Software Defined Radio
This is my homebrew SDR based on K5SDR's design (SDR1000). The board layouts are my own and worked perfectly first time.
This is an amazing radio! Performance is absolutely outstanding and keeps getting better with every new software release.
Here is the parallel interface board. This interfaces the PC to the individual boards.
This is the DDS board (with QSD). It mounts to the back of the PIO board.
You'll notice the large heatsink on the DDS chip. The filters to the left of the DDS chip differ from the SDR1000 design and are optimized to suppress the 200MHz DDS clock.
I don't like the 3.5mm audio jacks on the SDR1000 so my board interfaces directly to the Delta 44 sound card cable (no need for the break- out box).
I did use 3.5mm jacks for the speaker and key connections.
The filter boards are my own design. All use relays for band selection (no IMD) and are built using silver mica caps and high Q toroidal inductors - overkill I know.
The filters are optimized for ham band coverage.
This is the BPF board.
And this is the LPF board used between the LNA and the QSD (Quadrature Sampling Detector):
The 2 filter boards are mounted on top of each other with a shield plate separating them:
This is the LNA / transmit buffer board. This board also contains an impulse generator for channel equalization.
And here is the PA. It uses 2 x MRF150's for an easy 250W PEP output.
The small box on the left is a homebrew SWR coupler. It feeds an A/D inside my SDR housing which displays forward and reverse power on the main console.
Not shown are a set of diplexer output filters (LPF/HPF with the HPF leg terminated into a 50 ohm load).
I have been using this radio for about 2 yrs now and it continues to be my favorite - especially for listening to vintage AM!