In article <37cdda81.100732@news1.c2i.net>,

axeleng@online.no (Axel Eng) wrote:

> I trired to set up my TX (a Veronica 1W mono VFO) today, but I got

> some trouble. As soon as I switch on the TX, my CD player (a Phillips

> portable) refuses to operate. It works fine if I just uses the TX with

> a dummy, or if I operates the TX with an antenna but not the CD player

> connected. It's when I connect them *both* it all goes wrong. I tried

> to make filters like these on the power and audio lead, but it still

> wouldn't work.

>

> o--|--15uH--|--o o--|--15uH--|--o

> 1nF 1nF and 1nF 1nF

> ---|--15uH--|--- ---|--------|---

>

> The inductors are the ready-made "looks-like-resistors"-type. I even

> tried to place the discman in a shielded metal box, with no noticeable

> effect.

> Would it to use another type of inductors? Should I go for the

> "balanced" or "unbalanced" approach? Is this a common problem with

> cheap CD players?

> ______________________________________________________________________

> Axel axeleng@online.no

>

To Axel,

I have had your problem as well as with other pieces of equipment. It has taken me years to figure out exactly what was going on . One night it clicked!!! RF(your fm signal) is getting into your equipment via the wires. Sometimes the board can directly pick up the rf. It can be cured. Equipment in metal cabinets is easier to filter since the width of the cabinet has low resistance to rf. Bear with me! A wire of several inches at fm frequencies has a resistance of @50 ohms. All wires, 120ac, audio and all grounds too! must be rf bypassed to ground, the metal cabinet. Don't try grounding it to a metal pipe etc it won't work. Don't allow anymore than about 2" of wire to enter the cabinet without bypassing it with a .001-.01 uf capacitor. One end of the cap simply goes to the wire coming into the unit and the other end to ground, the metal cabinet. If the unit is in a plastic case it can still be rf-proofed but with more work. One must then add a metal sheet such as copper than can then be used as the rf ground reference kind of like a metal cabinet. Make sure that the metal sheet does not short out the circuitry!. Using a multimeter(or visual be sure!) find out the other dc grounds in the circuit. 5 or so connections should do it. Solder these to the metal sheet via the caps. Bypass the all the leads going into and out of the unit via the caps, just like in a metal cabinet.