View Full Version : Alternator whine in 3.4's? whine filter

05-05-2009, 11:01 PM
I couldn't help but notice Squishy's subtle net noticable whine in his radio while on a run on Saturday. I think someone else on the run commented on it as well. So tonight I find myself searching about Ham radio on Yotatech (:doh:) and run into this general Ham thread http://www.yotatech.com/f97/two-meter-ham-155889/index8.html I then followed to a guy's build up thread which then leads me to this build thread: http://home.comcast.net/~jbperkins/alternator_whine_filter/

That whine filter seems pretty easy to make.. anyone have one of these? Or anyone care to explain the logic behind it?

05-06-2009, 07:03 AM
Do you need it? I've never noticed noise when you TX.

What's to say about theory, it's just a low pass filter that allows only extremely low frequencies to pass and attentuates everything above almost 0 Hz. The link or shackle has to be steel and it along the wraps of wire around it are the inductor. The cap is obviously to ground. See the attached picture and see how the circuit and response look similar?

05-06-2009, 05:13 PM
I don't know if I need it or not, as I'm yet to hook up a radio to the 3.4 But if I do get some QRM I know what to do..