uSDX SDR 1.02 Custom Design

The following design will fit with Bard WB2CBA Octoband or quadband Filter. This main board is not including Class E amplifier since the output power is already embedded on the LPF filter.

This current design is all through hole and only the SI5351 is a SMD .

The LCD1602 display is connected to the main board but remotely install on the casing. In addition the design is offering a sandwitch configuration with a front and back panel. You have the choice !

The design is providing :

• CAT Control output plug for the FTDI Adapter
• Digital input/output plug for digital modes with galvanic insulation
• PA Control plug
• I/Q output plug for external software
• LM386 Audio amplifier with a tiny speaker
• A connector plug for the connectivity with the quadband or octoband filter (Not tested with the octoband but it should not be an issue).

The current design is using a LM4562 Op amplifier with a 82k resistor and 1nf capacitor but you can use also a NE5532 but you will need to use a 10k resitor with a 220pf capacitor (for this current design i am refering to R9, R16, C13 and C20).

According the 5532 and 4562 chips . for my 2 other Usdx i am using both chips.  the USDX using the 4562 is less noisy and have a better noise floor , the one using the 5532 the noise floor is little bit higher but the bandwith is better . In addition for digital modes in particular FT8 the AF restitution and decoding is a bit better in lower and midrange (The 4532 AF range seems to be better from mid  and up range) . The 4562 slew rate is far better compare to the 5532 and during SSB swing it provide less distortion. Roughly the differences are not so huge and i am satisfy with both . For SSB modes i guess is according our personnal perception and some operator are more comfortable from low to midrange and other maybe different.  Both the 4532 and 5532 are not the best performer but they are doing quit a good job considering the simplicity of the design. If you are planning to use your uSDX for digital only i will say the 5532 is better, for CW and VOICE the 4532 is my choice.

I am using both configuration and working well.