Re: Getting a buzz, the wrong way

Posted by Mike WA8BXN on Jan 08, 2011; 3:19am
URL: http://elecraft.85.s1.nabble.com/Getting-a-buzz-the-wrong-way-tp5901644p5901659.html

Tony,
 
I think its closer to 0% of the 60 Hz stuff will really make it into a good
receiver. Take a look with your scope at what gets past the first tuned
circuit of a receiver. Noise that you hear in a receiver is really at the
frequency you are tuned to, not a harmonic of 60 Hz. Some simple receiver
circuits can hum on signals but I think the effect is for a reason different
from picking up 60 Hz on the antenna.
 
 
73 - Mike WA8BXN
-------Original Message-------
 
From: Tony Estep
Date: 1/7/2011 10:05:06 PM
To: Elecraft
Subject: [Elecraft] Getting a buzz, the wrong way
 
I dragged my scope up to the shack to measure the voltage on antenna A when
I transmit on antenna B. I got the answer to that, but I also got a look at
A sorry phenomenon that probably affects a lot of others on this reflector.
 
If you have a wire antenna, disconnect it, put 50 ohms across the coax and
Hook it to your scope. If you are like me, you will see a hideous waveform
Of mixed harmonics of 60 Hz, along with a witch's brew of various components

Of hash and buzz. And not a small amount, either; I have more than 200 mV
RMS of that crap coming in on one of my antennas. It's like a vlf 1mW qrpp
Transmitter feeding directly into your receiver, while you're trying to
Listen to HF. And I live in a fairly sparse suburban neighborhood -- it has
To be worse as you move in closer to town. Of course, 99.9% of it doesn't
Make it through the bandpass filters in the rx, but there are just enough of

Those evil buzzy harmonics that do get in, and end up right on top of the
Weak signals we're trying to hear. I guess we all know that the noise is
There, but seeing it on your scope with such a pronounced amplitude is a sad

Experience.
 
73,
Tony KT0NY
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