[Amps] crossmodulation in PA ? Thanks for all good  advice

[k7fm]

While I only have sufficient knbowledge on the subject to ask questions, 
logic seems to tell us that "bonding" could be counterproductive.  If the 
purpose of bonding is to provide a good ground for lightning, that would be 
a meaningless act, since lightning is indifferent to less than perfect 
joints.  But, if the purpose of the bonding is to provide a zero ohm 
connection, then the only thing that would prevent that is corrosion - which 
could occur by placing the copper bonding strap at the connection.  What 
would start out as a good connection could be made less than perfect by 
corrosion created by the addition of the unnecessary copper bonding strap.

As I understand it, even though the joint has substantial pressure, the 
process of fretting can create corrosion on the surface of the joined 
surfaces - which would then act as a less than perfect conductor despite the 
pressure.  If that occurred, then we no longer have a zero resistance 
connection.  That process would not be likely to happen without the copper 
bonding straps.

Colin

"My point was that with rare exception bonding a tower joint
is a waste of time. There are tens or hundreds of thousands
of sheer pressure on the bolts in a typical cross-bolted
tower joint.

While I agree dissimilar metals should be avoided, placing
them across a tower joint is meaningless. How good would the
diode be if it is shorted end-to-end with what we could
consider a zero ohm connection? The same is true for
lightning. Lightning doesn't care a bit if the joints are
bridged or not.

There are some rumors that bonding the joints helps things,
but they probably came from looking at early broadcast
towers with pad joints. In many cases those joints would
have brazed connections jumpering the joint, but in later
installations that was practice abandoned after it was found
unnecessary. This probably spawned the idea Hams should
jumper joints. Anyone who thinks a couple stainless steel
clamps with a few dozen pounds per square inch clamping
force will significantly change the connectivity in a joint
bearing tens of thousands of pounds force probably hasn't
thought about the system.

It really is meaningless. The possible exception is in
systems ready to fall down anyway."