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XF-9 Home Made

CRYSTAL FILTERS

      Couple of years ago, I got 50 crystals with the  frequency 8.999200 MHz plus/minus from my friend. Together with the boards and some covers for home made crystal filters. Now, when I am still playing with HM TCVR circuits, I decided to try to make filters from that crystals. I used LADPACK 2002 software (LadBuild, GPLA 2002, FineTune} from CD, included in the book "Experimental Methods in RF Design" from ARRL. My friend sent me also table with all necessary crystal parameters. After manual studied very carefully, I started to calculate first SSB filter. Result looked very good, so I tried CW filter, too. it was  little difficult to reach middle of the SSB filter. Second attempt was succesfull. Narrow CW filtr was more diffficult to set to the middle of the CW filter. Third attempt was ok, also. Result is visible on the next pictures.


     Center of the SSB filter is shifted abt 70 Hz to the higher frequency, but in practice it would have no effect. If I tried in the beginning of this attempt to order original 9 MHz 500Hz and 250 Hz filters, one of known european manufacturer asked 350,- Eur per piece plus VAT....My head turned twice 360 degrees around and  I said "thanks". I am not willing to support the loan sharks.  This HM solution will be usable, especially, when  Si5351 will be in use as a programmable BFO generator. Complete solution will be described somwhere in next parts....

Remark:  Stop band value of the filters will be better in the final board.  And, when roofing filters will be added, results can markedly improve.

Now, I continue the experiment with QT crystals (frequency 8.996920 Hz, very good quality). I sugggested testing board for crystal parameters measuring. When board arrives from OSH Park, I will continue with filters proposal... New filters will be proposed exactly to the 9 MHz.

 
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