[Elecraft] PX3 Anomoly (bug?) on AM

[Don Wilhelm]

Grant,

It would appear that you are running up against the bandwidth limit of the
KX3 audio when you widen the bandwidth with HiCut.
I don't know what the limits are, but from your observations, it may be 
that the maximum bandwidth is in the vicinity of 6.4kHz.

So if you have 4.2 kHz on one side, you will be restricted to 2.2kHz on 
the low side.
If you back off the high side to 3.1kHz, is the AM response centered?

I am just venturing a guess, the maximum audio bandwidth is not 
specified for the KX3.

73,
W3FPR

On 5/3/2016 8:46 PM, GRANT YOUNGMAN wrote:
> I posted this a week or so ago, and didn’t get any feedback from Elecraft or anyone on the list.  Soo .. I’m going to “bump” it and post again.  You never know …
>
> In further poking at it, it matters not whether the IF shift is set to 8 Khz on the KX3, or whether Hi/Low Cut or PB/Shift is selected etc.  It appears to be PX3 related.  My guess is that either it’s (1) some artifact of the direct conversion process on the KX3, or (2) perhaps just showing AF bandwidth in some odd way.  In any case … here’s the original post.  Anyone have a clue?
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> "If the bandwidth/shift or Hi/Lo cut is NORMalized, the green bandwidth band on the PX3 sits with it’s edges about 3 KHZ above and 3 KHz below the carrier frequency as you might expect.  It’s symmetrical around the carrier.  If I open up the HI setting to max (4.2 KHz) and set the LO to minimum, the green band is offset to the high frequency side of the carrier — with the low boundary about 2.2 KHz below the carrier, and the high boundary about 4.4 KHz above the carrier.  These points may not be exact, but they were roughly measured using the VFO A marker — close enough to make the point.  And just using the usual reduction in background hiss to retune the carrier, it appears most closely tuned when the VFO is set about 0.9 KHZ above the actual carrier frequency, although even then the green band is offset from either the actual or tuned carrier freq.
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