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> On Oct 8, 2013, at 19:06, Jim Brown <j...@audiosystemsgroup.com> wrote: > >> On 10/8/2013 2:42 PM, Tom W8JI wrote: >> the system should not be that sensitive to common mode issues on ports. > > Right. But first, we're not talking about common mode, we're talking about > chassis-to-chassis noise coupling into unbalanced interconnects, like > computers feeding radios, with or without various interfaces. And yes, > unbalanced interfaces are a lousy way to do it, but I don't know of a single > ham rig that has balanced interconnects for audio or accessories. > > So unless a ham wants to rebuild every rig and all accessory gear with > balanced interfaces, the simple power and bonding concepts I've outlined are > the lowest cost, most reliable, and a very robust solution. Yes, we could > add transformers, but transformers cost more, and shielded transformers cost > a LOT more. > > As Vice Chair of the AES Standards Committee Working Group on EMC, I was a > principal author of all AES Standards on the topic. It took a while to reach > a consensus, because some purists were unwilling to write Standards to work > with real world equipment. The path we took, and that the cool heads worked > very hard to achieve, was to write Standards defining the RIGHT ways to do > it, both inside and outside of equipment, but to define the right way to work > with vintage gear that was badly designed/built. Our first EMC Standard, > AES48, attacked the Pin One Problem, which was the most critical root cause, > both at baseband and at RF. We then wrote the protocols for balanced > interconnects, including the advice that when the cable shield needed to be > interrupted to prevent shield current, the interruption should always be at > the receiving end. This is counter-intuitive, but Bill Whitlock showed that > it is the only right way. > > The point of this digression is that there's no way in hell that hams are > going to replace our gear with stuff having balanced I/O for audio and > control, simply because it doesn't exist, and to assume that such gear will > exist in the foreseeable future is wildly unrealistic. Heck -- we can't every > get manufacturers to build gear without Pin One Problems. > > 73, Jim K9YC > _________________ > Topband Reflector _________________ Topband Reflector
