Amateur radio has been a part of Tim Koeth’s life since his early teens, helping turn an early fascination with electronics into a lifelong habit of experimentation, building, and learning by doing.
Tim earned his first amateur radio license, KB2IXD, at age 13 alongside his father, Bill Koeth (W2WK, Silent Key). The two attended evening licensing classes offered by the Piscataway Amateur Radio Club (K2VOA) in New Jersey. Tim recalls that his father had to persuade him to attend the first class—but only the first. Once introduced to amateur radio, he was hooked. For over a decade, Tim’s callsign was N2LPN. Now, Tim holds an extra-class license and has the best vanity callsign ever: KØETH.
Ham radio quickly became an extension of Tim’s growing interest in electronics and physics. During high school he experimented with antennas, radio equipment, and communications systems, often treating the hobby as an informal laboratory. One memorable experiment involved running a 2-meter directional antenna up the school flagpole early one January morning—an installation that attracted the attention, though fortunately not the lasting displeasure, of the school principal. He and a fellow student and radio amateur even passed messages by tapping Morse code on their desks during Spanish class.
More importantly, amateur radio gave Tim practical experience with many of the concepts that would later become routine in his scientific career: RF electronics, antennas, transmission lines, impedance matching, signal detection, instrumentation, propagation, and troubleshooting complex electronic systems. It reinforced the connection between theoretical physics and the satisfaction of actually constructing something, turning it on, measuring its behavior, finding out why it did not work as expected, and improving it.
Although Tim’s principal scientific interests ultimately led him toward nuclear and particle physics, accelerator science, and experimental instrumentation, the amateur-radio approach remained remarkably compatible with his professional work. His later projects—from building and operating a cyclotron to developing specialized scientific instrumentation—retain much of the same hands-on experimental spirit that first attracted him to ham radio.
For Tim, amateur radio therefore represents considerably more than a communications hobby. It was one of his earliest introductions to the culture of practical experimentation and remains part of a lifelong interest in radio, electronics, instrumentation, and the physics behind them.
Rising above the surrounding Maryland woodland is Tim Koeth’s amateur radio antenna tower, KØETH. Seen here from the air, the tower and its directional beam antennas emerge from an otherwise nearly continuous forest canopy, giving a sense of both the scale and isolation of the station.
The KØETH amateur radio station is anchored by this US Tower HDX-555, a heavy-duty, three-section crank-up tower capable of extending to 55 feet while retracting to approximately 22 feet for servicing. The self-supporting HDX series is engineered for substantial antenna wind loads, making it well suited to large directional HF arrays.
Mounted at the top is Tim’s tri-band Yagi beam antenna, providing directional operation on multiple HF amateur bands. A Yagi concentrates transmitted radio-frequency energy in a chosen direction while providing increased sensitivity to signals arriving from that direction—an important advantage for long-distance, or DX, communication. The antenna can be rotated to favor different parts of the world, allowing the station to exploit changing ionospheric propagation conditions.
Suspended high among the trees at KØETH is Tim’s 40-meter caged dipole antenna, designed for operation on the 7 MHz amateur band. Unlike a conventional dipole made from a single wire on each side, the caged design uses multiple parallel conductors held apart by circular spacers, clearly visible in this photograph. Electrically, the conductors act together as a much larger-diameter antenna element.
The principal advantage of this arrangement is increased bandwidth: the larger effective conductor diameter reduces the rate at which the antenna’s impedance changes with frequency, allowing it to maintain a useful match across a broader portion of the 40-meter band. The antenna is center-fed and suspended between tall trees, taking advantage of both its physical height and the substantial space available at the KØETH station.
At 40 meters, signals can support everything from relatively regional communications to long-distance DX, depending on time of day and ionospheric conditions. The photograph provides an unusual view from directly beneath the antenna, where the multiple wires and circular spreaders that give the “cage” dipole its name are especially apparent.
The KØETH amateur radio station combines modern software-defined radio technology with high-power HF equipment—and, on occasion, considerably older communications technology. Tim’s primary HF transceiver is the Icom IC-7610, a direct-sampling HF/50 MHz radio with independent dual receivers and spectrum displays. Its display is duplicated on the large monitor above the operating desk, allowing signals and activity across the amateur bands to be viewed in considerable detail.
For VHF and UHF work, including amateur-radio satellite communications, the station uses an Icom IC-9700. It covers the 144 MHz (2-meter), 430/440 MHz (70-centimeter), and 1.2 GHz (23-centimeter) amateur bands and includes dedicated satellite memories and capabilities suited to working spacecraft while they pass overhead.
