Don, a spike is not a concern with choke for RF in the range of a few millihenrys such as you created winding a few turns through the ferrite core, but a larger value choke such as is often used for suppressing generator hash and noise on a d-c line can do damage.
What happens is that whenever current flows through the choke a magnetic field is created around the windings. When the current stops, that magnetic field collapses producing a pulse in the winding. With small value chokes, such as the choke you made winding the wire through the ferrite core, the pulse is very tiny and of no concern. But that pulse can be as high as several hundred volts with larger value chokes, even working from a 13V supply. That would be plenty to do serious damage to the K3 and most other 13V electronics you may have on the circuit. Batteries are typically lousy conductors at RF. Putting a capacitor across the d-c line provides a low-impedance path for any RF on the line. That capacitor is usually built into any good rig, and the K3 is no exception. It has both a capacitor across the line and an RF choke in series with the power line where it enters the rig. 73, Ron AC7AC -----Original Message----- I am asking the question simply because I was warned by another ham to consider the possibility of a power spike on the feed to the K3 with the choke by another ham. He was not fully sure and suggested that I post the question to the folks who might really know the answer. Plus if it is good practice to put a CAP across the batteries for the way I am doing my power to help with a clean signal, clean power and better battery life I want use good practice. If I had not been prompted by the ham who suggested a CAP I would have never asked the question. Power is an SGC power cube good for 500w. Antennas are a 2 WL loop for 160m and a dipole and the shack is on the second floor. Maybe the answer to the question is so obvious that it just shows my total ignorance. Hey but I do learn slowly at times :-). Example I now work split and if you remember those posts from me on that topic I think everyone wanted to hit me in the head with a baseball bat. Like I indicated right now everything is working real good and I have no problems, but I dont want to be in the process of creating new ones. Cheers Don ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
