phasing for real-time antenna pattern adjustments, optimizing signal clarity and strength while reducing noise. This integration enhances the station's capabilities, placing it at the forefront of radio communications technology.
The DoD project research has equipped K0UO with tools for implementing the SMART system for ham radio.
One of the primary characteristics of the Beverage antenna is its design, which allows for the transmission of radio waves as a traveling wave along its length. This design is similar to that of the fast wave Rhombic antenna, which also utilizes a long, directional configuration to enhance signal reception. However, the performance of the Beverage antenna can vary significantly depending on its termination and placement. Primarily, Beverage antennas focus on the concept of signal to noise, which is closely associated with the Relative Directivity Factor (RDF). The RDF is defined as the antenna gain in the forward direction compared to the gain in all other directions. This metric is crucial as it assesses an antenna's capability to focus its reception in a specific direction while minimizing interference from other directions.
A very simple and inexpensive antenna
• 200-400 feet long / 4-6 dB RDF / 100 degree beam-width
• 500-700 feet long / 10 dB RDF / 70 degree beam-width
• 800-900 feet long / 12 dB RDF / 60 degree beam-width
Think about the RDF on the 1200 foot ones in use at the K0UO site number 2 on 160 meters
The primary purpose of using receive antennas is to enhance signal-to-noise ratio and improve directivity.
• Receive antennas perform significantly better than transmitting antennas, particularly on 160 and 80 meters
Overview of the Commercial Project at site number 2 with Smart Control System, with is also utilized for ham radio remote.
Coherent GPSDO Phase-Matched Beamforming
Sample-Accurate IQ Streaming: Install GPS-disciplined oscillators (GPSDO) at both sites to lock internal 10 MHz reference clocks. Streaming synchronized raw IQ data over the fiber link via the SmartSDR API enables true multi-site phase-coherent processing.
Dynamic Software Null-Steering: Processing simultaneous IQ streams from Site #1 and Site #2 through processing software allows you to electronically steer deep spatial nulls directly onto co-channel noise or QRM while constructively combining weak DX signals.
Zero-Desense Cross-Site Full-Duplex
Physical TX/RX Isolation: Take advantage of the physical separation and fiber isolation by running full-power transmissions at Site #2 while actively receiving on high-gain arrays at Site #1 on the same band (or vice versa).
Bypassing Receiver Overload: Physical distance completely eliminates local front-end overload and heavy desense without requiring aggressive inline bandpass filters, allowing you to monitor and work weak signals while transmitting.
Automated Sounder Integration: Connect the SmartSDR API to real-time ionosonde or GNU Chirp Sounder receiver feeds monitoring ionospheric layer heights and critical frequencies with an update ACE program.
Instantaneous Array Smart Switching: When software with help of AI detects HF (E, F1, F2) openings, and D layer absorption, the control can automatically reconfigure slice receivers, select optimum beam headings at Site #2, and queue alerts before the band peak becomes widely active (an outstanding advantage for any contest).
Smart Remote Control Feedpoint Phase & Takeoff Angle Tilting
Active Feed Control: For large wire structures (such as Sterba curtains, delta loop arrays, or stacked rhombics), deploy digital RF phase and amplitude controllers at the feedpoints managed over the fiber link.
Elevation Pattern Tuning: Dynamically altering the phase relationship between array elements allows you to electronically tilt the vertical radiation angle (e.g., adjusting between -3 to 30 Degrees to match exact ionospheric hop geometry in real time.
Phasing: By adding two or more arrays together to improve gain, cover geographic areas requiring more coverage, adjust the Front to Back ratio, add more directions simultaneously, and modify the tilt and take-off angles.
Interference Nulling: To automatically suppresses QRM, noise and QRN.
Increases Capacity: Allows more stations the use of the X-Rhombic multi-arrays for the remote DXer and Contesters.
Utilizing high-speed fiber and FlexRadio's SmartSDR architecture enables software to function as the central nervous system for both Site #2 and Site #1. By integrating these advanced software-driven processing techniques, so to fully leverage the phase-locked dual-site topology.
