Re: ubitx circuit, wiring, source code on github

Jerry Gaffke

To scan the 12mhz filter passband, I'm thinking we drive CW-KEY high to unbalance the first mixer,
freeze clk1 at 57mhz, then scan clk2 and clk0 around 45mhz and 12mhz respectively,
monitoring the resultant audio beat note with scope or AC voltage meter.

Since the first mixer is unbalanced, anything on clk2 will continue on through to the second mixer
where it mixes with the 57mhz clk1 to create something near 12mhz. 
If clk0 varies from 12.000mhz down to 11.990mhz while clk2 varies from 45.000mhz to 45.010mhz, we should hear a constant
1khz audio tone that varies in intensity according to the 12mhz crystal filter's response to the 57mhz-clk2 frequency that
is passing through it.  This could be plotted on graph paper while reading the AC audio voltage and the frequency
of 57mhz-clk2 from the display, 

At any rate, nothing I am bringing up today should slow hfsigs down in building those rigs.
They will likely work fine as shipped, and all these minor adjustments will give the tinkerer's among us something to do.

Jerry, KE7ER

On Thu, Dec 7, 2017 at 10:09 am, Jerry Gaffke wrote:
An alternative would be to scan clk2 and clk0
through the crystal filter passband such that a constant frequency audio beat note is heard, and have the
user identify where the amplitude falls off at each edge of the 12mhz crystal filter passband.

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