[CQ-Contest] IC756PRO vs International Radio filters

bogus at does.not.exist.com bogus at does.not.exist.com
Thu Mar 9 17:49:54 EST 2000

In a message dated 3/9/2000 17:16:57 Eastern Standard Time, k6ll at juno.com 

> The best way to tell
>  is for a sharp operator to run the rig in a CONTEST, and give
>  us a report.
>  Dave Hachadorian, K6LL

This (sharp :-) operator used factory fresh TS870 with "out of this world" 
DSP filtering and crapy Kenwood crystal filters in two IFs ahead of it. Rig 
was just overwhelmed with strong signals and I almost threw it out. 
When I got service manual and looked at the guts, it was what I suspected, 
mediocre 8.8 MHz IF crystal filter followed by 455 kHz IF ceramic junk 
filter, and then the DSP "filtering". I gave it a try to replace 8.8 and 455 
filters with InRad 2.1 kHz filters and it was completely different 
(excellent) radio.
The selectivity as measured is one thing, but having RF/IF stages that get 
overloaded with signals is another thing, and it is too late for DSP to sort 
out the intermods, doesn't matter how many bits DSP processor is used. 
Measured passband curves with kenwood filters followed by DSP filtering were 
very similar to ones with InRad filters (thanks to DSP "filtering"), but real 
life band performance is like day and night. It has to be tested with 40 over 
9 signals slowly approaching receive frequency and see when it starts 
bothering you (modulate the band). That is the real test and not the 20 kHz 
bla bla bla test.
Info on my TS870 mods can seen on my  <A 
HREF="http://members.aol.com/ve3bmv/index.htm">VE3BMV Home</A> page.

73 Yuri, K3BU, VE3BMV

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