Racal RA1772 IF Crystal Filter profiles. Testing. Help wanted. - UK Vintage Radio Repair and Restoration Discussion Forum

stuartfurbank · 23rd Jan 2019, 1:58 pm

Hi,
I am testing a number of 1.4Mhz I.F. Crystal Filters as used on the Racal RA1700 series radios, RA1772, with a Spectrum Analyser and Traking Gene.
I have tested a number of symmetrical filters and all have a similar shape, profile and the Spectrum Analyser displays the corresponding BW for each filter tested eg 400Hz 9Khz, 6Khz etc. All OK

However I have one filter marked USB 3Khz, on test, the filter shape/ response is the same as the symmetrical filters (ie non LSB/USB filters).

My Q., is this correct? Or should I see a different shape for this Filter as I assume it should have an Asymetrical response.
Or
Should a USB filter response just be shifted away from the 1.4Mhz centre.?
Any help gratefully received.
Stuart

23rd Jan 2019, 1:58 pm	#1
stuartfurbank Triode Join Date: Aug 2007 Location: Altrincham, Greater Manchester, UK. Posts: 31	Racal RA1772 IF Crystal Filter profiles. Testing. Help wanted. Hi, I am testing a number of 1.4Mhz I.F. Crystal Filters as used on the Racal RA1700 series radios, RA1772, with a Spectrum Analyser and Traking Gene. I have tested a number of symmetrical filters and all have a similar shape, profile and the Spectrum Analyser displays the corresponding BW for each filter tested eg 400Hz 9Khz, 6Khz etc. All OK However I have one filter marked USB 3Khz, on test, the filter shape/ response is the same as the symmetrical filters (ie non LSB/USB filters). My Q., is this correct? Or should I see a different shape for this Filter as I assume it should have an Asymetrical response. Or Should a USB filter response just be shifted away from the 1.4Mhz centre.? Any help gratefully received. Stuart