Operational Description

FCC ID: CCXTC100

Operational Description

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FCCID_26186

Professional Testing (EMI) Inc. FCC ID: CCXTC100 PROFESSIONAL TESTING EUT DESCRIPTION AND OPERATION TRIMBLE NAVIGATION TC100 TRANSCEIVER 1.0 EUT DESCRIPTION The Trimble Navigation (Limited) TC100 Transceiver is a VHF Airborne Communications Transceiver. The TC100 is a 7 watt, 2 way radio intended for use in general aviation aircraft. This radio tunes over the frequency range of 118.000 to 136.975 MHz. The radio has a memory and display functions to allow frequently used channels to be stored in memory and then quickly recalled. This equipment is not marketed with an antenna or associated wiring or adapters. 2.0 MODE(S) OF OPERATION The transceiver was tested in the normal mode of operation. An audio tone was injected into the EUT in accordance with Part 2 of the Rules for intended transmit tests. Most tests were performed at 3 frequencies (lowest, middle and highest) over the range of operation. A one meter cable with a 50 ohm load was placed on the end of the EUT to simulate a wiring load. For antenna conducted emissions, occupied bandwidth, modulation characteristics, and frequency stability tests, the antenna port was connected directly to the spectrum analyzer input. 3.0 Theory of Operation The theory of operation for this device is described in the following pages. These pages were extracted from the Maintenance Manual for the TC100. It should be noted that some references may appear for the TX 760D. The TX 760D was the initial reference designator for the TC100. The EUT does not possess any operator adjustable components which would affect the output power level of the device. The operator may change the transmit/receive frequency turn the device off and on, adjust the squelch, but cannot change the overall power output or maximum modulation bandwidth.

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ProfssionalTesing (BMQD c reein.coxtcioo s.1 controrter Bonrb asseMezy (Continued) Pins 22 and 23 are used to tell the software what radio it has been installed in. For the TX 760D, both pins 22 and 23 are held low. Pins 27 and 29 along with 28 and 30 of U701, are used for reading the tuning inputs from $W701. Using the pull up resistore on pins 1 and 2 of RP701, and depending on the switch position, a high or a low is placed on the two control lines, A and 8, of SW701. When SW701 is rotated, the voltage on each control line changes at every other detent. When the knob is turned clockwise, the voltage sequence is as follows; A is high when B goes low, A is low when B goes high, B is high when A goes high and B is low when A goes low. This sequence triggers the software to increment the standby frequency with each clockwise detent. Conversely, a counterclockwise rotation of S#701 generates a pulse pattern exactly opposite of that described above. This triggers the software to decrement the standby frequency with each counterclockwise detent. The speed at which SH701 is rotated determines how much the frequency is changed with each detent. A software— confiquzed, microprocessor tiner measures the elapsed time between detents. If the time is greater than 150 mSec; the stendby frequency is changed by 25 KHz. If the time is less than 150 mSec, the standby frequency is changed by 200 Kiiz. when the shaft of SH701 is pressed, the high, from pin 7 of RB7O1, on pin 21 of 0701 is taken low. The software then lights the memory digit on the display. The digit will be ‘0* if the memory has not been used since power up. If memory has been used it will be the last used memory register. Holding the shaft in while rotating the switch will cause the nunber to increment or decrement. The voltage pattern described in the frequency tuning description will determine the increment or dectement. This causes the recall of the memories stored in each of the EEron registers and displays then in the standby window. Pin 25 of U701 monitors the transfer (<——>) switch control line. This control line is held high by pin 3 of RP701 until a low is generated in the display assenbly. When the low occurs, the standby and active frequencies in the display and E€rom are swapped and a new data bit stream is sent to the synthesizer. 48

