Jim, Looks like the addition of an inline audio transformer between the wireless transmitter's miniplug and the KX3 (or any device powered by the vehicle) would resolve the potential problem which you have addressed.
73, Rich - K1HTV = = = -----Original Message----- From: Jim Brown [mailto:[email protected]] Sent: Monday, May 30, 2011 13:54 PM To: [email protected] Subject: Re: [Elecraft] KX3 Audio output On 5/30/2011 8:50 AM, Rich - K1HTV wrote: > Do a Google search for "Coby CA-745", an FM wireless transmitter that > plugs into a cigarette lighter. You can find them at Amazon, Wal-Mart > and Best Buy for between $16 and $19. The input is via a stereo > miniplug at the end of an attached cable. There is potential for significant difficulty using a device powered from one point in the automotive DC power with another device powered from a DIFFERENT point in the same automotive power system. The reason is simple -- there can be a lot of DC resistance between different parts of the system, and a lot of noise, both audio and RF, between those points. The audio interconnect is unbalanced, so any noise that is present is likely be added to the audio feed. Consider the use for which these modulators were designed -- a BATTERY-powered personal music player, like an iPod or CD player. With these devices, there is only ONE connection to the automotive power system, the lighter plug. Ditto with a wired AUX plug-in for those players. BTW -- this issue requires VERY CAREFUL attention to the design of DC busing and both audio and RF interfacing between the KX3 and the power amp if those units are to be physically separated (for example, the power amp in the trunk or under a seat). 73, Jim Brown K9YC ______________________________________________________________ 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