Phase-Coherent IQ Digital Beamforming
GPSDO Sample Synchronization: Stream raw 24-bit I/Q data via SmartSDR DAX over the fiber link, phase-locked to 10 MHz GPS-disciplined oscillators at both sites.
Adaptive Smart Null-Steering: Process dual I/Q streams through custom algorithms or GNU Radio DSP blocks using LMS adaptive filtering. This electronically synthesizes a combined smart steerable array pattern, placing sharp, deep nulls on localized noise or co-channel QRM while phase-combining weak DX signals.
Sounder-Driven AI Smart Control Automated Azimuth & Smart Band Switching
Real-Time Propagation Interfacing: Connect the SmartSDR API to local HF ionospheric sounders (such as a GNU Chirp Sounder) or real-time F2 and MUF data feeds.
Smart Control Automated Matrix Routing: As propagation software detects band openings or shifting ionospheric tilt, Node-RED or Python scripts automatically trigger the Smart Array System18-position relay matrix at Site #2, selecting the optimum 20° X-Rhombic array heading before the band peak becomes widely active.
K0UO is undoubtedly the only ham station in 2026 utilizing large HF Smart Antennas.
Digital Phase Control for Takeoff Angle Tuning
Feedpoint Phase Shifting: Manage IP-addressable RF phase and amplitude controllers at array feedpoints over the fiber network using Modbus/TCP or MQTT.
Dynamic Elevation Tracking: Adjust relative feed delays via software to dynamically tilt vertical radiation patterns (from 3° up to 30°), keeping the beam elevation locked onto real-time ionospheric hop geometry throughout changing solar conditions.
Digital Feed-forward Cancellation for Full-Duplex
Digital Reference Cancellation: Send a digital sample of Site #2's transmit I/Q waveform over fiber directly to the receive DSP pipeline at Site #1.
Zero-Desense Operation: An extensive adaptive filtering subtracts residual transmit energy in software, enabling zero-desense, simultaneous transmit and receive on identical frequencies without needing heavy physical inline filter networks.
Unified API Station State Machine
Centralized Middleware: Deploy Node-RED or custom Python services interacting directly with SmartSDR IP APIs, amplifier telemetry, and array switching matrices.
Automated Smart Interlocks & Telemetry: Continuously monitor feedline SWR, thermal levels, power out, phase stability, nearby storms, automatically executing self-healing re-routes if hardware anomalies are detected.
Self Healing Smart Systems: To help the station stay on the air, by moving to alternate antennas, computers, PLCs, radios, power supplies, switches, by-passing relays and other controls.
Racks of FlexRadio 9600X transceivers and amplifiers, PLCs and HF Filters in a one of the 40 foot shipping containers
Key Components of Remote Operation
To successfully establish and operate a remote accessible ham radio station, several key components must be considered. These components are essential not only for the functionality of the station but also for ensuring reliable communication, security, ease of use, and overall effectiveness in various operating conditions. Below are the critical elements that should be taken into account:
Hardware
Remote operation hardware consists of a mix of radio transceivers, antennas, and computer systems. The transceiver needs to be remotely controllable, and many contemporary models are designed with built-in features that facilitate remote access. Antennas, essential for signal quality and range, should be strategically positioned to enhance performance. Furthermore, a dependable internet connection is vital for smooth operation, acting as the communication backbone between the operator and the station.
As a Host Station, K0UO exclusively uses FlexRadio 8000 & 9300/9600X, engineered to manage modern multi-carrier and high-speed data waveforms with the aid of high-speed fiber internet and StarLink connected to the equipment. It employs high-power 1500+ legal limit commercial FlexRadio amplifiers. True Continuous Operation, rated for a 100% duty cycle across all modes, supporting demanding 24/7 communication and data needs.