ProfssionalTesing (BMQD c reein.coxtcioo controrze® BoRRD ASSEMBLY (Continued) Pin 24 of U701 is used to monitor the store (5T0) control line. This control line is held high by pin 12 of RP?01 until a low is generated in the display assembly. If a memory register has been called up on the display, a low on this line will place the standby frequency currently in the window into that register of the EBron. Pin 33 of U701 is the lock detect line from the PL 1C in the oynthesizer. If this line is low, the software in U7O1 inhibite all trensmit capabilitics and causes an error code (01) on the display to flach repeatedly. Pin 34 of U701 is used to monitor the receive indicator line. This line is held high, with pin 8 of P701, untii the equelch opens on the receiver board assembly. When the equelch opens a low is placed on the cathode of CR7O2, causing pin 34 to go low and the "R" on the display will light up. This will not happen if the transmitter is on. CR702 is used to block the 5 volte (on RE701) from affecting the equelch circuit of the receiver. Pin 44 of U701 is the PPP monitor line. This line is normally held high by pin 13 of RP7O1. . When the PTT switch is depressed and a low is placed on pin 2 of PB, a "T" is illuninated on the display. An internal timer is also started within U701, if the PP line is held low for nore than approximately three minutes (stuck micrephone condition), the TX inhibit line 4s enabled, and a flashing error message (02) appears in the standby window of the display. CR701 blocks the voltage normally on the PMT line on the TH/R board assenbly. Pin 45 of 0701 is the TX inhibit line mentioned above. This line is nornally held low by the software, allowing the first L.0. anplifier within the transmitter section to function, 1f the software senses a low on pin 33 (eynthesizer unlock) or a stuck microphone condition, it allows pin 45 to go open, pulling the line high through 2708. This disables the first L.0. anplitier. Pins 38, 40, 41, 42 and 43 of W701 control the serial bit stream used for the PLL IC and the EEron (0702). Pin 36 is an enable line for the PLL IC, this is high only when a new frequency is shifted to the active window of the dieplay. Pin 40 is the chip select line for the EBrom (U702). This line will go high vhenever a frequency is stored or recalled from the menory. Pin 42 is the serial output line from U701. as

ProfssionalTesing (BMQD c reein.coxtcioo conmrorter monto assemett (Continued) The software calculates a nineteen bit serial data stream corresponding to the frequency shown in the active window of the display. This bit stream is used in the PUL 1C. The data strean is calculated and arranged in the manner described in Section 5.3. Pin 41 of 0701 is the serial data in line. the EBrom (U7O2) sends the data from its registers, upon start up or when a menory channel is recalled, on this line. Pin 43 of U7O1 is the serial clock line which the Efron (U702) and the PLL IC (U6O7) use to clock the data bit stream into their respective registers. €703 and the resistor on pin 12 of RP7O1 provide a RC time constant for a soft start of the reset voltage. A Tow to high transition on pin 7 of U701 vill cause a reset within the software of the microprocessor. ¥701 is a 4.19 Mte ceramic resonator used as a time base for the microprocessor (pins 6 and 9). C701 and €702 provide the loading for the resonator. U704 supplies a regulated 5 volts fron the switched 13.75 volte. the 5 volts is used to power the microprocessor (U701) and the Eron (¥702). it is also used for various pull—up resistore (RP701 and 2708) and in the automatic dimming circuit (R701) for the display, The 5 volte is also exported to the synthesizer portion of the hudio/Synthesizer board assembly. C709 is used for additional filtering of the 13.75 volt input Line while C708 improves the transient response on the 5 volt 1ine. U703, a DC to DC converter chip, is the heart of the high voltage power supply for the planar gas discharge display. C704 is a timing cepscitor thet governs the frequency of an oscillator internal to 0705.| C705, C711 and 8711 form a low pass filter thet reduces noise, generated by the high voltage power supply, on the switched 13.75 volt line. Current through 2702 creates a sense voltage on pin 7 of U703. when this voltage reaches 330 mWolte below Vee, the internal circuitry acts to reduce the output current. The output across the primary of 2701 is a rectangular waveform vhose duty cyele is controlled by a feedback loop as described below. R710 reduces noise in the system by reducing the Q of the primary. ‘The secondary is coupled to half wave rectifiere, CR7O3/E706 and CR704/€707 to produce both positive and negative DC voltages. so ‘

