Hi,
use a PLL.
Klaus
See application note AN1994, says 200mV LO level.
Frank
Change the first IF with a proper value so that your Xtal would be easily available.
You don't have to use 183 MHz helical filter, use another proper one associated with xtal..
Only two choices here that I can see.
Purchase a custom ground overtone crystal for 172.3 Mhz.
I recently ordered one for 73.500 Mhz, for a very similar application, still recovering from the $53.00 price shock though.
That is probably the simplest minimum components solution.
Another way to do it might be with a phase locked loop using an E-bay ready to run DDS circuit board.
**broken link removed**
Now these only go up to 70 Mhz output, and struggle to get even that high from a 180 Mhz clock source on the DDS board.
The trick would be to turn the DDS around, and drive it from a VCO running at 172.3 Mhz instead of the 180 Mhz internal clock.
You then program the DDS to provide any output frequency to match some other conveniently available reference source.
This can be ANY frequency from audio up to 70Mhz in about 0.04 Hz steps !
Then use that to phase lock your VCO to 172.3 Mhz (within maybe a couple of Hz). The DDS becomes in effect a divide by N counter with very fine resolution that you can set to better than one part in four billion fractional division.
Its still slightly complicated, because the DDS frequency (40 bits) needs to be programmed in at power up.
If your spectrum analyser already has a microcontroller, that should be very easy.
The fewer frequencies you generate, the fewer spurious "mystery" signals will make themselves right at home on your spectrum analyser.
A comb generator feeding into a broad band mixer would be about the very last thing you would want.
One example datasheet.
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