K3 filters

[Scott McDowell-4]

I have a k3/100 ordered and am trying to decide on filters. I would
like the 250 hz 8 pole filter for cw. Should I also get the 400 hz
filter for ssb.
Scott N5SM
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[dave.wilburn]

The narrowest filter for SSB is the 1.8khz filter.  I have the 2.7,
1.8, 1k, and 400 hz, and it has worked well for my needs.  The 1.8 has
been the least useful.  The 1k and 400 are very handy for CW and RTTY.
  I have not tried the 250 hz 8 pole, but it is only a bit narrower
than the 400 hz.  You can check out the plots here.

http://www.elecraft.com/K3/K3_8_pole_plots.htm

David Wilburn
K4DGW
www.k4dgw.com
www.k4rc.net
Williamsburg Area Amateur Radio Club (K4RC)

My Current LOTW/DXCC/WAS status
www.k4dgw.com/WAS.DXCC.info.html



Scott McDowell wrote:

> I have a k3/100 ordered and am trying to decide on filters. I would
> like the 250 hz 8 pole filter for cw. Should I also get the 400 hz
> filter for ssb.
> Scott N5SM
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[Vic K2VCO]

Scott McDowell wrote:
> I have a k3/100 ordered and am trying to decide on filters. I would
> like the 250 hz 8 pole filter for cw. Should I also get the 400 hz
> filter for ssb.

It's important to remember that the selectivity is dependent on the DSP
setting and the filter is just a backup for very strong nearby signals.
For CW the 400 or 500 Hz. filter will be fine; you can adjust the
bandwidth down to 50 Hz. with the DSP controls.

The 250 Hz. filter is probably narrower than you will need for CW 99% of
the time. It is useful for RTTY or PSK, however.

For SSB the stock 2.7 kHz. filter will do a good job. Some contesters
like the 1.8 kHz. filter so they can operate closer to very strong
signals. 400 Hz. would be way too narrow for SSB.

So if you are a CW/SSB operator I would recommend the 2.7 kHz. filter
(for ssb) plus the 500 or 400 Hz. filter (for CW). If you are especially
interested in digital modes, then maybe the 250 could be useful -- but
it isn't necessary.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Joe Subich, W4TV-3]

> I would like the 250 hz 8 pole filter for cw. Should I also get
> the 400 hz filter for ssb.

The 400 Hz filter is far too narrow to be useful in SSB - you don’t
want a bandwidth less than 1500 to 1800 Hz for voice use although
bandwidths as low as 800 - 1000 Hz may be useful for some digital
modes.  

I would not recommend both the 400 Hz and 250 Hz in the same radio.
The reference plots for the 250 Hz and 40 Hz filters on the Elecraft
web site: http://www.elecraft.com/K3/K3_8_pole_plots.htm show the
250 Hz filter to have a bandwidth of 370 Hz and the 400 Hz filter
to have a bandwidth of 435 Hz.  

There is not enough difference between the 250 and 400 Hz filters
for you to notice in actual operation.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Scott McDowell
> Sent: Saturday, August 30, 2008 11:32 PM
> To: [hidden email]
> Subject: [Elecraft] K3 filters
>
>
> I have a k3/100 ordered and am trying to decide on filters. I
> would like the 250 hz 8 pole filter for cw. Should I also get
> the 400 hz filter for ssb. Scott N5SM

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