The site utilizes the FPA-5K HF and FPA-1K power amplifiers from FlexRadio Inc., making it an outstanding option for dependable and efficient HF communications for both voice and data. This power amplifier is designed to deliver continuous HF frequency coverage at consistent power levels, rated for 100% continuous operation in all HF modes. It is easy to configure and monitor via a secure, straightforward web interface with fault-reporting capabilities and visible external LEDs. Advanced switch-mode power supplies enhance efficiency and minimize heat, while the amplifier’s LDMOS devices are safeguarded against adverse load conditions and excessive heat sink temperatures. The amplifier also offers intuitive, user-friendly operation and straightforward maintenance procedures, making it cost-effective, and perfect choice for reliable and efficient HF communications for voice and data.
Everything is managed by AI SMART Systems that control the antennas and equipment, (this is not a FlexRadio project, but a DoD contractor activity, and under a binding Confidential Non-Disclosure Agreement NDA.)
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Software-
On the software side, there are numerous applications and platforms that enable remote control of ham radio stations. These programs allow operators to adjust radio settings, tune frequencies, and participate in digital communication modes. Some software solutions feature user-friendly interfaces that make connecting to the station easier, while others offer advanced features for experienced operators aiming to optimize their setup. K0UO now exclusively uses the FlexRadio platforms (for K0UO's own use, sometimes Icom IC7760s), equipped with specialized filtering. The station operates with a synchronized Local Area Network (LAN) and Wide Area Network (WAN) architecture.
It utilizes IP-switched matrix systems and AI Smart Control for comprehensive remote control of the station as needed.
K0UO's innovative design for an automated AI-assisted SMART DX station is noteworthy. This cutting-edge approach to acquiring rare DX integrates or Contest points using real-time propagation telemetry, automated Voice & CW skimmers, dynamic antenna array switching, and automated contact management. As of the fall of 2026, these components are fully operational at K0UO and its remote sites (as part of a DoD project with Frequency Agilty, FHSS, and ALE )
Self-healing:
The system boasts a variety of Smart AI-driven self-healing features, with ongoing efforts to boost its performance and resilience. These capabilities utilize advanced algorithms to monitor system health in real-time, detecting potential issues like resource spikes or downtime before they escalate. The system can automatically trigger recovery protocols, such as reallocating resources or applying software patches, thus reducing downtime and ensuring optimal performance. The team is integrating machine learning to enable the system to learn from previous incidents, thereby enhancing its capacity to predict and address failures. For instance, these advanced AI-driven Smart features can autonomously detect anomalies in system behavior, such as unusual increases in resource usage or unexpected downtime, in conjunction with system controls.
For example, circumventing malfunctioning components such as control boxes, power supplies, switches, relays, filters, PLCs, transceivers, amplifiers, antennas, and other switching equipment. Additionally, overseeing standing wave ratio (SWR) on feed-lines, temperatures, current, voltage, HVAC systems, generator systems, sensors, lightning protection systems, security CCTVs and backups, weather conditions (WX), network feeds, indicator warnings, and central processing units (CPUs). Upon detecting these irregularities, the system can activate predefined recovery protocols, which may involve reallocating resources, restarting affected services, or even applying patches to software components without manual intervention. Additionally, we plan to enhance self-healing functions to handle complex scenarios using intelligent decision-making frameworks that prioritize actions based on impact. This development represents a significant advancement in system maintenance and low downtime reliability, while surpassing user expectations in performance and dependability.
Grounding, Bonding, Shielding, and Lightning Protection (GBSLP): Engineering robust grounding grids, carbon-based conductive back-fills, and EMP hardening to meet stringent defense standards. Electromagnetic Pulse (EMP) and LPS to meet DoD specifications, with Ground Enhancement Material (GEM) which is an electrically conductive back-fill placed around grounding electrodes or buried grounding conductors to improve their electrical contact with the surrounding earth. It is utilized at numerous communication towers, broadcast transmitter locations, cellular facilities, radio repeater installations, substations, and other sites where effective grounding is crucial. At this hilltop site, the use of non-leaching, carbon-based conductive back-fill, grounding-grid geometry, bonding, and surge protection is essential, along with maintaining conductor integrity. Numerous days were dedicated to working on the grounding system.
With the construction now finished, there remains a tangible excitement among the family, RSI Corp, and the friendly local ranchers. The site will seamlessly integrate into the landscape of the KS Red Gyp Hills. This new hilltop location is set to become a lively center for HF Contest, DX, and DoD research activities, allowing for a full appreciation and enjoyment of the natural beauty surrounding it.
