Hi Duncan, See my plots and a little mod in the files section -Filters for lite.doc- of may 19. &3 de Henk, PA0KEP
--- In [email protected], Duncan Clark <[EMAIL PROTECTED]> wrote: > > Hi Folks, > > I have a completed working 8.3 Lite with an LVDS Si570. However gut > feeling said it was bit deaf on 20m up. 80m and 40m appear fine. > > Having stuck the little BPF's on an analyser the two high frequency ones > appear way out, for no apparent reason. > > Put analyser across the secondaries with tracking generator across the > input. > > 80/40m filter appears spot on with a peak at 80m and again at 40m with > minimum loss. > > 20m Filter shows two peaks, one at 7.36MHz and another at 16.59MHz with > a smooth dip in between. Roughly 4dB loss at the peaks and -11dB at 30m, > -9dB at 20m and -8dB at 17m. Transferring analyser to input shows two > notches, one at 7.36MHz and other at 16.59MHz. > > I've counted the turns again, checked the right capacitors are in the > right place and primary and secondaries are connected correctly. > > The 15/12/10m filter is just as far out. > > Peaks at 12.8MHz and 21.8MHz, down -7dB and -11dB respectively. Loss at > 15m is -10dB, 12m is -18dB and 10m is -24dB. > > Notch at 12.8MHz and 23.6MHz. > > Again right capacitors, turns, correct coloured toroids (Hi!) etc. > > I didn't expect what I am seeing so am I just measuring these wrongly > and they should look like that or is something really out ? > > Thanks > > Duncan > -- > Duncan Clark >
