[TowerTalk] Antenna interaction tests

[K4SAV]

I am getting ready to mount a 4 element SteppIR at 55 ft, and an XM240 
on the same mast only 5 feet above the SteppIR. I am concerned about 
degrading the SteppIR.  I don't think there will be a problem degrading 
the 40M antenna because I can always retract the SteppIR elements.

Can any of you suggest some good tests to perform to see if the SteppIR 
is being effected?  Tests which don't require removal and replacing 
antennas on the tower would be most useful.  Is 15 meters likely to be 
the biggest trouble frequency?

I am locked-in to a maximum of 5 feet seperation using the mast I have.  
Ordered an HDX555 tower and mast from Texas Towers and ended up with an 
M15 mast from US Towers.  I called them up and asked for the mast 
strength rating and was told "they range from about 35 KSI to 55 KSI". I 
was amazed.  That's about the same range as common water pipe (as I am 
told by people who think they know, even though water pipe doesn't have 
a rating.) Anyway, with 70mph wind ratings around here, I think I can 
get only about 5 ft seperation and have any safety margin.

Or do you think there is no chance and I should get another mast?  
Turning the antennas 90 degrees may not be a solution, because the XM240 
may then be effected by the SteppIR boom.

Jerry