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  • KC0TA commented on rfeigenblatt's instructable QYT KT8900 PACKET MOD3 weeks ago
    QYT KT8900 PACKET MOD

    I did! And I think it was pin 18 or 20 (can't remember exactly, it's been a few months) . The signal can be seen on the IC pin using an O-scope. However, on the back of the KT-8900D there is a data connector and a connector that looks like it could be for external speaker, but is actually for a headset. It uses a 4-conductor 1/8" stereo plug which allows for PTT, RX audio, TX audio and GND. The ring, shell & tip signals can be found in the owners' manual that came with the radio. It is a good idea to capacitor isolate the device that uses this jack for audio to ensure no DC to the attached equipment (this is necessary for the method of using the MIC jack also). If you use a sound modem interface, use a 10:1 pad to drop the audio levels to and from the sound card. Check ...

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    I did! And I think it was pin 18 or 20 (can't remember exactly, it's been a few months) . The signal can be seen on the IC pin using an O-scope. However, on the back of the KT-8900D there is a data connector and a connector that looks like it could be for external speaker, but is actually for a headset. It uses a 4-conductor 1/8" stereo plug which allows for PTT, RX audio, TX audio and GND. The ring, shell & tip signals can be found in the owners' manual that came with the radio. It is a good idea to capacitor isolate the device that uses this jack for audio to ensure no DC to the attached equipment (this is necessary for the method of using the MIC jack also). If you use a sound modem interface, use a 10:1 pad to drop the audio levels to and from the sound card. Check out the interface called "Easy-Digi" made by KF5INZ (on Ebay). They are reasonably priced and he offers them in a kit form also. It is the one I use with my KT-7900D. If you need it, I can supply the modification I made to my Easy-Digi to incorporate the 10:1 voltage dropping network.

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  • KC0TA commented on rfeigenblatt's instructable QYT KT8900 PACKET MOD10 months ago
    QYT KT8900 PACKET MOD

    Yes, I agree with analyzing with oscilloscope. I was hoping to make this simple with the aid of a data sheet but, as usual, things I do are rarely ever simple. Thanks.73, Mike, KC0TA

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  • KC0TA commented on rfeigenblatt's instructable QYT KT8900 PACKET MOD10 months ago
    QYT KT8900 PACKET MOD

    I'm wondering about the compatibility of the HM9170 and the HT9170D. The HM9170 is a 20-pin chip while the HT9170D is an 18-pin chip. I just can't find any data on the HM9170 to verify the pinouts of the device. The KT-8900D has a 2-tone and 5-tone decoder function which may explain the different chip (HM9170 with 20 pins) in my radio. It would certainly help if I could locate a schematic of the radio and/or data sheet for the HM9170 chip. Any ideas on getting a radio schematic?73, KC0TA

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  • KC0TA commented on rfeigenblatt's instructable QYT KT8900 PACKET MOD10 months ago
    QYT KT8900 PACKET MOD

    I have a newer model (KT-8900D) which has a 20-pin chip, HM9170. Pin-1 is opposite of your picture and there are some similar features of the main board and the front face board. I have not been able to find information on this IC to implement this mod on the newer model radio. Any help out there? Thanks.I also have a KT-7900D that might require this mod, also.

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