Radio and television DXing has been a long time hobby of mine.
My first interest was DXing AM radio. Initially, the stations I received were not real technically challenging given that at the time clear channel allocations existed, so there were frequencies such as 1200 Khz where WOAI in San Antonio, TX, was the only station at night.
I received a Sony Earth Orbiter receiver as a gift from a close family friend and that receiver had greater sensitivity, selectivity, and an external antenna terminals.
At first I tried a long-wire antenna but found that the receiver severely overloaded resulting in spurious signals all over the band. Living in Seattle, WA, there was a plethora of high power (5-50 KW) AM stations nearby.
Then I learned of a type of antenna called a box-loop. I’ve given instructions on how to build one like I had built. I highly recommend this type of antenna, the performance exceeds that of just about everything else I tried. The selectivity of the antenna eliminated the problem of overload by strong local stations, and the directivity allowed another way to reject unwanted signals.
At the time the environment was just too noisy to receive the really weak signals of interest and my reception was limited to stations in the US, Canada, and Mexico.
Another area of interest for me is television DXing. At one time I had a reasonable setup consisting of a Wineguard deep fringe yagi antenna, Wineguard mast mounted pre-amp, and twinax (shielded twinlead) downlead.
A yagi antenna in which the elements come out 90 degrees from the mast, most modern TV antennas have gone to the log periodic design which has the elements swept back.
For DXing I prefer Yagi antennas to log periodic. I found the directivity of the yagi to be superior to log periodic.
One thing I have subsequently read that others have done, but I did not think of, is to orient the antenna so the elements are vertical rather than horizontal. Some VHF stations have gone to circular polarization because it provides rejection of reflections which causes ghosting if the receiver is equipped with a similar circular polarized antenna. But for those still using horizontal polarization, mounting a Yagi with the elements vertical provides rejection of ground based signals. This was frequently an issue for me as E-skip happens most frequently on channels 2 and 3 and we had a powerful local station on channel 4 that tended to bleed onto channel 3 and to a lesser degree 2.
Most of the E-skip I received came from the mid-west region, only rarely from the south. The local station was to the south, but I was near the top of a ridge, the station was on Queen Anne hill, and it was 100 Kw line of sight so even with the Antenna aimed away the signal was considerable and if I was trying to receive something from the south then it was really bad. Multi-hop E-skip when it occurs often results in a change to the polarization, so a vertical polarized antenna might be helpful both in rejection of local stations and double-hop E skip reception.
I found some interesting resources on the Internet.
- EMT, SETI, Radio Astronomy, DSP, and Amateur Radio
- Radio Line of Sight Plot Server
- Real Time Propagation Information
- A really cool TV DX site. This guy has taken it to the extreme.
- W9WI.com – TV technical information for DXers
- An interesting article on TV signal propagation.+
- An article on DX history mostly dealing with TV/FM.