Re: K3 in CQ WW RTTY
Hmm ... the 30 Hz Fc offset with the 1445 pitch setting is quite
clearly visible with the tools I am using (a zoomed
waterfall/spectrum display in MixW using RX noise with a dummy load).
At a 150 Hz DSP width (too narrow for decoding, but it makes the
offset easier to see) the mark frequency is within or on the edge of
the bandpass (maybe 5 dB down) but the space frequency is obviously
well outside (response down by around 30 dB).
The effect is not as large at 1275 and 2125 settings with only a 10
dB Fc offset, but it seems to me that I can still see it with my
filter - but as you say, perhaps that is mainly due to inaccuracy in
the IF filter offset.
--- In Elecraft_K3@..., "Joe Subich, W4TV" <lists@...>
perhapsbe the inability to set the filter Fc accurately enough with theI asked this question some time ago and was assured that the filter
isbe the inability to set the filter Fc accurately enough with the
is1530 Hz, but the current granularity of Fc is 50 Hz and Fc NORM
Hzactually set to 1500Hz. At a filter bandwidth of 400 Hz, this 30
filtererror is not important, but if you were trying to use a 200 Hz
thean error of 30 Hz would probably destroy the ability to copy.
beingfilter and establish copy, but at the price of losing the CWT
inoutside the filters at the other end of the QSO.
forFc is only 10 Hz. The 915 pitch setting has zero Fc error, but
thethose using AFSK that might not be an optimal choice (second and
shouldNORM Fc to the exact value corresponding to the selected pitch
thatbe possible (e.g. NORM Fc in PSK D is 1010 Hz), and I would hope
samea 10 Hz granularity for the IS; software command would also be
PSK31capability extended to the line input setting (I use Line 4 for
softwareand Line 8 for AFSK RTTY - I'd like to be able to have my
PSK31,set these automatically when changing digital modes).
RTTYandCW use in high-QRM situations. The bandwidth was selected in
twocontesting. I believe they've had very good results with it.
whichcapacitors -- C4 and C5. I'd suggest using 820 pF or 750 pF,
result in a -6 dB bandwidth of about 270 Hz or 300 Hz,respectively.This should also decrease loss through the filter by about 1 dB(setyour FLx GN menu entry accordingly). Return loss and passbandflatnessare essentially unchanged.