Re: K2: KSB2 T1/T2 Turns Ratio Question

Posted by Don Wilhelm-5 on Apr 25, 2011; 11:46pm
URL: http://elecraft.85.s1.nabble.com/K2-KSB2-T1-T2-Turns-Ratio-Question-tp6304006p6304185.html

  John,

Given that information, I conclude that you have an unusual situation
with your KSB2 filter.
The easy way to attempt a fix is to replace both the crystals and the
capacitors (SSBCAPKT).  Total cost is only $30 plus shipping, and your
aggravation is likely more costly than that amount.

The design works and produced the proper results - if the components are
the correct values.

73,
Don W3FPR

On 4/25/2011 7:35 PM, John Magliacane wrote:

> Hi Don.
>
> Thanks for the reply.
>
>>   John,
>>
>> I cannot answer your exact question (the impedance ratios), but I need to ask a
>> question about your "narrower than expected" filter response.
> I plotted a sweep of my TX chain a number of years ago, the results of which can be seen here:
>
>         http://www.qsl.net/kd2bd/sweep2.png
>
> It's a linear plot, so the ripple and other imperfections really stand out.  It was taken by sweeping audio through the KSB2 well below the level of ALC action while measuring the corresponding audio level picked up by a nearby crystal controlled, direct conversion receiver having no filtering or AGC.
>
> Looking at the red LSB curve, if we estimate the center of the passband to average around "70" in amplitude, -3dB would be around "50", and -6dB would be around "35".
>
> > From this, I estimate the -6 dB bandwidth to be around a 2.2 kHz.  And this is with the 2.5 kHz -3dB bandwidth (2.6 kHz -6 dB bandwidth) coupling capacitors in the ladder.
>
> And, lastly (although less scientific), if I optimize my CAL FIL settings so that my transmitted audio has the identical quality on LSB that it has on USB (as observed on a wideband receiver), my BFO settings are only 2.3 kHz apart.  This is 400 Hz less than the spacing suggested in the KSB2 instruction manual for a 2.2 kHz (-6 dB) bandwidth.
>
>
> 73, de John, KD2BD
> K2/100 #3563
>
>

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