UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Improving Selectivity In Vintage Receivers

G0HZU_JMR · 26th Oct 2022, 9:07 pm

A few years ago, I measured one of the little yellow 2 pin 455kHz resonators on a VNA and exported a two-port model. I had a go at making a USB ladder filter to suit the 450kHz IF of the 840. It took eight resonators to get the performance below. It's fairly reasonable for an SSB filter but it would be a labour of love to actually make one. Every resonator is identical as I used the same model for all 8 resonators. In reality, they won't be identical so this would require some select on test caps to get it aligned.

The filter below only uses series resonators. I think it could be improved if I used some shunt elements, but this was just a first attempt.

The impedance of the filter is about 1200Ω.

26th Oct 2022, 9:07 pm	#17
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: Improving Selectivity In Vintage Receivers A few years ago, I measured one of the little yellow 2 pin 455kHz resonators on a VNA and exported a two-port model. I had a go at making a USB ladder filter to suit the 450kHz IF of the 840. It took eight resonators to get the performance below. It's fairly reasonable for an SSB filter but it would be a labour of love to actually make one. Every resonator is identical as I used the same model for all 8 resonators. In reality, they won't be identical so this would require some select on test caps to get it aligned. The filter below only uses series resonators. I think it could be improved if I used some shunt elements, but this was just a first attempt. The impedance of the filter is about 1200Ω. Attached Thumbnails __________________ Regards, Jeremy G0HZU