[hpsdr] IP3 testing of Mercury

[Ronald Cox]

Phil ,
Our 2009 ARRL Handbook now says that the preferred method for IP3  
measurement is to use S5 signal levels instead of MDS signal levels  
due to avoiding many receivers' non-linearity at the noise floor  
level. Thus the Third Order Intercept = (3 x (S5 IMD level)- (S5  
Reference))/2
This test would be done with Dither and Random enabled at 3.5/off/20,  
14/off/20, 14/on/20, 14/off/5, 14/off/2, and 50/off/20 (MHz/PreAmp/ 
Spacing) to compare with the ARRL's review of the Flex-3000.
Would this meet expectations?

Ron W9KFB
Indianapolis

On Oct 27, 2009, at 1:32 AM, Phil Harman wrote:

> I hope you extend your range of tests to include IP3. I expect you are
> aware of this but, unlike an analogue receiver, with a DDC receiver  
> the
> IP3 varies with signal level. Also  enabling Random and Dither will  
> have a
> significant (beneficial) effect on the IP3 performance.
>
> 73's Phil...VK6APH


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