Here are some simple RFI prevention techniques that I have learned here at home with the rigs and computer, so thought I would pass them along in hopes they might help someone.
I live in an old house with a 2 wire AC distribution system (Hot and Neuteral). My 40M Inv Vee is only 10 ft away and broadside to the back of the house. My 40M CW was raspy, as RF was getting into the AC distribution system. I was using power strips with EMI and Surge Protection circuits, but they were effectively disabled. Here is why: The EMI circuit consisted of two small inductors, one in series with the hot and neuteral inside the power bar, and there were two .001 uF capacitors from the hot and the neuteral lines to ground inside the power bar, but No Ground. My station ground was a 10 ft copper clad ground rod just outside the window. I used some # 14 stranded wire and soldered banana plugs to the end. I used this to connect my station ground to the ground side of an unused receptacle on all my power bars. Now my 40M CW signal is clean as a whistle. I share a computer with the family which is in the den just across the hall from the shack. The computer and printer are plugged into a power bar also, but no ground. Everytime I keyed the rig on 40M, I rattled the printer. Running a ground wire to the power bar for the computer was out, so I did a little math. The Xc of a .01 uF capacitor at 7 MHz was 2.27 Ohms. At 60 Hz, the Xc of the capacitor is 265 KOhms. I connected the .01 uF capacitor (a 2 KV silver mica) across the hot and neuteral side of the power bar by soldering the leads to an old 2 prong AC plug and used shrink tubing for insulation. I plugged the .01 uF in the power bar, and now no more printer rattle on 40M. I had previosly tried several different torroids on the printer AC line, but no go. If you have a 2 wire AC distribution system in your home and are plagued with RFI to your computer or rigs, connect your station RF ground (ground rod system) to your power strips using a banana plug, plugged in to the ground connector of an unused receptacle. If this is not feasible (as in the case of my computer) a .01 uF capacitor across the hot and neuteral should be good for RFI at 30M and lower frequencies. For RFI at 20M and above, use a .001 uF capacitor to get the Xc down low. For 120Vrms, the peak voltage on the positive and negative alternation is 170 Volts, so use a capacitor with a voltage rating of at least about twice this (500 VDC should be good). The surge protection circuit in most power strips consists of two MOV's, one from the hot side to ground, and another from the neuteral side to ground. With no ground connection, however, they are doing no good. So, in my situation with the computer, I soldered the two leads of an MOV to a two prong AC plug, and plugged it in the power strip so that it is across the hot and neuteral. For a two wire AC distribution system, the neuteral is connected to ground (by a ground rod) at the service entrance, but after many feet of run, the neuteral line acts like a good antenna. 73/GL, Larry K4WLS Subscribe/unsubscribe, feedback, FAQ, problems http://njdxa.org/dx-chat To post a message, DX related items only, [EMAIL PROTECTED] This is the DX-CHAT reflector sponsored by the NJDXA http://njdxa.org