Benefits of Rural, Isolated Tower Locations
The rural ranching setting offers several advantages:
Minimal RFI: Far from urban noise sources, signals are clearer.
No Antenna Crowding: No other users on the towers means no interference or competition for space.
No Zoning or HOAs, but no neighbors for 10 miles or more in any direction.
Stable Environment: Open land reduces multipath reflections and signal distortion.
Privacy and Security: Remote locations limit unauthorized access (the gate is almost 2 miles from the "Open Range Land" county road.
Unlimited: Expansion opportunities
Towers: Height not limited by near by airports
Fiber: The site still has access to the new Rural Broadband high speed internet
These factors combine to create an ideal environment for serious ham radio operations.
Geographic Propagation Advantage of Kansas at this station: Thanks to its prime location, K0UO is perfectly positioned to excel in DX and radio contests, giving operators the chance to skyrocket their scores! Nestled in vast rural expanses with endless acres of land, the RF noise floor is practically non-existent. With neighbors miles apart, the station can pick up those faint signals that urban or suburban operators only dream of.
With arrays operating at take-off angles of 5 to 8 degrees, K0UO consistently leads the way, being the first to open and the last to close to Europe, Asia, and across the poles to Western Asia and the Middle East, while also keeping a steady connection to South America.
Contesting is not won by size alone—it is won by rate, accuracy, and signal advantage. Multiple sources emphasize that operator skill is the most important factor in contesting, even more than hardware. However just think about using new AI technology, Smart Antennas and Controls along with that experienced DX & Contest operator. The K0UO X-Rhombics provide massive forward gain, extremely low noise, and instant direction switching—advantages normally not available even in superstations. With AI nower even faster recognition, real time propagation knowledge, with fast accuracy in over all management .
The K0UO site has miles of wire with incredibly high-gain "Rhombic Curtain and V Beam arrays". They truly reign supreme as the King of HF Wire Antennas, unmatched by any yagi.
To construct an X-Rhombic antenna, modify the diamond configuration by intersecting the wire elements. This phase-reversal design enhances the forward beam and reduces side lobes. As a multi-wavelength traveling-wave antenna, it requires substantial space and robust support structures.
Step 1: Calculate the Dimensions
Rhombic dimensions are dictated by your lowest target operating frequency. For high gain, each leg should be at least 2 to 4 wavelengths long (λ), the longer there is even more gain.
Calculate Wavelength (λ)
Leg Length (L): Multiply λ by your chosen factor (e.g., 3λ or 4λ).
Tilt Angle (φ): The internal apex angle typically ranges between 50° and 70°, depending heavily on the leg length to align the wire radiation lobes cleanly with the center axis.
Step 2: Lay Out the Geometric Footprint
A sloping X-Rhombic requires just one tall support masts (utility pole, tower or tree) arranged in a precise shape .
The Center Axis: A straight line from the input mast to the termination mast.
The Side Masts: Perpendicular to the center axis, defining the width of the array.
The "X" Crossings: Instead of routing the wires directly around the side masts like a standard rhombic, the wires cross over each other at the side positions. They must be insulated from one another at the crossover point using a heavy-duty ceramic or fiberglass spacer.
Step 3: Wire Routing
High-tensile, copper-clad steel wire or wire rope is highly recommended to withstand the mechanical tension across long spans.
Input End: Secure two separate wires to the input mast insulators.
The Crossover: Run Wire A from the input mast toward Side Mast 1. Run Wire B toward Side Mast 2. At the mid-point (the side apex position), cross the wires past each other using the non-conductive spacer, anchoring the spacer assembly securely to the side masts via guy lines.
Termination End: Not need, but id you want it just continue routing the wires down to the far termination mast, completing the array. Because it is a traveling-wave system, it can be terminated to remain directional.
Step 4: Construct the Feed and Termination System
The Feedpoint: Connect a balanced, high-impedance open-wire transmission line (typically 600-ohm ladder line) to the input wires. Wire this into a high-power 12:1 current balun at ground level before running coaxial cable back to your transmitter.