ProfssionalTesing (BMQD c reein.coxtcioo conrrottz® BoMRD asszMBLY (Continued) The duty cycle of the waveforn applied to the transformer deternines the magnitude of these voltages. The transformer is being driven at approximately 40kz. Feedback is generated from the positive DC voltage at the cathode of CR703. Because pin 5 of U703 is the inverting input of an internal comparator with a 1.25 volt reference voltage, the voltage at the cathode of CR703 tends to Mluctuate around 1.23V + V‘ where Vt is the zener voltage of CR705 V* is nominally 91 volts. R703 provides a path for current through CR705 while 2709 is used to provide an equal load current on the negative side. 8704 is used to set the total drop across the +90/—90 volt lines to 180 voite. The feedback loop works as follows: When the voltage at the cathode of C8703 gets above approxinately 1.37 volte + ¥, the internal conparator in 0702 produces a low output. This tends to reduce the duty cycle of u7os‘s ourput. This in turn reduces the magnitude of the +90/—90 volt lines. When the voltage at the cathode of CR703 drops below approximately 1.13 volte + Y‘ the conparator has a positive output and tends to increage the duty cycle and thus brings the voltages up. The total ripple across the +50/—90 volt lines is approximately 0.24 ¥p—p. $#702 is a double shafted switch used for On/Off/Yolume and Manual/auto squelch. Turning the small. knob clockwise past the detent places a ground to a relay K601, on the synthesizer/audio board assembly, enabling the aircraft power to be applied to the radio. Turning the knob further clockwise increases the anount of low level audio returned to the audio amplifier cireuitry on the RX/TX board assenbly. Turning the lerge knob clockwise past the detent will take the radio out of auto equelch. The auto equelch level is set by resistore on the RK/TX board. When out of auto equelch the pot in S#702 deternines the squelch point along with R707. s.2 otsptay assmety Use Schematic #9—1100—0080—03, Component Locators #7050—0024—02, 7050—0025—02 and Display Schematic #9— 1200—0107—02 to aid in understanding the following cireuit description. s1

ProfssionalTesing (BMQD c reein.coxtcioo s.2 DISPIAY ASSEMBLY (Continued) When the transfer (<——>) switch, $#902, is pressed, it places a ground on pin 25 of the microprocessor, U7OL, which initiates the transfer sequence described in Paragraph 5.1. When the store (§70) switch, SW901, is pressed, it places a ground on pin 24 of the microprocessor, U7O1. This initiates the store function described in Paragraph 5.1. Anbient light on the photo—resistor, LDRSO1, determines the brightness of the gas discharge display. The photo—resistor varies from approximately 11 kn (strong light) to 1 MM (dark) and forms a voltage divider with R701 on the controller board assenbly. The microprocessor uses this voltage to deternine the pulse width of the anode sweeps and thus the brightness of the displey. CBO1 helps to control brief {luctuations of light intensity. The gas discharge display, D8901, is driven by two different signals, one for the anodes and one for the cathodes. The software controls the synchronization of the anode and cathode pulses. Por a segnent (cathode), at a particular anode location, to be illuminated it must receive a —90 volt pulse at the same time the anode receives a +90 volt pulse. The 5 volt anode pulses for anodes 1 through 8 are applied to the high voltege anode driver, U901. the anode 9 pulse is applied to the base of Cransistor, 903. The arrangement of 0903, Q901, R912, R913, #914 and R915 works in the same way as the driver 1C, 0901 to put the +90 volt pulses on the gas discharge display. The 5 volt cathode pulse for segments a through h and the ® and M buss are applied to the high voltage cathode driver, UBOL. The i seqment and 7 buss pulse is applied to the emitter of transistor 9904. The arrangement of 0902, 0904, R9I1, R916, R917 and Ro18 work together in the sane way as U8O1‘to place the ~90 volt puises on the gas discharge display. R801—R805 and R904—8910 are used for current requlation of the display. R901 controls the current for the cathode "keep alive" while 8902 and 2903 provide current regulation for the left and right anode "keep alive* respectively. s

