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Re: Topband: Low band noise

To: "topband@contesting.com" <topband@contesting.com>
Subject: Re: Topband: Low band noise
From: David Aslin <david@aslinvc.com>
Date: Wed, 12 Feb 2014 21:50:10 +0000
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Bruce,
I live in 'wind farm central' (Devon, southwest UK) and have direct experience 
of wind generator EMI.
The small generators (up to 50kW) almost universally use an induction principle 
and are RF silent.  But the type that sit on 160-300ft towers and generate in 
the 1-5MW range are effectively SMPS on a stick.  The generator+inverter that 
converts the mechanical rotation to a steady state voltage is just like a 
switch-mode power supply and is most often located at the hub - perfect for 
radiating anything from the electronics!  That said the EMI level is relatively 
low, but detectable as a slight noise floor lift with a cyclic component out to 
2-3 miles from a big wind farm array (K3 + 9ft whip antenna on SUV, 1.8-30MHz 
sweep at 1-5 mile radius from the center of the wind array).  Unlike domestic 
SMPS they don't seem to generate major trash, so maybe the European EMI 
standard is set at a good level and actually achieved (amazing!).  But a top 
band enthusiast won't want a wind farm closer than a couple of miles if you can 
avoid it.
Just my 2c/2pence
73
David G3WGN  M6O  WJ6O

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