[Boatanchors] [Milsurplus] Question on distorting coax shape

[Jim Wilhite]

The best way to visualize the problem is to terminate the coax in its native 
impedance and use a TDR to look at it.  You will see little aberrations 
where the tie wraps create the distortion.    No aberrations, no trouble 
with the installation.  Same method can be used on any cable that your TDR 
can match.

Or you can use an analyzer like a MFJ 259B and measure the coax into a 
terminated load before it is distorted then make your measurement after 
installation.  You won't see much difference but it will be there and the 
instrument should give you a bit different readings.  Since the installation 
of tie wraps will vary the size due to the amount of pressure on the coax, 
there really isn't any chart or other printed material that will tell you 
anything.  Each installation is different and must be measured.

Jim
W5JO

----- Original Message ----- 



>>
>> I'm looking for some test data, preferably a chart or two, which  might 
>> show how the technical specifications of coax (impedance,  frequency 
>> efficiency, et al) are affected when the coax shape is  deformed, e.g. as 
>> the coax cross sectional shape is distorted or  changed.
>> For example, imagine a worker dropping coax down from a tower and,  using 
>> a tie wrap gun, over tightens the tie wrap so that the coax is  squeezed 
>> out of shape.  Or, imagine the coax is flattened at a point  because of 
>> some other event.
>> QSO via private or list email is okay.
>> Thanks,
>> John W5JV