ProfssionalTesing (BMQD c reein.coxtcioo s.3. avpro/srnmizstzer assmisty Use Schematic #9—1100—0097—04 and Component Locator #7050—0033—03, if the unit is a Mod 6 or lower, and Schematic #9—1100—0122—04 and Component Locator #7050— 0042—04, if the unit ie a Med 7 or above, to aid in the understanding of the following ciruit descriptions. Relay K601 is used to switch the incoming aircraft A+ for the entire radio. as enters the relay on pin 4 and when pin 1 is pulled low the A+ is applied to pin 2. R63 provides current limiting for the coll on the relay. C659 and C660 bypase any stray RF while inductive kickback is controlled with CR603. Uperating pover for the board is supplied through R6S2 and filtered by C657. The circuitry that is operated directly by this voltage is U602, the loop filter operational anplifier, which requires the full supply voltage to achieve the necessary voltage swing, 9604, the 600 D sudio anplifier to achieve the audio power output, and the intercon VX circuit. The intercom VOX cireuit requires this voltage to provide adequate microphone bias current, along with enough voltage swing on the conparator and amplifier circuitry. +5 volts is inported from the controller board for use by U601, the phase lock loop chip and U603, the divide by 40/41 chip. A TX A+ voltage is imported from the receiver/transmitter board, via 37, to pover the final &F anplifier during tranomit. The remaining voltages on the board aze derived from U606, an adjustable voltage regulator set to +8.5 volté by adjusting R648. The date, clock and enable lines, (J6, Pin 4, 3 and 2) are control signals from the mictoprocessor to the synthesizer. They are 5V CHOS logic input level compatible, The lock line (J6, Pin 5) is a 5V CHOS logic level output to the microprocessor indicating the lock condition of the synthesizer. Analog input lines consist of audio sun (37), sidetone (37), VOX key (37), Push To Talk (PMT)(37), microphone audio (37), and VO% equelch adjust (37), Analog output lines include ¥—Ture (37) headphone audio (37) and VX squelch A+ (37). On Mod units and above an output line of Vox audio and an input line of Vox audio adjust are added to 37. Signal RP output line (P11) drives the tranemitter anplitier on the receiver/transmitter board. s3

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ProfssionalTesing (BMQD c reein.coxtcioo 5.3 avpro/onmiretemn assemeuy (Continued) Fine tuning of the oscillator frequency is achieved by adjusting C605 to alter the 6.4 Miz reference frequency, as this frequency is divided by a set nunber. Te reference 25 Kiz eignal can then adjust the oscillator‘s 25 iz signal. The frequency of the voltage controlled osciliator is therefore a function of the division ratio of the "A Counter® and the "N Counter®. This division ratio is input digitaily, from the microprocessor, through a shift register and a latch internal to V6OL. The corresponding input format is listed as follows: <————A Counter Bite————>< ——w Counter Bits=——»<———3i@ 142— aivige divide aivice divige on s by A by A by N by w a 2 Lk wise Lse xsn __ Last data bit in (Bit 19) First data bit in (Bit 1) The corresponding equation for progranning the *A Counter® and the "N Counter® 0: N Counter = the binary equivalent of the ifle portion of the desized synthosizer frequency. A Counter = the binary equivalent of the Kiz portion of the desized synthesizer frequency after dividing by 25. SW 142 are always logic 0 in this application. ror Exanple: a desired synthesizer frequency of 147.675 mie. (136.975 Mz plus the 10.7 Mz local oselllator frequency) N Counter = 147 = 0010010011 A Counter = 675/25 = 27 = 0011011 sw 1 a 20— oo Therefore the data bit strean Se: (Zast Bit) (riret Bit) i 10 11 0 0 11 0 0 1 0 0 1 0 0 o o (a counter) (1 counter) (s) ss

