Thank you Don, that was clear and concise. I'm not an expert on radios or RF like some on this list. I just try to go with what works. I was a firefighter in my previous life. We adapt and overcome. I make things work, then I make them 'pretty'. (Pretty in this case means safer, more reliable and sometimes putting a 'bow on it.) Simple is good; it's often easier and elegant too.
We're basically saying the same thing but coming in from different points. Chassis to chassis bonding is wanted, whenever possible. It's not always possible. My old shack laptop has a two wire (ungrounded) mid line wart power connection and bonding the laptop chassis to the station is an exercise in futility (no grounding point on the laptop; the third wire if any, grounds the power supply not the laptop). A desktop chassis should be bonded to the station (yes, as required by code but one size doesn't always fit). And yes, audio 'ground' (return) is rarely chassis ground these days. We agree again though I may have phrased it poorly or used the wrong terms (floating ground) or examples, it was something I was trying to point out. But that is a very common mistake to make too. The two 'grounds' aren't the same and connecting one to the other can cause huge problems, balanced or not. Don't assume that audio ground is chassis ground, it's not that way anymore. Considering the floating pin one problem, that makes many 'ground' wires, (audio return, power, chassis and 'pin 1') each with a different meaning. It'd be easy to presume they're all the same, but they aren't. It makes noise reduction even more difficult. To the original problem of serial data noise: With so much electronics generated RF crud floating around a shack from numerous sources, it's often difficult to find the cause(s) or cure(s) for that noise. Better cables, ferrites, common bonding and similar help but it's a long process to have a quiet shack. A product may meet FCC spec, but be ham lousy with noise. What is working for noise reduction for me (K3, bonded to P3 bonded to KPA500) was moving the antenna farther from the shack and using common mode chokes to keep as much crud off of the feed as I could (reduced by more than 75%). Next was finding quieter laptop power supplies or running off of batteries. I'm still chipping away at the rest (mostly Ethernet CAT 5 wires radiating, switching to WiFi). It has limited success with noise sources not on my property, but its better. And lastly, (then I'll go back to lurking since I'm no expert) when bonding a station to ground (or at least to each other per NEC for those of us in upper stories, not close to dirt or plumbing in the shack), while solid wire meets the NEC code, we're also talking about RF. So braid is best, followed by multi-strand wire, and if nothing else at least a solid #10 wire. Guess what; if you bond for high RF environments, it works to help keep RF in its place and meets the code too (you've exceeded the code with wide braid). Hopefully I was more clear this time. I get the code, concepts and means though I may not state it clearly. Comments, if any, can be made off group, I'm sure the others are tired of this thread. 73, Rick WA6NHC -----Original Message----- From: Don Wilhelm I will only comment on the part reproduced below - audio return is NOT audio ground. In the case of the Motorola amp cited, I suspect the audio amp output is a bridged amplifier, and for those, neither speaker lead should be grounded (it shorts half of the audio amplifier. BUT, Jim Brown was talking about unbalanced audio inputs, not speaker outputs. In the ham world and the world of consumer audio, most audio inputs are unbalanced, with one conductor (the shield) connected to "ground". That ground used to be the equipment enclosure, but more recent implementations circumvent that and put the connection to the shield onto the PC board rather than the enclosure - and often the enclosure is plastic which creates yet another set of potential problems. We used to connect our audio (and RF) jacks directly to the enclosure and then inside the enclosure, we would route that connection to the circuit contained in that enclosure - no "pin 1" problems because the shield of connected cables were connected first to the outside of the enclosure.. In today's implementations, pin 1 problems abound because jacks for any and every purpose are designed to connect to the PC board and may or may not have any connection to the equipment enclosure. That allows noise and other undesired signals to be introduced onto the device circuit board without being first stripped off by the (grounded) metallic enclosure for the device in question. We have come a long way in convenience for manufacturers, but several problems have occurred along the way, and they are not easy to correct. 73, Don W3FPR ______________________________________________________________ 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
