Hi Jim,
On 2019-02-13 14:24, jimlux wrote:
On 2/12/19 6:31 PM, Bob kb8tq wrote:
Hi
The normal approach as you head from HF up through stages to
microwaves is to stop
at various points along the way. Just where depends on the actual
noise you measure on
the sources you have. (Yes you have to measure them yourself).
Once you have your noise plots, you can pick likely crossover points
for a PLL. You then
design the PLL to hit those targets. After that you measure the
result to see how close you
got to your target. Then it’s off to teak this or that to improve
things.
The step by step process continues through VHF to UHF to microwaves
as you move through
various steps. Indeed you may change your plan once you see what your
measurements tell
you about each design iteration.
A lot also depends on just what your target actually is. Running PSK
32 at 22 GHz is a bit
different than running WBFM HDTV at 5 GHz. What works for one may not
be ideal (or even
close) for the other.
So yes, it’s a great way to spend a couple of years fiddling around …..
Bob
Decades -
This is what people who design deep space transponders (particularly
for radio science measurements) spend their time on.
One set of requirements says "we want to make carrier only
measurements with ADEV <1E-15 at tau=1000 seconds with Doppler"
Another set of requirements says "we want to send data at rates
between 10 bps and 10 Mbps"
Also, you want to maintain link capability for up to 4 decades or so, so
stability of equipment needs to be long term stable in that environment
for that context.
Reading up on these systems is really interesting in their system
design. I really enjoyed reading up on the self-stabilization and
orientation routines to re-establish home-link and orientation in space
if lost.
Cheers,
Magnus
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