[Elecraft] K3 Filter questions

[Dave Hachadorian]

Igor,

You are missing the point.   K8ZOA's measurements were for a
continuous carrier. You can't measure speech intelligibility with
the K3's dBV meter.

My  recommendation for DSP bandwidth of 2.1 KHz and 1.8 crystal
filter were based on what I consider the best compromise between
bandwidth and intelligibility for SSB human speech.

Look at it this way - My ears find SSB speech very
intelligible with a DSP bandwidth of 2.1 KHz.  You can put a 1.8
crystal filter in front of that DSP and SSB STILL is very
intelligible, plus you have the advantage of a nice tight roofing
filter to keep the hardware AGC from pumping.  When you start
reducing the DSP bandwidth below 2.1 KHz, intelligibility starts
to become very dependent on the voice characteristics of the
received signal, so you have to keep fiddling with the DSP
controls.  You don't want to be fiddling with the controls if you
are running at 200 QSO's per hour.  I'm saying that with DSP 2.1
and a 1.8 roofing filter, one can pretty much leave the controls
alone for the duration of the contest.

After the contest is over, you can go back to 2.7/2.7 filters for
more natural-sounding audio.

Dave Hachadorian, K6LL
Yuma, Arizona


-----Original Message----- 
From: k.igor at comcast.net
Sent: Wednesday, March 28, 2012 11:05 AM
To: jim at audiosystemsgroup.com
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3 Filter questions



If it pleases you to use DSP set wider than roofing filter - by
all means, go for it.

I would not, however, clame objectivity based on my subjective
experience  or somebody's valuable opinion and simplistic
explanation , I perefer measurements performed on good lab
equipment. K8ZOA did some of the measurements on 500 Hz filter,
but most of them probably applicable for the 1.8kHz filter. See
report here:
http://www.cliftonlaboratories.com/elecraft_k3_noise_blanker_and_crystal_dsp_filtering.htm

In his measuremetns, setting DSP wider than the actual roofing
filter actually degraded the total response in the stop band.



73,

Igor, N1YX