On Fri, 30 Jun 2006 03:36:28 +0000, David wrote:

Thanks for the feedback (no pun intended I appreciate it.

I will add a shield between input and output circuit. I do remember
seeing this in other designs. In my prototype construction I do have the
input and output coils fairly close and in the same orientation so I
imagine there very well could be coupling between them.


I had a similar problem with a 2M RF amp. I cured it by
reversing the winding direction of one of the inductors.


Can anyone suggest a reasonably simple method to determine noise figure
of this stage ?

I'm a bit reluctant to suggest a method that I haven't tried
mysef, but you should be able to calculate NF by measuring the
receiver noise output with a hot and cold resistor connected
to the input. The usual method involves boiling water and
melting ice. http://tinyurl.com/psdfo

73, Ed. EI9GQ.

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