RigExpert GPSDO Instructions manual

Tokenblauser

Low-noise GPSDO,
quad clock source –

0.16 to 200 MHz

RigExpert®

User's manual

Table of contents

Tokenblauser – a versatile GPSDO platform.......................................................4

High stability and low noise...............................................................................6

The first use......................................................................................................7

Menu description...............................................................................................8

Serial port interface..........................................................................................12

Arduino serial plotter.........................................................................................13

TimeLab interfacing...........................................................................................13

Updating the firmware.......................................................................................16

Compiling the firmware from the source code....................................................17

SI5338 configuration presets............................................................................17

Annex 1 – Specifications...................................................................................18

Annex 2 – Glossary...........................................................................................19

Tokenblauser –
a versatile GPSDO
platform

The Tokenblauser is a GPS disciplined clock source with very low noise output,
suitable for QO-100 and SHF applications, including operating FT8 and other
narrow band digital modes. Unlike many other GPSDOs with fixed 10 MHz output,
it additionally generates up to four arbitrary frequencies simultaneously. This
functionality is provided “out of the box” and does now require advanced skills
from the user. Just apply power to the device and connect a GPS antenna, then
enter or change output frequencies.

Example of use for operating the QO-100 satellite

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User's manual

However, we designed the Tokenblauser to be also a versatile platform for
experimenters. The device is Arduino-compatible, and the firmware is open-source.
With no or minimal changes in the code or in the hardware, an advanced user may:

• Connect the GPSDO to a computer for debug purposes or data processing

(such as plotting ADEV/MDEV graphs);

• Modify the firmware to experiment with different PLL and FLL algorithms;

• Use own GPS modules and GPS antennas;

• Use different types of OCXOs and Rubidium oscillators.

Structure diagram of the Tokenblauser GPSDO

The Tokenblauser is based on ideas of Brooks Shera, Lars Walenius and many
other enthusiasts.

Tokenblauser 5

High stability
and low noise

where the OCXO is good. In opposite, during long periods, the GPS is a winner.

By locking the frequency of a
local oscillator to the reference
GPS receiver, GPSDOs are

capable to have good stability
in both short-term and long­term areas. The position of the

intersection point depends on the
type and the quality of oscillator
used; for OCXOs, it is usually 100
to 1000 seconds. Thus, OCXO­based GPSDOs are able to provide
good frequency stability for
laboratory and hobby use.

The next chart is one of

standard models of an
oscillator phase noise.

Obviously, for a better GPSDO,
the corner frequencies fc1 and
fc2 need to be located as close to
the carrier frequency as possible.

Just look at a simplified Allan

deviation chart, which compares the
stability of different types of
generators over time. The GPS receiver

itself has a bad short-term stability,

If the GPSDO output is
multiplied by the PLL-based
oscillator, we usually think of 20

dB/decade as a noise increment. However, this is not an axiom: much more noise
is added for frequencies to the left of fc1. By using a professional-grade OCXO, as
well as carefully designing the RF circuits, very good noise parameters of the
GPSDO can be achieved.

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User's manual