[Elecraft] K2: KSB2 T1/T2 Turns Ratio Question

[Ron D'Eau Claire]

Following up Don's response, I have an older K2 (ca 2000) and its "native"
crystals yielded barely 1.8 kHz bandwidth. Replacing them with the new
crystals available from Elecraft (order K2KSB2XTLS) fixed the issue.

Ron AC7AC

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of John Magliacane
Sent: Monday, April 25, 2011 4:01 PM
To: Wayne Burdick
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K2: KSB2 T1/T2 Turns Ratio Question

--- On Mon, 4/25/11, Wayne Burdick <n6kr at elecraft.com> 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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