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

GW3OQK Andrew · 2nd Jan 2023, 5:58 pm

Hello Bazz
The HRO mods were published in a past Signal but I didn't go into great detail, just the paragraph below. In the final event I am not satisfied with the skirt bandwidth for it is still too wide for CW, which is all I use, and probably too narrow for voice. To work in a proper block filter might be the answer but I don't think its worth the bother when our modern radios have such steep sided IF filters.
73
Andrew

Fitted a narrow band 456 kHz filter in the IF chain which usefully reduces the skirt bandwidth. This consists of 2 tuned top-coupled 455 kHz ceramic resonators on a strip of PCB mounted in a diecast box under the chassis. The HRO’s crystal filter works very well giving nice single-signal reception. Bandwidth is approximately –55 db at +/- 2KHz. (I did similar to my R1155)

2nd Jan 2023, 5:58 pm	#99
GW3OQK Andrew Pentode Join Date: Apr 2011 Location: Swansea, Wales, UK. Posts: 144	Re: Improving Selectivity In Vintage Receivers Hello Bazz The HRO mods were published in a past Signal but I didn't go into great detail, just the paragraph below. In the final event I am not satisfied with the skirt bandwidth for it is still too wide for CW, which is all I use, and probably too narrow for voice. To work in a proper block filter might be the answer but I don't think its worth the bother when our modern radios have such steep sided IF filters. 73 Andrew Fitted a narrow band 456 kHz filter in the IF chain which usefully reduces the skirt bandwidth. This consists of 2 tuned top-coupled 455 kHz ceramic resonators on a strip of PCB mounted in a diecast box under the chassis. The HRO’s crystal filter works very well giving nice single-signal reception. Bandwidth is approximately –55 db at +/- 2KHz. (I did similar to my R1155)