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If you operate an LR station very long, you most likely will find other signals wanting to share your antennas set frequency. If you move your antenna off the 11.025 kHz center frequency of LR's band pass, then your sliding down the skirt of the filter and loosing a lot of sensitivity and S/N ratio. This project lets you move the antenna frequency to a clear area but convert it back to 11.025 kHz to keep LR happy. An added ability is to shape the band pass with brick wall filters that increase the S/N ratio out of sight compared to the usual S/N. Shown at right is the kind of band pass were talking about. This one is for the 5 kHz filter in LR. The plot below that is the final converted to 11.025 kHz signal, that LR sees on its input. 60db above the noise and other signals. This project uses Spectrum Lab V2.76 b16.. Some earlier versions WILL NOT work.. This program if your not used to it can be quite a learning curve to follow. It does have the ability to save setups, so by doing that you can have 95% of what you need for LR. The setup file "LR_converter1.usr" can be loaded and run to make things happen. The only thing needed then is to move the L.O. frequency to tune in your antenna. You can see what your doing right on the displays and readings of the markers. The example shown here is moving a Delta 15 antenna on about 4 kHz back up to 11.025 kHz. Make sure both loops are on the same frequency. Its real easy to get in trouble if you go messing with settings, so keep that in mind if things stop working. As long as you don't over write the original file you can always reload the .USR file to restore things. The sound card input goes to your antenna preamp as usual. Then the output goes to the LR computers sound card, line input. This has been done using two sound cards on the LR computer. To move your antenna's frequency on to the proper 11.025 kHz frequency, just add the antenna's frequency to 11.025 kHz and type it into the LO's box on the components window. If you have 50Hz power you need to change the Hum frequency to 100 Hz on the hum menu. There are two of these on each channel. One on the input, one on the output, where the "?"box is located. If your antenna is on 11.025 already, then just enter a LO frequency of zero for no frequency change.
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