A drop down box just would not accept “retired” or “retired Engineer”. Bah! Humbug! I could have helped the youngster who was having selectivity troubles with his VHF receiver.
Years ago I developed a small helical resonator filter for VHF. It was for an aircraft band and 2 metre receiver. It had less than 0.5dB loss in band. a bandwidth of 0.5MHz for -3dB. When silver plated resonators were used the loss went down to -0.2dB. I was going to help the youngster with the ‘issue’, but I can’t ‘join’ the web site… Because you have to be employed!