As suggested, try to identify the RFI source, and eliminate it first. You can do a walkabout with an inexpensive battery powered BC radio which usually has a built in loopstick or ferrite rod antenna inside. You can probably pick up one from a thrift store for less than $10 or even a new one for perhaps not much more. These radios typically exhibit a very sharp null in one direction, but a very broad peak in most other directions. May help you find the RFI. Go outside and see if you get a good null on the RFI. It may be 2 or possibly many more S units deep If this is the case, you could build a small TERMINATED loop, perhaps like the one written up in QST within about the last few years. It was about 2 feet by 3 feet, had a termination resistor on one end of the loop and was fed from the other end. Pay attention to how the author matched it. You may get lucky and just run your coax from your yard back to the shack, but also may need a preamp at the antenna feed point. Probably you will need a good common mode choke on the coax perhaps near the antenna, another near the house, and finally one just before the radio. If the loop works without a preamp out side away from your house, great, but if not, power the preamp with a battery. If that still works bring power out from your house, but you will need to decouple the power with common mode chokes like the coax. Something like perhaps 15 turns on an FT 240-31 ferrite core would be ok, but other designs may be better for the BCB. My remote loops use something like around 11 turns on this core, and are very effective in preventing feedline pickup of RFI. They work great on all of the BCB and 160 through at least 40 meters. My loops work great on the whole BCB without a preamp since signals are usually strong, but better with a 20 dB preamp at the antenna if signals are week. Frequently I listen to BCB stations over 2000 miles distant with my loops, but my loops are larger, so possibly your 2 or 3 foot loop will require 20 or more dB of amplification. Personally, I use Cat 5e ethernet cable to feed both dc and signals and I have a balanced 110 ohm system. The DC suppy in the shack and the signals are all on the same single cable. I designed and wound my own matching transformers. Having a balanced feed all the way from the antenna to the shack may have some advantages. Plenty of good preamps avaible, either to buy or build your own IF THEY ARE NECESSARY. a deluxe system could even use a rotary terminated loop which would be great on the BCB and the HF ham bands.
A terminated loop like mine, and the QST RFI sniffer, will be quite broadband, possibly from below the BCB up to at least 20 MHz. Much good info since 160 meter operators have the same problems as BCB DXers.
Rick KL7CW
