Topband: Best Outlet sttrip

[Tom W8JI]

> 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.

It's actually a related issue, because it is common mode and bad port 
design.

I'm perplexed by recent trends to impose unrealistic requirements in 
consumer installations to work around poor port designs. Wide ranges of 
real-world installations are just not going to be able to have zero 
potential between chassis on isolated pieces of gear. Once a cable is out of 
a cabinet, the designer has to face the fact he has little control over 
common mode and surges. The port should be designed with reasonable 
immunity, rather than telling the rest of the outside world they need to be 
perfect in every way.

>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.

I agree with you 100%, Jim. I have MOV protected surge protection outlets at 
every computer and entertainment group in my house. I also have outlet 
strips like that in my shop and in my house. While I generally do not depend 
on MOV's, and do not have lightning arrestors on my feed cables, I do use 
outlet strips like that for two reasons:

1.) To protect a device that is particularly sensitive to power line surges

2.) As a common point for RF grounding and bypassing in a hub, usually with 
a piece of gear that generates or receives RFI from a poorly filtered power 
line connection

I think advising against MOV protected strips because some remote piece of 
gear might have a bad port design is not a good first choice.

The trend to correct for bad port designs by demanding the rest of the world 
have zero or nearly zero cabinet ground potential differences is 
unrealistic, and will only lead to progressively worse port designs as blame 
for any damage or operating maladies is shifted to use of reasonable 
installations.

There is a radio, for example, that has a ~0.7 volt logic threshold on a QSK 
transmit activation line. The manufacturer blames external interfaces and 
wiring when the radio malfunctions, but they are the ones who used an 
unreasonable 0.7 volt threshold in their design. This blame-shifting trend 
by people who do poor port designs is seemingly expanding. This is really 
why we are having so many problems with noise or damage on ports.

73 Tom