[TowerTalk] Coax Losses on 160 and 75?

[Jim Brown]

Nothing "however" about it, Roger. Of course it's all skin effect, and 
copper-coated or clad onto steel has much greater loss than solid or 
stranded copper at these frequencies.

BUT - there's a big difference between copper-clad Aluminum and 
copper-clad steel. RF resistance of copper-clad Al is NOT significantly 
different from solid/stranded copper at any frequencies where we are 
likely to use it.

Yes, at HF the most reliable comparative of cable loss below UHF is the 
total resistance of their conductors at the frequency of interest. For 
solid copper conductors, DC resistance can be compared, because 
resistance at RF is a multiple of the DC resistance. For copper-clad Al, 
the resistance of a solid copper conductor representative of the DC 
resistance of the center. So -- there's nothing wrong with using LMR400 
and other cables with Cu-clad Al center on the lower HF bands, except 
that they are NO BETTER than a lower cost coax that provides the same RF 
resistance. That's why my table in k9yc.com/Coax-Stubs.pdf lists coax 
cables in order of their DC resistance, and why the last column in the 
table is cost.

73, Jim K9YC

73, Jim K9YC

On Thu,8/4/2016 10:29 PM, Roger (K8RI) on TT wrote:
> However on the lower frequencies, such as 160 and 75 skin depth plays 
> an important roll.  I believe the flash plating as is found on steel 
> core, center conductors is insufficient to keep I^2*R losses down.
>
> I'd avoid those cables with small, solid center conductors.
> That brings to mind the question of LMR400 which has a "relatively" 
> large copper plated, solid Aluminum center conductor versus cables 
> like BuryFlex with stranded, copper center conductors.  LMR-600 is 
> larger yet.
>
> They give loss ratings per 100 feet, but what about 160 and 75 meters?
>
> 73
>
> Roger (K8RI)
>
>
> On 8/4/2016 Thursday 2:37 PM, Jim Brown wrote:
>> On Thu,8/4/2016 11:23 AM, Mike Fahmie via TowerTalk wrote:
>>>   power loss (I^R is usually negligible).
>>
>> Mike,
>>
>> Exactly the opposite is true -- below at least 300 MHz, loss in 
>> transmission lines is ALL I squared R. Dielectric loss doesn't begin 
>> to be significant until you're well into the UHF region.
>>
>> 73, Jim K9YC
>>
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