Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Long distance MW reception
Some of you may wonder how really long distance MW reception occurs,
such as the ! Kw Fresno CA station reported here in South Africa the other day. This is a station over 10,000 miles / 16,000 km's away from us. Theoretically these signals take several bounces off the ionosphere to get here, but the experts will tell you that theoretically such a low power station over such a long distance will expend it's energy and it is therefore not possible to receive such a long distance station even on the most powerful receiving antenna. However, it does happen and last year, 2007, various MW DXer's around the world were getting very long distance DX the likes of which had not been heard since the 80's. How is this possible then? Well, the more scientifically minded hams that work 1.8 MHz have a theory that these phenomenal long distance signals come in as a result of "ducting". The theory is that the outgoing transmission goes up into the ionosphere and gets trapped there, and then travels a considerable distance before coming down to earth in some very far distant space. These signals, when they arrive at the DXer's location, are usually very faint though and may not last for more than a few seconds, or maybe up to ten minutes if you are lucky, so you have to be very vigilant and alert to catch something like this, but when you do = BINGO! - extreme joy and euphoria = lovely! Alas, this is not the sort of thing you are going to pick up in your suburban back yard - all these catches were made by very experienced DXer's at prime coastal DX sites using 1000ft/300m or longer beverages. Don't worry about the radio though, anything from a Frog (Yaesu FRG-7) will do. The important thing with IDing faint MW signals is to have a radio that produces a good audio spectrum that catches all the sibilants and harmonics, or otherwise you are not going to be able to read the signal. If you want to listen to an audio clip of my 1410 kHz CFUN Vancouver Canada catch 10,000m/16,000km's away, go to my good DX pal Gary Deacons website http://www.capedx.blogspot.com/ and on the RHS you will find the audio clip box, then search for CFUN Canada. you will see it is very faint, but if recorded on a decent MP3 recorder you will be able to decipher the call sign ID with a little practise and skill. A serious DXer can always expect the unexpected Have fun, good luck and good DX. John Plimmer, Montagu, Western Cape Province, South Africa South 33 d 47 m 32 s, East 20 d 07 m 32 s Icom IC-7700, Icom IC-756 PRO III with MW mods ERGO software Drake SW8. Sangean 803A Sony 7600D, GE SRIII, Redsun RP2100 Antenna's RF Systems DX 1 Pro Mk II, Datong AD-270 Kiwa MW Loop. http://www.dxing.info/about/dxers/plimmer.dx |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
IC-M710 long distance communication, how long ? | Digital | |||
good long distance radio | Scanner | |||
FYI - Need a Long-Distance AM Radio? Here's Two ! | Shortwave | |||
"zenith long distance" | Boatanchors | |||
Long distance | Swap |