Model 81000-A

0.45Mhz- 2300MHz/100mW-10kW ´ë¿ªÀÇ RF ¿ÍÆ®¹ÌÅÍ
¡¾5 % ÀÇ Á¤È®µµ
4-1/2ÀÎÄ¡Å©±âÀÇ ½ºÄÉÀÏ
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N Type Female Ä¿³ØÅÍ  

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Description

The Model 81000-A includes a meter and a line section with quick-match RF connectors contained in an aluminum housing having a removable metal enclosure at the rear. The unit has four rubber bumper feet on the base. Storage is provided for 2 extra elements. For mechanical protection the meter is shock mounted. Below the meter is a socket for the plug-in detector element.

Model 81000-A RF Wattmeter is normally supplied with type "N" female connectors. To avoid measurement errors caused by the use of "between series adaptors" we recommend the use of proper Quick Match Connectors.

To make RF power measurements, the plug-in detector elements are inserted in the socket of the line section. Each element is designed for a particular RF power and frequency range. A retainer is provided on the casting face to maintain alignment and assure bottom contact of the element body. The contacts on the plug-in detector element make connection with the DC pick-up loop only when the plug-in detector element is in the precise forward or reverse position. The stylized arrow indicates the direction of power flow.

The meter scale, as described above, is read according to the full scale rating indicated on the cap of the plug-in detector element.

Purpose and Application

The Model 81000-A is a directional RF wattmeter, which measures power flow and load match in coaxial lines. It is for use with CW, AM, FM, and TV modulation envelopes, but is not for use on pulsed transmitters.

The wattmeter is designed for 50-ohm application. The insertion VSWR of this equipment is very low, less than 1.05:1 for frequencies up to 2300 MHZ in a 50-Ohm circuit. The meter is direct reading, expanded down-scale for easy reading. The fifty divisions are graduated or 25, 50 and 100 full scale. By adjustment of the decimal point, these graduations may be used for any plug-in elements that are provided with this equipment.

Coupling Circuit

When the wattmeter is inserted in a transmission line the RF power flows thru a precision section of 50-ohm air line. The element installed in the line section socket is coupled capacitive and inductive to the main line. Voltages proportional to the RF voltage and current in the main line are therefore induced in the element circuitry. The coupling is so adjusted that the induced voltages add in the sensitive direction and cancel for the opposite direction. These voltages are rectified and the resulting DC current is applied to the meter which is calibrated to represent the RF power in the main line.

Theory of Operation

Traveling Wave Concept

The operation of this wattmeter is based on the traveling wave concept of RF transmission. As RF is applied to a transmission line, there is a forward wave traveling from the transmitter to the load, and a reflected wave traveling from the load to the transmitter. The closer the load is matched to the transmission line, the smaller the reflected wave will be. To determine the RF power dissipated in the load, it is necessary to determine the RF power of the forward wave and the RF power of the reflected wave. The difference between the two will indicate power absorbed by the load.

Voltage Standing Wave Ratio (VSWR)

VSWR is an index of the magnitude of the mismatch between the power source and the load. The interference between forward and reflected waves produces a standing wave in the system. VSWR is a widely used tool. There is a simple relation between forward power, reflected power and VSWR:

VSWR Formula

For example, 1% reflected power is about 1.2:1 VSWR and 10% is about 2.0:1 VSWR.

Power Range

100 mW to 10 kW

Frequency Range

0.45 MHz to 2300 MHz

VSWR

1.05:1 max. (with type N connectors)

Accuracy

¡¾5% of full scale

Impedance

50-Ohms

RF Connectors

Type N Female standard (see note below)

Dimensions (H x W x D)

7.3 in. (18.5 cm) x 5 in. (12.7 cm) x 4 in. (10.2 cm)

Weight

3.6 lbs. (1.6 kg)

Case Finish

Textured Blue Polyurethane Enamel


 

 

                   

 
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