ITrip Amplifier

From IPodWizard.net Wiki

Contents 1 Introduction 2 Equipment needed 3 Prerequisites 4 Constructing the Amplifier 5 Cases/Housing 6 Credit

Introduction

This Tutorial will show you how to amplify the signal of our iTrip without any circuit modification of the iTrip. The Problem with amplifying a small FM transmitter such as the iTrip is that they were never intended to broadcast long ranges. Although you can boost the range you may also boost the interference. This is handy for getting a clearer quality signal within short ranges, but depending on the placement of the amplifier, long range broadcasting is possible, but with any transmitter, the further you are from the source, the worse the quality of the transmission.

• NOTE This information is for educational purposes only! By reading this you agree that the author of this text will not be held responsible for the way you intend to use this information. This violates FCC regulations, use at own risk! iPodWizard is not responsible for any damages caused by the information on this page to any equipment or the user.

Equipment needed

• iTrip with exposed antenna
• Transistor - 2n4401 or MPS918
• 220 ohm resistor (1/2 watt)
• 10k Ohm resistor (1/2 watt)
• 0.001 Capacitor
• 10 uH RF Choke - If unable to find a suitable choke, making one is quite easy. The purpose of the choke is to generate a small magnetic field which produces a phase shift (if you want a further why ask the nearest electrical engineer). It is an inductor. Magnet wire is copper or aluminum wire with a thin insulation to prevent short circuits. It is single-strand wire insulated with enamel, varnish, cotton, glass, asbestos or some combination of these. It is common and can be found almost any place that sells wire. Take about a foot of it and wrap 15-17 turns around a pencil. You should wrap it tightly, but loose enough so that you can slide it off. Make sure you leave a length of wire on both ends equal to the length of the leads (the wires sticking out both ends) of the 1k ohm resistor. Take a razor blade or knife and scrape of the very thin insulation around the wire on both ends (where you will solder it). Put the resistor inside the coil (make sure it is not touching). Solder each end of the magnet wire to opposite ends of the leads. The final result should be a resister inside a coil of magnet wire, and the only place the two touch is where the solder is.
• 65-85 cm telescoping antenna or solid wire
• 2"x2" circuit board
• Soldering iron
• 12v car adapter/ 12v wall adapter
• 2 alligator clips

Prerequisites

Before you can mod your iTrip you will need to open it and expose the antenna*

Constructing the Amplifier

First look over the diagram

Second, a few notes

It is not important to cut the alligator clips and solder the ends to the circuit board. It is possible to just solder the materials in place and then attach the alligator clip. The pictures on the Proof of Concept site has some pictures of this mod with alligator clips that aren’t soldered.

Now that that is out of the way we will move on to the instructions

• Step One

Ok here we go!!! First things first, open the contents of the jumper wire set so we have them at hand for when we need them. Make sure the work area is clean of anything except the materials and tools needed for this mod. Were going to start off slow with one step per connection. Place the parts on the circuit board as we go along soldering connections (ONE PART AT A TIME).

NOTE* All soldering of connections should be done on the bottom of the board unless told otherwise

• Step Two

Ok this will be our first soldered connection. Place the following parts on the circut board so you have room to place on the other partsz; the 2n4401 or MPS918 transistor and 10k ohm resistor. Now, it does not matter which lead you use to solder the resistor to the transistor. After the parts are placed on the board solder the following leads together on the bottom part of the circuit board, middle pin and one of the pins on the resistor. Now the middle pin on the transistor and one pin on the resistor should be soldered together, on the bottom of the board.

• Step Three

Now take on the wires from the jumper package you bought and cut off one of the two alligator clips and bear up the wire (take casing off to show the wire). Now solder the bear wire to the connection you just made in "Step Two" so now the wire, resistor and middle transistor pin should all be connected to each other.

• Step Four

Now this next one is going to tie in 4 things all together in one solder connection. Take another one of the wires from the jumper wire pack and cut off both alligator clips and bear up both ends of the wire. Take the right pin of the transistor, other pin on the 10k ohm resistor from "step Two", one the ends of the wire you just beared up, one of the pins on the 10 uH RF choke. Make all these parts touch and solder them. So now both pins on the 10k ohm resistor should be used up and all those 4 parts should be in one connection.

• Step Five

Take the other end of the wire you just beared up and soldered in "Step Four" and wrap it around the bottom of your telescoping antenna and soldered it on there since this gives the best results. Just a brief overview of what has been done so far; the 10k ohm resistor is completely used up, one end of the RF choke is soldered, antenna is soldered in, 2 of the pins on the transistor are soldered, wire that connects to the iTrip should be soldered (Step Three).

• Step Six

Now take one 220 ohm resistor and the other and only available end of the RF Choke and solder them together. So now the 220 ohm resistor and RF Choke are soldered together.

• Step Seven

Cut the antenna wire in half and bear up each side of the wire and take the 0.001 capacitor and solder each the wires you just beared up to each end of the capacitor. So now the capacitor should be somewhere in the middle of the antenna wire so it goes wire capacitor wire then antenna.

• Step Eight

Now take the negative (usually black wire) and positive (usually red wire) of the 12 volt adaptor and were going to solder them into the circuit. Solder the positive end on the other pin on the 220 ohm resistor and solder the negative end of the adaptor to the left pin of the transistor. This is your power source. If you don't want to solder these connections move right onto "Step Nine" which will use alligator clips instead.

• Step Nine

This step is the same as "Step Eight" except using alligator clips instead of soldering. Ok now take two wires from your jumper pack, cut off one alligator clip per wire so that each wire has one clip. Bear up the other end of the wires and solder one wire to the 220 ohm resistor pin and the second wire to the left pin of the transistor. Now you should have two wires with alligator clips that will clip onto the positive and negative wires of the adaptor so you don’t need to solder them. Just make sure to clip the alligator clips to the proper wires, clip coming off the 220 ohm resistor goes to the positive (red) wire and clip coming off the left pin of the transistor to the negative (black) wire.

• Connection Check

The connections should be as followed (shouldn’t need this if followed the steps properly) 10k resistor, middle pin of the transistor, and wire with one alligator clip. - Connection 1 Right transistor pin, other pin on 10k ohm resistor, antenna wire, RF choke pin - Connection 2 Wire connected to the bottom of antenna - Connection 3 RF choke and 220 ohm resistor - Connection 4 0.001 capacitor, wire going to connection 2, wire going to antenna - Connection 5 wire with clip going to the 220 ohm resistor or positive wire connecting to the 220 ohm resistor - connection 6 wire with clip or negative wire connected to the left transistor pin - Connection 7

Cases/Housing

Here are some examples of cases made for the iTrip amplifier

Credit

Steps written by Lone_Wolf (later edited on the Wiki by SuperStupified and diagram edited by SuperStupified to avoid confusion with the non existent ceramic disk)

Lone_Wolf would like to say

Thanks to SuperStupified to all the questions he cleared up for me and Thanks to my Friend who helped me a little with the tutorial.
Credit too the folks at http://www.binaryelysium.com/itrip_amp/

[Proof of Concept]

[Original thread on iPW.net that brought about the tutorial and information of the amplifier]

[iPW.net Thread with tutorial]