[CQ-Contest] Sherwood Engineering and DSP

Tree tree at kkn.net
Fri Jun 8 13:02:03 EDT 2007

This article is a little hard to follow without the speech:


But - I think I might understand what is trying to be pointed out.

If you look on page 19 at the plots of the 3 tone test - look at how
far down the IMD products are especially the ones about half way 
across the plot.  On the R4C, they are pretty much gone at that point.
Same on the IC781.  The IC7000 shows very poor performance.

I believe this is the issue that some operators complain about when a
radio sounds "mushy" when there is a pileup - or perhaps a lot of 
noise (noise is very similar to having a bunch of little signals in
your passband).

Often, this IMD in band perfomance is improved by backing off the RF
gain.  I have seen my TS850 and a friends FT1000MP have an improvement
from having the first product down about 35 db to well over 50 db using
a two tone in-band test.

And - like Rob - I am anxious to see how the K3 performance ranks.

73 Tree N6TR
tree at kkn.net

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