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[RFI] impedance mismatching in coax

To: rfi@contesting.com
Subject: [RFI] impedance mismatching in coax
From: Aaron Kreider <aaron@campusactivism.org>
Date: Wed, 28 Dec 2016 13:02:32 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Over Christmas I built a temporary/quick beverage antenna in a rural area, but it had a very high noise level. I had chokes on everything which helped, but as I hadn't a lot of planning - I ended up connecting two pieces of coax together with 50 ohm and 75 ohm reactance.

Would this impedance mismatch cause any problems with the Type 43 toroids?

If not, then I'm guessing I wasn't far enough away from the house (50-75 feet away), and/or the house had a very dirty AC power. The location was perhaps 20-30 acres - so I could get further away from the house and electrical lines.

The noise level at 500 khz was around 20-30 uV and below 100 khz there were spikes up to S9 + 40 db. It was pretty clean above 3-4 mhz (so this also points to the toroids working better at higher frequencies).

Aaron

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