Club Sandwich Block Diagram and Block Specifications

CLICK to view Block Specs:
...RX BPF ...RX PREAMP ...RX MIXER ...IF AMP w/ AGC (1)
...IF FILTER ...IF AMP w/ AGC (2) ...PRODUCT DETECTOR w/ BFO ...AF PREAMP
...RX MUTE / AF AGC ...AF FILTER ...AF AMP ...AGC GENERATOR
...TX MIXER / OSC ...RF DRIVER ...POWER AMP ...LOW PASS FILTER
...VFO ...KEYING CONTROL ...ANT T/R SWITCH ...SIDETONE GENERATOR
Module: Receiver Band Pass Filter

Function:

Provides filtering at input of receiver to reduce image and reduce unwanted out-of-band signals

Input/Output:

Key Specs or Limitations:

Frequency range: To be determined

Misc Notes:

Typically, this is a double-tuned circuit, or a high-Q preselector with a "peaking" control
Adding a switchable attenuator might be useful here also

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Module: Receiver Preamp

Function:

Improve noise figure and sensitivity, and provide 10-12 dB of pre-mixer gain

Input/Output:

Operator Controls:

Key Specs or Limitations:

Gain: 10 - 13 db (fixed)
Noise Figure: < 3 dB

Misc Notes:

May be narrow band (i.e., single band) or broadband 3-30 MHz (for broadband, please equalize gain)

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Module: Receiver Mixer

Function:

Convert pre-filtered RF to IF (or to audio if direct-conversion receiver)

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

If an active mixer is used (like the NE602/SE612), an output amplifier will probably not be required; if a passive (diode ring) mixer is used, a VFO input amplifier and an IF/AF output amplifier will be required. Amplifiers, if used, should have tank circuits to minimize unwanted responses

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Module: Post-Mixer IF Amplifier

Function:

Reduce Noise and provide gain/AGC prior to IF filtering

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: IF Filter

Function:

provide narrow-band filtering at IF Frequency (not required for direct-conversion receiver)

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: Post-Filter IF Amplifier

Function:

Provide gain/AGC after IF filtering

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: Product Detector / BFO

Function:

Provide product detection for CW / SSB; includes BFO

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

  1. This stage not used in direct-conversion receiver
  2. If an active mixer is used (like the NE602/SE612), an output amplifier will probably not be required; if a passive (diode ring) mixer is used, an AF output amplifier will be required. An amplifier, if used, should have low-pass roll-off to minimize hiss and eliminate IF feedthrough to the output.

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Module: AF Preamp

Function:

Provide gain for Direct Conversion Receiver (not needed for receiver with product detector)

Input/Output:

Operator Controls:

Key Specs or Limitations:

Voltage Gain: 10-15 db (fixed)
Output: AC-coupled

Misc Notes:

This stage not required for receiver with product detector stage

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Module: Receiver Mute and AF AGC Circuit

Function:

Provide for muting of receiver during keying; optionally provides AGC for receivers with IF AGC (and preferrrably for direct conversion receivers)

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: AF Filter

Function:

provide audio bandpass shaping or filtering, as appropriate for CW or SSB

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: AF Power Amplifier

Function:

Monoraul Audio Amplifier, with two inputs, one for audio, one for sidetone, capable of driving 8-ohm headphones

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: AGC Generator

Function:

Based on an IF or AGC sample provided, generate AGC Voltage to be utilized by AGC-controlled stages

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: Transmit Mixer and Oscillator

Function:

converts VFO frequency to output RF frequency; includes crystal-controlled conversion oscillator

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: Transmit Driver

Function:

Gain and Filter; provides drive to RF Power Amplifier

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

Pay attention to keying waveshape, as this will influence final transmitted signal

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Module: RF Power Amplifier

Function:

provide 3-5 Watts RF output

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: Output Low Pass Filter

Function:

Provides harmonic rejection

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: VFO

Function:

Provides injection for Receiver Mixer or Transmit Mixer, as appropriate; includes R.I.T. offset

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

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Module: Keying Control Circuit

Function:

Provides transmit/receive control signals with sequenced delays, to be used by other circuits that need to be keyed

Input/Output:

Key Specs or Limitations:

Misc Notes:

Trimmer or programmable control of KEY3 delay, to accommodate unknown receiver recovery time

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Module: Antenna T/R Switch

Function:

Provides switching for antenna circuirt, between transmit and receive

Input/Output:

Key Specs or Limitations:

Misc Notes:

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Module: Sidetone Generator

Function:

generate keyed CW sidetone for injection into audio chain

Input/Output:

Operator Controls:

Key Specs or Limitations:

Misc Notes:

This stage not required in receiver that self-generates sidetone from transmit mixer

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