The performance of a receiver or transmitter depends on careful impedance matching between its sub-systems: its mixers, filters, and amplifiers. Mismatches can cause loss of signal strength, inter-modulation distortion, and deep ripples in the audio passband that can make human speech hard to understand. A termination-insensitive amplifier (TIA) such as this one always presents a 50Ω impedance at both its input and output ports, providing a stable and predictable impedance to whatever it's hook up to.

Adding automatic gain control (AGC) makes the audio coming out of the speaker or headphones stable as well. AGC boosts faint audio, and it keeps strong signals from blasting-out your eardrums. Though it's far from a necessity, AGC is a nice thing to have. The circuits on which this broadband TIA IF amp is based was devised by Wes Hayward, W7ZOI, and Bob Kopski, K3NHI.

The TIA-AGC broadband IF Amp has these features:

• Input and output port impedance is always 50Ω and does not pass through or "telegraph" to the other port.
• AGC responds to the input of a filtered DC voltage derived from the audio signal.
• "Programmable" gain from 7 to 24dB.
• Useful from 1 to 30MHz (with slightly-lower gain above 14MHz).
• Uses 12VDC power.
• PCB pads for edge-style SMA connectors (not included). Usable also for direct solder connection.
• Mounting holes for 4-40 (M3) screws.
• 1.55 x 2.20" (4.0 x 5.6cm).
  

Available as a bare PCB, a kit of PCB and components, or as a fully-assembled and tested unit. Be sure to select desired option in the selection box above. Assembled and tested units are produced on demand and shipment is within fourteen days of order.