Ways to tell if you are experiencing problems is that your transmitted signal will be Under Modulated meaning you are not supplying a large enough signal ;or the reverse will be true, your transmitted signal will be Over Modulated meaning it will sound distorted, will be wide, and generally, unlistenable. Take heart that both can be cured and all you need is a little knowledge! What you need is a matching network , more commonly known as a PAD, between your program audio and Mic Input of your transmitter. I present you a simple circuit that should work about 99% of the time - Chauncy's Magik Matcher. See Figure 1.
Before we jump into the circuit and talk about it's uses, I need to lay down a little ground work first. You should be aware that you have a Mic Gain or sometimes called Audio Gain control on your transmitter somewhere. What you would like to end up with is a Program Audio Level that will sound correct at about 3/4 of this controls range. This will ensure that you are supplying enough audio without Over or Under Modulating your transmitter. Another recommended item is a way to control the output level of your tape deck. If you are going to purchase a tape deck, it will help if you get one that has a output level control on it. If the one you use does not, you can use the audio part of a Radio Shack Video Processor box to control the line level audio up OR down. These are quite available and are typically $20.
For those sharper readers, You may have noticed I haven't mentioned anything about mixing boards! Well, since this manual is geared to the neophyte, live broadcasting can bring on all sorts of problems with RF Feedback into equipment that the beginner doesn't need to deal with. Not that I am opposed to live broadcasting; it's just much easier to produce programs on cassette and then feed the transmitter with a tape deck. You still might experience RF Feedback problems with simpler setups but the cure will be much easier and less overwhelming to deal with. There is another chapter to this manual that discusses RF Feedback and how to cure it.
OK, now that we have gotten that information out of the way, let's talk about our matching network or Pad. A Pad simply is a buffer that will bridge the impedance mismatch between two pieces of equipment. The circuit we are presenting does this, and also will "Knock Down" the signal level to an acceptable level your transmitter will like and will also "Roll Off" the Low Audio Frequencies that your transmitters audio section won't transmit anyway.
You might have noticed there are no values given for the components. This has been done for a reason as it would be impossible to determine the correct values for every type of installation. What I am going to do is give you a Starting Value and then it's up to you to experiment with the values by increasing or decreasing them until you find the proper ones. R1 should start out at around 10,000 Ohms or 10K. R2 is a variable resistor with a value of 20K. C1 should start out around .05 uF and can be Ceramic Disc or Mylar. When you use this circuit to pad your transmitter, you can plug the components into a solderless breadboard. While transmitting, listen to yourself Off the Air and adjust the values of the components until you find the ones that sound the best to you.
R3 is optional to better match the impedance of the transmitter. A possible starting value of around 20K would be a good place to start.
Once you have determined the best values, You can solder the mess up and wrap it with electrical tape right into the cable feeding your transmitter! Or if you want to get fancy, you could mount everything into a box. Either way is fine and not critical.