Hi Brady A 1 minute look at it 1) I think you will striggle to get sufficient TX/RX isolation with that style diode switch- ideally you should reverse bias the PIN diodes when you want to shut down that path .
IE have say 5V on the cathodes, and switch 0 or 10V onto the wanted / wanted path, that way you get a decent amount of current and volts. ie 0V = reverse bias, 10V = forward bias check the performance, anyway. 2) I think that you will need a few iterations of that LC BPF before the mixer on a PCB- you have some very small capacitances, and I think that you should try a less ambitious filter in order for it to be easily realisable.... relax the filter. what Q did you model the inductors with ? 10,20 ? What facility for tuning do you have ? I would suggest a parallel cap on the resonatorcapacitors say 0402 type, so you can fine tune the capacitance by adding 1-2pF as required. for a SDR experimenters board, I think it is probably fine. On 14/04/2015 12:37 PM, Brady O'Brien wrote: > Hi everybody, > > I've been helping out with the development of VHF and up FreeDV and the > minimalist VHF SDR. I've gotten to the point, on the analog side of things, > that it seems appropriate to get a board made. What I've designed is a VHF > frontend for further experimentation. It's based heavily on the VHF section > of the DSP-10 transceiver, a DSP based radio described in the links below. > Before I buy parts and send the board off for fabrication, I'd like someone > with a little more radio design experience look over the schematic and maybe > PCB layout. I'm using Kicad to design this. As this board is just a stepping > stone, I'm going to keep it out of the Freetel SVN repo, at least for now. > > > Schematic for the front > end:https://github.com/baobrien/vhf-radio/blob/master/exp-1/exp-1.pdf > Github repo:https://github.com/baobrien/vhf-radio > > DSP-10 Part > 1:http://www.arrl.org/files/file/Technology/tis/info/pdf/9909033.pdf > DSP-10 Part > 2:http://www.arrl.org/files/file/Technology/tis/info/pdf/9910034.pdf > DSP-10 Part > 3:http://www.arrl.org/files/file/Technology/tis/info/pdf/9911042.pdf > > Thanks, ------------------------------------------------------------------------------ BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
