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. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
