UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 6-gang FM stereo tuner heads

G0HZU_JMR · 21st Nov 2022, 8:39 pm

About 30 years ago, Minicircuits released some software that could plot the predicted spurious levels of their range of mixers. I still have our works copy of it even though it dates back to the dark days of DOS. In the plots below I've compared my measurement of an ancient SBL1-1 mixer against the Minicircuits SW.

The SW only allows a choice of two RF drive levels, so I chose -10dBm. The RF frequency is 88MHz and the LO frequency is 98.7MHz.

The analyser plots have a start frequency of 8MHz and a stop frequency of 300MHz in both cases. You can see that the old SW agrees quite well with the real measurement.

Note that the amplitude scale of the Minicircuits plot is normalised to the IF output level. Therefore, 0dB on the Minicircuits plot is really -16dBm and this agrees well with the real measurement.

21st Nov 2022, 8:39 pm	#247
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: 6-gang FM stereo tuner heads About 30 years ago, Minicircuits released some software that could plot the predicted spurious levels of their range of mixers. I still have our works copy of it even though it dates back to the dark days of DOS. In the plots below I've compared my measurement of an ancient SBL1-1 mixer against the Minicircuits SW. The SW only allows a choice of two RF drive levels, so I chose -10dBm. The RF frequency is 88MHz and the LO frequency is 98.7MHz. The analyser plots have a start frequency of 8MHz and a stop frequency of 300MHz in both cases. You can see that the old SW agrees quite well with the real measurement. Note that the amplitude scale of the Minicircuits plot is normalised to the IF output level. Therefore, 0dB on the Minicircuits plot is really -16dBm and this agrees well with the real measurement. Attached Thumbnails __________________ Regards, Jeremy G0HZU