[Elecraft] K3 filter performance

[Joe Subich, W4TV]

David, 

Some time ago I did a "numerical comparison" using the published 
-6dB and shape factor values.  Perhaps these will help until the 
"official" lab results are published. 

>                200      250     400      500 
>    -------------------------------------------------
>     - 6dB      224      370     435      565  Hz
>     -60dB      896      777     913     1751  Hz 
>      slope     6.22     3.77    4.43    10.98 Hz/dB  
> 
>     -10dB      274      400     470      653  Hz
>     -20dB      398      475     559      873  Hz
>     -30dB      522      550     647     1092  Hz
>     -40dB      647      626     736     1312  Hz
>     -50dB      771      702     825     1531  Hz
 
In my opinion, the 200/500 pair is the best value.  That 
is reinforced by comments on IMD performance and receiver 
design by people like Rob Sherwood.  The only reason to 
look at the 8-pole filters might be the need for a slightly 
wider "narrow" filter if you were into RTTY (I don't know 
if 224 Hz is too narrow for 170Hz shift RTTY - particularly 
with fading and/or multipath).  For a died in the wool 
RTTY DXer, a steep sided 270 - 300 Hz filter would be nice
instead of 370 Hz from the "250 Hz" filter.

73, 

   ... Joe, W4TV 
  






> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of David Lankshear
> Sent: Sunday, January 27, 2008 12:11 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] K3 filter performance
> 
> 
> Sorry to ask this of the list, but there's been so much 
> comment on K3 filters, I seem to be going round in circles 
> trying to find where, if anywhere, evaluations have been done 
> on the 5-pole filters.  I'm resigned to never getting my 
> detectve's badge, Sherlock.  HI!
> 
> Elecraft have (most of?) the 8-pole ones on the website but 
> I'd like to compare those details with similar tests done on 
> the 5-pole.
> 
> Also, there has been mention of variable filters.  As new 
> orders placed now are estimated for May shipping, perhaps the 
> varibles would be available by then, so is there any 
> technical information on them yet, please?
> 
> 73 all.  DaveL  G3TJP
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