I noticed that I have the 7180-7182 KHz VCO stability problem. Discovered that when I began loosening the screws on the bottom cover, the buzzing sound disppeared. Experimented with this for a while and found that if I remove the screw that holds the cover on the right side of the chassis viewed with the unit placed upside down on the table, front panel facing you. The problem goes away. I used a stable signal from my HP8640B sig gen and moved the frequency between 7170 to 7190 and no longer observed the instablity.
On my unit the problem appears to be caused by a ground loop around the VCO through the bottom cover right side circuit board stud. I am going to try using a piece of Kapton tape placed over the inside of the cover where the stud makes contact and a nylon screw to keep this from happening 73, Bob Johansen WB2SRF _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
