A
Andrew Holme
Front end gain of a Marconi 2383 spectrum analyser I bought on eBay is about
6 dB less than it should be and the noise floor is about 6 dB higher as you
might expect. I suspect a lack of LO drive. The 1st mixer drive level is
specified as +17 dBm nominal. Between this and the YIG there is only an
amplifier and a power splitter. Annoyingly, the service manual does not
give signal levels for all points in the drive path and is
self-contradictory on stage gains; however, I think the amplifier is 6 or 7
dB and the splitter is -3 dB so the YIG output needs to be +13 dBm. I
measured it at +10 dBm. According to the article below, YIG outputs vary
between +10 and +15 dBm so mine is at the bottom end of this range. Do YIG
outputs decrease with age? Mine is 20 years old. Any advice appreciated.
http://www.vhfcomm.co.uk/pdf/A Simple Approach tyo YIG Oscil.pdf
6 dB less than it should be and the noise floor is about 6 dB higher as you
might expect. I suspect a lack of LO drive. The 1st mixer drive level is
specified as +17 dBm nominal. Between this and the YIG there is only an
amplifier and a power splitter. Annoyingly, the service manual does not
give signal levels for all points in the drive path and is
self-contradictory on stage gains; however, I think the amplifier is 6 or 7
dB and the splitter is -3 dB so the YIG output needs to be +13 dBm. I
measured it at +10 dBm. According to the article below, YIG outputs vary
between +10 and +15 dBm so mine is at the bottom end of this range. Do YIG
outputs decrease with age? Mine is 20 years old. Any advice appreciated.
http://www.vhfcomm.co.uk/pdf/A Simple Approach tyo YIG Oscil.pdf