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Why Choose the
AMT5000?
If your application falls in one of the following
categories, the AMT5000 is your best choice:
- low-power broadcasting
- information station for your retail business
- "parking lot" information
- real estate advertising near a property for sale
- full coverage over a large personal property
Range
FCC rules limit the power input to the final RF
stage to 100 mW. High efficiency enables more of that precious power to be
transferred to your antenna. The AMT5000 combines super-high efficiency
class E mode RF generation with an efficiency-optimized toroid loading coil
for nearly the best efficiency possible. The toroid loading coil is
designed for best efficiency in the frequency range of 1350 kHz to 1710
kHz. At the top end of the AM broadcast band, this coincides with best 3
meter vertical antenna efficiency.
Read "About Transmitting Range and
Antennas" on this page for details about range for indoor and outdoor
installations.
Built-In Audio Processing
Uses the same, proven compression and limiting
circuit as the AMT3000, ensuring a constant high modulation level
independent of the variations in audio source level.
Consumer and Pro Audio Inputs
You can choose either the Consumer Audio RCA
jacks or the Pro Audio screw-terminal inputs depending on your needs. If
your transmitter will be located outdoors, and possibly a long distance
from the audio source, you should consider using the Pro Audio input. This
input allows long distance audio feeds via balanced twisted-pair wires,
which reject noise and hum. The Pro Audio input has protection against
static electricity buildup and static surges on the audio wires.
130% Positive Peak Modulation Range
This capability simply refers to the available
modulation "headroom". Normally, distortion will rise rapidly as
you transition above 100% modulation. However, some commercial audio
processing devices, such as the Inovonics 222,
have asymmetrical peak limiting controls allowing you to set positive and
negative peak limiting levels separately. You can connect asymmetrical
processors and gain their full advantage.
For educational purposes, you can use the
AMT5000 as a teaching aid or classroom demonstrator for instruction related
to Class E mode RF principles.
Highlights
- Designed to equal or exceed the range and audio
quality of all other FCC Part 15 AM transmitters currently being sold
at any price.
- Fully compliant with all applicable FCC part 15
rules for operation in the AM broadcast band without licensing.
- The
RF output stage uses a low-on-resistance power MOSFET transistor
operating in the Class E switching mode at 98% drain efficiency when
tuned per instructions. Only 2% of the available 100mW input power is
dissipated in the transistor. Power input to the final RF stage is
adjustable to comply with the 100mW limit mandated by the FCC for
license-free Part 15 AM transmitters. You can reduce the input power
below 100mW to prevent overloading nearby receivers when using the
transmitter indoors.
- Various antenna options: a 118" length of
wire is included for indoor use. For outdoor installations, you can
mount the transmitter in a weatherproof box and connect to a 102"
CB antenna or 118" copper or aluminum pipe antenna. No external
loading coil or length adjustment is required.
- A
large custom toroid coil tunes the antenna in the 1350 kHz to 1700 kHz
frequency range. The toroid has an iron-powder core selected for
maximum efficiency in this frequency range.
- Crystal controlled frequency synthesizer covers
entire AM broadcast band in 9 kHz or 10 kHz steps, depending on order
option.
- Professional quality audio compression and
limiting maintains 100% modulation regardless of audio input
level. Adjustable 1:1 db to 5:1 db compression ratio. Audio levels above
the adjustable limit level are compressed at 15:1 db ratio.
- Audio
response at the final modulation transistor output is 20Hz to 20 kHz ±1 dB.
- Modulated RF 3-dB Response: 20 Hz - 16.5 kHz with 20-30 ohm RF ground
(typical for a reasonably good RF ground).
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- Consumer Audio and Pro Audio inputs: Two RCA
input jacks are mixed to convert a Consumer Audio stereo source to
mono or to mix two separate Consumer Audio mono sources.
Screw-terminal inputs for Pro Audio +, -, ground.
- Jumper selectable flat or treble-boost audio
curves. Treble boost pre-emphasis will compensate for the typically
poor high frequency audio response of most AM radios.
- Two voltage regulators and an on-board,
RF-bypassed, bridge rectifier assure clean, hum-free power. The
standard 120 VAC to 12 VAC wall adapter is included.
- Jumper options for operating from unregulated 12
VAC, 12-15 VDC or 12 VDC battery power sources.
- Very low 2 Watt AC power consumption for
worry-free continuous operation.
- Highest quality double-sided printed circuit
board has top and bottom solder masks and a top silk screen legend to
clearly identify component locations.
- The three surface-mount components are
pre-soldered on the board.
- Designed for ease of assembly. All components
mount on the printed circuit board. No time consuming discrete wiring
required.
- High-strength ABS plastic enclosure. Front and
rear panels are pre-drilled and screen printed.
- The instruction manual guides you, step-by-step,
through the assembly process to reduce the chance of errors during kit
assembly.
- Kit is educational and fun to build.
About
Transmitting Range and Antennas
Indoors
When using your AMT5000 indoors with the
included antenna wire, expect a very strong signal throughout the building
(you may need to reduce the input power adjustment below 100mW to prevent
receiver overload).
The range outside the building depends on two
major factors: (1) the shielding effect of the building siding and (2) the
amount of your signal that is radiated out over the power lines feeding
your building.
Aluminum siding and stucco-over-wire-mesh are
two siding methods that shield the signal the most. Power line radiation is
quite unpredictable. So, you can expect anywhere from 50 ft. to several
thousand feet range from inside a building. That information isn't very
helpful, but reality doesn't make a useful range prediction possible.
Outdoors
You can maximize your range, and make it
independent of your building and power-line radiation effects, by installing
the transmitter outdoors, well clear of surrounding obstacles. Use a
102" stainless-steel CB whip antenna or a copper or aluminum pipe
118" long. A standard 8 ft. long copper-clad electrical ground rod
should be driven into the ground at the base of the antenna for lightning
protection. Four or more 15 ft. (or longer) radial wires fanning out from
the ground rod connection on or buried slightly below ground will greatly
improve your range. With such an installation, expect 3/4 to 1 mile range
for a fairly strong signal on a car radio. A listenable signal can often be
heard in some directions at 2+ miles. High building density and a high local
ambient electrical noise level will reduce the range.
The AMT5000 has a jumper option for completely
bypassing all internal RF output tuning inductors, including the toroid,
for those who would like to experiment with an antenna using a large
external air-core loading coil. Such an antenna will require a tapped air
core coil and a method for adjusting the antenna length for fine tuning.
VIEW ANTENNA
CONSTRUCTION PLANS
Thanks to a great contribution from one of our
very inventive customers, here is a PDF file showing how to modify the
antenna with a sleeker in-line coil.
MODIFICATIONS
TO ANTENNA PLANS FOR IN-LINE COIL
Constructing the base-loaded antenna is made a
lot easier thanks to Carl Van Orden. He sells the
complete tapped coil, wound on a section of 3” white PVC pipe as
shown in the plans. This is the most difficult part of the antenna to
fabricate. Carl also sells ground radial systems. For more
information and prices, click on the following link to see Carl’s page.
PRE-FABRICATED
COIL AND GROUND RADIALS
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