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	Security (anti-spam) Question: How many dits in 72?
Dits
Description	Record # 3
RevDate	Sun, 26 Oct 2008 07:52:47 -0500
Details	This is the only way I can think of to make a crystal filter for a superhet when we only have three crystals at the same frequency. One for the filter, one for the product detector BFO, and one for the TX mixer oscillator. At least crystal matching is not a problem. - Jason Jason, you might try using two Xtals. In one leg of one Xtal, insert some variable capacitance. I did such a circuit and found out that I could tweak the bandpass from SSB to CW. I used a fixed 56pF in parallel with a 40pF trimmer. Then you can use the 3rd Xtal in the set for BOTH the BFO and xmtr mixer sources. I did such a circuit in the multiPIG+. Maybe I should post those circuits here. -Diz, W8DIZ 11/21/06 Diz, yes it later occured to me that I might be able to use a 3 dB hybrid to split up a single oscillator source. I`ve already modeled this filter in LTSpice, I think I will also model your version and see what it looks like. - Jason, NT7S 21 Nov 2006 Capacitor C1 was added to allow the shifting of the peak response of the filter. Without this, it is much harder to align the RX correctly. -Jason, NT7S 28 Jan 2007
Schematic=NT7S_IF_Filter.gif   AuxFile=NT7S_IF_Filter.zip                   Return to SEARCH

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