Wider IF modification for SSB

[recarter]

I found a whitepaper written by K16WX that discusses various modifications to the K2 to widen the IF.  I do a lot of digital mode operations.  Widening the the IF would let me scan through a wider AF window.   I have a very recent K2, complete just last month.  If I understand the document, I don't need the 2nd Xfil ssb modification.  It is already incorporated.  I also don't have to worry about ordering a better set of crystals because the K2 ships with the better parts.  I think that all I need do is replace the caps per the table shown in the document.  I don't think anyone sells a prepackaged bag of parts for this, so I'll be ordering parts online from Mouser unless someone knows a better place to order a few odd caps.

As long as my BFO can trim to 4916.5khz, I see no reason that I shouldn't open the IF to 2.5khz.  I suppose that I might lose something if there is a strong signal close to my frequency.   There is no IF shift so I can't move the IF filter, but I can switch in a narrower xfil.  I don't see this as an issue.  Any comments?

Rich - KE1EV
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[Don Wilhelm-3]

Rich,

The 2.3 kHz wide filter that is detailed in that paper has since been incorporated into the KSB2, but is referred to as a 2.4 kHz filter (now the 'stock' width - the difference can be found in the measurement of filter width - John, KI6WX measured at -3dB and Elecraft measures at -6dB.

If you want to increase the bandwidth to the 2.6 kHz filter (2.5), Elecraft sells a kit of capacitors to do that job.  Look on the K2 Spare parts and mods order page.

If your BFO range was as specified in the K2 manual, you should be able to align it with no problem - I believe the IF crystals are now a bit lower than they were when KI6WX wrote that paper.  I have built many filters with the 2.6 kHz bandwidth and have not had any alignment problem for normal SSB - should you try to move the passband upward in frequency for digital modes, you could run into BFO limitations.

73,
Don W3FPR

> -----Original Message-----
>
> I found a whitepaper written by K16WX that discusses various
> modifications to the K2 to widen the IF.  I do a lot of digital
> mode operations.  Widening the the IF would let me scan through a
> wider AF window.   I have a very recent K2, complete just last
> month.  If I understand the document, I don't need the 2nd Xfil
> ssb modification.  It is already incorporated.  I also don't have
> to worry about ordering a better set of crystals because the K2
> ships with the better parts.  I think that all I need do is
> replace the caps per the table shown in the document.  I don't
> think anyone sells a prepackaged bag of parts for this, so I'll
> be ordering parts online from Mouser unless someone knows a
> better place to order a few odd caps.
>
> As long as my BFO can trim to 4916.5khz, I see no reason that I
> shouldn't open the IF to 2.5khz.  I suppose that I might lose
> something if there is a strong signal close to my frequency.  
> There is no IF shift so I can't move the IF filter, but I can
> switch in a narrower xfil.  I don't see this as an issue.  Any comments?
>
> Rich - KE1EV
>

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