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

GW3OQK Andrew · 5th Feb 2023, 8:52 pm

Hello,
More on my HRO. I removed the filter I had fitted between 1st and 2nd IF, but 1st IF amp still remained biased. Just to be clear, there was no wire connection from the IFT going to the 1st IF amp grid. A 1 microvolt signal at 3.6MHz could still be heard clearly from the loudspeaker. With that amount of feed-through its no wonder the skirt bandwidth is so wide. The crystal filter works well but on CW you can hear signals out to +/- 5Kcs and I suppose that's what it was always like. You ears select the note you want.

I once had a Drake R4C receiver. You could unplug the crystal filter and still receive signals, though I improved that somewhat by fitting adhesive aluminium tape to various wires and ground as screening.

73, Andrew

5th Feb 2023, 8:52 pm	#123
GW3OQK Andrew Pentode Join Date: Apr 2011 Location: Swansea, Wales, UK. Posts: 144	Re: Improving Selectivity In Vintage Receivers Hello, More on my HRO. I removed the filter I had fitted between 1st and 2nd IF, but 1st IF amp still remained biased. Just to be clear, there was no wire connection from the IFT going to the 1st IF amp grid. A 1 microvolt signal at 3.6MHz could still be heard clearly from the loudspeaker. With that amount of feed-through its no wonder the skirt bandwidth is so wide. The crystal filter works well but on CW you can hear signals out to +/- 5Kcs and I suppose that's what it was always like. You ears select the note you want. I once had a Drake R4C receiver. You could unplug the crystal filter and still receive signals, though I improved that somewhat by fitting adhesive aluminium tape to various wires and ground as screening. 73, Andrew