Hi all, I operate a spectrum analyzer model HP 853A with a 8558B RF unit, which has a strange problem around the first LO, a YIG oscillator. As some of you will use these also, I think it is OK to ask this question.
When switching on the unit, the noise floor on the screen is 20 dB above the usual value, from 0 thru 700 MHz, then declining to normal at 900 MHz and higher. The effect will vanish if I tune to a CF of 1100 MHz or higher. It will appear only if the unit has been in daily use for my usual 8-10 hours, for several weeks continuously. Some months ago, I did a lot of paperwork (and my vacation!) and didn't use it, the effect was gone during the following several weeks of heavy usage, only to appear again after some time. I would like to know if anyone can give me a tip as to the particaular cause of this failure mode, or perhaps point me in a direction where I could start to dig for a new component. Is it indeed the YIG osc, is it the first mixer or some circuitry around this assembly (e. g. heater, driver, voltages)? Thanks, Jochen Feldhaar DH6FAZ Telejet GmbH ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
