I used to work for a military radio manufacturer and I saw first hand what vibration can do to frustrate the best intentions of design engineers (hint: it gave new meaning to the term "flying capacitor")! The K2 wasn't designed to withstand serious (military test-like) vibration. A few years back Wayne posted his recommendation to NOT to glue the toroids. I had built a few K2s by then and, thinking that I was improving the design, I hot-glued the toroids. I felt a level of guilt after reading Wayne's post but the hot-glued radios performed very well so no harm, no foul, I guessed. Besides, I had seen hot glue and bees wax used in all manner of commercial AM/FM radios to secure air-wound coils and wires.
The assembled toroids have low mass so damage from vibration is unlikely unless the rig is shot from a cannon or dropped from an unreasonable height. The K2s seem to survive the real world just fine based on the anecdotal comments offered on the Reflector so there is no need to "make it better" with hot glue. What has been posted recently in the Reflector on the subject seems to be centered on the difficulty of repairing the radios with hot-glued toroids. That is adequate reason alone to avoid using hot glue. (Are you really certain that you counted those turns correctly?) Applying hot glue in tiny amounts takes a level of creativity and skill not found with every kit builder. It doesn't serve Elecraft to recommend the use of extraordinary skills when they mean to demonstrate the fun and ease of building their kits. And there is electronic justification for not gluing toroids. Anything used to adhere the wound toroid to the PCB will likely have a dielectric constant different than that of air, which is the environmental condition in which the toroids were designed to operate. Those tiny inter-winding capacitances and their dissipation factors are affected by whatever surrounds the turns. The result is not exactly what the designers intended, though it may work nonetheless, tolerances being what they are. But why risk it? Rick KC0OV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
