Experimenter Crosses the Atlantic on 8.971 KHz

While researchers are finding ways to make communications at 60 GHz practical (see "Researchers Develop Innovative Solutions for 60 GHz 5G Networks"), experimenter Dex McIntyre, amateur station call sign W4DEX, transmitted signals from North Carolina on 8.971 kHz that were received by Paul Nicholson in the United Kingdom in early June.


McIntyre didn't need an FCC license to transmit the signal across the Atlantic as the FCC hasn't designated any allocations below 9 kHz.

It’s very difficult to build an antenna that's efficient at such a low frequency. The effective radiated power (ERP) of the 8.971 kHz signal was on the order of 150 microwatts. Nicholson used sophisticated digital signal processing (DSP) software to receive the signal over both daylight and nighttime paths over a distance of about 6,194 kilometers or 3840 miles. The carrier was GPS-locked, allowing nighttime reception with a bandwidth of 46 microhertz with an SNR of around 12.5 dB. A 23 microhertz bandwidth was used during daylight hours.

To confirm that Nicholson was actually receiving the signal, McIntyre shifted the frequency slightly. Reception was confirmed at 8.971100 kHz at the same signal strength.

McIntyre, located in North Carolina, used a transmitter consisting of a Hewlett Packard HP 3586B selective level meter along with a tracking generator. The low-level generator output was amplified by a Wandel & Golterman A-160 level regulator feeding a Hafler P3000 stereo audio amplifier, which had been strapped for mono output, resulting in about 400 watts of audio into an 8 Ohm load. The antenna, which was used in the 29 kHz and other VLF experiments previously reported, is the same one McIntyre uses for 160 meters, but is equipped with a gigantic base-loading coil containing nearly a mile of wire.

"The vertical wire is spaced 1.5 meters from the tower, hanging from an insulator 29 meters above ground," said McIntyre. "[The] ‘top hat’ consists of about 170 meters of number 18 Copperweld. Most of the top hat wires run about seven to 20 meters over the top of a combination of oak and pine trees. Total antenna capacitance is close to 1200 pF."

More information about the experiment and the experimenters is available in the American Radio Relay League(ARRL) news release Radio Amateur’s Sub-9 kHz VLF Signal Detected Across the Atlantic. McIntyre told ARRL, "I’ll probably make more transmissions on 8.9 kHz when there is no chance of thunderstorms. Then, maybe sliding down in frequency to see how low I can go for Paul to detect the signal."

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. As vice president of Broadcast Technology for NBCUniversal Local, H. Douglas Lung leads NBC and Telemundo-owned stations’ RF and transmission affairs, including microwave, radars, satellite uplinks, and FCC technical filings. Beginning his career in 1976 at KSCI in Los Angeles, Lung has nearly 50 years of experience in broadcast television engineering. Beginning in 1985, he led the engineering department for what was to become the Telemundo network and station group, assisting in the design, construction and installation of the company’s broadcast and cable facilities. Other projects include work on the launch of Hawaii’s first UHF TV station, the rollout and testing of the ATSC mobile-handheld standard, and software development related to the incentive auction TV spectrum repack.
A longtime columnist for TV Technology, Doug is also a regular contributor to IEEE Broadcast Technology. He is the recipient of the 2023 NAB Television Engineering Award. He also received a Tech Leadership Award from TV Tech publisher Future plc in 2021 and is a member of the IEEE Broadcast Technology Society and the Society of Broadcast Engineers.