MODEL
9DDA
VLF/LF RECEIVER
• Provides all that is necessary for frequency com-
parison to NBS
• Monitoring of atomic standards against national
standards
• Simple and effective means of checking counter
tim~base accuracy
The Model 900A VLF/LF Receiver compares the phase of a
local frequency standard with the received carrier of a
frequency stabilized transmitter. Most of the U.S. Navy
VLF transmitters, as well as the NBS LF transmitter
WWVB, derive their carriers from atomic frequency stan-
dards. A local standard can, therefore, be checked with an
accuracy approximating one part in 10
11
using the Model
SOOAReceiver.
By means of front panel switches, a wide variety of
transmissions can be selected in the VLF band from 10 to
25 kHz, or in the LF band from 60 kHz to 75 kHz.
Reception is, therefore, not limited to one or
two
trans-
missions as has previously been the case with economy
model VLF or LF receivers.
Some of the transmissions
which can be received strongly in the United States are:
NAA
NLK
NSS
NWC
NBA
17.8 kHz Eastern Maine
18.6 kHz Jim Creek, Washington
21.4 kHz Annapolis, Maryland
22.3 kHz Australia
24.0 kHz .. Canal Zone
(These transmISSions can be received even when MSK
keying is used.) .
An increasing number of Omega transmissions in the
11.0 to 12.0 kHz band
Other stations which may be received elsewhere in the
world are:
MSF 60.0 kHz Rugby. England
GBR 16.0 kHz Rugby. England
40.0 kHz Japan
77.5 kHz Mainflingen, Germany
FUB 16.8 kHz Paris
The Model 9DDA Receiver is supplied complete with roof-
mounting whip antenna unit, 100 ft. antenna cable. and
front panel chart recorder. The Model 900A may be or·
dered without recorder and a local unit can be used if
desired.
FREQUENCY
COVERAGE: 100 Hz stepsfrom 9.9 kHz to 25.6 kHz
100 Hz stepsfrom 59.9 kHz to 75.6 kHz
