Note
The MFJ-8621(A) is a dedicated 2-Meter FM-AFSK transceiver designed specifically for packet radio operation. Unlike converted voice radios, it is engineered "from the ground up" for fast, clean packet communications at data rates through 9600 baud. It is a dedicated-channel unit that eliminates unnecessary features like squelch, repeater offsets, and speaker amplifiers to focus entirely on signal recovery and throughput. It is compatible with virtually all TNC-2 style modems equipped with Data Carrier Detect (DCD) and can also be used with computer sound cards.
Features
– Packet-Only Performance: Designed exclusively for data, offering high performance at a lower cost than multi-purpose voice radios.
– Dual Modulators: Features a reactance modulator for 1200-baud mic-level signals and a "true-FM" varactor modulator for 9600-baud line-level FSK signals.
– Made-For-Data Filtering: Includes optimizeable receiver filters for wide 9600-baud or narrow 1200-baud signals.
– Cool and Efficient Operation: Draws only 25 mA on receive and less than 1 A on transmit, making it suitable for continuous 24/7 use or portable operation.
– Lightning-Fast T/R Switching: Uses PIN-diode switching and a continuous-running receiver to allow for ultra-fast Transmit Delay (TXD) settings.
– Unsquelched Data Output: Employs a DC-coupled line driver for flawless signal recovery, requiring a TNC with DCD capability.
– Sound Card Compatibility: Includes dedicated audio input and output jacks for direct connection to a computer sound card.
– Easy Rechanneling: Uses plug-in crystals (shipped for 145.01 MHz) that can be easily exchanged to operate on different frequencies without expensive test equipment.
Specifications
Receiver
– Frequency Coverage: 144–148 MHz.
– Sensitivity: 0.6 µV for 12 dB Quieting.
– Selectivity: –6 dB at 20 KHz (data-passband filter).
– Image Rejection: –45 dB or better.
– Intermediate Frequencies (IF): 1st IF: 10.7 MHz; 2nd IF: 455 KHz.
– AFSK Output: Unsquelched, 0 dBm @ 3.0-KHz deviation (typical 2.2 V p-p into 600 Ohms).
Transmitter
– RF Power Output: 4.0–5.0 Watts into 50 Ohms.
– Frequency Control: Crystal-controlled (18-MHz range fundamental mode, multiplied 8 times).
– Deviation: 0–5 KHz, adjustable at the TNC.
– Input Level: 150 mV p-p @ 1200 baud; 800 mV p-p @ 9600 baud.
– VSWR Tolerance: 3:1 Maximum.
Power Requirement:
13.8 Volts DC @ 1 Amp (operates from well-filtered sources or battery packs).
Power Connector: Standard 5.5mm x 2.1mm coaxial-type plug.
Protection: "Crowbar" diode protection for incorrect polarity and a thin foil trace on the PC board that acts as an line fuse.
Current Drain: Transmit: 1.0 Amp @ 13.8 Volts; receive: 25 mA
