Re: Getting a buzz, the wrong way

Posted by Don Wilhelm-4 on Jan 08, 2011; 3:34am
URL: http://elecraft.85.s1.nabble.com/Getting-a-buzz-the-wrong-way-tp5901644p5901668.html

  Tony,

That is the reason receivers have bandpass filters - to filter out all
that off-frequency trash.
Yes, there is a lot of stuff that can be seen on any antenna.  I see
much of the same in my very sparely populated suburban/rural area - I
cannot see any neighbor's house and I am sitting in the middle of 11
acres with a 1/4 mile driveway.

If you want a better picture, put a bandpass filter for the band of
interest between the antenna and the 'scope, and you should see a much
more clear picture of what the receiver is "seeing".

73,
Don W3FPR

On 1/7/2011 10:04 PM, Tony Estep wrote:

> 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.
>

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