Hi Ross, I have a couple of mods that you may or may not have. For the TH-75A MARS/CAP mod, removing D4 will allow TX across entire tuning range, except that actual TX range will be limited by tuning of the PLL. For the TM-731A, there is a "Beyond MARS/CAP transmit Modification". It provides TX from 136 to 174 and 400 to 500 MHz. Again, actual TX range limited by PLL tuning. If you don't already have this and would like it, I'll send a copy if you furnish me your address. It involves cutting R25 on the control unit, and installing a jumper (diagram required to locate position), then two resets in a row. I have tested these mods on my own rigs. 73 - Kevin, KD2SL @ KC3BQ ллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллл TH75-A MARS/CAP MODIFICATIONS This modification will allow the TH-75A to transmit from 142 to 152 MHz and 420 to 450 MHz. Specifications are guaranteed for the Amateur bands only. Though the transceiver will display 136 to 174 MHz and 335 to 512 MHz, the PLL circuit may not lock through the entire range. MODIFICATION PROCEDURE : 1. Disconnect the battery and antenna. 2. Remove the three case screws and two battery plate screws. 3. Lift the front panel from the body of the transceiver, but do not disconnect the two flex cables. 4. Cut the green jumper wire (W1) that is located to the left side of the CPU in the front panel assembly. 5. Assemble the transceiver by reversing steps 1 - 3. 6. Reset the CPU by holding the M key as the power is turned on. ллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллл From: WA6TKV@N6IIU The Kenwood approeed MARS mod for the TH-75A is very simple. Remove the 3 exterior screws. There are 4 screws where the battery pack slides on. Remove the 2 screws toward the face of the radio. You now have access behind the front panel. You will see a green wire near a square chip. Cut the wire. You will now have transmit from 142-152 and receive from 136-174. Transceive from 420-450. Although you can actually key in 385-512. This is truly a fantastic radio! You can take the mod two steps further. You wyll definitely need a service manual and a very delicate touch. (Not for the weak!) Locate and remove D4. It is in the same vicinity of the green wire. The radio will now transceive from 136-174, some VCO adjustment may be required for the entire range. It is also now capable of transceiving from 385-512. The UHF VCO's have approximately a 50 MHz band- width so you will only get a 50 MHz wide portion of 385-512. The second step is adjusting the VCO's. There are separate adjustments for transmit and receive for both VHF and UHF. This calls for complete dis-assembly of the radio. Refer to your service manual. I have found these mods extremely valuable. Now I have a dual band ham rig and a police scanner in one. Have fun and please use EXTREME caution in transmitting only on your amateur and MARS frequencies. ллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллл Date: Thu, 26 Oct 89 15:19 CDT From: SURESH KAGOO N9GSA/4S7??? Subject: KENWOOD TH-75A MOD TH-75A MARS/CAP MODIFICATION ---------------------------- This modification will allow the TH-75A to transmit from 142 to 152 MHz and 420 to 450 MHz. Specifications are guaranteed for the Amateur Bands only. Through the transceiver will display 136 to 174 MHz and 335 to 512 MHz, the PLL circuit may not lock through the entire range. CAUTION ------- Protect your license. Make sure that you operate on authorized frequencies only. MODIFICATION PROCEDURE ---------------------- 1. Disconnect the battery and antenna. 2. Remove the three case screws and two battery plate screws. 3. Lift the front panel from the body of the transceiver, but do not disconnect the two flex cables. 4. Cut the green jumper wire (W1) that is located to the left side of the CPU in the front panel assembly. 5. Assemble the transceiver by reversing steps 1-3. 6. Reset the CPU by holding the M key as the power is turned on. I have tried it and it works. Suresh Kagoo N9GSA/4S7??? Memphis State University Memphis, Tennessee Internet : SKAGOO@MEMSTVX1.BITNET Bitnet : SKAGOO@MEMSTVX1 лллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллллл Msg Nr. : 159412 Da : EA7FHR Per : RIG @WW Tipo/status : BF Data/ora : 0302/2040 Dimensione : 3343 Bid (Mid) : 21923_EA7FKB Titolo : Alcune modifiche per il TH75 Date: Thu, 26 Oct 89 15:19 CDT From: SURESH KAGOO N9GSA/4S7??? Subject: KENWOOD TH-75A MOD TH-75A MARS/CAP MODIFICATION ---------------------------- This modification will allow the TH-75A to transmit from 142 to 152 MHz and 420 to 450 MHz. Specifications are guaranteed for the Amateur Bands only. Through the transceiver will display 136 to 174 MHz and 335 to 512 MHz, the PLL circuit may not lock through the entire range. CAUTION ------- Protect your license. Make sure that you operate on authorized frequencies only. MODIFICATION PROCEDURE ---------------------- 1. Disconnect the battery and antenna. 