The Termination Resistor: At the far apex, connect a 600 to 800-ohm non-inductive resistor. This resistor must be rated to handle roughly half of your transmitter’s total output power, as the remaining forward RF energy is dissipated as heat to maintain the sharp forward beam pattern, or better use the K0UO re-phasing system for 90% efficiency
Traditional rhombic antennas are known for their simplicity and high gain over a wide bandwidth, but they require large physical space due to their long wire elements with lower efficiency. The re-entrant rhombic array addresses this limitation with several unique features:
Improved Bandwidth: The re-entrant structure can support a wider frequency range due to the increased electrical length and better impedance characteristics.
Enhanced Directivity: The shape modification focuses the radiation pattern more tightly, improving directivity and reducing side lobes.
Enhanced Efficiency: The design reduces losses due to reflections and mismatches, resulting in increased radiation efficiency and redirecting the power previously lost in termination back into the array, now up to 90% efficient.
These features differentiate the K0UO Re-entrant rhombic arrays from traditional wire antennas and other directional antennas like Yagi or log-periodic arrays.
Why Stand-Alone Towers Matter for DX Operations
When it comes to ham radio, antenna height and location are critical. Stand-alone towers that reach up to 500 feet provide significant elevation above the surrounding terrain. This height allows antennas to operate at low takeoff angles, which is essential for long-distance signal propagation. Signals sent at low angles travel farther by bouncing off the ionosphere, enabling communication with distant stations across continents.
Real-World Example: Contest Success with Stand-Alone Towers
A ham radio club used one of these 500-foot towers with a high-gain Yagi antenna during a major DX contest. The elevated antenna and clean environment allowed them to reach stations across multiple continents with strong, clear signals. Their score improved dramatically compared to previous contests where they used lower, shared towers in suburban areas.
Features of RSI Corp and K0UO/R Stand-Alone Towers
Exclusive Use: No other users share these towers, so you have full control over antenna placement and orientation.
Height: Towers up to 500 feet tall provide excellent elevation for HF antennas.
Fiber Optic Connectivity: Each tower is served by fiber optics, supporting fast and reliable data transmission for remote control or digital modes.
Rural Location: Positioned in quiet, rural ranching areas, these towers avoid urban noise and interference.
Versatile Orientation: Antennas can be oriented in various directions to maximize signal strength and reception quality.
Far Field: Expanded testing area site.
K0UO uses AN-SOF and Scilab model programs, however testing is still required.
K0UO with the RSI Corp antenna Far Field Test Range uses advanced RF measurement to confirm all the antennas preformance.
Located at a distance of up to 20 miles from the main 4KS airport and K0UO/R site on the east side of the Kansas Red Gyp Hill ranching area, these towers for lease are part of an extensive test range that facilitates a variety of radio frequency experiments and competitions. All can be connected with a private microwave internet point-to-point backbone network or fiber.
The towers are registered with the FCC Antenna Structure Registration (ASR) system. Several notable structures are listed, including the following:
#1,216,715 at a height of 59.5 meters on site, with HF LPDA & large HRS Curtains
#1,252,737 reaching 70.2 meters,
#1,252,738 towering at 89.6 meters,
#1,260,299 standing at 42.6 meters,
#1,314,639 at 88.4 meters,
#1,216,786 reaching a height of 97.5 meters, HF antennas and many spare 7/8in hadline coax for antennas as needed, this tower is on a 300ft hill 800ft AGL
#1,252,503 at 77.7 meters,
#1,235,485 at an impressive height of 149.4 meters dedicated to FM broadcasting, It has had many ham antennas and feed line are in place
and finally, ASR# 1,252,009 standing at 85.30 meters.
Practical Uses for Stand-Alone Towers
These towers are perfect for:
DX Contests: Compete with the best by using high-gain antennas on tall towers to reach distant stations quickly.
Projects: For DoD and Commercial equipment testing including IRS.
Far-Field Antenna Testing: Test antenna designs in a clean environment without interference from other antennas.
