The use of FT37-43 cores isn’t the best choice for this application and also the low pass filter is designed for 50 ohm impedance input and output. It’s hard to find out what the input impedance of an SA612 is, but supposedly definitely above 1k and more likely a few k.
I added an extra couple of poles to my filter, so like I said, it will be interesting to sweep the filter!
I salvaged a ferrite rod antenna and mounted it on a scrap piece of wood yesterday. The antenna seems to work OK and is directional, so that’s my plan B antenna.
73, Colin