[TowerTalk] Wire for prop pitch?

[Jim Lux]

On 12/6/12 1:08 PM, Frank wrote:
> Rick Karlquist wrote:

>>
>> No.  I originally had the shack 1000 feet from the low
>> band vertical.  It's nice to have 0.1 dB loss over 1000 feet
>> of line on 160 meters.  They don't really sell aluminum much
>> smaller than #4.  The light weight is great for suspending
>> it.  I have been extremely pleased with this line.
>>
> Sounds great.
>
> You can buy 250 foot rolls of #17 aluminum electric fence wire.  Costs
> about $7 a roll.  Good for wire antennas.  Probably not all that good
> for a 1000 foot run of lader line.
>


#17 will have somwhere between 4-16 times the resistance of #4.  Every 6 
gauges is half the diameter, so if skin depth is <<diameter it would be 
4 times the resistance.  If skin depth is a good fraction of diameter it 
will go more as the cross sectional area, so more like 16 times.

Skin depth at 2 MHz in aluminum is 0.0023 inch or 58 microns.

AWG 4 is 0.204 inches
AWG 17 is 0.045 inches.. (20 skin depths)

so I'd go more for the 4 times the resistance....

So loss would be around 0.4 dB/1000 ft... (based on Rick's number)

Given the inexpensive nature of that wire, you could make quadroline (or 
just double/triple/quadruple it up, like "bundled conductors" for HV 
transmission lines) and get down to the 0.1 dB range at the cost of 
(signficant) additional complexity.