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HEWLETT-PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - d p - L A B O R A T O R I E S
VOL. 4 No. 11-12
UBLISHED 1953 THE HEWLETT-PACKARD COMPANY, 395 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JULY-AUGUST, 1953
Measurements to 100 Megacycles
with the -hp- Frequency Counter
' I "* HE -hp- Model 5 24 A Frequency Counter method has generated a wide demand to ex
J- has substantially simplified measure tend the method to much higher frequencies.
ments of frequency wherever it has been used. Thus far, this has not seemed practical in
To measure frequencies up to 10 megacycles commercial instruments although under
with the 524 A, it is only necessary to con laboratory conditions counters can be made
nect the unknown frequency to the counter. to operate considerably above 1 0 megacycles.
The counter does the rest, displaying the It is practical, however, to provide a sim
measured frequency quickly and accurately
ple, straightforward heterodyne device to
on a direct-reading digital system. The coun
enable the counter to be used with frequen
ter is in wide use in laboratory and produc
cies as high as 1 00 megacycles. Such a device
tion frequency measurement applications in
which non-technical personnel easily make is the -hp- Model 5 1 2 A Frequency Converter
precision frequency measurements that for shown in Fig. 1. This converter subtracts an
merly required skilled personnel using a integral multiple of 1 0 megacycles from the
combination of several instruments. frequency to be measured and provides the
The 524A circuits directly count frequen remainder at its output terminal to be meas
cies as high as 10 megacycles, the highest fre ured by the counter. For example, if a fre
quency capability of any commercially- quency of, say, 98.75 megacycles is to be
available counting circuits. Nevertheless, measured, the converter will subtract 90
the inherent attractiveness of the counter megacycles from this value and will pass
8.75 megacycles to the frequency counter.
Since the 8.75-megacycle value is within the
10-megacycle capacity of the counter, the
counter will display this value directly. To
determine the unknown frequency, then, it
is only necessary to add the frequency coun
U D ter reading to the value subtracted by the
converter. This addition can easily be per
formed mentally, because the converter di
rectly indicates the frequency value it has
subtracted and because this value is always
an integral multiple of 10 megacycles. Thus,
the operation of the equipment is still very
Fig. 1. Neu- -hp- Model