Sunday, October 15, 2017

XF-9 S42 9Mhz AM filter from the Telrad board.

On previous post I made a simple crystal tester, that was needed because I was short on 9Mhz crystals and thought that a good place to get them would be the AM filter from the Telrad board. It's referenced as XF-9 S42, 3.6KHz at 3db bandwidth with 560 Ohm impedance.

I was right, there are plenty of them now available, either for USB and LSB:


Inside, the PCB supporting the crystals

 The schematics is more or less like this:
 Interesting, the input goes to the middle of a crystal, first time I see it.

 Another view
 Side view
 It was not that easy to open the box
 The input details, see the terminal going to the middle of the crystal
 The cover, underside and top side.
 The matching numbers to be tested:
 The values

It was not easy to open the filter, I used the "sardine can" method, previously had tried to unsolder the bottom but there was to much thermal mass and still not sure if it would possible.

So, now I have 9Mhz  crystals for the BFO of the boards and for other projects, one of them already take place in the S9 signal generator.

Have a nice week!


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