FX 146
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8
A MESSAGE TO HAM RADIO BEGINNERS:
If you have just earned your Novice or Technician license, or are studying for
either of them right now, we'd like to say a special Thank You for choosing
this Ramsey VHF/UHF transceiver as part of your ham radio beginnings. We
have tried to make this instruction manual as clear as possible. However,
there are some VHF radio "basics" covered by the FCC question pools for all
ham license study guides that we must presume that you have studied and
understood.
Here is a simple guide to selected Technician Class questions to help with
any review you wish to make before building:
FCC Subelement 3AA (Selected Rules):
4.2 11-1.1 12.5 15.2
FCC Subelement 3AB (Operating Procedures):
2-1.1 2-1.2 2-1.3 2-1.4
2-1.5 2-2. 1 2-2.2 2-3.1 3.2 6-3.1
FCC Subelement 3AC (Propagation):
It's up to you to understand the
characteristic differences among HF
(shortwave), VHF and UHF
communications.
FCC Subelement 3AD (Amateur Radio Practice):
All of this is fundamental
know-how for hams. In working on this
project, be especially familiar with: 1-1.1 1-
1.2 1-1.3 7.1 9.1 through 9.5 (dummy
loads)
FCC Subelement 3AE (Electrical Principles) 3AF (Circuit Components)
Please know ALL of this.
FCC Subelement 3AG (Practical Circuits):
4.21
FCC Subelement 3AH (Signals and Emissions):
1.1 2-1.1 2-4.1 2-6.2
2-7.1 4.1 6-1.2 7-1.1 7-2.1 7-2.2
FCC Subelement 3AI (Antennas and Transmission Lines):
You will want
to know all of this, if you don't want to take
all your savi ngs from building your own
transceiver and spend it on a commercially-
built antenna. Very good VHF antennas are
easy and inexpensive to build yourself!
FX-146
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139
FX-146 TECHNICIAN’S NOTES
Throughout production of the “FX” series transceivers, the technicians here
at Ramsey have been speaking with customers, making repairs,
experimenting, and compiling notes on the FX-146. These notes, and the
circuit overview and theory of operation sections of your FX-146 manual,
provide extensive information on the inner workings of the FX-146. Should a
nasty gremlin jump into your trusty new FX-146, this information will help
lead your foray into troubleshooting.
Several voltages and testpoints are given throughout this guide. Keep in
mind that, due to differences in test equipment, power supply voltage, etc.,
your readings may vary slightly. Any voltage within 20% or so should be
considered ok. It may also be difficult to lead you to a specific component or
fault right off.
Now clear off that workbench, lock the doors, put up the “do not disturb”
sign, and let’s get started!
Preliminary Checks: (Many times these first few checks will solve the
problem.)
1. Proper DC voltages. (+13.8VDC, +8V, +5V, +8T, +8R)
2. Solder connections. All joints should be clean, shiny, and solid. (You
won’t need a magnifying glass. If a connection is suspect, reflow the
solder.) Also, check for stray solder shorts or bridges.
3. Easy to confuse items. Now let’s see, was that a 10K ohm resistor
or 1K ohm? Some of those color bands look quite similar to tired
eyes. Let another pair of eyes check your work.
4. Component lead length. VERY IMPORTANT! Make sure all
component leads are as short as possible. In other words, pull the
leads through the board until the component body rests on the
board. The hand wound coils of buss wire should not touch the
board! (One exception - obviously)
5. Make sure only one channel is activated at a time. A diode installed
backwards in another channel can turn on two channels at once!
Your voltmeter should indicate voltage on only one bus wire at a
time. This is true for the offsets too.
6. Reread those sections of the manual where you feel the possible
fault could be. A thorough understanding of each circuit just may