Re: K2: KSB2 T1/T2 Turns Ratio Question

Posted by Don Wilhelm-4 on Apr 25, 2011; 11:12pm
URL: http://elecraft.85.s1.nabble.com/K2-KSB2-T1-T2-Turns-Ratio-Question-tp6304006p6304141.html

  John,

Do you have the older or the newer crystals installed?  The newer ones
have a "-S" suffix.  If yours have a "-20" suffix, they are older and
should be replaced with the newer ones.

It is not a question of crystal matching - the crystals in a set are
matched, but one of the crystal characteristics - mainly the motional
inductance (Lm) parameter.

73,
Don W3FPR

On 4/25/2011 7:00 PM, John Magliacane wrote:

> --- On Mon, 4/25/11, Wayne Burdick<[hidden email]>  wrote:
>
>> I started with textbook impedance ratios, then adjust the windings 1 turn at a time to find
>> the optimal combination of power transfer and passband flatness. This can vary with crystal
>> characteristics, circuit strays, etc.
> Thanks, Wayne.
>
> When I built my K2/100 back in 2003, I changed the coupling capacitors in the crystal ladder network according to KI6WX's 2.5 kHz bandwidth mod.  I ran a TX sweep, and found my 6 dB bandwidth was only around 2.1 kHz.  I never measured the bandwidth prior to this change, but I know the change made the rig "sound wider", with less ripple in the passband.
>
> So, I'm looking for reasons that might explain why the bandwidth is so narrow.  According to what I've read, the crystals I received with the kit in mid-2003 should have been matched well enough for the bandwidth mod to work.  This is what directed my attention elsewhere, such as the transformers surrounding the ladder.
>
> However, I'm beginning to think the crystals I received were not matched well enough to provide much beyond a 2 kHz bandwidth.
>
> If crystal matching is indeed the problem, are new crystal sets available to match the calibration number (3.7 in my case) from earlier KSB2s, or will all 14 crystals need to be changed so all filters have well matched center frequencies?
>
>
> 73, de John, KD2BD
> K2/100 #3563
>
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