Post #1963281

Using a NanoVNA to test the centre frequency of the filter on this 1940s GR-10 receiver, I found it is 445 kHz, not the 455 indicated in the manual. Because this was maintained by the Canadian airforce at least into the 60's, someone retuned the local oscillator to around a 445 kHz offset, too, which is why the filter sounds so good.