Supplement to R.A.C. bulletin 01-011E

This bulletin supplements R.A.C. Bulletin 01-011E on the M.A.R.C. News page.

TransAtlantic QSO on LF completed (2001-February-19) Report by Larry Kayser, VA3LK

On February 19th, Laurie Mayhead, G3AQC and Larry Kayser, VA3LK completed a Trans Atlantic QSO between the UK and Eastern Ontario on 136 kHz.

The QSO began February 5, 2001 and was completed on February 19th with the reception of VA3LK's report by G3AQC. The QSO was made using a visual adaptation of Morse, a 2/1 dash/dot ratio and using the visual signal receiving program ARGO. The dits were 90 seconds long, the dahs 180 seconds long.

The participants agreed in advance to a “firewall” between them for the duration of the QSO. All QSO information was exchanged over LF radio. The QSO was of long duration. It included time for antenna failures and repairs at VA3LK, the effort was however continuous, VA3LK made 27 separate trips to his remote radio site.

The message exchange used was based on a QSO model offered by Mike Dennison, G3XDV. Mike outlined the process in an email dated January 26, on the LF Reflector, the format used was very close to this model.

G3AQC Station description:
Laurie's 136 Khz station consists of a phased locked loop exciter driving a 1000W audio amplifier which can only manage 400W at this frequency. The Antenna is a top loaded vertical 48ft high with 450 ft of top load. This is not in one length but zig zags in order to cover as much ground as possible. This fed via a transformer, loading coil and variometer. There is an extensive ground radial system. The antenna radiation resistance is about 0.06 ohms and the total loss resistance 38 ohms, so with 400W, the Effective Radiated Power (ERP) is about 350mW. The receive antennas are two large grounded loops switched into a pre-amp with a Band Pass filter. The receivers are an ICOM 756PRO for normal CW and a Racal 1792 for QRSS. The ARGO spectral analysis program is used for viewing QRSS.
Station description by L.V. Mayhead, G3AQC.

VA3LK Station description:
The LF transmitter consists of a DDS exciter from David Bowman, G0MRF, with software by Johan Bodin, SM6LKM. The exciter output is put through a hard limiting buffer that is keyed in the power lead. The amplifier is a much modified ex-commercial unit from the UK Decca system that was decommissioned at just the right time. For the duration of the Trans Atlantic QSO the amplifier was running at 65 Volts DC at 10 to 12 Amps. The antenna is a 100-meter semi vertical wire to the top of a 240-ft self-supporting tower. The wire is pulled out from the side of the tower by a rope anchored some 450 feet away from the tower. Extensive ground radials were pulled into place during the fall of 2000. The loading coil is approximately 2.1 millihenry. Computing resources used a Pentium 166 with dual booting DOS/Win95.

Larry, VA3LK, thanks those who have helped with this project, including my pre-retirement employer, Bell Canada for the use of the radio site for the HF station and other research work. The UK LF gang who struggled to transfer to him the lessons they had learned about LF, Canadians from VO1 to VE3 and VE7 who worked through the learning curve with me and last and most importantly. my wife, Joyce, VE3JAK who put up with all this and me for the last year and a half.

Larry Kayser, VA3LK

Thanks to Larry Kayser, VA3LK for providing the additional information for this update and the Radio Amateurs of Canada for permitting me to reproduce this item from the R.A.C. web page.

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Created: Friday, February 28, 2001
Revised:

Version 1.0