[TowerTalk] Effects of Oxidation on Copper Antenna Wire

Steve Maki lists at oakcom.org
Tue Apr 24 17:45:52 EDT 2018

On 04/24/18 17:03 PM, Grant Saviers wrote:

> Andrew published some research that shows the PIM (passive intermod) 
> differences between braid and solid copper shields for coax.  I couldn't 
> find that pdf on the web, but it shows how braid generates more IM 
> products than solid Cu tubing.  I think its pretty insignificant for HF 
> ham radio.

Mostly true. For HF it's insignificant. For UHF and above it's 
insignificant for receive only or simplex. For UHF duplex (repeaters) I 
*think* it can be significant. LMR style cables have very poor PIM 
performance (like 25 dB worse or more) compared to Heliax/hardline style 
cables. I've measured PIM on LMR400 & LMR600 at 700 MHz and above, and 
it's horrendous by cell service LTE standards (which is -143 dBc using 
two 20 watt carriers).

Kinda surprising given that the *RF* foil shield is solid for all (or 
most) practical purposes.

-Steve K8LX

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