Posted by
Geoffrey Mackenzie-Kennedy-2 on
Nov 13, 2005; 11:23pm
URL: http://elecraft.85.s1.nabble.com/CW-Pitch-600-Hz-or-700-Hz-or-what-tp383635p383640.html
Hi Vic, Paul,
Not quite Vic. The BFO knob would control the frequency of a BFO thus
establishing the frequency difference between the BFO and a desired signal
in the receiver passband, as done in receivers for decades.Its output is fed
only to the product detector when in use. So the knob allows you to vary the
beat note or pitch. Tweaking the BFO knob would and should not affect the
sidetone at all, since sidetone is usually only a transmit aid. Because in
the K2's system the sidetone is also used when measuring the frequency of an
incoming signal and/or zero beating the K2's Tx with an incoming signal, my
early thought is that the BFO knob would control the frequency of a second
BFO #2 that is used only during receive, and also provides the means to
switch back to the existing BFO #1 if SPOT is to be used. I suggest this
second BFO because I don't think that it would be wise to have one BFO
hopping frequency when going from Rx to Tx and back. This separate BFO #2
should be capable of being set say +- 1500 Hz from the passband centre
frequency, which gives you "Reverse CW" as well.
The added BFO #2 is completely divorced from the microprocessor. The
existing BFO #1 carries on as usual but is disconnected from the product
detector when BFO #2 is in use. BFO #2 would have to be properly shielded,
ground fenced, and interface leads filtered. Big question is where to put
it?
Paul, I think that to be able to tweak the sidetone (monitoring) frequency a
separate keyed AF oscillator directly feeding the audio is required because
of the existing sidetone's connection with SPOT etc, but I am not at all
sure about this.
73,
Geoff
GM4ESD
Vic Rosenthal wrote:
>> This would be nice, and I presume that you mean that the knob would
>> maintain the location of the BFO in relation to the passband along with
>> the sidetone pitch. Currently it's possible to adjust the pitch from the
>> menu (although this is not a one-knob operation!), but in order to keep
>> the selected pitch inside a narrow passband, you need to do the CAL FIL
>> procedure.
>>
>> So the knob that you refer to would have to cause the microprocessor to
>> recalculate the VCO offset that is used to place the selected pitch at a
>> given location in the filter passband. This is what happens when you run
>> CAL FIL.
Paul Heller wrote:
> This is the one feature that I really wish the K2 had. My TS-940 and
> 756-ProIII both have this, and I find it very helpful. It's not only nice
> to be able to customize the sidetone pitch, but I like to tweak it easily
> via a front-panel knob every so often during long operating periods, like
> contests - adjusting the sidetone (and zero-beat point) up or down a
> little from time to time seems to help minimize ear (or is it brain?)
> fatigue.
>
> /Paul
> W3PH
>
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