Alignment Procedures - Ramsey Electronics AM25 Assembly And Instruction Manual

PROGRAMMING YOUR AM25
Programming your AM25 is very easy, involving nothing more than dividing
(by 10!) and subtraction. The output frequency in KHz is divided by 10 and
this 'Program' number is then set on DIP switch, S1. These switches are
programmed in Binary, you simply add up the closed switch positions: 1, 2, 4,
8 all the way up to 128 to make any 'Program' number between 0 and 255.
Next to the DIP switch, there are numbers printed on the PC board from 1 to
128. For the AM broadcast band, 540 - 1710 KHz, we'll only need to program
between 54 and 171. For example, if a broadcast frequency of 550 KHz if
desired, we'll need a 'Program' number of 55 (55o KHz divided by 10 equals
55). Closing switches 32, 16, 4, 2 and 1 all adds up to 55, our desired
'Program' number. As another example, what would we need for 1520 KHz?
Our desired program number is 152 (1520 KHz divided by 10 equals 152)
and we'll have to close switches 128, 16, and 8 which adds up to 152!
Another example: 930 KHz, 'Program number is 93 (930 KHz divided by 10 =
93). Close switches 64, 16, 8, 4, 1. How about another? 1460 KHz, program
number is 146, close switched 128, 16, and 2. A calculator comes in handy
when you successively subtract the binary numbers (128, 64,...4,2,1). It
really is quite easy and fun to find the right switches to close!

ALIGNMENT PROCEDURES

Keep all tests very brief until you have carefully chosen an open operating
frequency in the AM broadcast band. Remember, to optimize the
performance of your AM25 the PC board ground should be connected to
earth ground. The simplest way to accomplish this is to run a jumper from
the board ground to a cold water pipe or to a ground rod implanted several
feet into the earth. A good ground connection will greatly decrease the
chance of noise entering the AM25 circuit.
1. Find a quiet spot on the dial where you wish to receive your
transmitter and tune a nearby radio to that frequency.
2. Connect an antenna to the RF OUT jack.
3. Program in your desired operating frequency.
4. Verify that you have installed the correct components in the low pass
filter section (C3,4,5,7 and L1,2,3) and the jumper block is in the correct
position on Header block H1.
5. Set trimmer pots R23 and R31 to mid-rotation.
6. Connect a power source capable of 12 VDC at 500 mA.
7. Measure the voltage on resistor R34's lead closest to C23. R34 is
located between the heatsinks. Adjust 'Bias" pot R23 for 7.1 VDC.
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