[Elecraft] Co-ax for the K2

[Doug Person]

Don and All,

I agree that many of the RG-59 and RG-6 coax available will work just 
fine.  In two cases I found RG-59 CATV-type coax purchased at a big box 
store that showed real signs of heat-stress after a few months of 
operation at 100+ watts.

My observation is that quality and suitability of typical RG-59 
CATV-type coax varies widely.  Some, certainly not *all*, may not be 
suitable for amateur transmission service.  And I'm quite sure that when 
the stuff sold in poly bags and off the racks in the mass-merchandisers 
was manufactured, the materials selected was *not* based on its ability 
to handle 100 watts or more of rf.

Doug -- K0DXV

I
Don Wilhelm wrote:
> Doug,
>
> I beg to differ.  There are physical properties that give rise to the 
> characteristic impedance which are related to the dielectric 
> properties and the relative conductor diameters for the center 
> conductor and the braid.  These same properties will create a 
> particular RF voltage handling characteristic for the coax in question 
> (or any coax for that matter).
>
> The real difference in coax quality is the shielding percentage of the 
> outer braid.  That has nothing to do with the RF voltage handling, but 
> it certainly has a lot to do with the leakage from the coax.  In the 
> extreme, a coaxial cable could have similar leakage characteristics as 
> open wire line, but again that is not related to the RF voltage 
> handling characteristics.
>
> So look for a coax that has 90% or greater braid coverage.  There is 
> the 'quad shield' RG6 that is quite good in shielding characteristics, 
> but I do not know if it is available in white jacket material.
>
> As it has been mentioned, the white jacket is not as UV protective as 
> the black, so for use indoors, it really does not matter, but outside, 
> use the cable jacket that is rated for UV protection.
>
> 73,
> Don W3FPR
>
> Doug Person wrote:
>> There are many types of cable designated RG-6 and RG-59.  Many are 
>> not designed to handle rf voltages typical of ham transmissions.  My 
>> suggestion is to be *careful* what you select.  Good quality RG-59, 
>> the type broadly used by hams many years ago, is hard to find right 
>> now.  We're not talking about what the cable companies are using - 
>> we're talking about what you can buy at Wal-Mart or Home Depot.
>>
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