r 33460 Data msg: 09-Dic-92 Ora msg: 18:50 Nr. : 33460 BID : 13585_KB2LPW Byte : 3125 Tipo : B Stato : F Da : KB2LPW Per : MODS @EU Titolo : 9600 Bd MODS for TM721/731 R here Path: !IK3BLZ!IW1BBL!IW1BRX!IK2TTU!IW2FPO!IW2DXI!IW2DNI!IW2GKO!I5SGG!5B4TX! !OZ5BOX!OZ2BUL!SR1BOX!SP1NQN!SP4KTO!SP4DGN!SP5OXO!SP5PBE! The mods to do 9600 baud packet using a K9NG or G3RUH modem are fairly simple continua nnulla => to do with the Kenwood TM-721/621 radios. Look at your schematic. Receive data is taken from the dicriminator output. Look for the 3.3K resistor comming off pin 9 of the last IF stage. Connect a 1K series resistor from the modem RX input to the junction of the .001 and 3.3K. PTT is taken off pin 2 on the microphone connector. TX data is fed through a 1K series resistor to the top of VR3 (the deviation conltrol). This method has been tested and works quite well on 440 MHz and 220 MHz. The mods haven't fully been tested on the 2 meter portion of the radio. The TM-731 radio is different enough to cause problems. What needs to be done is to add another RX Mute transistor. (Look at the schematic and see how the TX deviation is shorted to ground during receive.) Use a plain NPN and a pair of 10K resistors (copy the one used on VR3 in the schematic). Take the TX data and feed it to the collector through a series 1K resistor, and then feed that through another 1K resistor to the wiper of the deviation pot. This was a result of Kenwood changing the deviation pot value from 10K to 100K. (It continua nnulla => wasn't broken, but they fixed it anyway.) As with any modifications, take reasonable care, and I won't be responsible if you trash your radio. BE CAREFUL; it is full of surface mount devices. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- This MOD file was written by Jeff, WA6FWI @ WB6YMH.#SOCA.CA.USA.NA Schematics and layouts are available by request through the author. Good Luck! 73 de Chris KB2LPW @ KB2LPW.#NYC.NY.USA.NA SYSOP of PDSNET ARC and the Helping BBS's ============================================================================== Fine del Msg #33460 di KB2LPW per MODS @EU -|- Port 3 IK3NGU de I3XTY cmd:> Msg Nr. : 32403 Da : LU7AKC Per : NET9K6@WW Tipo/status : B$ Data/ora : 0815/0242 Dimensione : 3771 Titolo : TM721 & 9600 Bps Bid (Mid) : 12261_LU7AKC TM-721 & 9600 Bps. The mods to do 9600 baud packet using a k9ng or g3ruh modem are fairly simple to do with the Kenwood TM-721/621 radios. Look at your schematic. Receive data is taken from the discriminator output. Look for the 3.3K resistor coming off of pin 9 of the last IF stage. Connect a 1K series resistor from the Modem RX input to the junction of the .001 and 3.3K. PTT is taken off pin 2 on the microphone connector. TX data is fed through a 1K series resistor to the top of VR3 (The deviation control). This has been tested and works quite well on 440 MHz and 220 MHz. The mods haven't been fully tested on the 2 meter portion of the radio. The TM-731 radio is just enough different to cause problems. What needs to be done is the addition of another RX Mute transistor. (Look at the schematic and see how the TX deviation is shorted to ground during receive). Use a plain npn and a pair of 10K resistors copy the one used on VR3 on the schecmatic. Take the TX data and feed it to the collector through a series 1K resistor, and then feed that through another 1K resistor to the wiper of the deviation pot. This was a result of Kenwood chaoging the deviation pot value from 10K to 100K. (It wasn't broke, but they fixed it anyways.) This message is being uploaded to the local BBS with the modified TM-731. As with any modifications, take resonable care, and I won't be responsible if you trash your radio. BE CAREFUL it is full of surface mount devices. TM-721 & 9600 Bps. The interface to my 721 was guessed at and seems to work quite well. Audio directly from pin 9 of FM IF chip, and PTT on pin 2 of mic connector. TX input to the collector of muting transistor of PLL audio input. The local 9600 node seems to be quite busy and that may be the cause of seemingly poor operation. A local friend of mine is about to get another 9600 card for his 1278 TNC so we will have a clear frequency to do testing between our rigs. 73 & God bless from Chris/AB6FA Lompoc CA. Msg Nr. : 142593 Da : IW3GRX Per : TEMP Tipo/status : PN Data/ora : 0129/1242 Dimensione : 2197 Bid (Mid) : 11521_IW3GRX Titolo : Modifica 9600 baud per il TM721 ************************************************************************** From: LU7AKC@LU7AKC.#COL.CF.ARG.SOAM To : NET9K6@WW TM-721 & 9600 Bps. The mods to do 9600 baud packet using a k9ng or g3ruh modem are fairly simple to do with the Kenwood TM-721/621 radios. Look at your schematic. Receive data is taken from the discriminator output. Look for the 3.3K resistor coming off of pin 9 of the last IF stage. Connect a 1K series resistor from the Modem RX input to the junction of the .001 and 3.3K. PTT is taken off pin 2 on the microphone connector. TX data is fed through a 1K series resistor to the top of VR3 (The deviation control). This has been tested and works quite well on 440 MHz and 220 MHz. The mods haven't been fully tested on the 2 meter portion of the radio. The TM-731 radio is just enough different to cause problems. What needs to be done is the addition of another RX Mute transistor. (Look at the schematic and see how the TX deviation is shorted to ground during receive). Use a plain npn and a pair of 10K resistors copy the one used on VR3 on the schecmatic. Take the TX data and feed it to the collector through a series 1K resistor, and then feed that through another 1K resistor to the wiper of the deviation pot. This was a result of Kenwood changing the deviation pot value from 10K to 100K. (It wasn't broke, but they fixed it anyways.) This message is being uploaded to the local BBS with the modified TM-731. As with any modifications, take resonable care, and I won't be responsible if you trash your radio. BE CAREFUL it is full of surface mount devices. TM-721 & 9600 Bps. The interface to my 721 was guessed at and seems to work quite well. Audio directly from pin 9 of FM IF chip, and PTT on pin 2 of mic connector. TX input to the collector of muting transistor of PLL audio input. The local 9600 node seems to be quite busy and that may be the cause of seemingly poor operation. A local friend of mine is about to get another 9600 card for his 1278 TNC so we will have a clear frequency to do testing between our rigs. 73 & God bless from Chris/AB6FA Lompoc CA. ****************************************************************************