Most electronics technicians are finding more and more need for a high accuracy digital frequency counter. Communications shops and commercial broadcast stations need both a wide frequency range and high accuracy in their frequency counters to meet the FCC requirements for accurate measurements of various transmitter frequencies. Service technicians find that a frequency counter is a valuable piece of test equipment for troubleshooting the digital circuits found in UHF and VHF television tuners and the modern digital FM receivers. Other applications (like video tape recorder, medical equipment, and industrial maintenance) require frequency counters for many tests and adjustments. The FC51 offers both a wide input frequency range and high accuracy for work in any of these applications where the signal is between 10 Hz and 1000 MHz. Extra features, like all pushbutton operation and automatic selection of prescalers, are normally found only on frequency counters costing much more than the FC51. A review of the following section will cover these special features and explain how they simplify the operation of the FC51 and offer versatility not usually found in a frequency counter in this price range. FEATURES The FC51 1 GHz Frequency Counter allows direct readings of all frequencies from 10 Hz through 1 GHz with accuracies that exceed the FCC specifications for all communications work up to 1 GHz. The metal case of the FC51, along with internal RF shielding, provides interference-free measurements in practically any type of RF field. The large (.5”) 8 -digit display allows direct readings with automatic placement of the decimal. Special indicator lights show whether the counter is measuring "Hz" or “MHz”, and an overflow indicator indicates that a reading requires more than the full 8 digits of readout. The FC51 features large, comfort-sized pushbuttons for ease of operation. These buttons select the desired input jack, read rate, and frequency range. Three inputs are available. The first is a fuse-protected 50 Ohm termination for proper reading of high frequency signals. The 50 Ohm termination prevents cable ringing which could cause inaccurate readings. The second input is a high sensitivity input with 1 Megohm loading to allow direct connections to lower frequency circuits. This input is controlled by a frontpanel sensitivity control which allows many noisy signals to be measured which normally will produce erratic readings on a high sensitivity counter. The sensitivities of both of these inputs have been designed for fast signal tracing in most applications. If additional sensitivity is required for special applications, the optional WBA52 1 MHz through 1 GHz Wideband Amplifier provides an additional 30 dB of input gain. The WBA52 is powered from the accessory jack on the front of the FC51. The third input is Sencore’s exclusive crystal check which allows any crystal to be tested by simply inserting it into the special front panel test socket. Two read rates give a choice of fast updates or maximum resolution, depending on the type of signal you want to measure. Four different frequency range buttons provide the best resolution for any measurement. Two built-in prescalers extend both the high and low frequency capabilities of the FC51. The first prescaler allows frequencies from 100 MHz to 1 GHz to be measured and the second “audio prescaler” provides additional digits of resolution when measuring frequencies below 20 KHz. Both prescaled options provide automatic decimal placement for direct readings. The high accuracy timebase oscillator is built into a proportionally-controlled oven to assure the highest accuracy possible over a wide range of ambient temperatures. The entire oven and oscillator is contained in a single plug-in module to allow the option of exchanging the module with one that is freshly calibrated so that it is not necessary to return the entire counter for accuracy calibration. Finally, the FC51 offers a choice of 110-120 VAC line operation or 12 VDC operation for versatility of use in bench or portable testing. Input connections are made with the supplied counter probe, pickup loop or adjustable antenna.