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> On Oct 8, 2013, at 19:06, Jim Brown <jim@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
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Topband Reflector
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