This discussion is beginning to confuse me. I thought the issue being
debated was the optimal way to provide surge protection to safeguard
our radios from unexpected line transients, and not how to reduce hum
in unbalanced audio circuits caused by ground loops or ground return
currents. I believe the conventional wisdom is that both whole-house
surge protectors and local surge protectors in combination provide the
most effective safeguard. I'm afraid I don't understand how a surge
protector that clips an, e.g., 1KV spike on a 120 VAC line can end up
doing more damage than no protection all. I understand that the
clipped current pulse returns through the ground line and will cause a
voltage spike on the ground, and I also understand that other
interconnected equipment connected to different grounds may
potentially see part of the spike, but on balance that seems to me to
be a less dire situation than having no protection at all.
73,
Jim W8ZR
Sent from my iPad
> 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
_________________
Topband Reflector
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