[Elecraft] My Five Filters

[Joe Subich, W4TV]

> Ditto.  W4TV (?) measured the 250 (actually 370 Hz) versus 
> the 200 and the latter had more rejection at ALL frequencies, 
> even though it's only a 5-pole.

Actually, I compared both of my 200 Hz filters (measured) to 
the curves for the 250 Hz filter on the Elecraft web page: 
http://www.elecraft.com/K3/K3_8_pole_plots.htm specifically 
http://www.elecraft.com/K3/filter_plots/250.gif. 

The stated conclusion is correct ... my filters were 190 and 
200 Hz at -6dB and 440 Hz wide at - 30dB  vs. 360/525 Hz for 
the INRAD/Elecraft 250 Hz filter.  Note, according to Wayne 
only the first 30 dB or so of rejection is significant as that 
is enough to protect the AGC and mixers and after 30 dB the 
DSP is the dominant bandwidth determining factor.  

As recommended by others, I would use 400 Hz for general CW 
and RTTY with the 200 Hz for critical CW only (200 Hz is 
too narrow for 170 Hz shift RTTY which, in theory, needs 
around 300 Hz to properly pass the keying sidebands).

My own rigs have 13 KHz, 2.8 KHz, open, 500 Hz and 200 Hz 
filters.  I'm waiting on Elecraft to allow use of the 13 KHz 
filter for AM and ESSB transmit (there is no reason to not 
allow it) and will eventually add the 1.5 KHz "narrow SSB" 
filter.   If I were to do it again, I would have saved the 
money on the 2,8 KHz filters and gotten the 400 Hz filters 
instead.  The savings in sticking with two stock 2.7 KHz 
filters (even with matching for the sub receiver) would 
have paid for the 13 KHz Hz and 200 Hz filters. 

73, 

   ... Joe, W4TV 
 





> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill W4ZV
> Sent: Wednesday, February 17, 2010 10:23 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] My Five Filters
> 
> 
> 
> 
> Craig D. Smith wrote:
> > 
> > But I would recommend the 200 Hz 5 pole rather than the 250 
> Hz 8 pole.
> > 
> 
> Ditto.  W4TV (?) measured the 250 (actually 370 Hz) versus 
> the 200 and the latter had more rejection at ALL frequencies, 
> even though it's only a 5-pole.  I only use my 200 ~1% of the 
> time (500 Hz 8-pole the other 99%) but there are times when 
> it's nice to have (such as large simplex pileups).
> 
> Someone previously commented on the 1000 Hz (actually ~1100 
> Hz) for CW.  I had one but found it too wide to be of much 
> use.  If there are NOT a lot of strong signals around, the 
> stock 2.7k will work about as well.  If there ARE a lot of 
> strong signals around, the 1000 allows too many of them to 
> desense the rig.  This is especially true if you use a low 
> pitch as I do (3-400 Hz). 
> In that case the bandpass is shifted upwards from 200 Hz such 
> that signals as much as 1000 Hz above zero beat will desense 
> the K3 (e.g. a 200-1300 Hz bandpass for a 300 Hz pitch).
> 
> 73,  Bill
> 
> -- 
> View this message in context: 
> http://n2.nabble.com/My-Five-Filters-tp4586377p4586571.html
> Sent from the Elecraft mailing list archive at Nabble.com. 
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