Over the past three days I have made two-way amateur radio contacts (a “QSO” to hams) via an unusual short wave propagation path – the long way, over the south pole – from my home in Glade Park, Colorado to amateur radio stations in the Arabian Peninsula, each day in the late morning my time. Signals have been surprisingly strong and audible for hours.
Short wave radio signals usually follow the shortest path from point A to point B, the ‘great circle path.’ From my house to the United Arab Emirates this is approximately 13,000-km. Since the circumference of the earth is just over 40,000-km the long path to the UAE is around 27,000-km and crosses the equator twice! The DX Atlas Map below has markers for my home (QTH), where the map is centered, and the UAE and also shows the location of the sun, dusk/dawn zones and areas of darkness for 1744z on January 5, 2013 (this is the time for one of the YouTube videos I made of this event).
Here are the QSOs I’ve made over this path (so far, fingers crossed this path will be here tomorrow and beyond):
- Jan 3 1805z A65BR 28076-kHz JT65A
- Jan 4 1839z A65BP 24893-kHz CW
- Jan 4 1844z A45XR 24902-kHz CW
- Jan 5 1702z A45XR 28009-kHz CW
My four contacts were made with a simple vertical antenna and 100-watts transmitter power (except for the JT65A mode contact which was made with a mere 10-watts). The footprint of the propagation was very specific – the southern Arabian/Persian Gulf area on one end and western North America on the other. Here is what the A65BP DX Cluster spots looked like as of this morning. You can get a feel for the where the signals were landing in this part of the world from the spotting stations’ locations:
Why did this path open now? A recent spike in the solar flux above 140 helped refract the 25/28-MHz radio waves a long distance, a ‘quiet sun’ (low Kp and Ap indexes) helped the signals transverse the auroral zone around the south pole and a double crossing the trans-equatorial zone – where radio waves from the upper HF all way up to low UHF can get a turbo boost plus the seasonal geometry of the sun and earth which puts a lot of solar radiation in the southern hemisphere all played a part. I wonder if higher solar flux would have resulted in a rare (for the USA) long path opening in the amateur 50-MHz (6 meter) band?
Here is a recording of A65BP operating from the United Arab Emirates with a great signal on 28,012.26-kHz as heard in Glade Park, Colorado (DM59pa) today 2013-Jan-05 morning at 1743z with a simple vertical antenna. The signal was propagating via long path over the south pole. A45XR was also strong on 10m CW on this path around this time. I completed QSOs with A65BP and A45XR on 24.9-MHz long path on January 4th and had a 28,076-kHz JT65A QSO with A65BR on January 3rd. Nice to hear some 10m long path in Cycle 24!
Here is a recording of A65BP operating from the United Arab Emirates just a little later with a great signal on 24,902.00-kHz, also captured with a simple vertical antenna.
These last few days have really lit a fire under me to get off my ass and build the 3-element 12-meter LFA Yagi and 5-element 10-meter LFA Yagi from InnovAntennas that are sitting in my shed. If I can work stuff like this on my vertical what will I be able to do with a pair of state-of-art antennas? Who cares that hasn’t been above freezing here since December 17th when there is DX to be worked!
(Sunday morning update – A92GR & VU2XO are audible on 10m SSB at approximately 1600z, looks like another good morning on the long path.)