Kenwood TS790
Contents
1. there will be a perfect eye at the data output The output voltage at 38400 Baud is typically 0 5 volt pp 6 Questions and Answers Q why is the IF signal fed through the IFD Wouldn t it be easier to connect the IFD in parallel to the mixer output A directly after the mixer the signal passes a quartz filter As with every filter the input impedance varies significantly with frequency within the passband the filter is matched outside the passband the filter reflects the signal The amplitude spectrum at the filter input shows a sharp notch at the passband Attaching a parallel demodulator here would cause severe distortions due to the varying load So the signal after the mixer has to be buffered The amplified signal is attenuated again to get the same or a few dB more signal level as without amplifier Q is a AFC output available A There is an unconnected pair of pins on the printed circuit board M60 M61 These pins can be connected to the joint of R52 C52 DET out via a 100 k resistor to pin M60 The voltage measured at this pin will depend on the center frequency of the received FM signal Q how do I decode a fast packet radio signal of 38kBaud or more A The TNC2 with the Z80 processor cannot decode signals beyond 19200 Baud The newer TNC3 or TNC31 series is capable of receive and transmit baudrates up to 1 Mbit s There are modems with all common baudrates 9600 19200 38400 76800 153600 and above Special modems with dif2. Ohm side of both transformers go to the input and output of the IFD via a thin 50 Ohm coax cable The other pin of the 50 Ohm windings are connected to ground Connection to filter input Use a 1 3 step up transformer Solder the 450 ohm output to the tap of L208 where the Q 203 mixer was connected before the other pin to the joint of R213 56 Ohm C218 and L208 Connect the 50 ohm input of the transformer to a thin 50 ohm coax cable Cable shield is soldered to ground Feed this cable marked filter below the fan motor to the bottom compartment of the transceiver Carefully reinstall the RF 430 MHz board Use insulating tape to avoid short circuits and damage of the transformers at the solder side of the board Important Due to the differences in impedance L208 needs to be readjusted now Receive a weak signal and carefully turn the core of L208 to maximum S meter reading if the transceiver to IFD RF IN Mixer to IFD RF OUT Filter Mixer Installation of the IFD board Printed 8 Sep 06 Installation manual for SYMEK IFD wideband receiver Kenwood TS790 A E Page 4 6 There is a corner at the bottom compartment of the TS790 where you can easily install the little IFD circuit board Find the unused hole with a M 2 5 thread in the frame of the transceiver It is in the front left corner transceiver bottom up You can directly fix the IFD to the spare thread using a single M 2 5 x 6 screw As the IFD is mounted top down you have to so
3. 14 1 3 V Q 80 Oscillator Emitter 2 8 V U2 IF IC Pin 20 2 6 V U2 IF IC Pin 11 1 5 V
4. 44 to maximum af signal 1 Vpp at data out L12 and L13 can be readjusted for maximum signal measure RSSI signal with a weak 90 dBm input signal With the input open there should be approx 2 V peak peak noise at the data output For applications where larger input signals are present the input attenuator R1 R2 R3 may be used Normally a capacitor is used for R2 and R1 R3 are open The oscillator components depend on the quartz frequency and fundamental overtone mode The values of L12 L13 C10 to C15 depend on the desired IF input frequency The filters F20 and F30 are selected according to the desired IF bandwidth Printed 8 Sep 06 Installation manual for SYMEK IFD wideband receiver Kenwood TS790 A E Page 6 6 Modifications IFD option TS790 Oscillator quartz TQ730518 65 225 MHz for IF 75 925 MHz standard R80 560Ohm L80 0 33 uH C80 22pF C81 33pF C82 33pF Values for the band filter C10 68pF C11 12pF L12 0 33uH C12 2 2pF C13 2 7pF L13 0 33uH C14 22pF C15 22pF Between joint U1 Pin 3 R10 and the joint C11 C10 a 22 Ohm resistor was added to reduce influence of the filter input impedance on amplifier gain Typical voltages measured wit dc voltmeter U1 ERA 3 Amplifier Pin 1 2 6 V U2 IF IC Pin 1 1 1 V U2 IF IC Pin 18 1 3 V U1 ERA 3 Amplifier Pin 3 3 5 V U2 IF IC Pin 4 4 2 V U2 IF IC Pin 16 1 3 V Q 80 Oscillator Base 3 2 V U2 IF IC Pin 8 4 6 V U2 IF IC Pin
