[time-nuts] Synthesizers for Rb standards

[Gerhard Hoffmann]

A relatively easy way to go to ...13.6 GHz is the ADF5356 made by Analog 
Devices.
< 
https://www.digikey.de/product-detail/de/analog-devices-inc/ADF5356BCPZ/ADF5356BCPZ-ND/9485473 
       >

All you need is your reference frequency, 10 or 122.8 MHz or whatever,  SPI
and a clean supply. Frequency resolution is without limit for all practical
purposes. VCO is on-chip, de facto multiple switched VCOs per octave
for phase noise reasons. The chip price reflects that.

The chip in the pic is about 4*4 mm. there are two LT3042 regulators to
produce / clean up the supply voltage on adf5356_test_circuit.png.
The synthesizer itself takes about a square centimeter.

A weak point is the 6.8 to 13.6 GHz doubler. The suppression of the
fundamental is a joke. The doubler has a serious symmetry problem.
Even AD comes to their limits there. See .gif of eval board.

But I have a nice microstrip filter on Rogers TMM6 to deal with that.
(I don't really like TMM6. It has the consistency of candle wax, nearly.
I broke a board by attaching a SMA connector with 2 fingers.)

cheers, Gerhard



Am 13.10.20 um 19:28 schrieb Attila Kinali:
> On Wed, 7 Oct 2020 10:22:43 -0400 Bob kb8tq <kb8tq at n1k.org> wrote:
>> People have successfully mounted eBay synthesizers in 5065’s. They 
>> work and it is one way to take care of that. 
> Some time ago, I had a "quick" look on how I would design
...

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