To: | LineOne <[email protected]> |
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Subject: | Re: LF: RE: Simple transverter for 472kHz |
From: | Andy Talbot <[email protected]> |
Date: | Sun, 15 Jul 2018 07:50:05 +0100 |
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Yes, I agree with your figures and they are terrible. -125dBm MDS means -128dBm of noise in a CW (call it 300Hz) bandwidth, that means a noise figure of around 21dB so there is no front end gain, and almost certainly some loss before mixer.
So a -36dBm IP3 is appalling. The increases to -14dBm at 75kHz just means there is some filtering in place. That low an IP3 is the sort of figure you'd expect, perhaps, from a single bipolar mixer; the sort of thing used in the 1960s and 1970s (as I did in my first homebrew HF receiver !) Could there have been something wrong with the test unit perhaps? LO power drastically reduced into a mixer? It would be difficult to make a mixer with that low an IP3 othewise Andy On 15 July 2018 at 00:54, [email protected] <[email protected]> wrote:
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