On 09/13/2017 03:47 PM, jdow wrote:
selective cuts above
If the LNA4ALL is not being overloaded and the problem is simply AIRSPY saturation moving the filter after the LNA will purchase a modest noise figure improvement. If the LNA4ALL is generating IMD then the filter must go up front.Joanne is correct, of course, and in my earlier posts, I suggested putting the filter after the preamp, for obvious technical reasons, but in this case, it seems that the purpose of receiving the signals
the OP wants to hear is fulfilled as he/she desires. I don't think we need to go into a discussion of cascaded noise figure and third-order intercept here. It really is sufficient to almost all users to
connect things in whatever order works, and to explain, as Joanne and I have tried to do, what will work, and what might not. To possibly simplify things, I remember one contributor to this discussion
saying, use as little preamp gain as necessary to reduce overload problems. Amen to that!