Using the 10.11 MHz Crystals

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Using the 10.11 MHz Crystals

Post by wsprowls » Tue Nov 17, 2009 3:56 am

Hi All,

It will be a few days before Jerry begins mailing out the Crystal Sets but I wanted to write a quick blurb for those who will be using them.

They are manufactured as thru-hole crystals, but have been "stamped" to bend their leads for surface mounting. The pwbs are designed for thru-hole lead Crystals. This will necessitate straightening out the leads and removing the plastic carrier before inserting into the pwb. The crystals are mounted from the bottom side of the pwb and the leads are soldered on the component side. No insulator is required. This should not be a problem for anyone, but just a warning that re-flexing the leads more than once could result in a lead fracture. Once the crystals are soldered on the component side, add a ground wire from the ground plane to the top of each crystal. This makes for good case grounding and it minimizes crosstalk.

I have built 3 different bandwidth filters with these crystals, 900 Hz, 2 KHz, and 3.8 KHz. There is no reason you cannot design for narrower or wider. Your crystal sets are matched using two parameters, Fs (serial resonant frequency) and Rm (Motional Resistance). Your 4 sets of crystals will have one set of 5 crystals that have lower Rm than the other 3 sets. Use this set with the lowest Rm for your very narrow bandwidth design (1 KHz or narrower.) This will give the least amount of insertion loss. They will not be marked. If you need to know which set has the lowest Rm, you will have to retest them. All of the sets will have Rm from 10 ohms to 18 ohms. A set of 5 will not deviate more than 2 ohms.

Fs is matched to within 50 Hz. That is, a set of 5 will not deviate more than 50 Hz from each other.

They will arrive in 4 plastic carriers. Each carrier will contain a matched set of 5 crystals. Do not remove the crystals from the carrier until you are either ready to use them or wish to retest them. In other words, DO NOT mix them up or you will need to retest them all to get them back into matched sets.

This was a great job of crystal matching, given that we had several thousand crystals to select from. For those who did not respond to our original Crystal Poll, there will be a "Group Buy" of these crystals at a later date.

I love this stuff.


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