Build an RS-232 Serial Programming Cable
by Bob Desgrange KV4NF
No more hassle with USB ports.
Project 232

Here's a level 2 project that eliminates the need for the standard USB programming cable by using your computer's COM Port (RS-232).
The example shown here is for a 2 pin Kenwood / Baofeng connection, but can be adapted to any connector requiring the standard GND, RxD, TxD configuration.

It's a Level 2 project because it involves the etching of a small PC board, so prior PC board experience is a plus.

The Parts List

(2)  2N3904 transistors
(3)  3.3K resistors
(1)  2.5 mm stereo plug
(1)  3.5 mm stereo plug
(1)  RS232  DB-9 connector

To make the PC Board, you'll need:
-  A LaserJet printer (not inkjet)
-  Gloss photo paper
-  Blank copper PC Board
-  Ferric chloride etching solution (Radio Shack)
-  Acetone (preferred), or nail polish remover
-  Small Drill  (Dremel)
-  1/32" (.8mm)  drill bit

If you are new to the world of Printer Circuit Boards, here is a tutorial that will familiarize you with the process:
How to Make a PCB at Home


The PC Board

The first step is the creation of the board. A template (negative) can be found  HERE  (.docx)  and  HERE  (.pdf) 
Print this page using a Laser Jet printer and Glossy Photo Paper. This is required as the toner will be transferred from the Photo Paper to the copper board.

Use a standard household clothes iron to dry transfer the image to PC board.

During this transfer process, the iron must at its highest setting - no steam - and apply a lot of pressure to the paper/PC board to ensure a good transfer of the plastic toner to the board.

Once cooled, slowly lift the paper from the board. The plastic toner and the first layer of paper should remain. When done, remove the paper and plastic film with acetone (preferred), or nail polish remover.

Then etch the board with ferric chloride (Radio Shack).
Residue can be cleaned from the PCB using Acetone (nail polish remover).

Important Note: Always take precautions during the etching process. Rubber gloves and eye protection are a must, as well as a dust mask when drilling.

Drill the holes and then start soldering away.

Below is the component layout on the PC board.

Click to enlarge

The schematic below shows the DB-9 connections as well as the 2.5 and 3.5mm stereo plugs.

Depending on the stereo plugs used, you may need to shave a little off the cases if the fit is too tight to avoid damaging the jacks in the radio.

click to enlarge

In Summary

I hope you had fun with this project.  If you've never etched a PC board before, this is a perfect beginner's project.  Say goodbye to driver issues.
My thanks to Bob Desgrange KV4NF for this project.
Bob KV4NF 

John 'Miklor'

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