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AMT5000
Transmitter Specifications
The
AMT5000 AM transmitter kit is an FCC Part 15 compliant transmitter designed
specifically for high efficiency to provide nearly the highest RF output
level practical for any 100 mW transmitter.
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Frequency
Coverage
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Model
AMT5000: 530 to 1700 kHz in 10 kHz
steps.
Model
AMT5000-9K: 522 to 1710 kHz in 9 kHz
steps.
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Carrier
Frequency Generation
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Crystal
controlled PLL synthesizer
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Frequency
Selection Method
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8-position
DIP switch
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Frequency
Tolerance @ 25șC
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±.003%
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Modulation
Type
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Amplitude
Modulation (AM)
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Maximum
Modulation Level
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Normal
100%, 130% positive modulation with
external processor
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Power
Input to Final RF Stage
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100 mW,
adjustable to compensate for varying load conditions
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RF
Circuit Configuration
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MOSFET
Class E switching mode, 98% RF transistor efficiency.
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RF
Spurious Emissions
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43 dB
below carrier level.
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Antenna
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Standard:
118 wire (supplied with kit)
User-supplied:
102 CB whip or 118 copper or aluminum pipe
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Antenna
Matching
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Low-loss
iron-powder toroid loading coil series resonates with antenna capacitance.
Jumper-selectable option for user-supplied external loading coil.
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Output
Tuning
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1350kHz
- 1700kHz: jumper select toroid inductance, screwdriver adjusted air piston
trimmer capacitor for peak tuning.
530kHz
- 1350kHz: jumpers select supplemental inductors and toroid tap,
screwdriver adjusted FILMTRIM trimmer capacitor for peak-tuning.
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RF
Output Metering
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Test
points on circuit board for measuring RF stage input voltage and current
with inexpensive user-supplied digital or analog multimeter.
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RF
Grounding Options
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Jumper options
for including/excluding RF isolation inductors in power feed lines to
suppress conducted emission
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Modulation
Circuit Configuration
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Common-source
MOSFET modulation driver in series with RF output MOSFET drain.
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Internal
Audio Response
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20 Hz -
20 kHz ± 0.5 dB
Jumper
selects flat response or NRSC standard pre-emphasis.
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Modulated
RF 3-dB Response
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20 Hz -
16.5 kHz audio response) with 20-30 ohm RF ground (typical).
Modulated
audio frequency response is higher when supplemental inductors are
jumper-selected at frequencies below 1350 kHz.
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Audio
Distortion
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Less
than 0.5% THD through audio stages to final high-level modulator stage.
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Audio
Input Level
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Consumer
Audio: -10 dBV, 0.316 Vrms
Pro
Audio: +4 dBu, 1.228 Vrms
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Audio
Input Impedance
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Consumer
Audio: 18k ohms at 1 kHz
Pro
Audio: 14.3k ohms differential at 1
kHz
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Audio
Compression
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Compression
ratio adjustable from 1:1 to 5:1. Attack
time less than 1 ms. Medium release time suitable for both voice and
music.
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Audio
Limiting
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Adjustable
threshold. 15:1 compression above
threshold. True RMS limiting ensures no distortion in limiting region.
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Front Panel
Controls and Indicators
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Audio
input GAIN, MODULATION level, COMPRESSION ratio. Green LED power light.
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Rear
Panel Jacks
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Consumer
Audio (unbalanced): 2 RCA audio-in jacks mixed equally on board for
stereo-to-mono conversion or two mono sources.
2.1 mm
power input jack.
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On
board screw terminals
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Antenna
RF
ground
Mono
Pro Audio (balanced): +, -, Gnd
Power:
AC or DC(+, -)
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Input
Power Options
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12VAC
wall adapter, DC wall adapter, 12V battery.
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On-Board
Power Conditioning
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RF bypassed
bridge rectifier for 12VAC operation mode.
Low-dropout
12V regulator provides stable, regulated and filtered voltage even when
operating from 12V battery (nominal lead acid battery voltage is 12.63V).
Below 12.3VDC, input voltage is passed to output without regulation.
Separate
5VDC regulator provides stable, regulated and filtered power to ICs.
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Power
Consumption
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120
VAC, 2 watts with standard 12VAC wall adapter.
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Circuit
Board
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7W x 3.9D
x .062H FR4, two layers, 1 oz. copper, top and bottom solder masks, top
silkscreen with component identifiers and labels.
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Enclosure
Options
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Indoor
option: 1.5H x 8.1W x 4.2D ABS
plastic, color bone and black.
Drilled, silk-screened front and rear panels.
Outdoor
option: NEMA 4, 4X. 8.66H x 4.72W x 3.54D, fiberglass, color gray
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