Sunday, November 29, 2009

Sometimes it's what you can't hear that's important

When I get bored with contesting I often try to find "feats of radio magic". I try to find situations that are almost untenable to work in. One year in a 160 contest with my SDR-1000 I was able to separate 2 DX stations into single signals. The DX stations were in different parts of the world both being called by US stations. I worked each station as a single signal and the stations were only 40HZ apart!! 20 is often considered a band that separates the men from the boys. Lots of big signals big beams and high power bullys. I was tuning 20M this afternoon, and here is one I found:

If you look closely at this pic you will see super contest station W0AIH, a little below is LU8YE, a little below that is the green arrow of where my RX"s are tuned and a little below that is W1EM working K2TV, The signal you see is W1EM. The band width is about 1khz total and notice the clickiness of the 2 US stations. The effective band width between W0AIH and W1EM is about 600hz and between LU8YE and W0AIH is less than 100hz. In fact sometimes Lu8YE was inside of W0AIH's bandwidth

Note the S meter readings on both of my receivers. RX 1 is connected to a 55ft high 136ft long flat top fed with open wire and a Johnson KW Matchbox. RX 2 is fed with a resonant 5/8 wave 20M vertical about 150ft south of the flat top. I made a recording of what this sounded like when this picture was being shot

Green Arrow

What you hear is basically nothing, except a tiny bit of backgroud noise. No beeps no boops no clix. My noise floor is -119 dBm on RX1 (flat top) and -125dBm on RX2 (vert)

Next I tuned to LU8YE and made a recording of his signal between these two loud clicky stations.


You easily copy the Argentinian station Q5 as a single signal even with the very loud W0 super contest station blasting along less than 100hz above.

All of this with dozens of other loud US stations all around.

Once again it becomes so obvious how well this RX performs.