2. Remove the three case screws and two battery plate screws. 3. Lift the front panel from the body of the transceiver, but do not disconnect the two flex cables. 4. Cut the green jumper wire (W1) that is located to the left side of the CPU in the front panel assembly. 5. Assemble the transceiver by reversing steps 1-3. 6. Reset the CPU by holding the M key as the power is turned on. I have tried it and it works. Suresh Kagoo N9GSA/4S7??? Memphis State University Memphis, Tennessee Internet : SKAGOO@MEMSTVX1.BITNET Bitnet : SKAGOO@MEMSTVX1 73S DE JERONIMO EA7FHR @EA7FKB.EAAL.ESP.EU. Msg Nr. : 159936 Da : EA7FHR Per : RIG @WW Tipo/status : B$ Data/ora : 0303/2210 Dimensione : 2773 Bid (Mid) : 21908_EA7FKB Titolo : MODS TH75A TH75-A MARS/CAP MODIFICATIONS This modification will allow the TH-75A to transmit from 142 to 152 MHz and 420 to 450 MHz. Specifications are guaranteed for the Amateur bands only. Though the transceiver will display 136 to 174 MHz and 335 to 512 MHz, the PLL circuit may not lock through the entire range. MODIFICATION PROCEDURE : 1. Disconnect the battery and antenna. 2. Remove the three case screws and two battery plate screws. 3. Lift the front panel from the body of the transceiver, but do not disconnect the two flex cables. 4. Cut the green jumper wire (W1) that is located to the left side of the CPU in the front panel assembly. 5. Assemble the transceiver by reversing steps 1 - 3. 6. Reset the CPU by holding the M key as the power is turned on. 73s de EA7FHR @EA7FKB.EAAL.ESP.EU Jeronimo Quesada Garcia P.O.BOX 322 04080 ALMERIA Msg Nr. : 192983 Da : IW3GRX Per : TEMP Tipo/status : PN Data/ora : 0521/1516 Dimensione : 3267 Bid (Mid) : 61911_IW3GRX Titolo : Alcune modifiche per il TH75 ***************************************************************************** Hello everybody. To expand the frequency coverage on the TH75E to approx 138-170 and 385-470 Mhz do the following. 1. Cut the jumper wire W1 at the CPU (green wire), this opens both TX and RX. 2. Take away diod D4 also at CPU (surface mounted), this will inhibit the transmitter from transmitting outside the original range of 144-146 and 430-440 Mhz. Good Luck 73 Jan SM7ETW @ SK7AF ***************************************************************************** From : EA7FHR To : RIG@WW Type/status : BX Date/time : 03-Mar 10:07 BID (MID) : 21923_EA7FKB Message # : 27761 Title : MODS TH-75A Path: !PI8MBQ!PI8WFL!PI8JYL!PI8AWT!DB0NDR!DB0SAO!DB0RBS!DB0LX!DB0AAA!DB0CZ! !DB0KCP!DB0AAB!DB0MFG!OE7XCI!IW3AQL!IN3TUR!IK4NZD!IK4MGV!I4EUM!I4FP! !I4UJB!IW4BYK!IK6PYS!IK6RUY!I6BNW!CT1ASP!CT1AFS!CT1DGZ!CS1AAS!CT1BT! !EA7UH!EA7MU!EA7BF!EA7DSS!EA7CNM!EA7FKB! From: EA7FHR@EA7FKB.EAAL.ESP.EU To : MODS@WW Date: Thu, 26 Oct 89 15:19 CDT From: SURESH KAGOO N9GSA/4S7??? Subject: KENWOOD TH-75A MOD TH-75A MARS/CAP MODIFICATION ---------------------------- This modification will allow the TH-75A to transmit from 142 to 152 MHz and 420 to 450 MHz. Specifications are guaranteed for the Amateur Bands only. Through the transceiver will display 136 to 174 MHz and 335 to 512 MHz, the PLL circuit may not lock through the entire range. CAUTION ------- Protect your license. Make sure that you operate on authorized frequencies only. MODIFICATION PROCEDURE ---------------------- 1. Disconnect the battery and antenna. 2. Remove the three case screws and two battery plate screws. 3. Lift the front panel from the body of the transceiver, but do not disconnect the two flex cables. 4. Cut the green jumper wire (W1) that is located to the left side of the CPU in the front panel assembly. 5. Assemble the transceiver by reversing steps 1-3. 6. Reset the CPU by holding the M key as the power is turned on. I have tried it and it works. Suresh Kagoo N9GSA/4S7??? Memphis State University Memphis, Tennessee Internet : SKAGOO@MEMSTVX1.BITNET Bitnet : SKAGOO@MEMSTVX1 73S DE JERONIMO EA7FHR @EA7FKB.EAAL.ESP.EU. ***************************************************************************** Hi Ross, I have a couple of mods that you may or may not have. For the TH-75A MARS/CAP mod, removing D4 will allow TX across entire tuning range, except that actual TX range will be limited by tuning of the PLL. For the TM-731A, there is a "Beyond MARS/CAP transmit Modification". It provides TX from 136 to 174 and 400 to 500 MHz. Again, actual TX range limited by PLL tuning. If you don't already have this and would like it, I'll send a copy if you furnish me your address. It involves cutting R25 on the control unit, and installing a jumper (diagram required to locate position), then two resets in a row. I have tested these mods on my own rigs. 73 - Kevin, KD2SL @ KC3BQ *****************************************************************************