[Elecraft] K3S DSP filter plots

[Jeff AC0C]

Oops.  Hit the go button too fast.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Jeff AC0C
Sent: Monday, November 16, 2015 8:25 PM
To: George Fritkin ; k6dgw at foothill.net
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3S DSP filter plots

It's easy to measure this.  Here's one way to do it - assuming you already
have a functioning  AFSK/PSK interface working with a rig/PC.

Download and install the WD6CNF Audio Spectrum Analzyer.  Set it up to
listen to your rig interface AF feed.

On the rig, turn of the AGC and the rig's preamps.  Turn of NR, DNR -
whatever the noise reduction and noise blanking stuff is called.

Set the mode to SSB or CW (I forget if there are min DSP BW restrictions in
SSB).  Set the roof selection manually to something wide relative to the DSP
(so you don't comingle the two transition bands).  The 2.7 Khz filter

Feed a stable S8 (-80 dBm) into the antenna and tune it so you have roughly
a 700 hz signal.

Fiddle around with the AF spectrum analyzer to show a clear picture of the 
bandwidth and the top 40-60 db of the signal.

Turn on the PEAK HOLD setting of the AF spectrum anal.

Set the average setting to "2"

Swing the VFO back and forth to pain the passband on the peak hold display. 
Depending on how you have the AF SA setup, you may need to crawl along.

Voila, there's your passband.  Hard data and no MSEE required.  Have fun!

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: George Fritkin via Elecraft
Sent: Monday, November 16, 2015 7:49 PM
To: k6dgw at foothill.net
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3S DSP filter plots

And I will add a filter is not a filter.  No, I am not crazy.  There are
many types of filters with various trade-offs.   In band
ripple.....loss......phase shift.......skirt shape....are just some of the
trade offs.  DSP software can emulate any or combos

George, W6GF


Sent from my iPad

> On Nov 16, 2015, at 5:03 PM, Fred Jensen <k6dgw at foothill.net> wrote:
>
> No doubt Wayne is qualified, however he has deferred on several occasions 
> to Lyle who I believe actually writes the code.
>
> And a teeny point from a math major ... inasmuch as arithmetic is a part 
> of math, it is clearly "done mathematically."  The "real" math however is 
> in figuring out what arithmetic to do.  At the implementation level, it's 
> all arithmetic, generally in base-2.
>
> I'll bet my next paycheck, if I got one anymore, that both Lyle and Wayne 
> understand both.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the Cal QSO Party 1-2 Oct 2016
> - www.cqp.org
>
>> On 11/16/2015 4:18 PM, Bob McGraw - K4TAX wrote:
>>
>> Perhaps Wayne is better qualified to define the performance of the DSP
>> filter system, usually limited by the number of poles and is done
>> mathematically.
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