LF Experimentation by Radio Amateurs Continues Quietly

John Andrews, W1TAG, in his Holden, Massachusetts, ham shack.

The Oklahoma station of Laurence Howell, KL1X/5.

Laurence Howell, KL1X/GM4DMA, checks out 137 kHz reception during a visit to Ghana in 2003.

NEWINGTON, CT, Nov 3, 2005--Experimentation by radio amateurs on the nether regions of the radio spectrum continues quietly and largely unnoticed outside of the LF community. Since the FCC turned down the ARRL's 1998 petition to create an Amateur Radio "sliver band" in the vicinity of 136 kHz, some US amateur licensees have obtained FCC Part 5 Experimental licenses to research the possibilities of LF, including transatlantic and transpacific propagation. A few hams in Canada have obtained special permission from Industry Canada to operate on LF using Amateur Radio call signs. The latest noteworthy accomplishment was a QSO between US Experimental licensees. LF enthusiast Laurence Howell, KL1X--operating as WD2XDW--and John Andrews, W1TAG--operating as WD2XES--completed their LF contact October 29 on 137 kHz.

"This is the second two-way between US Experimental licensees in that frequency range, the first being a 25-mile CW contact between K2ORS/WD2XGJ and myself last year," said Andrews. "There is an increasing amount of activity in that band in the US and Canada, but it has virtually all been one-way." The QSO between Andrews, in Massachusetts, and Howell, in Oklahoma, spanned some 1340 miles.

In 2001, Larry Kayser, VA3LK (SK), and Laurie Mayhead, G3AQC, received a special Transatlantic Challenge plaque for completing the first two-way Amateur Radio LF contact--between the UK and Canada--earlier that year. Another plaque went to Dave Bowman, G0MRF, John Currie, VE1ZJ, and Jack Leahy, VE1ZZ, for completing a crossband (HF/LF) transatlantic QSO in 2000.

A year ago, New Zealand LFer Mike McAlevey, ZL4OL, copied Howell's WD2XDW 137 kHz carrier "bursts" over a path of more than 13,000 km (8000 miles), while Jim Moritz, M0BMU, copied LF signals from WD2XDW, Andrews' WD2XES and Joe Craig, VO1NA, in Newfoundland. Craig and Alan Melia, G3NYK, described their LF exploits and experiences in "The Transatlantic on 2200 Meters," in July 2005 QST.

More recently, the first confirmed transpacific reception of Canadian Amateur Radio LF signals occurred October 4 when the the slow-speed (QRSS) CW signals of VA7LF were heard by ZM2E in New Zealand. "Signals from the ZM2E club station were heard in Canada as well, but propagation was not of sufficient duration to enable a QSO to be completed," said Steve McDonald, VE7SL, one of the VA7LF operators. ZM2E and UA0LE hold the current Amateur Radio two-way LF world record at a distance of 10,311 km (6393 mi). The distance between VA7LF and ZM2E is approximately 11,700 km (7254 mi).

An antenna matching network at WD2XDW (KL1X). Antenna systems at LF often must handle high current flow.

Canadian LF experimenter Joe Craig, VO1NA. Craig and Alan Melia, G3NYK, described their LF exploits and experiences in "The Transatlantic on 2200 Meters," in July 2005 QST [Rick Lindquist, N1RL, Photo]

For their late October QSO, Howell and Andrews used WOLF software developed by Stewart Nelson, KK7KA, and enhanced by Wolf Buscher, DL4YHF, to decode the signals on each end of their contact. "We had pre-arranged the frequency of 137.422 kHz, which is in a small gap between sidebands of the Loran-C signals on 100 kHz in North America," Andrews explained.

LFers typically use very low data rates and process the incoming sound-card audio in real time. Andrews says WOLF is a highly error-corrected binary phase shift-keyed mode that provides usable copy at signal levels where CW at a 60 seconds-per-dot rate is just copiable. ARGO is another popular software package among LFers.

During the contact, which took more than two hours to complete, Andrews was running 200 W output into a large, tree-supported vertical loop. "I used the large transmit loop as a receiving antenna, connected directly to an ICOM R75 receiver with no external preamp," he said.

In Oklahoma, Howell was running 1 kW into a tree-supported vertical loop. He uses a Kenwood TS-870 with a transverter for transmitting and tuned directly to 137 kHz for receiving.

Experimentation under FCC Part 15 rules in the vicinity of 160 to 190 kHz has been going on for years by radio amateurs and non-amateurs alike. Amateur Radio licensees in Europe and elsewhere have an allocation at 135.7 to 137.8 kHz, and most Amateur Radio experimentation takes place in this band.

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