Group Operations: Clubs or groups can share tower access for coordinated contesting or experimentation.
Remote Operation: Fiber optic connections allow remote control of radios and antennas, enabling operation from anywhere.
Setting Up Your Antenna on a Stand-Alone Tower
To get the most from these towers, consider the following:
Choose the Right Antenna: High-gain directional antennas like Yagis or phased arrays work well for DX.
Optimize Orientation: Point antennas toward target regions or rotate them as needed for contests.
Use Quality Feedlines: Low-loss coax or balanced lines preserve signal strength. K0UO still has rolls of hardline to use.
Implement Grounding and Lightning Protection: Tall towers are vulnerable to lightning; proper grounding protects equipment.
Plan for Maintenance Access: Ensure safe climbing or use of hoists for antenna installation and upkeep. RSI Corp has an OSHA trained tower contractor crew
Final Thoughts on Using Stand-Alone Towers for DX
Access to dedicated, tall stand-alone towers and K0UO site #2 in quiet rural settings offers ham radio enthusiasts a powerful tool for maximizing DX operations. The combination of height, isolation, and fiber optic connectivity creates an environment where antennas perform at their best. Whether you are a contest operator, antenna experimenter, or serious DXer, these towers provide the space and conditions needed to reach distant stations with clarity and reliability.
If you want to elevate your ham radio experience, consider how these stand-alone towers could fit into your plans. Their unique advantages can open new possibilities for communication and experimentation.
Ready to take your DX or contest operations to the next level? Explore the options for stand-alone towers, along with K0UO/R site number 1 & 2, and see how they can transform your ham radio setup.
In short, the new site X-Rhombic array farm provides instantaneous direction switching, while a stacked Yagi beam is constrained by the mechanical rotation speed of the antenna's mounting hardware.
So if you're considering a fixed-wire setup to eliminate rotor maintenance and require frequency flexibility, choose a Rhombic or V Beam.
"Over the past 30 year since moving to Kansas, my primary passion in amateur radio has been the design, modeling, and empirical testing of large-scale, high-gain HF wire arrays—particularly rhombics, V-beams, and multi-element configurations. Because of the physical space required for these traveling-wave systems, the station has evolved into a comprehensive outdoor test range. For those interested in the technical side, I’ve published the complete far-field test data, antenna models, and construction logs openly on my Blog and QRZ.com. I always welcome connecting with fellow builders and engineers who share a fascination with classical HF propagation."
Active Facility Clearance (FCL)
The K0UO antenna site number 2 is not a FlexRadio project, but a DoD contractor activity, and under a binding Confidential Non-Disclosure Agreement NDA.)
RSI Corp. and Steve Walz ensures strict, continuous compliance with the National Industrial Security Program Operating Manual (NISPOM) regulations.
RSI Corp has active Classified contracts or has a documented, ongoing business need to access classified data, this antenna site number 2, and the RSI test range, is under a binding Confidential Non-Disclosure Agreement (the "Agreement") NDA.
RSI has a continuously employed designated Facility Security Officer (FSO) who holds a personal clearance at or above the level of the FCL
In addition to formal DCSA reviews, the company's FSO performs and documents comprehensive internal self-assessments at least annually.
The Test Range Site continuous monitoring protocols, tracking mechanisms, and security education awareness logs.
The sites objective is to always have Superior / Commendable status. Which is only Granted to pristine operations with zero critical issues, highly active security communities, and proactive vulnerability self-reporting
Key Components of Remote Operation
To successfully establish and operate a remote accessible ham radio station, several key components must be considered. These components are essential not only for the functionality of the station but also for ensuring reliable communication, ease of use, and overall effectiveness in various operating conditions. Below are the critical elements that should be taken into account:
1. Radio Equipment
The heart of any ham radio station is the radio equipment itself, which typically includes a transceiver capable of both transmitting and receiving signals across various frequency bands. When setting up a remote station, it is crucial to select a transceiver that is compatible with remote operation features, such as remote control capabilities via software or hardware interfaces. Additionally, other essential radio equipment includes power supplies, antennas, and any necessary filters or amplifiers to enhance signal quality and range.
