Since I have been testing a number of amplifier designs recently, I needed to be able to attenuate the output of my function generator to a lower level. To accomplish this, I decided to build a switched attenuator box to have some flexibility on the level of attenuation.

After designing the tuned IF amplifier, I wanted a second IF amplifier that handled most of the receiver's gain. This ended up being more of a learning experience than I anticipated.

Continuing along with my HF superheterodyne receiver project, I designed and tested a tuned IF amplifier to feed the crystal filter. The tuned IF amplifier determines the receiver's ultimate performance by providing stable, high-gain amplification and precise bandpass filtering.

When designing a superheterodyne receiver, terminating mixers properly is important. This is especially important for the second mixer which is responsible for converting the intermediate frequency (IF) into audio. Even at this stage of the circuit, maintaining a consistent 50 Ω termination across all frequencies is required to minimizing distortion products and maintain a high dynamic range.

In an RF receiver, a broad spectrum of signals is present at the input. Because of this, a narrow bandwidth filter is required to pick out only the desired signals. In the case of an amateur radio HF receiver, a bandwidth of 3 kHz is needed to receive single sideband (SSB) transmissions.

To optimize signal integrity and internal reflections within the HF superheterodyne receiver I am designing, I need to address mixing products. I tend to do this through the use of diplexers.

With my University Degree complete, I had much more free time to work on my superheterodyne reciever. Armed with more knowledge than my 2025 self, I decided it was worth redesigning most of it. Beginning with the frontend amplifier, I decided to try the cascode amplifier once again.

Among my radio equipment, the one tool I didn't have was a 50 Ω dummy load. Using a 250W rated RF resistor, I created a dummy load with a wattmeter made from an old VU galvonometer.