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Lex dealing with RFI and home misfortunes

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Zoidberg:
Yup, I've never found those single bead ferrite chokes to do much good to reduce household RFI to the radio, including on commercially made shielded cables supplied that way. For the various audio and patch cables I've used at times, including power supply cords, I've had better results looping at least two, preferably more, layers of cord through ferrite chokes at both ends.

Those single bead chokes probably do okay for the intended purpose with computers, camera and video gear, etc. But for reasonably clean radio reception, especially on the HF spectrum, I've found it helps to wrap two or more loops through ferrite chokes large enough to handle the cord/cable diameter.

With some shielded cables, I've had pretty good results winding the receiver end of the cable multiple winds, neatly, around a hollow core of some kind. A large empty pill bottle, stiff cardboard tube leftover from kitchen wrap, an empty plastic cylindrical container -- whatever you have handy. Wrap all the extra cable around the tube, neatly, single layer, and tape it in place. Often that reduces common mode noise. But on some HF frequencies it'll also reduce the desired signal. Experiment to find what works best in your area.

One problems I've noticed with using ferrite chokes or those hollow core type chokes is an increase in the capacitance effect. The receiver and antenna become much more sensitive to where we sit, stand or even moving our hands around. That also varies with the frequency we're tuned to. Very hit or miss approach to reducing household and local RFI.

And a directional antenna can help. I've rigged up simple homemade small loops with the null aimed at the worst neighborhood offenders, usually outdoor lights around the apartment complex and parking lot. Pretty much the same theory for the crude but effective Villard antenna, which has a sharp null for local RFI, while remaining sensitive to skywave propagation.

And I've noticed the telescoping whip on my Sony ICF-2010 has a fairly sharp null off the end. So if I aim the whip at the worst neighborhood RFI source, it'll reduce RFI enough to copy fairly weak stations. I don't get that effect with my smaller Panasonic portable.

I don't recall whether my old Magnavox D2935 has that null off the end of the whip. I need to load it with D-cell torpedoes and try it again outdoors. Great radio, other than the thin plastic layer over the buttons. That plastic layer with the button labels has deteriorated so badly it's unreadable and I'm mashing buttons by memory after owning that radio for about 30 years. Too bad because that Netherlands-made Philips/Magnavox D2935 was one of the best large portables for shortwave and MW DXing. I've had it running 24/7 for years and it's still chugging along, although the built in lamps burned out many years ago.

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