Am 20.01.20 um 22:57 schrieb Attila Kinali:
On Mon, 20 Jan 2020 12:50:09 -0800
Mark Haun <[email protected]> wrote:
True enough, but remember that my motivation for using the OCXO in the
first place was to combine the required phase-noise spec with
OCXO-class frequency stability (this is for narrowband coherent
modulation schemes on the shortwave bands where short-term stability of
~ 10^-10 is nice to have). The alternative is what Attila said,
VCXO phase locked to an OCXO. The advantage of doing it this way is
that I [potentially] reduce complexity, board space, and power.
For an SDR application, the ABLNO allone would be the best option, IMHO.
It's low power and low noise. Even for narrowband SW applications.
If you look at the data, you see that the cross-over between the
ABLNO is lower noise to the OCXO is lower noise is around 100Hz.
Unless you are operating at much lower than 100baud, the ABLNO
is going to be enough. If you are using something like AFSK31/PSK31
it's probably borderline which one is better and I would go with
the ABLNO only for simpler construction and easier sourcing.
If you are thinking about trpoposcatter, EME or similar things
with really low baud rates, then I would go for the VCXO+PLL
approach for one simple reason: Flexibility. With a PLL you
have a choice what kind of reference you want to use.
For a back burner project, motorcycle based portable 432 MHz EME,
(i.e. collecting squares with a friend of mine who has a _huge_ antenna),
I decided to use one of these
< https://www.digikey.de/de/product-highlight/e/ecs/ecoc-2522-smd-ocxo >
and call it a day.
432 - (4*100) = 32 MHz = somewhere in the middle of the Red Pitaya passband.
And the Red Pitaya could also run on the 100 MHz. There happen to exist nice
SAW-Filters for both 400 and 432 MHz. No tuning.
There is no Baud rate on EME, just a 600 Hz side tone. :-) Or WSJE.
regards, Gerhard, DK4XP
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