5. Printed 8 Sep 06 Installation manual for SYMEK IFD wideband receiver Kenwood TS790 A E Page 1 6 Modification of TS790E A for UO 12 operation Instructions for use of the IFD demodulator Printed 08 09 2006 16 40 00 Uplink TX any frequency 144 146 MHz 430 440 MHz etc FSK modulation 4800 up to 19200 kBaud Downlink RX 430 440 MHz 38400 76800 Baud FSK 153 kBaud with wider filters optional Material required SYMEK IFD B amplifier mixer demodulator board option TS790 two 1 3 rf micro transformers 2x30cm thin coax cable wire shielded audio cable and other hardware heatshrink tube and other parts as needed The transformers are marked 7003 NEOSID The both 50 pins are located at the side with the dot and the 7003 text the 450 pins at the side with NEOSID text on the upper side In other words If the pin marked with the dot is assumed pin 1 and the pins are counted counter clockwise as usual with IC the 50 input is pin1 2 and the output is pin 3 4 However the text would be bottom up if you have pin1 dot oriented to the left The transformer has a winding ratio of 1 3 which results in a impedance ratio of the square which is 1 9 With 50 at pin 1 2 the impedance at the pins 3 4 is 450 to match the filter 1 Transmitter modulation The TS790 can be simply modulated with up to 19200 Baud if the following modifications are made Open carefully the transceiver case bottom Locate the connec
6. additional IF amplifier the s meter may show few dB difference In the Kenwood service manual 430 Mhz receive system sensitivity adjustment is as follows 1 apply 3 2 100 uV FM signal 1 Khz modulation 5 Khz deviation I used 3 uV at 440 Mhz 2 Tune in sequence L214 L215 L210 for maximum S meter reading then repeat 3 Tune in sequence L211 TC203 L208 L209 for maximum S meter reading then repeat It requires this full series for me to get the sensitivity back up Just adjusting L208 only helps a very little TC203 was a big help These really are easy adjustments Only L209 is a little touchy the others are broader at the peak Although the service manual is quite specific about signal level Printed 8 Sep 06 Installation manual for SYMEK IFD wideband receiver Kenwood TS790 A E Page 5 6 deviation etc I suspect the average ham could do this with any weak constant strength signal source in the 435 Mhz band Adjust the output level of the TNC to get the desired frequency deviation modulation index Do not overmodulate as the transceiver will totally switch off the modulator The modulator should work perfectly for all FSK baudrates from 9600 to 19200 baud Note the input voltage determines the bandwidth of the transmit signal You will need more signal amplitude for higher baudrates The RSSI output should be near zero volts lt 0 1 V signal and go up to 4 volts 1 mV rf input When receiving a 19200 38400 or 76800 baud signal
7. ally only to a tap of L 208 You have to carefully cut this trace between Q203 and L208 Printed 8 Sep 06 Installation manual for SYMEK IFD wideband receiver Kenwood TS790 A E Page 2 6 TS790 case opened RF unit with added coax cables shown Solder side of RF 430 unit with the added transformers You can see where to cut the trace 3 blue lines center Note the SMD type transformes are connected with short 0 3 mm copper enamelled wires Remove parts of the green solder resist to solder the ground connection Top side of the transceivers case where the IFD can be installed bottom up IFD Input lt gt Mixer out IFD Output lt gt Filter input Printed 8 Sep 06 Installation manual for SYMEK IFD wideband receiver Kenwood TS790 A E Page 3 6 Connection to mixer output Use a 3 1 step down transformer Connect one of the 450 ohm input pins to the drain of Q 203 where the tap of L208 was connected before The other 450 Ohm pin is soldered to the joint of R213 56 Ohm C218 and L208 Connect the 50 ohm side of the transformer to a thin 50 ohm coax cable Cable shield is soldered to ground So the FET is supplied via the 450 Ohm winding with power Feed the cable marked mixer below the fan motor to the bottom compartment of the transceiver Version with 1 3 transformers 50 450 Ohm Note with the SMD transformers the input and output is not dc coupled The 50 Ohm in and out is just the 50 Ohm winding of the transformers The 50