2. Antenna Systems
Antenna systems play a pivotal role in the effectiveness of a ham radio station. For remote operation, the choice of antenna is especially important, as it must be suitable for the intended frequencies and capable of being remotely adjusted or tuned. Options may include vertical antennas, dipoles, or more complex beam antennas, depending on the desired coverage area and operating conditions. Furthermore, considerations regarding antenna placement, height, and grounding are critical to optimize performance and minimize interference.
3. Remote Access Technology
Remote access technology is a fundamental component that enables operators to control their ham radio station from a distance. This can involve the use of various software applications that allow for remote connection to the radio equipment. Popular methods include Virtual Network Computing (VNC), Remote Desktop Protocol (RDP), or specialized ham radio software that provides a user-friendly interface for managing operations. Additionally, reliable internet connectivity is essential to facilitate seamless communication and control over the remote setup.
4. Power Supply and Management
Power supply and management are critical considerations for any remote ham radio station. Operators must ensure that their equipment has a stable and adequate power source, which may involve the use of dedicated power supplies, backup batteries, or even solar panels for off-grid locations. Effective power management systems should also be in place to monitor power usage and ensure that the equipment remains operational during extended periods of use, especially in remote areas where access to electricity may be limited.
5. Environmental Considerations
When establishing a remote ham radio station, environmental factors must be taken into account to ensure the longevity and reliability of the equipment. This includes assessing the location for potential weather-related challenges such as extreme temperatures, humidity, or wind. Proper housing or enclosures for the radio equipment can protect it from the elements, while also ensuring that antennas are securely mounted to withstand environmental stresses. Additionally, operators should consider any local regulations regarding antenna installations and ensure compliance to avoid any legal issues.
6. Licensing and Regulatory Compliance
Before operating a remote ham radio station, it is vital to understand and comply with the licensing requirements set forth by national and international regulatory bodies. This typically involves obtaining the appropriate amateur radio licenses, which may require passing examinations to demonstrate knowledge of radio operation, regulations, and technical skills. Compliance with these regulations not only ensures legal operation but also promotes responsible usage of the radio spectrum.
7. User Interface and Control Systems
A user-friendly interface is crucial for effective remote operation of a ham radio station. This may involve the use of graphical user interfaces (GUIs) that allow operators to easily control various aspects of their station, including frequency selection, audio levels, and antenna configurations. Additionally, integrating control systems that allow for automation of certain functions can enhance the operating experience and reduce the likelihood of errors during operation.
8. Security Measures
As with any remote operation, implementing robust security measures is essential to protect the ham radio station from unauthorized access and potential cyber threats for this DoD project. This can include using strong passwords, enabling encryption for remote connections, and regularly updating software to patch vulnerabilities. Ensuring that the remote operation is secure not only protects the equipment and data but also maintains the integrity of communications conducted through the station.
Conclusion
In summary, establishing a remote accessible ham radio station requires careful consideration of multiple key components, including radio equipment, antenna systems, remote access technology, power management, environmental factors, licensing, user interfaces, and security measures. By thoroughly addressing each of these aspects, operators can create a robust and efficient remote operation that enhances their ability to communicate effectively, regardless of their physical location.
Epilogue
The KØUO Rhombic Antenna Farms and Test Range: Home to the World's Largest Amateur Radio (Ham) High Frequency (HF) Wire Antennas, Also Known as "Antenna University" We are leveraging artificial intelligence, an increasingly sophisticated tool, to analyze, develop, and enhance research in RF and antenna technology. This blog also seeks information about other large HF amateur wire arrays around the world that remain operational. This is a significant challenge, as extremely large active ham wire arrays are rare, particularly those spanning multiple locations with both transmission and reception capabilities. Documenting similar stations is essential for preserving the technical history of the entire radio community. If you have any information, please contact us.
See the ARRL news letter featuring K0UO SMART Station Nov. 5 2026, https://mailchi.mp/arrl/the-arrl-letter-for-october-1-20253411?e=43e56aab26
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