Re: Modular uBitx - "Ex: Harmonics"

Jack, W8TEE
 

That's exactly where we hope to take it. I've had 4 SDR radios and enjoyed every one of them. However, I don't like being tethered to a PC or laptop. I'm hoping that, collectively, we can create a standalone SDR radio that doesn't cost an arm and a leg.

Jack, W8TEE


On Wednesday, August 15, 2018, 6:06:33 PM EDT, Dr. Flywheel <Dr.Flywheel@...> wrote:


By utilizing a Teensy 3.6 board you are opening the way for DSP-based generation and reconstruction of SSB and other signals. For example a pair of 45 deg. symmetrical Hilbert transforms can take care of precise phasing to effectively suppress the carrier and unwanted sideband. Such Hilbert filter can simultaneously replace the second IF crystal filter, if the conversion is brought down to audio frequencies. Being a programmable filter, the Hilbert transform can also provide variable bandwidth for the desired mode of operation. Further audio processing, like the audio band equalizer that you apparently implemented is just as icing on the cake. With appropriate CODEC, the Teensy 3.6 with its DMA capabilities, can easily support 192 kHz sampling rate, which means that in principle you could show FFT an waterfall diagrams in real time for a much wider bandwidth. This becomes essentially a hybrid SDR architecture at a very low cost.

--Ron   N7FTZ   

On Wed, Aug 15, 2018 at 10:19 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
Carl:

Some very good ideas.

I'm showing the Rev 2 JackAl board here, partly to show what we done, but also to show the mistakes we made along the way. (We're doing
Inline image
the Rev 4 board now.) First, we've taken the buck converter off simply because it was too fragile when adjusting...far to easy to rip the adjusting screw right off the board. Second, the 7W audio amplifier (big IC on lower left) is stupid for the nano acres it takes plus its cost. Most users have powered speakers or can easily add them. We don't have a direct I2C connection, but we do have an SPI interface for the touch screen display. (Our display handles the video processing.) The rest are connections that work through the exiting µBITX headers, which would not be the same for a new design. Still, the above is less than 100mm x 100mm and parts are being taken off. Obviously, we have the Si5351 chip onboard, but that probably should be on the main board. The SMD parts will be part of the PCB when sold.

To me, perhaps the most important thing we've done is bring out a bunch of pins, both digital and analog, for others to use. I hope the selected processor for such a project has a bunch available.

Jack, W8TEE



On Wednesday, August 15, 2018, 12:27:03 PM EDT, RCBoatGuy via Groups.Io <ijnfan-HamRadio=yahoo.com@groups.io> wrote:


Here's some features I'd like to see in any new design that shouldn't cost much, but would make life/testing/experimentation easier:

- Sockets for CPU boards on any new Raduino design.  (Teensyduino has this already, and I think the JackAl does, too)

- Sockets for relays, as these have been a frequent source of failure

- Move any pull-up resistors required onto the Raduino/Teensyduino/JackAl board and not rely on the user to wire them up.  Many users either failed to wire up the 4.7K external resistor correctly or had the connection fail later, causing the rig to immediately go into transmit on power-up.  This is easily avoided by having the required pull-ups on the Raduino/Teensyduino/JackAl board itself.

- Add 3-pin 0.1" input and output headers/jumpers to each section (Bi-di Amps, Audio Amp, Mic Amp, BPF, PA, LPF, etc) on a given board so that the given section can be isolated and tested independently.  For inputs to a section, 1st pin is output from prior section, 2nd pin is input to current section, 3rd pin is GND.   For outputs from a section, 1st pin is output from section, 2nd pin is input to next section, 3rd pin is GND.  Normal operation uses shorting jumpers across pins 1 and 2 to allow signals to flow thru, but jumpers can be removed and test inputs/outputs connected via molex/etc connectors to pins 2 and 3 (or to all 3 pins if desired).  This also makes it easier to replace a given section with an external circuit for experimentation/modification.

- Room for extra I2C headers on the Raduino (Teensyduino already has this, not sure about the JackAl) that the user can install later if desired

- Would be nice if the modular design had the PA on a separate board so different PAs can be used based on user preference.  Having different boards for a IRF510 PA, a RD16HHF1 PA, etc, would be nice as the user can pick and choose what they want, or build their own much easier.

- Support for adding additional BPF/LPF for those that want 160M, 6M, etc

- As for the LPF relays, I'd recommend using a relay scheme like that on the mcHF transceiver.  Their approach minimized the number of relays (only 4 DPDT relays needed for 4 filters), but still had filter inputs and filter outputs going to different relays.

- Design board so that the Raduino/Teensyduino/JackAl board has no obstructions from parts and/or connectors along the entire edge of the radio board.  The Teensyduino had to design in special cut-outs to use with the current uBitX due to obstructions. It would be nice if cut-outs like this were not needed in the future.

- Si5351 on main board, not on Raduino/Teensyduino/JackAl

That's my 2 cents.  Take it for what it's worth.  :)

73, 

Carl, K0MWC

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