AM25
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8. Measure the voltage at TP1, located near the center of the board.
9. Using the plastic tuning tool, adjust coil L5 until you read between 1
and 3 volts DC at TP1. You should also see the red LED light up and be
able to hear the AM25’s carrier signal.
10. Connect a 1 volt peak-to-peak audio source to the AUDIO IN jack.
Adjust ‘Audio level’ pot R31 for best sounding undistorted audio. The
best audio source for testing is the line level output of a tape deck or CD
player. Most stereo systems have a line level output jack.
11. Adjusted as indicated, your AM25 will produce 100 mW of RF power
which conforms with FCC rules. If you live outside of the USA you may
jumper across resistors R33 and R34 to allow the AM25 to generate 1
watt of RF power.
TROUBLESHOOTING INSTRUCTIONS
While we had hoped that it wouldn’t come to this, if you are having trouble
with your transmitter, here are a few suggestions. By far the most common
source of problems is misplaced parts or poor solder connections. It’s always
best to take a break before searching for bad connections. A good way of
checking component placement is to double check the assembly steps going
backwards from the last step to the the first. Bright lighting and a magnifying
aid can be helpful in identifying soldering problems.
Use a methodical, logical troubleshooting technique. Most problems can be
solved using common sense. A volt-ohm meter and a clear head are usually
all that are needed to correct any problem. Please understand that it is
nearly impossible to “troubleshoot” by email or fax; phone is better. If you
call, please have your kit in front of you.
PLEASE READ THIS IMPORTANT FCC INFORMATION
The AM25 is classified by the FCC as an “intentional radiator,” and its
operation is covered by Part 15 of the FCC rules which were updated in June
1989. In brief, what you need to know about these rules is that your AM
broadcaster must not interfere with AM radio or TV reception of other people.
As designed and adjusted, the AM25 complies with FCC technical
requirements for devices used in the AM broadcast band. The individual kit
builder and all end users of this device assume responsibility for lawful uses
conforming to the FCC part,15 rules.
Operation is subject to the following conditions:
1. This device may not cause any harmful interference
2. This device must accept any interference received, including
interference that may cause undesired operation.
Summary of Contents for AM25
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