The HF station is complemented by a Palstar HF-AUTO automatic antenna tuner, which provides impedance matching between the transmitter/amplifier and Tim’s various antenna systems. Rated for operation from 160 through 6 meters and power levels up to 1,800 watts, it allows the station to accommodate high-power HF operation while automatically finding an appropriate antenna match. An ACOM 2000A automatic HF linear amplifier provides the station’s high-power transmitting capability.
The operating position also reflects Tim’s broader interests in the history of communications and cryptology. Prominently displayed—and very much functional—is an Enigma cipher machine. In 2023, Tim used the Enigma at this station while participating in the KPH Enigma Challenge, an event combining amateur radio with historical cryptography: encrypted messages transmitted over the air were received and then deciphered using Enigma technology.
Together, the station spans nearly a century of communications technology—from mechanical rotor cryptography and Morse code to digital signal processing, spectrum displays, satellite communications, and modern high-power HF radio—a fitting intersection of Tim’s interests in amateur radio, electronics, instrumentation, and cryptologic history.
On July 22, 2023, the Maritime Radio Historical Society (MRHS), working with the Cipher History Museum, staged an unusual experiment combining historic maritime radio, amateur radio, and World War II cryptography. From the restored commercial coast station KPH near San Francisco, an authentic wartime German U-boat message was transmitted by shortwave radio in encrypted five-letter groups, using both CW (Morse code) and RTTY (radioteletype). Listeners around the world were challenged to intercept the transmission and successfully decrypt it using the German Enigma cipher system.
The ciphertext was based on an actual message sent in 1942 by Kapitänleutnant Hartwig Looks, commander of U-264, and intercepted in the North Atlantic by the British destroyer HMS Hurricane. The original message came from the period when the German Navy’s introduction of the more sophisticated four-rotor M4 Enigma temporarily prevented Bletchley Park from reading U-boat communications.
Tim, KØETH, took the challenge a step further by attempting the decryption with an original Enigma machine rather than a computer simulation. According to WIRED’s account of the event, Tim was the only one among 145 participants attempting the challenge with an actual Enigma machine. Working from the K0ETH station in Maryland with a small group that included Noah Hoppis, Larry West, and Jim Krutzler, the team received the radio transmission, worked through the historical keying procedure, and ultimately recovered the plaintext. A particularly difficult problem turned out to be an ambiguous character in the reproduced wartime key information; identifying it correctly allowed the machine settings to work.
The decoded U-boat report described being forced to submerge during an attack with depth charges, gave the last known enemy grid position, and reported that the submarine was continuing to follow the enemy.
The Certificate of Cryptographic Achievement shown here was awarded by the Maritime Radio Historical Society to Noah Hoppis, Larry West, Jim Krutzler, and Tim Koeth for successfully decrypting the KPH transmission using original Enigma equipment. The exercise effectively recreated an extraordinary chain of communications technology more than 80 years later: a wartime German naval message was once again transmitted over HF radio, intercepted at a listening station, and transformed from seemingly meaningless groups of letters back into intelligible text by a genuine electromechanical Enigma machine.
The team’s efforts were subsequently chronicled in WIRED in “The Low-Stakes Race to Crack an Encrypted German U-Boat Message,” providing a detailed account of the challenge at K0ETH and the eventual successful decode.
The team participated in the 2025 KPH Enigma challenge, which was reported on in the UMD Terp publication in an article titled “Keeper of the Codes.”
“Radio-active Hams” — QST, August 1995
In 1995, Tim Koeth, N2LPN (now KØETH), and fellow Rutgers University Ham Radio Club member Stu Hanebuth, KBØQXR, took amateur radio experimentation into an unusual part of the electromagnetic spectrum. Their work was featured in the “Up Front in QST” section of the August 1995 issue of QST, the magazine of the American Radio Relay League.
The pair reported what they believed to be the world’s highest-frequency amateur-radio QSO, operating not at conventional radio frequencies but at 285.1 THz—corresponding to gamma radiation from small cesium-137 radioactive sources. Because FCC amateur allocations extend only to 300 GHz, frequencies above that were described in the article as essentially open territory for experimenters.
For their approximately 12-centimeter contact, Tim and Stu devised a remarkably unconventional CW communication system. They mechanically keyed the gamma-ray beam by moving a lead shield in and out of its path, effectively transmitting Morse code with ionizing radiation rather than ordinary radio waves. At the receiving end, scintillation detectors and portable radiation ratemeters detected the modulated radiation.
At 0702 UTC on March 17, 1995, they exchanged amateur-radio call signs and 599 signal reports, completing what QST described as apparently the first recorded QSO in this region of the electromagnetic spectrum.
The experiment neatly combined several interests that would continue throughout Tim’s career: amateur radio, nuclear physics, radiation detection, electronics, and hands-on experimental science. QST appropriately featured the two Rutgers experimenters under the headline “Radio-active hams.”