Topband: Skin effect on RG6U at top band

jeremy maris jeremy at
Mon Jan 31 02:19:15 PST 2011

We've used 1 km of coax to feed a remote Beverage (3 wavelength, 60   
degrees, for VK and far east). 750m of the coax is RG6U, with copper  
braid. The results were poor, despite a 10dB head amplifier at the end  
of the Beverage, so we measured the coax attenuation on part of the  
run by putting 25W into the coax and measuring power into a 50 ohm  
power meter. I appreciate this isn't 75 ohm like the coax but extra  
losses from 1.5:1 SWR should be low.

The measured loss in the first 250m segment was ~ 6dB and about ~9dB  
in the second segment, 15dB total over 500m. This is way higher than  
published figures (eg at 
   which suggest about 3dB per 250m.

I'm thinking that the copper plating on the RG6/U inner conductor is  
too thin. N6LF gives the skin depth at 2MHz as 40uM (Conductors for HF  
Antennas, Rudy Severns, QEX November/December 2000). Does anyone have  
any typical figures for the plating thickness of RG6/U or have  
evidence that attenuation figures at 2MHz are much higher than expected?


Jeremy G3XDK

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