[time-nuts] 5065A Rb Cavity RX - Varactor repair?

[Gerhard Hoffmann]

Am 22.10.20 um 17:09 schrieb Bob kb8tq:
> Hi
>
> The device in the cavity that takes the 60 MHz up to 6.x GHz is a
> step recovery diode ( SRD ). The actual device used (apparently)
> was unique to the 5065.
>
> One proposed “fix” is to eliminate the whole synth / multiply empire
> and replace it with a very high resolution DDS generating the 6.x GHz.
> My guess is that will turn out to be a lot of work ….
Not too much hardware nowadays.
This is a ADF5356 with 2 LT3042 to clean up the supply voltage.
I measured the successor to this board yesterday on 10 GHz out
with my new 1/8 prescaler and the SR620 counter and some
IQD clock source @20 MHz and the SR620 showed only
mHz excursions on 1250 MHz. Could be just the SR620.
Not bad for a VCO on a silicon chip. Well, there are more
VCOs and band switching.

The evil details are in the programming.
See
< 
https://ez.analog.com/rf/f/q-a/536893/adf5356-doubts-about-bleeding-current-programming 
 >
with 2 more photos.

It seems AD EngineerZone is mostly a write-only device.

cheers, Gerhard



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