In my attempts to eliminate the interference, I tried a commercial AC filter, coiling the lamp cord on some ferrite material and other such approaches without success. When the lamp is plugged in, the lamp signal is present at all times, regardless of whether the lamp is on or off. At frequencies from 20 meters up, my operation is undisturbed.Ī box inside the lamp contains a circuit board through which AC line voltage is routed and which has a wire connected to the metal base of the lamp. The lamp signal is present from 40 meters down. Later I discovered a raspy, S8 signal at 1875 kHz - it was coming from the lamp, which was located three rooms away on a different AC circuit. I found that my transmitted signal would cause the lamp to operate exactly as if I had touched its metal parts. When my wife told me she had bought a three-way lamp that switched on and off at the touch of any of its metallic parts, I did not realize she had purchased a transceiver. Colin Hall, G4JPZ/W6, Marina Del Rey, CA Touch-Lamp Transceiver
Touch lamps series#
The final answer turned out to be both the RF choke and a 1.8k ohm resistor in series with the signal-input lead to the touch-control circuit. The choke alone may be enough to clear up the problem in some cases. On 80 m, the interfering signal was considerably attenuated by the choke, but the lamp still switched. When the resistor was replaced with an RF choke (100 uH, 139 mA), the problem abated on all bands except for 80 m. A 1-k ohm resistor was not a complete cure in my case.Ī 3.3k ohm resistor in series with the signal input on the lamp helped on all bands except 80m (an additional 1.8k ohm prevented the lamp from functioning). The problem occurred during operation on the 80- through 15-m bands, but 10-m operation had no effect. I had the same problems as W7OTC with a touch-controlled lamp switched on and off by my transmissions (100 W to a roof-mounted vertical, with two radials per band). I suppose the required resistor value would vary with the RF-field intensity and frequency. An AC-line filter at the lamp did not eliminate the problem.)Ī 1k ohm resistor (in series with the signal input lead to the encapsulated circuit that operates the lamp) cured the problem for me. (I use a ground-mounted vertical antenna for 80, 40 and 15 meters, and the lamp is approximately 150 feet from the antenna. In my case, 40-meter operation gave the most trouble, with 75-meter operation a close second. I have found a simple cure for those touch-controlled lamps that turn themselves on and off during nearby radio transmissions. Note: Ed Hare, W1RF suggests trying a ferrite core if it can be used. Ideally, one would use a small RF choke instead of the large PI wound one I found in my junk box. I found that the wire between and RF choke and the input to the IC chip needs to be as short as possible. Just spent two hours fixing interference to a touch lamp-it was fine at 75 watts, but 80 to 100 watts on 80M would occasionally turn on the lamp.These modifications must only be performed by qualified service personnel! For a number of different reasons (you may be blamed if anything EVER goes wrong with the lamp or house wiring) you do not want to perform this modification on equipment that is not your own. When the latter happens, the circuitry inside the lamp reacts the same way that it would when the plate is touched - the lamp changes states from "off" to "on".Īlthough cases of moderate interference can sometimes be cured by using a "brute-force" type AC-line filter and/or a common-mode choke, most cases will require internal modification to the lamp. When the former happens, it can interfere with other services. Unfortunately, this plate also acts as an antenna, radiating some of the energy of the oscillator, or picking up nearby radio signals. This oscillator is hooked up to a touch plate that changes the frequency of the oscillator when a hand is placed near the plate.
Touch lamps free#
They have a free running oscillator that is very broad and rich in harmonic energy. RF Touch lamps are RF-operated devices that often cause, or are susceptible to, EMI problems.
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