Cubic Astro 103

 Discussion

I finally found an Astro 103 on eBay from a fabulous seller who understated its flawless condition.

;     The Astro 103 is an Astro 102BX with the following updates

  • WARC bands added
  • RTTY mode added (LSB transmit with CWN receive)
  • Provision for optional 6 pole 400Hz CW filter
  • Addition of receiving antenna jack and receiving antenna selector switch
 Accessories  

ST-3B PSU-6
Matching Network Speaker/Power Supply

 General Specifications

Frequency Coverage:

  • 160M     1.8 → 2.0MHz
  • 80M       3.5 → 4.0MHz
  • 40M       7.0 → 7.5MHz
  • 30M   10.0 → 10.5MHz
  • 20M   14.0 → 14.5MHz
  • 17M   18.0 → 18.5MHz
  • 15M   21.0 → 21.5MHz
  • 12M   24.5 → 25.0MHz
  • 10M   28.0 → 30.0MHz
Frequency Control: Dual PTO (permeability tuned oscillator) with 6 digit frequency counter and RIT control

PTO Modes of Operation:

  • A only
  • B only
  • Receive A - Transmit B
  • Receive B - Transmit A
  • External
Modes of Operation:
  • SSB with selectable sideband
  • CW with automatic 800Hz offset in transmit. Features full or semi break-in
  • CWN is mode is CW with 400Hz crystal filter in receive
  • RTTY - Operates LSB with 400Hz crystal filter in receive

Power Input:  12 → 14 VDC negative ground only.  No damage will occur over the range of 10 to 15 VDC.  20 Amperes peak current required

Electromagnetic Interference Reduction:

  • Transmit  -  Five element low pass filter on each band
  • Receive  -  Three pole bandpass filter on each band
Dimensions:
  • Height  -  6.375"  (16.2 cm)
  • Width  -  14.25"  (36.2 cm)
  • Depth  -  13.25"  (33.7 cm)
  • Weight  -  23.5 lb.  (10.6 kg)
Power Connector:
  • Pin 1  -  13.6 VDC
  • Pin 2  -  Ground
  • Pin 3  -  Ground (used for tuner meter lamps)
  • Pin 4  -  13.6 VDC
  • Pin 5  -  Ground
  • Pin 6  -  13.6 VDC (for tuner meter lamps fused at 3A)
Antenna Connector: UHF type SO-239

External Speaker/Phones: ¼" Phone jack (4 → 8 Ω)

External Relay: RCA jack, grounded when keyed

Key: RCA phono jack

EXT Modulation: RCA phono jack

Fuse: 3 Ampere fast blow

External LO: RCA phono jack

Auxiliary Antenna: RCA phono jack.  Slide switch chooses auxiliary receive antenna or common antenna with transmit

 Receiver

Circuit:  Single conversion to 9.00165MHz IF using  double balanced mixer.  Exceptional immunity to overload and cross modulation

Sensitivity:  0.35µV for 10dB S+N/N ratio

Image Rejection: Better than 60dB

Receiver Selectivity:

  • SSB and CW -  2.4KHz, two 8 pole crystal filter with shape factor of of 1.4:1, 6dB to 100dB (16 pole equivalent)
  • CWN and RTTY -  400Hz bandwidth. 6 pole crystal filter in series with one 9-pole SSB filter (optional)
Passband Tuning:
  • SSB and CW -  8 pole continuously variable highpass or lowpass.  LED readout shows approximate audio bandpass
  • CWN and RTTY -  4 pole crystal filter continuously tunable over 300-3000Hz.  LED shows approximate audio bandpass
Dynamic Range:  AGC greater than 100dB; third order intercept +5dBm.  (IMD products down 90dB at -40dBm input)

Audio Output Power:  Greater than 3 watts into 4Ω

Meter:  S units from 1 → 9  and 20, 40, 60 dB over S-9

 Transmitter

Circuit Design: Conversion from 9.00165MHz IF.  ALC limits SSB peak output power and CW power to 100 watts

Power Input: 235 watts PEP at 13.8 VDC supply

Power Output: 100 watts PEP into 50Ω non-reactive load at 13.8 VDC supply voltage. ALC limits peak power to 100 watts PEP

Unwanted Sideband Rejection: 60dB down at 1000Hz audio frequency

Harmonic Output: 45dB below peak power level

Carrier Suppression: 50dB below peak power level

Transmit Control:

  • SSB -  PTT or VOX standard
  • CW -  Full or Semi break-in with sidetone standard with an 800Hz offset on transmit frequency
Microphone Input: 47KΩ input impedance

Audio Response: 300 → 3000Hz  ±6dB

Meter: Reads peak power on transmit selected by meter switch; forward power 100 watts full scale, reflected power 10 watts full scale, or ALC

Cooling: Large capacity heat sink fins supplied.  For SSTV, RTTY, and semi continuous transmitting, forced air cooling supplied by a muffin type fan on heat sink fins is required

VSWR Shutdown:

  • Full power up to VSWR of 1.7:1
  • 80% at 2:1 VSWR
  • 60% at 3:1 VSWR
  • 25% into open or short
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