Hi
Unless you measure the change of the device over a controlled temperature
range ( like 0 to 70C ) at a controlled rate ( like < 0.1C / minute ) it’s hard
to
know if this or that restriction / insulation on an OCXO has “upset” its
temperature
compensation. If you “make the heater work half
This may give some idea of how fast things can happen when the OCXO is
subject to drafts. I have this dual GPSDO box that usually is open for
experimenting, and have a setup comparing one of the 10 MHz outs to my
portable Rb reference. The 10 GHz multiplied output from the Rb is
indicated on a
Hi
> On Jul 5, 2022, at 9:00 AM, Erik Kaashoek via time-nuts
> wrote:
>
> Mike.
> One concern I have with active components as mixer is noise. For an SA I
> designed only a passive DB diode mixer had low enough output noise. Would a
> PF detector as being an active component, not create more
Hi
The mixer sensitivity is based on both ports being saturated. You
are trying to check the circuit end to end in it’s “as used” configuration.
There is no real need for an added calibration source, provided you
pay attention to the basics.
Bob
> On Jul 5, 2022, at 12:04 PM, Erik Kaashoek
Bob, See below
Thanks.
Erik.
On 5-7-2022 19:37, Bob kb8tq wrote:
Hi
One “cute trick” that can be done on the lowpass filter:
Ideally you would like to terminate the mixer properly at the DUT and DUT x 2
frequencies. Open circuit (or short circuit) is ok at audio. The quick and easy
way
to do
Hi
One “cute trick” that can be done on the lowpass filter:
Ideally you would like to terminate the mixer properly at the DUT and DUT x 2
frequencies. Open circuit (or short circuit) is ok at audio. The quick and easy
way
to do this is to put an appropriate resistor ( 50 ohm, 500 ohm, whatever
Why would using a calibrated noise source into a 1Hz per bin FFT not be a
good level check? Just subtract 3 dB due to both widebands folding and you
have a reference.
A noise source should also be great for checking flatness I think.
A noise source at -90dBm/Hz around 10 MHz is cheap on eBay.
Hi
One of the “gotcha’s” with this is the need for dual supplies. That’s what lets
you
get to an 30 something volt peak to peak output on the initial amp. It also
keeps
all the signals ground referenced through the system.
The downside ( as noted in posts from a number of years ago) is that
Mike.
One concern I have with active components as mixer is noise. For an SA I
designed only a passive DB diode mixer had low enough output noise. Would a
PF detector as being an active component, not create more noise as output?
Erik
On Tue, Jul 5, 2022, 18:20 Mike Monett via time-nuts <
Hi
If you need that sort of isolation, it certainly can be done.
NIST has papers on very simple / DIY compatible cascode
amps that will do the trick. ( chain of common base stages
driven by a common emitter). Some folks on the list have
gone a lot further in terms of complexity than NIST did.
Here a small schematic of the simple Phase Noise Analyzer
Hope this answers some of the questions.
The +5 V reference from the OCXO is buffered by U1.
The 3 ports of the used ADE-1 mixer are galvanically isolated greatly
helping to reduce ground loops.
The output of the mixer is low passed
Eric,
Another problem I forgot to mention, the exclusive-or phase detector has a
severe output ripple. This will cause frequency shift in the oscillator
frequency which will show up in the measurements.
The phase-frequency detector has zero ripple at lock. There is a small
transient at the
You stated:
Mike,
The phase detector is an ADE-1 mixer, the IF output of the mixer goes
into a loop filter that has a corner frequency of about 0.2Hz to enable
Phase noise measurements down to 1Hz offset
That is your problem. A double balanced mixer is an exclusive-or phase
detector. The lock
I've tried to do a simple and low-cost sound-card PN system too back in the
days. It's fun, when you see the broadband thermal resistor noise in your
FFT plots :) But when doing experiments with the crystal oscillators, I've
found out that one of the *MOST* important things to worry about is
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