ProfssionalTesing (BMQD c reein.coxtcioo s.3 aupro/syizhestze® AssEMBLY (Continued) The headphone (600 M) audio output stage consists of an audio power amplifier (U604) and an output transformer T602. ‘The gain of 0604 is internally fixed at 20. The auxiliary audio signals, sidetone, microphone sudio when in Vox mode, and low level audio fron the receiver are all introduced into the output anplifier stage. supply de—coupling is provided for the audio anplifier by R6S0 and C633. The audio signal is stepped up by the transformer and passes to the receiver/transmitter beard via 37, Pin 9. The load cen be either an audio panel, one or two high impedance hesdsets or a single low impedance headset. The circuit will deliver a minimun of 250m# of audio output pover. 606 is a switch for the VOX circuitry. when a low is applied to 37, Pin 3, current flow through R635 causes 9606 to turn on. This applies +13.75 to the VoX circuitry. The +13.75 is also applied to the microphone audio line to excite the microphone element through R633. When in the VOX mode, microphone audio is applied to Pin 2 of U604, the audio anplifier, through R630. ‘The audio signal is also supplied to Pin 2 of anplifier U6OSA. The signal is then rectified, filtered, and applied to Pin 6 of U605B, which is configured as a conparator. The voltage on Pin 5 of W6O5B is set by either R642 or an external pot. This voltage then sets the equelch or break point of the VOX intercom feature. Q608 is a squelch mute switch. Whenever a DC voltage is applied to either Pin 7 of U6O5B or the collector of 9607, 0608 turns on and places a ground on the mic audio input to the audio amplifier. 0607 will only turn on when the PM line is taken low, thus muting the VOX mode and using sidetone audio. recerven/mavoutmmen assemoty Use Schematic #9—1100—0096—04 and Component Locator #7050—0032—03 to aid in the understanding the following cireuit descriptions. The primary power supply voltage is applied to the system at P9, Pin 1. This voltage is filtered by 1407, ©499, C502 and C503 before being exported on 35, Pin 2 to the controller and audio/synthesizer boards.‘ _The ewitched voltege then comes back on J5, Pin 1. The +13.75 volt switched voltage is used to generate the +9 volte that is used in the receiver section. se

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ProfssionalTesing (BMQD c reein.coxtcioo recerven/mransmtmme® ASSBMBLY (Continued) Mte signal to produce a second IP of 455 Kie. The mix of the two frequencies leaves U401 on Pin 15 and the 455 KHe signal is filtered with PL403 and returned to U402, via Pin 12. The signal is then anplified and has AGC applied to it. The signal then leaves 0402 on Pin 7 to be applied to T407 and detected by CR4OB. The modulation from the signal is then developed across the load resistor 418. From the detector the sudio proceeds to the series automatic noise limiter (ANL). The ANL circuit consists of forvard biased CRA09, C423, C424, Ré19, R420, R422 and R423. Audio from the AKL is coupled to an operational anplifier, U402B that is confiqured as an audio pre—amplifier. ‘The output of the pre— anplifier is then exported to the controller assenbly on 35, Pin 6 for use in the volume pot of SW702. The wiper contact of the volume control connects back through J5, Pin 7 to the input of 0403, the speaker output audio amplifier, and to the Audio Sum Line that is taken through ®7, Pin 6 to the headphone output audio anplifier, The gain of 0403 is set to 404B for sufficient amplification to drive a speaker to full volune. AGC voltage is taken from the cathode of CR4O7, filtered, and applied to the 455KHz anplifier internal to U401.‘ The AGC is also applied to the AGC anplifier U404B. This amplifier takes the AGC voltage and amplifies it by a fector of 1000 and applies it to the source of Q401 and the base of 416. U404® serves as an anplifier for the equelch circuits. When in the autonatic squelch mode, 2439 sets the equelch level. when in the manual equelch mode, the potentioneter within 5#702 sets the squelch level. U404B serves as the controller for the squelch gate, ©403. when 0403 conducts, it connects the input signal of Ué02B to ground and prevents receiver noise from reaching the speaker. When a signal, strong enough to break squelch, is received, Q403 becomes non—conductive and the audio circuitry functions normally. The output of U402B also controls the receive indicator on the display of the radio. The RP signal from the eynthesizer is capacitively coupled to the base of 0412. Q412 is class "A" biased and functions as a buffer amplifier. se

