I have needed some RF/IF amplifiers for my receiver, so I have decided to use the design by Wes Hayward, W7ZOI, and Bob Kopski, K3NHI, originally published in 1999. This amplifier has two main advantages – first, it has a wide bandwidth lacks any tuned circuits, so it is easy to use in a multiband receiver. All that would need to be switched is the input bandpass filter. The second advantage is the rigid 50 Ohm output impedance on the input, no matter what is the output load thanks to the additional emitter follower at the output. That simplifies the receiver construction.
I have built an SMD version of this amplifier as a module that can be used as both the input RF preamp and the IF amplifier in the receiver. My version is not bidirectional – if you need that, you will need to tie two of these side-by-side.
More pictures and video of a working receiver using these is available here.
If someone is interested, here are design files:
- KICAD project
- Orderable PCB from OSHPark
- Original article by Wes Hayward & Bob Kopski that includes the resistor values for various gains
All the passives are 0805 sized and the boards use oversized pads so all components are perfectly hand solderable, without any special tools or magnification.
UPDATE: fixed the Kicad project to be openable with Kicad 4.0.7