Is there some magic to using the 72 MHz oscillator? Gigahertz synthesizers
are cheap and simple these days. Back in the bad old days multiplication
was the cheap and easy way to get stable high frequencies. Today, that
helical resonator would probably buy the synthesizer chip and associated
support circuitry, and you needn't fiddle around with stage after stage.

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"Alan Peake" wrote in message
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Hello all,
I am trying to muliply a 72MHz crystal oscillator to 1296 MHz. My
first approach was to just make a series of X2 or X3 transistor mulipliers
to get the require X18 multiplication fact. However, I have found two
pieces of equipment in the junk box which just use diode multipliers. One
is an old Electrophone UHF CB radio which multiplies the crystal
oscillator by 17 (I think, from memory)then uses helical resonators to
filter the desired harmonic. The same approach is used in an old King
aircraft transponder where the 138 MHz crystal is multiplied to 960 MHz
with just a diode and uses the first two stages of an interdigital mixer
to get rid of unwanted harmonics.
So, the question is, which is the better approach? I just want a
reasonably clean signal source to test a 1296 MHz down-converter.
The diode approach seems simpler but is it likely to contain more spurious
signals than a transistor multiplier chain?
Alan
VK2ADB