[CQ-Contest] IC-756PRO

K3BU at aol.com K3BU at aol.com
Tue Feb 15 19:32:50 EST 2000

WW2Y  writes:

>  I would be highly suspicious of this thing. First, the 15 Khz filter in
>  the 1st IF  is useless because too much
>  energy from all of the signals passing through will clobber the DSP. And
>  these signals that are many Khz away will modulate the AGC while
>  listening to the desired signal at a narrow bandwidth. I've seen this
>  happen to an radio that's on the market today on CW during Field Day
>  last summer. I swapped out the  "X" brand radio for an old TS-930 after
>  playing with it for 20minutes with total frustration.
>  The second design fault is that there's no narrow  crystal filters in
>  latter IF stages to protect the fragile DSP stuff
>  from crunching over that will create digital artifacts in the passband,
>  ugh.

Was brand X - TS870S?
Same experience here, when I fired up TS870S in the contest on 160, the junk 
choked on strong signals. Kenwood then had modification for the gain 
distribution between RF and IF stages which made things a bit better. The 
major improvement was when I installed InRad 2.1 kHz filters in both IFs 8.8 
MHz and 455 kHz, it made it completely different radio. DSP now works and I 
am glad I didn't thorw the radio away. For more info and on 2nd RX antenna 
mods see my notes at
 <A HREF="http://members.aol.com/ve3bmv/index.htm">VE3BMV Home</A> 
There is no substitute for good sharp filters as close to the antenna 
circuits as possible. DSP way out in the IF or AF chain is of some help, but 
by no means match for good filtering up front, definitely not for contesters. 

Yuri, K3BU, VE3BMV, VE1BY, P40A

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