8. ferent RX and TX speed e g TX 9600 RX 38400 for UO 12 are also available When using WISP software with a TNC3 packet controller you may use the modem 2 for receiving and modem 1 for transmitting As WISP uses kiss mode both modems are received simultaneously the data will be transmitted via the default port 1 Options and Jumper assignments J80 Close if fundamental quartz oscillator is used L80 is NOT used in this case Open if overtone crystal oscillator mode is used L80 must be installed J82 84 Close to enable internal local oscillator Open if external oscillator is used X80 L80 may be omitted J85 Close if external local oscillator is to be used Open if internal local crystal ostillator is used J91 Close if the supply voltages is to be derived from the IF input or IF output pin e g FT736 L1 L16 installed Open if the IFD is to be supplied via the 12V in pin L1 L16 must be removed for IC821 operation J92 Close if the internal voltage regulator is used Open if the IFD is supplied from an external regulated 5V source R74 Offset adjust Adjust for 0 1 Volt RSSI output with no input signal R76 Gain adjust Adjust for 4 Volt RSSI at 50 dBm input signal level R76 and R74 habe to be adjusted 2 3 times for best result The IF output before the limiting amplifier is available at pin IF out To use this feature install U100 and L100 For best symmetry apply a wideband modulated FSK signal to the IF input and adjust L
9. lder all connections before 1 solder the coax cable mixer to the RF IN terminal M1 shield to M2 2 solder the coax cable filter to the RF OUT terminal M11 shield to M12 3 solder a 30 cm red wire to terminal M90 12V The other end of this wire is soldered to Pin 7 of the ACC4 connector at the rear side of transceiver permanent 12Volt connection 4 The demodulator output terminal M63 data out goes to ACC 4 Pin 5 originally unused via a thin shielded audio cable 5 Ground connection for power supply is not necessary cable shields are already grounded 4 Connection of the packet radio controller TNC You need a 3 wire screen cable from the TS790 to the packet controller When using the 8 pin DIN Type H pins not arranged in a circle pin 6 7 are nearer to circumference connector ACC 4 connector as described above you only need an apropriate cable between the ACC 4 connector and TNC Pin 2 Ground connect to TNC pin 2 GND Pin 8 center pin PTT connect to TNC pin 3 PTT Pin 3 Modulation connect to TNC pin 1 Mod Pin 7 12 5 Volt supply not used Pin 5 data output connect to TNC pin 4 Demod RSSI output may be connected elsewhere if necessary 5 Setup and test Before reinstalling all covers check if the transceiver works exactly as before For best RX sensitivity the resonant circuit L 208 needs to be readjusted Apply a 1 to 10 microvolt signal and tune L 208 to maximum S meter reading Because of the
10. tor 31 FMD frequency modulation The crystal oscillator 10 605 MHz is located nearby The connector is at the rear left side of the large IF board Solder a 10 kOhm resistor to the white wire which goes to the signal pin of connector 31 The other end of the resistor is soldered to the inner connector of a 30cm shielded audio cable The shield is connected to ground e g at connector 31 black wire For acessing this signal ACC4 pin 3 could be used This pin is not used with the original transceiver 2 PTT transmitter keying Pin 8 of the ACC4 connector is already available as PTT connection for keying the transmitter 3 Demodulator output Open the top cover of the transceiver front towards you Locate the RF 430 MHz unit it is found at the right side below the power amplifier unit To access the RF 430 unit you have to remove all screws around the cast aluminium assembly including two screws at the rear panel The RF430 unit is fixed at the same cast aluminium part as the power amplifier but bottom up The aluminium part can be turned with the plastic hinges so that the RF430 unit becomes easily accessible The total RF 430 unit is shielded with a tin cover Remove this cover many screws first and totally remove the printed circuit board some of the cables have to be plugged out You will have to make changes at the solder side of this board Locate the dual gate FET mixer Q 203 see photo under L208 The drain of Q 203 goes origin
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