ProfssionalTesing (BMQD c reein.coxtcioo recerver/meansntmzen AsSEMRLY (Continued) T408 is a broad band toroid transformer and forns the collector load for Q412. The signal is capecitively coupled from the top of T408 to the base of Q413. 0413 is class "AB" biased with both a fixed bias and additional bias being developed proportional to the signal level. This additional bias is developed by rectifying part of the signal with CR418. The resulting voltage created across R492 is added to the existing fixed blas voltage across R492. The broad band torold T409, is the collector load for Q413. The output signal of T409 is capacitively coupled to the driver stage, 0414. Q424 is class "B" biased with its collector load being T410, another broad band toroid. ‘The signal is taken from‘the top of T410 and copacitively coupled to the base of Q415, the final anplifier. Q415 is also class *B" bimsed, its collector load is Té41l. Téll also gerves as the inductor for the first section of the low pase output filter. The low pass filter serves two purposes. _It is used to transform the low collector inpedance of Q415 to the 50 & impedance of the antenna system. Tt also reduces the high order harnonics and spurious frequencies above 137 MHz. The filter consists of a Pi—section (Mé11, C489 and €490), an L~section (L404, C492), another L—section (I405, C493) and a final Pi—section (1406, C510, C494 and C496). The output of the filter is connected to the antenna connector. Q411 is used as a transmit inhibit gate. If the microprocessor on the controller board senses a synthesizer that is unlocked or a three minute time—out on the PPP line, it sends a voltage to the base of Q411. This saturates Q411, grounding the base of Q413 and the tranomit signal, thus inhibiting tranemission of signal. When the transmitter is keyed, a microphone bias voltage is obtaining from the collector of 0409. The audio obtained from the microphone is developed across the microphone gain control potentioneter R477. The wiper of R477 couples a portion of the audio to the inverting input of U40SB. The non—inverting input is connected to a voltage divider across the supply at a point equal to one half of the TX A+ voltage. R457 and R4S6 set the gain of this stage to 100 for the lower audio frequencies. Sone of the audio out of U90SB is routed to the gate of Q408, the conpressor. so

ProfssionalTesing (BMQD c reein.coxtcioo recervea/manshtmme® assemMBLY (Continued) A large positive pulse at the gate will pull the drain down and reduce the audio signal at the input to U40SB. The anount of the reduction is set by the conpression adjustment potentioneter R474. The output signal from U405B is also connected to the inverting output of U4OSA. The non—inverting input, like U4OBB is connected to one—half of the TX A+ voltage. This pernits an audio signal swing of nearly £1/2 of the TX A+ voltage. The supply voltage for the modulator comes through Q409 direct from the aircraft battery. Tt is not regulated, only awitched when the PrB line goes low. U405A is configured as an ordinary audio anplifier, whose gain is set to 10 by R46O and RMG2. The output of U405N is coupled to the base of 0405, which is configured as an emitter follower. 0405 drives 0406, another enitter follower, which drives 0407 another emitter follower. Q407, being in series with the supply to the RP driver and final anplifiex, functions as the modulator. The output power of the tranemitter is set with R4GS. With no audio applied, it adjusts the quiescent voltage available to the NP driver and final amplitier (Q414 and Q415 respectively) . so


Document Created: 2019-09-05 15:13:24
Document Modified: 2019-09-05 15:13:24
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