Introduction: QYT KT8900 PACKET MOD

Picture of QYT KT8900 PACKET MOD

QYT KT8900 mod for PACKET

This is a chinese cheap 20W 144/440MHz mobile radio, but have two wrong design thinks to connect friendly this unit with your sound card because them not have a external speaker jack, also the squelch operation is too slow.

A good idea is take the audio signal from the discriminator directly, here you have a opensql signal, a clean and good quality and audio signal.

To make this modification please use the ht9170d chip (used to decode a DTMF signaling) also use empty pin 8 on the mic connector with a 2,2uf electrolitic capacitor to audio coppling.

Step 1: Open the Radio to See the Main Board, and Back Display Board Too.

Picture of Open the Radio to See the Main Board, and Back Display Board Too.

Step 2: Locate the Ht9170d Chip on the Main Board, Near to Conecctor to Display Board

Picture of Locate the  Ht9170d Chip on the Main Board, Near to Conecctor to Display Board

Step 3: Locate the Mic Conector Exclusive Pin 8 and Install a Wire From This Pin to Ht9170d Chip

Picture of Locate the Mic Conector Exclusive Pin 8 and Install a Wire From This Pin to  Ht9170d Chip

Step 4: Install One End of the 2,2uf Electrolitic Capacitor on Pin # 2 Ht9170d Chip (vn Pin) and Another Capacitor End to Wire From the Pin 8 of the Mic Connector

Picture of Install One End of the  2,2uf Electrolitic Capacitor on Pin # 2  Ht9170d Chip (vn Pin) and Another  Capacitor End to Wire From the Pin 8 of the Mic Connector

Step 5: The Mod Is Done!, Now You KT8900 Have a Audio Signal From the Discriminator on the Pin #8 (mic Connector)

Picture of The Mod Is Done!, Now You KT8900 Have a Audio Signal From the Discriminator on the Pin #8 (mic Connector)

Reesamble your radio and make wires to your PC Sound card

The signal is clean and strong to your audio input on the sound card

Enjoy! 73

TI2BOX

Comments

KC0TA (author)2016-12-18

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.

rfeigenblatt (author)KC0TA2016-12-18

Hi KC0TA I have only a KT8900 to make test, if HM9170 as inverted position on the board in your radio, look for the pin #2 on your chip and follow my instructable to install a electrolytic capacitor

73, TI2BOX

KC0TA (author)rfeigenblatt2016-12-19

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

rfeigenblatt (author)KC0TA2016-12-20

I see, really I not have any idea about this datasheet, I think you will find the discrimnator signal easy with a oscilloscope test each pin of the HM9170 when the radio is on RX mode

73, TI2BOX

KC0TA (author)rfeigenblatt2016-12-21

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

sailorgriz (author)KC0TA2017-09-27

Did you make any progress finding the right pin using an O-scope? I'd like to make the same mod on my 8900D. Thanks!

KC0TA (author)sailorgriz2017-09-27

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.

Gogom (author)KC0TA2017-12-03

How did you modify the Easy-Digi to incorporate a 10:1 voltage drop network?

optiontrader53 made it! (author)Gogom2017-12-07

See the attached bitmap of the schematic for the 10:1 voltage divider.

Gogom (author)optiontrader532017-12-07

Thank you for the schematic. I'll give it a try when I put together the Easy-Digi.

optiontrader53 (author)Gogom2017-12-09

An error on my schematic. The 99k should be 9k. Changed out my keyboard since I'm starting to see key bounce with this capacitive touch keyboard. Apologies.

Gogom (author)optiontrader532017-12-09

Thank you for following up on that. I received the Easy-Digi yesterday and will put it together soon.

R2 and R3 of the Easy-Digi are replaced with the voltage dividers R1-R2 and R3-R4 of my schematic, respectively.

RobertA9 (author)2017-10-22

So this Provides a Discriminator Output to a PC or Packet Controller..

Is there a way to do this is Reverse i.e Inject a 9k6 Data into the Radio for say Digital Modes using MMDVM for example ?

optiontrader53 (author)RobertA92017-12-07

Still working on that one. Analyzing the 9k6 waveform and determining if the reactance modulator will take the waveform and try to pre-emphasize the signal or cause it to roll off.

About This Instructable

4,690views

6favorites

License:

More by rfeigenblatt:QYT KT8900 PACKET MODStrobos emergencia con Attiny85Radio FM Materiales Reciclados + Impresión 3D
Add instructable to: