AHM - TimeTech GmbH

Functions and Performance
• Generates an atomic frequency reference.
• Typical ADEV@10 000s = 5 x 10 -16
• Frequency drift < 1 x 10 -14 /day
System Description
Copyright © 03/2006, TimeTech GmbH
Data subject to change without notice.
24 Mar 2006
Active Hydrogen Maser
Part No: 10351
Generated outputs
• 5 MHz
• 100 MHz
• 1 PPS
The Active Hydrogen Maser (AHM) generates an extremely stable atomic frequency reference. It
uses the quantum transition between two of the hyperfine levels (F=1, mF=0 to F=0, mF=0) of the
ground electron state of atomic hydrogen. This corresponds to a frequency of approximately
1.420 405 751 770 GHz. A synthesizer-based frequency converter is used to derive the standard
frequencies of 5 MHz and 100 MHz from that atomic frequency reference.
The standard frequencies of 5 MHz and 100 MHz are available from 2 outputs each. All frequency
outputs are DC-decoupled.
TimeTech GmbH Tel.: ++49 711 67808-0
Curiestrasse 2 Fax: ++49 711 67808-99
D-70563 Stuttgart e-mail: info@TimeTech.de
Germany web: www.TimeTech.de

AHM
TIM part No 10351
Specifications of the EFOS_C Maser
Frequency Stability and Phase Noise
The main characteristics of the Maser are the frequency stability (Table 1) and the SSB phase
noise (Table 2):
Averaging time
tau [s]
Copyright © 03/2006, TimeTech GmbH
Data subject to change without notice.
24 Mar 2006
Page 2 of 5
Specification
Allan deviation
s y (2, tau)
5 MHz
ADEV typical
100 MHz
ADEV typical
1 1.5·10 -13 1.1 x 10 -13 9.0 x10 -14
10 2.0·10 -14 2.0 x 10 -14 1.5 x 10 -14
100 5.0·10 -15 3.2 x 10 -15 3.2 x 10 -15
1'000 2.0·10 -15 1.0 x 10 -15 1.0 x 10 -15
10'000 2.0·10 -15 5.0 x 10 -16 5.0 x 10 -16
Table 1 : Frequency stability
The phase noise specified in Table 2 is reached with the low noise OCXO (BVA 8607 OPT 08 from
Oscilloquartz, Switzerland).
Output signal
Specification
Output signal
typical
5 MHz 100 MHz 5 MHz 100 MHz
Frequency L(f) [dBc/Hz] L(f) [dBc/Hz] L(f) [dBc/Hz] L(f) [dBc/Hz]
1 Hz -129 ± 2 -100 ± 2 -129 -101
10 Hz -145 ± 2 -114 ± 2 -146 -114
100 Hz -152 ± 2 -122 ± 2 -153 -123
1'000 Hz -158 ± 2 -147 ± 2 -158 -147
10'000 Hz -158 ± 2 -155 ± 2 -158 -155
100'000 Hz -158 ± 2 -159 ± 2 -158 -159
Table 2 : SSB phase noise (with BVA 8607 OCXO)
TimeTech GmbH Tel.: ++49 711 67808-0
Curiestrasse 2 Fax: ++49 711 67808-99
D-70563 Stuttgart e-mail: info@TimeTech.de
Germany web: www.TimeTech.de

AHM
TIM part No 10351
Copyright © 03/2006, TimeTech GmbH
Data subject to change without notice.
24 Mar 2006
Page 3 of 5
Parameter Value
Frequency accuracy (after adjustment with
a Cesium standard)
≤ 2·10 -13
Frequency drift ≤ 1·10 -14 /day
Frequency adjustment range ± 3·10 -8
Frequency adjustment resolution 6.4·10 -15
Table 3: Frequency accuracy and settings
The sensitivities of the Maser to environment are given in Table 4.
Frequency sensitivity to
temperature:
Phase sensitivity to temperature
(between sine outputs):
Frequency sensitivity to Magnetic
field:
Operating conditions
Non-operating conditions
≤ 5·10 -15 /°C (Note)
≤ 10 ps/°C, (typical: 8 ps/°C)
≤ 1·10 -13/ Gauss (in a range of ± 1 Gauss)
+20 to +30 °C
50 to 90 % RH
0 to + 45 °C
5 to 95 % RH, (non-condensing)
Table 4: sensitivity to environment
Note : This value can be improved by using a heater/cooler box (TIM part No 10352) that improves
the thermal stability environment of the maser by a factor of 20.
TimeTech GmbH Tel.: ++49 711 67808-0
Curiestrasse 2 Fax: ++49 711 67808-99
D-70563 Stuttgart e-mail: info@TimeTech.de
Germany web: www.TimeTech.de

AHM
TIM part No 10351
Electrical Interfaces
Sine outputs and 1 Pulse per second output
The four sine outputs of the Maser consist of two 5 MHz signals (type “N” connectors), and two
100 MHz signals (type “N” connectors). These outputs are DC decoupled.
Output Level
(50 ohm)
Copyright © 03/2006, TimeTech GmbH
Data subject to change without notice.
24 Mar 2006
Page 4 of 5
Isolation
(between
outputs of the
same
frequency)
Spectral
purity
(2nd harmonic) Close-in
spurs
(Δf < 100 kHz)
Spectral purity
Non
harmonic
related
spurs
5 MHz (2 outputs) ≥ 12 dBm ≥ 60 dB ≤ -40dB ≤ -120 dB ≤ -105 dB
100 MHz (2 outputs) ≥ 11 dBm ≥ 60 dB ≤ -40dB ≤ -110 dB ≤ -90 dB
Table 5 : Sine output signals: 5 and 100 MHz
A “one pulse per second” (1 PPS) signal characteristics is also available (type “BNC” connector):
Connector type: BNC
Frequency output: 1 Hz
Output impedance: 50 Ohm
Output levels: TTL
Rise and fall time:

AHM
TIM part No 10351
Power connection
The Maser can be powered with:
• DC voltage (22 to 30 VDC) through two connectors “A1” and “A2” of “Amphenol type
(MS3102A, 5 poles male) connected in parallel.
• AC voltage from the main power (230 V, 50 Hz) through one connector “B1” of type IEC
320.
The two inputs are protected and isolated with diodes.
Power (normal operation) < 100 W, typically 70 W, 3A
Power (standby: ion pumps and heater) < 30 W, typically 20 W, 1A
Table 7: Power consumption
The maser has a redundant uninterruptible power supply (UPS) that consists of two external
batteries and a battery charger (24 V).
The batteries are of the type Dryfit A500 (Manufacturer: Sonnenschein GmbH, 63654 Büdingen,
Deutschland, http://www.sonnenschein.org/). The battery charger is of type Dryfit SM (24V, 7A) of
the same manufacturer.
Physical
The Maser is mounted in a standalone rack mounted on a trolley with the following dimensions:
Width: 65 cm
Depth: 65 cm
Height: total height: 107 cm
Copyright © 03/2006, TimeTech GmbH
Data subject to change without notice.
24 Mar 2006
Page 5 of 5
rack alone: 90 cm
shock dampers: 5 cm
trolley & wheels: 12 cm
Weight: < 100 kg
Table 8: Physical characteristics
TimeTech GmbH Tel.: ++49 711 67808-0
Curiestrasse 2 Fax: ++49 711 67808-99
D-70563 Stuttgart e-mail: info@TimeTech.de
Germany web: www.TimeTech.de