[RFI] impedance mismatching in coax

Aaron Kreider aaron at campusactivism.org
Wed Dec 28 13:02:32 EST 2016

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).



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