I was wondering about that transformer. Thanks for the cross-reference.
Ed
John Miles wrote:
Ed
If it helps I can send you some LTSpice schematics so that you can
simulate the circuit for yourself.
The breadboards behave as predicted by the simulations at 10MHz.
John Miles has done some preliminary phase noise measurements on his
version.
The transformers are wound on binocular ferrite cores.
I used some 14mm (long) cores intended for 40MHz to 220MHz (I had some)
operation in my breadboard which works well at 5MHz and 10Mhz.
You can also use an off-the-shelf Mini-Circuits transformer for low-power
applications. The T13-1 was the one I tried. I'll stick some of the plots
up on the web later tonight if possible.
Residual PN is very good with this circuit, with a broadband floor near -170
dBc/Hz at 10 MHz, and no excess 1/f noise relative to a passive mixer.
-- john, KE5FX
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