The build is pretty straightforward and all went to plan Part 2: Well i kind of expected that to not take forever, but anyway here is the update. Will update this post once i have built and tested each filter. Got the parts all sorted, just gotta build it now. It seems even good quality crystals have some in each batch that should be rejected. The pile in the bottom right corner are the outliers. Buying these crystals was certainly well worth it. Out of this pile of crystals I have 6 groups of 8 crystals all within 10hz of each other and a few more groups all within 20hz of each other. If i cannot make acceptable filters with such tightly grouped crystals, then there is no hope in hell i can ever make a good filter So I measured my crystals and sorted them into piles within 10hz of each other.
My function gen also has a frequency counter that counts down to 1hz resolution. 4.91520Mhz xtals sorted to within 10hz of each other.Įach crystal was loaded up into my you beaute xtal tester and the frequency measured to within an inch of its life. I am also using the good crystals for these also. The plan is for an SSB filter that is about 2200hz wide and a CW filter about 500hz wide. I thought about going down that route myself for a while, but in the end, settled on having 2 filters as I have lots of relays already. I have seen some use varactor diodes to solve this problem, by varying a voltage on the diodes you can vary the capacitance and this the width of the filter. The one thing that has always frustrated me with many SSB/CW homebrew rigs is that you get one filter and one filter only.
But for now, I am going to assemble it and see if I can make 2 filters worthy of use.
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