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Re: [TowerTalk] Effects of Oxidation on Copper Antenna Wire

To: towertalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] Effects of Oxidation on Copper Antenna Wire
From: Steve Maki <lists@oakcom.org>
Date: Tue, 24 Apr 2018 17:45:52 -0400
List-post: <mailto:towertalk@contesting.com>
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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