40 meter 100 watt Transmitter
The 40m receiver was complete and
it wasn’t long before the old girl was beginning to look forlorn. It was
obvious she needed a mate. Hmmm....perhaps something tall, dark, and handsome?
Nope. She would have to settle for something short, wide, and solid state.
This transmitter can operate on
the 40m band without time limit at an output power level of 100W carrier
on CW and RTTY, 100W PEP on SSB, and 25W carrier on AM (100W PEP with 100%
modulation). The final amplifier stage runs a pair of Motorola MRF150
high-voltage RF power TMOS-FETs in push-pull configuration, biased for
class AB linear operation. Although the PA stage is capable of substantially
more power, limiting the output to this level is an act of kindess to a
pair of very expensive transistors and provides a “standard” output
level for driving legal-limit amplifiers.
Some highlights:
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Modes of operation: CW, AM, USB, LSB,
FSK
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Dedicated connector on back panel for
a packet TNC (terminal node controller).
-
An electronic keyer, based on the ubiquitous
Curtiss 8044AB iambic CW keyer chip.
-
Front panel controls for these CW functions:
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Keyer speed
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Keyer weight
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Semi-QSK delay time
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Sidetone level
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Metering, left to right:
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Driver current, 250mA full scale
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ALC level
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PA current, 10A full scale
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RF output meter which can be operated
in peak or average mode
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Low-level generated AM signal bypasses
the narrow SSB filters for full fidelity.
-
Front panel controls for mic gain and
carrier level.
-
Rear panel connections for RX muting
and amplifier control.
-
Internal DC power supplies permit 120VAC
line operation.
You can download the schematics
(200K) for this transmitter, viewable with Acrobat
Reader. The ten pages of schematics were produced using VISIO Technical. 
February
28, 1998
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