Re: Crystal matching for the uBITX (was uBITX - A reboot of the old BITX)
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the G3UUR test circuit is all that I have used. but that's a start, after that, using the sweeperino, i build and sweep and tweak the values until an acceptable filter shape emerges. experimentation is a large part of filter design.
On Fri, Jun 23, 2017 at 3:28 AM, Master Ice <special@...> wrote:
Hi Ashhar.
?
I assume you use the G3UUR test
circuit?shown in Experimental Methods in RF design or something
similar.
If so, when calculating the values of Cm
and Lm, did you actually measure and include the stray capacitance of the
crystal holder and the wiring to the crystal switch circuitry?
Were the results significant?or are
they so minimal in effect as to be ignored?
?
Many thanks for your time
?
Slim Haines G4IPZ
?
----- Original Message -----
Sent: Thursday, June 22, 2017 5:50
PM
Subject: Re: [BITX20] uBITX - A reboot of
the old BITX
We have to first characterize the crystal. that's measure their
motional inductance and capacitance. i do this using the G3URR's method. it is
a very simple two transistor oscillator. after that, i use the same oscillator
to measure the frequency of each crystal and sort them into bins.
thanks to the bitx40 production, at least for 12 mhz crystals, i don't
have to match them. they are kept prematched in separate pouches. i just dip
into one!
- f
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