To amplify the IF portion of the 20m superheterodyne recievers signal chain, I though I would give the W7ZOI and K3NHI's termination insensitive amplifier design a try.

Termination insensitive amplifier (TIA) design

The TIA starts with a common emitter amplifier with negative feedback. The amplifier with feedback has a total gain of 15dB, and input impedance of 50 ohms. After the common emitter, there are two common collector amplifiers (buffers). These common collector amplifiers are what provides the insensitivity to varying output loads. Along side a 47 ohm resistor at the output, the total output impedance is close to 50 ohms.

Making the PCB

Since I have begun etching my own PCBs, I designed the layout in KiCad to be one-sided. I included some 4.5mm pads to solder the in and out coax/wire, and a pad for the input voltage.

I added some additional traces of varying lengths to test the resolution of the etching method (witch means the resolution and quality of the toner transfer).

Etching

The etching was simple and straightforward. I used some gloss paper and a laminator to transfer the toner onto the copper clad board. Next I put the board into a solution of ferric chloride acid.

Populating the board

Once the board was etched, I soldered all the necessary components to it.

Testing and Results

The resulting measurements of the amplifier match what was stated by W7ZOI and K3NHI in their document. The measured gain was 14.73 dB, with an impedance of 55.5 ohms at 14.34 MHz.