Quote:
I have never detected any signs of instability from it, but sometimes it hears far off things you might not expect to hear. Then you find it doesn't even have an antenna connected.
Sounds strange? It certainly is.
|
I think that one of the tricks used by Mutek on their bigger 2m boards was to use an unscreened inductor in the RF network ahead of the first LNA. This also didn't have a ferrite slug and so the overall Q of the inductor was higher. So this helped with the noise figure a bit but it would also act as a tiny pickup antenna. They also used unscreened Toko coils in the post LNA BPF and presumably this could pick up signals too.
By contrast, Yaesu often used screened coils with ferrite slugs ahead of the LNA and they used screened helical filters after it. This would have more loss but was probably less likely to pick up signals with no antenna fitted.
However, my little Mutek board in the 290R does use screened inductors so they didn't always try for optimum Q in the front end network.