[R-390] Re: Spurious Resonances

[Tony Casorso]

How lucky can I get? I posted a set of images this morning that had a 
"spurious response" in it. It turns out it was cause by the settings on my 
sweeper (DC Offset was cranked over to one side for some reason). The mailer 
wus unable to post it for some reason so I get to try again with good 
pictures.

Here are links to couple of pictures. I am sweeping the preselector in my 
R-390a. The left edge of the sweep is 1.5MHz. The right edge is 4.5MHz. The 
center is approximately 3MHz. The receiver is tuned to 3.00MHz and the power 
is off. I am measuring the response at the grid of the RF stage.

The broader response picture is with the 25 Ohm (gen with 50 Ohm 
rterminator) sweep gen directly connected to the balanced input. The sharper 
response is with a 2.2K resistor in series with one side of the balanced 
input.

It looks like I was right that low source impedance broadens the frontend 
response.

http://i25.photobucket.com/albums/c90/tonysradios/IMG_0825.jpg

http://i25.photobucket.com/albums/c90/tonysradios/IMG_0826.jpg

Tony

----- Original Message ----- 
From: "Tony Casorso" <canthony15 at msn.com>
To: <r-390 at mailman.qth.net>
Sent: Saturday, October 27, 2007 8:09 AM
Subject: [R-390] Re: Spurious Resonances


I should havethought about it for a few more minutes.

Maybe the sweeper has a strong second harmonic that is visible near 1.5.

Tony
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