KENWOOD TH-79 ALL COUNTRIES MODIFICATIONS ----------------------------------------------------------------------------- MODIFYING THE DESTINATION OF KENWOOD TH-79 DUAL-BAND HANDHELD TRANSCEIVER A set of diodes is factory-configured to give the TH-79 its correct properties for each export market. Since TH-79 is easy to bring, it is often bought in a country else than where it is intended to be used most of the time. The configuration you got at time of purchase may in other words need to be changed to get adapted to your country. A typical example is if the radio is bought in a so-called general version in the far east, when taken into Europe it needs to be modified to allow 1750Hz tone call. Before you open your unit for modification, you are advised to carefully study below tables in order to plan your preferred configuration before you start (you may also in some cases need to purchase additional diodes). Also read the below warning and disclaimer before you continue: 1. It is technically possible to achieve wider frequency range than what may be allowed in your country, doing so is of course against the law. This may apply not only to the ability to transmit but also the receiving range. Do not jeopardize the good reputation of HAMs by irresponsible action. 2. Modifying the configuration is a VERY delicate job, the diodes are in size 0402 (= 1.0 x 0.5 mm) which requires both the proper tools and practice how to handle such extremely small devices. You can forget about doing this with an ordinary soldering iron at your kitchen table. The operation calls for one or preferable two miniature soldering irons plus the skills to fiddle with these tiny things without destroying the board. If you are not completely sure you have understood this document and the contents of its tables - refrain from modifying your unit. 3. The manufacturer guarantee the performance only within the HAM bands. 4. This document does not claim to cover the subject 100%, it is merely a collection of hints and experiences, and shall be considered as such as there may be other aspects. 5. All modifications or attempts to modify, and any consequences thereof, are ENTIRELY your own risk and responsability. Also remember that your product warranty will be void in the same moment you open the case of your radio. Finally remember the possibility that this text-file may have been tampered with during copying etc. ------------------------------------------------------------------------------ TABLE 1: DESTINATION Model Area Operat. Display Initial values Tx-Rx unit no. range range Freq/Step/Offset/Tone TH79A-C China 136-180 144M/12.5k/+-5.7M/88.5 400-512 430M/25k/+-10M/88.5 TH79A-K America 144-148 144-148 144M/5k/+-0.6M/88.5 X57-4400-11 (118-174) (118-174) 438-450 438-450 440M/25k/+-5M/88.5 TH79A-K2 America 142-152 144M/5k/+-0.6M/88.5 rx-mod (118-174) marse 420-450 440M/25k/+-5M/88.5 TH79A-K3 America 136-180 144M/5k/+-0.6M/88.5 tx-mod (67-180) 400-512 440M/25k/+-5M/88.5 TH79A-K4 America 142-152 144M/5k/+-0.6M/88.5 rx-mod (67-180) marse 420-450 440M/25k/+-5M/88.5 +add. (400-512) TH79A-K5 America 144-148 144M/5k/+-0.6M/88.5 rx-mod (67-180) +add. 438-450 440M/25k/+-5M/88.5 (400-512) TH79E-T England 144-146 144-146 144M/12.5k/+-0.6M/1750 X57-4402-71 430-440 430-440 430M/25k/+-1.6M -7.6M/1750 TH79A-X Austral. 144-148 144-148 144M/5k/+-0.6M/88.5 X57-4400-71 (118-174) (67-180) 430-440 430-440 430M/25k/+-5M/88.5 TH79A-P Canada 144-148 144-148 144M/5k/+-0.6M/88.5 X57-4400-11 (118-174) (118-174) 438-450 438-450 440M/25k/+-5M/88.5 TH79E-E Europe 144-146 144-146 144M/12.5k/+-0.6M/1750 X57-4402-71 430-440 430-440 430M/25k/+-1.6M -7.6M/1750 TH79E-E2 Italy 136-174 136-180 144M/12.5k/+-0.6M/1750 X57-4402-72 (118-174) (67-180) 410-470 400-512 430M/25k/+-1.6M -7.6M/1750 TH79E-E3 England 144-146 144-146 144M/12.5k/+-0.6M/1750 X57-4402-73 430-440 430-440 430M/25k/+-1.6M -7.6M/1750 TH79E-E4 144-146 144M/12.5k/+-0.6M/1750 432-438 432M/25k/+-1.6M/1750 TH79E-E9 144-146 144-146 144M/12.5k/+-0.6M/1750 X57-4402-73 430-440 430-440 430M/25k/+-1.6M -7.6M/1750 TH79A-M General 144-148 144-148 144M/12.5k/+-0.6M/88.5 X57-4400-21 430-440 430-440 430M/25k/+-5M/88.5 TH79A-M2 General 136-174 136-180 144M/12.5k/+-0.6M/88.5 X57-4400-22 (118-174) (67-180) 410-470 400-512 430M/25k/+-5M/88.5 TH79A-M3 General 136-174 136-180 144M/12.5k/+-0.6M/88.5 X57-4400-22 (118-174) (67-180) 410-470 400-512 430M/25k/+-5M/88.5 TH79A-M4 General 136-174 136-180 144M/12.5k/+-0.6M/88.5 X57-4400-22 (118-174) (67-180) 410-470 400-512 430M/25k/+-5M/88.5 Notes to table 1: Intervals within parentheses show receive-only ranges. The range 118 - 136 MHz is used in AM mode only. Destinations C, K2, K3, K4, K5 and E4 are a bit uncertain regarding frequency ranges, do not go for one of these unless you are prepared to experiment. ------------------------------------------------------------------------------ TABLE 2: DIODE CONFIGURATION FOR EACH DESTINATION D D D D D D D 3 3 3 3 3 3 3 0 0 0 0 0 0 0 2 3 4 5 6 7 8 Diode final figures for safety double-check: C X X - X X - - 2356 K X X X X - X X 234578 K2 X X X X - X - 23457 K3 X X - X - - X 2358 K4 X X X X - - - 2345 K5 X X X X - X - 23457 T * X X - X X X - - 2456 P * E X - X X X X X 245678 E2 X - X X X X - 24567 E3 X - X X X X X 245678 E4 X - - X X X X 25678 E9 * M X X - X X X X 235678 M2 X X - X X X - 23567 M3 * M4 * Notes to table 2: Destinations marked above with an asterisk (*) do not have data, but are most likely duplicate diode configurations with another destination (can have to do with what accessories are supplied with delivery and so on). The (X) indicates that the diode is mounted, (-) indicates empty