Kenwood-PF-810-Service-Manual电路原理图.pdf

. TRIOFUNCTIONPOWERMETERPF-810“OPERATING INSTRUCTIONSf .-CONTENTSIntroduction. . . . . . . . . . . . . . . . . . . . . . . . . . 3Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Specifications. . . . . . . . . . . . . . . . . . . . . . . . . 4Principlesof operation. . . . . . . . . . . . . . . . . . . 5Operatingparts. . . . . . . . . . . . . . . . . . . . . . . . 7Cautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Schematicdiagram. . . . . . . . . . . . . . . . . . . . . . 12Smithchart. . . . . . . . . . . . . . . . . . . . . . . . . . 13Applications. . . . . . . . . . . . . . . . . . . . . . . . . 14-“-“ ,. INTRODUCTIONThe Function Power Meter ModelPF-810 is a passingtype power/SWR meter coveringa wide frequency rangeof 1.8MHzto 200MHz. It is a laboratory quality, profes-sional instrument for observing and measuring forwardpower from transmitter to load (antenna) and reflectionpower from load to transmitter.It is also capable of measuring power actually con-sumed in load (forward power minus reflection power)for convenience of checking the conditions of trans-mitter and load, in addition to measuringSWRat powergreater than 1W.Besides being used to monitor the operating condi-tions of transmitter or to adjust filters, matching circuit,etc., it is also used to monitor production lines andbusinessuse radio stations.3)FEATURES* Troidal core type directional coupler assures flat fre-quency response, eliminating the need for calibrationtables; calculations and handling knob of frequencyvariation.* Frequencies are practically flat over the range of 1.8MHz to 200MHz in full scale of meter even in 1.9MHzor 3.5MHz band, thus permitting measurements ofvarious functions in low bands with small power.* Radiant power (RAD) indicator (Pat. pending) to in-dicate forward power minus refrection power, isincluded in the instrument. This is particularly usefulto prevent trouble which might occur during matchingwork, and facilitates monitoring and adjustments oftransm itter.* Aritenna selector switch is self-contained to selecteither of two antennas for quick QSY. If a dummyload is connected instead of antenna, the instrumentfunctions as a terminal type power meter.* Large sized, linear scale for easy and error-free reading of SWR and power.4Measurement items:SPECIFICATIONSFrequency range:Power measurementrange:Range setting:SWR measurementrange:Minimum power forSWR measurement:Power measurementaccuracy:Residual SWR:Frequency response:Insertion Loss:Type of connector:Input/outputimpedance:Output terminal:Forward power, refrectionpower, radiant power and SWR1.8MHzto 200MHz1W to 150W5W, 25W and 150W(3 ranges)-+1.0 to 10IJ.11WWithin :t10% of full scaleLess than 1.2Within :t 0.25dBLess than 0.5dB“UHF“ type50-ohmTwo (selected by pushbuttonswitch)j,IIIJ-PRINCIPLES of OPERATIONThe Model PF-810 is composed of four major units,a directional coupler, a voltage converter, an indicatorand a switching unit; all units except the antenna selectorand the directional coupler, function as a DC circuit.Directional couplerThe directional coupler is used to pick up a very smallpower from the coaxial cable connected between trans-mitter and load by separating forward wave and refrec-tion wave components.The directional coupler used in PF-810 consists ofa wide band current transformer T1 and a voltage trans-former T2, both employing troidal cores as shown inFig. 1.iITXANTRfwd1 In Fig. 1, suppose that a current “il“ flows from TXto ANT, then a reverse current “i2“ flows into thesecondary of the current transformer T2. At this time, acurrent “i3“ is flowing into the primary of the voltagetransformer and, hence, a current “i4“ (=i2/2) developedfrom “i2“ and a current “i5“ developed from “i3“ to-gether flow into the secondary of the transformer.If these two currents (i4 and i5) are equal, no voltageappears across “Rref“ because the currents flowing into“Rref“ in reverse direction each other are cancelled,however, a voltage appears across “Rfwd“ because thecurrents flowing into “Rfwd“ have the same directivity.If power is refrected by ANT, the current “i5“ con-tinues to flow in the same direction, while the current“i4“ flows in reverse direction, thus a voltage appearsacross “Rref“, too. Such an action is independent offrequencies if T1 and T2 each ahve a wide frequencyband.The directional coupler of PF-810 uses wide bandtransformers constructed with troidal core and newlydeveloped windings, to pick up the diode detectedvoltage, proportional to forward power and refrectionpower, from the resistors of “Rfwd“ and “Rref“.Voltage converterThe voltage converter is used to provide linear read-ings of power on the scale. Without this converter, theDC voltage from the directional coupler, which is pro-portional to forward power or refrection power, isproportioned to the square root of power, thus the5T1i2“- i3“)-.i4 '$ Rrefi5Fig. 1readings on the scale are crowded which causes dif-ficulty in reading or loss of reading accuracy.The voltage converter uses specially selected diodes,resistors and capacitors. The same type of converter isconnected to both the forward power and refrectionpower terminals.Indication and selectionThe voltage signal from the voltage converter, whichis proportional to power, is indicated on the 100,uA DCammeter through the function selector switch. Thepower range is selected by the range selector resistors.Two sets of voltage converter and selector of the samedesign are provided for forward power and refrectionpower. These can be used simultaneously. Being sodesigned, PF-810 is able to indicate radiant power(RAD).This is achieved by the differential operation of thevoltage converters to wh ich forward and refrection wavevoltages applied respectively.In PF-810, two identical circuits are connected backto back to further improve the performance of thedirectional coupler.6TXANT.II4I J;V.REFV.FWDFig. 2TX.4ANT1() () ANT2.;'fig. olock DiagramOPERATING PARTSMeterPower rangeselectorswitchSWRcalibrator.T'UO FUNCTION POWER METER PF-8I0RANGE (W) FUNeT“,“REF RAO, ,“15'_SWROFF.CALeingused, creating an illusion thatthe refrection power was very small. However, thiscan be eliminated by setting the function switch to.'2.5a:;< 2(f)0.05 0.15 0.2Pr/PI0.25 0.3O. IFig. 7the RAD position with PF-810 connected near to theload. In this way, the power (Pf-Pr) consumed in theload is indicated on the meter, which not only offersa convenience to impedance matching work but alsoallows you to monitor both the forward power andrefrection power at the same time because the powermeasured is decreased as the refrection increases. Ac-cordingly, when PF-810 is used as a monitor, thefunction switch is normally set to the RAD position.Even when PF-810 is connected near to the trans-mitter, the power measured on the meter can beregarded as a radiant power as long as the return lossof the transmitting system is disregarded. When themeter indicates a maximum radiant power (RAD), itmeans that the transmitter or the antenna coupler isproperly adjusted.6. Antenna selectorThe antenna selector permits selection of antennas ordummy load. Two different antennas, such as 3.5/7-MHz 2-band dipole antenna and 14/21/28MHz 3-bandVagi antenna or HF band and 144MHz band antennas,can be connected to ANT1 and ANT2, respectively.A dummy load can also be connected to either ANT1or ANT2, instead of connecting an antenna, fortuning or testing the transmitter.By pressing the antenna selector pushbutton, ANT1is connected to the instrument. By pressing thebutton once again, it is releaspd and ANT2 is con-nected. Note that the power of the transmitter shouldbe turned off whenever the button is to be pressed.11