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I have been active on 136kHz both from home and,occasionally, from West Wales since 1988, and was the first G to work ON on 136kHz. One of a very few stations to make a transatlantic two-way contact. I was part of the first ever QSO on the now defunct UK-only band at 73kHz, and held the distance record for a two-way contact on that band for 13 months. I made two-way QSOs with more countries than anyone else: G, GI, GM, GD and GU, and was the only person to transmit on 73kHz from GW. Currently use 136kHz most days QRSS (extremely slow CW) and ccasionally on CW. Occasionally participate as a receiving station in test at 9kHz (yes kilohertz!). I have received a station in Germany on that frequency. More recently I have done some receiving on the UK experimental band at 500kHz, and the new worldwide band (allocated at present to only a few countries, but not the UK until 2013) at 472-479kHz. I was the first British station to receive an amateur station (DK8KW) on this band (see my blog). Location See Map Welwyn Garden City, Hertfordshire. Postcode AL. Loc IO91VT. 30km north of London. VFO and Transmitters Synthesizer designed by G0MRF and SM6LKM, and built by G0MRF.. Ex-Decca navigation station 1kW transmitter [details, circuits and mods for 136kHz] running about 800W on 136kHz from 60V PSU. 'The First', a commercially manufactured 12V 136kHz Tx capable of 100W. [only available second-hand these days] [documentation] A safety timer is used to limit the time the key can be down. An earlier transmitter, which I used originally for 73kHz, and later for 136kHz, was a modified BK Electronics 300 watts (nominally) mains driven audio amplifier, with an external free-running oscillator. I managed to get about 150W out on 73kHz and perhaps half of that on 136kHz. It is still available at around £100. I matched the few ohms output to the 100 ohms or so of the antenna by connecting the amplifier to a one or two turn coupling loop round the earthy end of the antenna loading coil. Transmit antenna Marconi, inverted-L, 14m high with three top wires 16m long. Top and bottom inductive loading, tuned against earth stakes. Drawing of the antenna system used from September 99. I have some of the inductive loading at the top of the mast and some about one-third of the way up - a total of about 7mH - with just a 0.3mH variometer at the bottom for tuning. Raising the inductance above ground has been found to increase the efficiency. In the past I have experimented with a large loop antenna (10m x 14m) and had some success on the now-defunct 73kHz band. It was capable of performing with similar efficiency to the equivalent size nverted-L, but it its directional properties made it less useful. Matching was by capacitive divider. Receiver Icom IC-706 Mk 1. It can be tuned in 1Hz steps and has excellent frequency stability, which is ideal for extremely slow speed (QRSS60) reception. The receiver is fairly sensitive, but benefits from the addition of a pre-amp which is described on G3YXM's site and is available ready-built from G0MRF. I also have a TS-850 which is very sensitive at 136kHz, but can only be tuned in 10Hz steps and does not have such accurate tuning as the IC-706. Receive antenna The Marconi works fine for most purposes. A 0.8m square loop has been used for portable work and when I needed to null out local noise. This was made from 40-wire ribbon cable, and the wooden spreaders were foldable to get the antenna easily into a car. A diagram of an old receive antenna is shown here. Modes Mostly extremely slow CW known as QRSS, with 3 or 10 second dot period for intra-Eu and 30-120s for inter-continental working. Occasionally I use conventional (fast) CW. I have experimented with receiving the BPSK mode specifically designed for LF, WOLF.
Best DX on 136kHz
Operating periods I monitor the 137.7kHz QRSS3 sub-band most of the day. Can transmit any day and time on request. Skeds and reports E-mail me (see below) Operation from Wales Follow this link. |
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Last updated 24 May 2013 |