position. ------------------------------------------------------------------------------ GENERAL INFORMATION PRIOR TO MODIFICATION 1. The functions (as described by Kenwood) of the so-called destination diodes are as follows: "The following functions are made available by removing the corresponding diode: D302 Channel display mode D303 (unknown) D304 (unknown) D305 Channel display mode and key lock D306 Crossband repeater, answerback D307 (unknown) D308 Frequency extension Clone and message paging reception is made possible by D308 frequency extension." Personally I have not thought so much about the meaning of this information since I found it quite puzzling when comparing different destinations and their diode locations. My advice: forget this. 2. Extra goodies that you may have already in your station, or that may get revealed by modification, are the extra bands that are almost without documentation, here is how to test if you have them (not all versions have) and how to reach them: a) The air-band 118 - 136 MHz (AM only) can be achieved with any unit by suitable modification (see tables above). b) The 300 - 400 MHz band can be reached by in VHF/VFO-mode first pressing the function key and then the power selector . c) The 800 - 1000 MHz band can be reached by in UHF/VFO-mode first pressing the function key and then the power selector . 3. As indicated in table 1, the frequency range that can be displayed by the unit is not necessarily the same as the radio is technically capable of. The easiest way to find out the range, is to set the lowest frequency possible and then do a VFO-scan from that point. The unit will beep for each step that is not supported until it reaches the real range. Also the range 118 - 136 MHz is forced into AM mode shown by a wider decimal point in the frequency readout. 4. Before you decide to modify you need to be aware of this; if you change the configuration between TH-79A and TH-79E the case printing will not be totally correct. On the TH-79A the button below the PTT actuates the backlight of the display, and the rightmost button of the four round buttons below the display actuates the CALL function, and the bottom left button actuates tone. On the TH-79E the button below the PTT will become the tone call button, while the right button below the display will actuate the backlight. Therefore the text printed on the case will not be valid for those two, personally I do not find it too irritating, but it can perhaps be the day you like to sell it. Changing from A to E version will also remove the CALL function (read more about it in your manual). ------------------------------------------------------------------------------ STEP-BY-STEP DESCRIPTION 1. Shut off the radio and remove the accumulator. Take standard precautions regarding electrostatic discharge hazards. 2. Remove the four screws that hold the case together, three of them are at the rear, while the last one is hidden under the rubber-flap beside the DC-inlet. 3. Fold apart the case halves. The volume knobs are fitted in the front and the BNC connector in the rear. 4. Remove the plastic cover (holder/keytop) covering the keyboard, the purpose is to prevent damage since you get close to it when soldering. Carefully examine the lock that makes it snap to the outer case half, no great force is necessary once you understand how to disassemble it. 5. Locate the row of configuration diodes D302 - D308 at the bottom right corner of board above the keyboard. Note the original positions of the diodes just in case something would go wrong. 6. Make sure your soldering iron(s) are clean and have the correct temperature for this delicate circuit. Personally I would not recommend using hot air soldering, there are plenty of components that if accidentally heated may take damage, and the risk that components around the diodes will start drifting around to a big (small) mess. 7. According to your choice from above tables, do your configuration by moving and/or removing diodes to their proper places. If you would need to add diodes, I would assume that any switch-type diode will do the job. However, I have not tried it myself. Take care with the polarity of the diodes. They are pointing down towards the edge of the board, all in the same direction. 8. Now you should be ready to reassemble the unit, take a note of the new diode positions and the type-number of the tx/rx-board to keep with the schematic diagram of your station. Also, take the opportunity to get impressed by the neat Kenwood assembly before closing the case again. Do not tighten the screws more than necessary, they are fitted directly into the plastic, which is also a reason for not opening too often. 9. You will note that when you turn on the power on your newly modified rig it indicates that it has been reset. All your programming has been lost when doing a modification (not really a problem, just as information). Also, remember the button swap (see point 4 in general information). ------------------------------------------------------------------------------ Finally I wish you good luck with your modification, hope it will give you extended pleasure with your rig. 73 de SM6MDH. ------------------------------------------------------------------------------ jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjH < KB2LJJ BBS RADIO MODS BATABASE < All the MODS are captured by packet. ijjjjjjjjjjjH jjjjjjjjjjjjjj* This BBS takes no responsability or jjjjjjjjjj* ijjjjjjjjjjjjjjjH liability for any damege resulting < KB2LJJ @ KB2LJJ.NJ.USA.NA < from any modification. ijjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj* 73s John kb2ljj SySoP