Tropospheric Ducting Explained You've always been taught that VHF communications are line of sight and that the height of your antenna determines how far your 2m communication might go. So if I tell you that last week I spoke with a station that was 300 kilometres away on the 2m band you might be forgiven in thinking that I had managed to climb up most of the side of Mount Everest to around 7 kilometres so I could make my line-of-sight communications 300 kilometres away. This week we find out how that works using a phenomenon called "Tropospheric Ducting". Foundations of Amateur Radio is a weekly podcast about the wonderful hobby of Amateur or Ham radio. You can catch it on-air, on-line or on-demand. Check out iTunes by searching for my callsign VK6FLAB for your personal copy, or visit the website at http://podcasts.itmaze.com.au/foundations/ Onno VK6FLAB
OH, DUCTING, I know how THT works, I WS wandering though hat 'Tropospheric Dusting' was. I am disappointed not to find out.
Tropospheric dusting is sometimes done with special high-altitude crop dusters spreading a heady blend of Magic Pixie Dust, Mixes 43, 61 and 72 ferrite dust , super-ionized ground meteorite powder and charged carbon particles when it appears that a tropo duct is about to form. It is basically a very expensive way to enhance propagation on the VHF bands that some of us gung-ho VHF/UHF DXers will resort to in order to grab a few more elusive grids or DXCC awards. Until now it has been kept under wraps (for fear that the ARRL might invalidate such "artificial" propagation enhancements for contest, award or DXCC credit). I believe that it came about in the 1990s after a meeting of several big gun hams, Boeing, Richard Branson and Spacex all decided to collaborate on the first fleet of "X-115 Tropo Dusters" in secrecy.
Super secret Tropospheric Dusting plane. Please do not look at this classified picture. You can tell how large it is by looking at the 40 foot long blue truck parked next to it in preparation for loading. Notice the Di-pole antennas. Half out each side to the wings. Looks to have 8 of them.
300km is my daily range with no ducting... heck I can hear the WD9BGA/b that is 50 watts to a stacked pair of loops at 301 miles most any day of the week! If the signal strength is down a bit band conditions are down. If it is a solid S2-3 band conditions are normal, above S3 we have some enhancement...
The only French maids that were ever well versed in such esoteric matters were the few that flew on the Concorde...most of the time they had other priorities, though.
No, no, no, it's working pings off meteor dust (which in fact people do). They are a bit higher than the troposphere, but one can always hope.
Last summer i was accessing a repeater in central qld with a 5w HT in brisbane, 500 odd km. Good fun.
Here in Eu I can hear a beacon ON0VHF at 550kms 365, this is without any tropospheric enhancement at all. The state of the art devices we use now to enhance out receiver's have made these distance's possible. This coupled with the fact there are better refraction surfaces in the Horizontal plain that vertical, I personally have never used a vertical antenna system, and very rarely use FM; it's mainly weak signal work that interests me. There are other Eu beacons well over 300kms I can hear too, and we all have to thank our dedicated beacon keepers too, sterling work where ever you are in the world. Thanks for reading this, just a little bit from my part of the world. 73 everyone de G8GXP in IO93FQ David
