Re: a simple spur fix

Jerry Gaffke
 

This might be an opportunity for somebody to create yet another new Raduino
Add buffer amps to all three clocks from the si5351 to help solve the spur problem.
Choose a processor clock that won't beat with the BFO, creating audio tones cases
where the Nano's 16mhz ceramic resonator happens to fall on an unlucky frequency .
Communicate with a host processor via well filtered 3v UART lines
that go off to a well shielded USB-to-UART dongle.
Processor is a little beefier, something like an STM32F*, not pressed for memory space,
more IO pins, and with the horsepower for a few simple digital modes such as PSK31.

This could easily be used to upgrade old v3 and v4 uBitx's.

Jerry, KE7ER


On Sat, Nov 10, 2018 at 06:41 AM, Jerry Gaffke wrote:
Unless we add an amp to each of the three clocks between the si5351 and the mixers,
we are trading off si5351 crosstalk, local oscillator injection level, and reflections due to 
driving the mixer from a source impedance higher than 50 ohms.
All three of these factors will contribute to spurs.

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