[Elecraft] Re: 2.7 kHz filter centering in CW mode vs. SSB mode, etc.

[wayne burdick]

Evert Bakker ((PA2KW)) wrote:

> Can someone tell if and why listing in CW mode with roofing filter 2.7 
> Kc
> and DSP set to 2.8 and centered sounds so different as when on SSB 
> mode with
> the 2,7 Kc roofing filter and the DSP at 2.8 Kc and centered? In this
> particular situation (in CW mode) it is impossible to "read" an SSB or 
> LSB
> signal as if filters are totally different.

Hi Evert,

In CW mode, wider crystal filters are positioned such that they provide 
a rapid cutoff about about 1 kHz lower on the high end (roughly 1.9 
kHz, vs. 2.9 kHz for SSB modes). This seemed like the best choice for 
QRM reduction in CW modes. You can SHIFT the passband up a bit to 
improve copy of SSB stations in CW mode, if required.

However, with the latest firmware you can now send CW directly in SSB 
modes, which is a much more convenient way of making cross-mode QSOs. 
(Tap '1' in the CONFIG:CW WGHT menu entry to enable this feature; set 
it for "SSB +CW".)


> I've got the feeling that this was not the case with the earlier 
> version or
> am I wrong?

As far as I know this positioning of the crystal filters in CW mode has 
not changed.


>
> When the roofing filter is 2.7 why does the DSP still have effect when
> changed from 2.7 to 4.0 Kc (no, the roofing filter is not switched
> automatically from 2.7 Kc (FL2) to 13.0 Kc (FL1)? At least the display 
> still
> says FL2. Are the slopes of the DSP so much steeper?

If you don't have a filter wider than 2.7 or 2.8 kHz enabled, the WIDTH 
control will still allow you to set WIDTH beyond this (all the way to 
4.0 kHz), but this may not be very effective since the crystal filter 
has steep skirts.

The 13 kHz filter will work in SSB modes if you have it enabled.

73,
Wayne
N6KR

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