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Thursday, January 16, 2014

Farhan's New Design: A General Coverage Transceiver: The Minima!

The homebrew phone QRP community has been waiting anxiously for the unveiling of Farhan's new design:  The Minima.  It is a general coverage transceiver with many innovative circuit features.  It has an Arduino in it and an Si570. Farhan's write up of the design process and the construction of the prototypes is really interesting.


I've built FOUR JBOTs and TWO BITXs.  I even built Farhan's Subway Sandwich Straw signal generator.   So even though I've been trying to keep my rigs all discrete,  I know I will build this one too. 

Three cheers for Ashhar Farhan!  Viva La Minima!

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  1. This is clearly not the same Bill I listened to a couple of years ago who had such mistrust of those black boxes with millions of transistors! I share some of your misgivings there too but I've never totally shunned them, just didn't know how to really incorporate them. But your podcast last year about the easy to build (and cheap) Arduino DDS has made me want to pick one up very soon.

  2. Am I blind or just getting senile? Where is the transmit 1W power amplifier chain in the schematic?

    73.......Steve Smith WB6TNL
    "Snort Rosin"

  3. I am looking at DigiKey's web site right now and I am wondering which Si570 CMOS chip I should order for this project. Does it matter what the max higest frequency specification is? It looks like I am going to order one with 10MHz ~ 160MHz range. Digi-Key Part Number 336-2518-ND

    O. Alan Jones

  4. This is very exciting! I love that he's running the arduino chip 'barebones' without the standard uno/due etc boards. After programming the IC, you only really need a 5 volt source and a 16mhz resonator to have that chip running, everything else is optional. (heck even the resonator is optional, but the timings will not be reliable). So much cheaper that way, and much less power hungry.

  5. Here is a (very hard to follow) video where he walks through the circuit.

    Looks like he's saying the 1Watt amp is Q6, Q7, Q8?


  6. Re the power amplifier; it seems that he is using his existing JBOT linear project at http://www.phonestack.com/farhan/jbot.html

    I guess that further LPFs and relays are being used?


  7. He says there are 2 filters, one for 0-15Mhz, and one for > 15Mhz. The arduino switches the relays to the appropriate filter based on what band you are set to.

    I was thinking about this today. I think this could really be my dream rig. If you could free up some digi pins on the chip (you could by changing the LCD to an IC2 interface, ebay $5, and save a lot of pins), the you could wire up an interface port that could be used to control a servo motor on a portable Magloop antenna, like Ricardo's design:

    Heck, you could even have the chip store general servo settings for each band and it will auto-tune the magloop for you when you change bands. The saved settings would get you close and you would just have to fine tune based on what frequency you are on.

    That would make it the ultimate home-brew portable rig.

    Another add-on could be to program a QRSS/MEPT beacon that you can activate with just a push button & no computer interface needed.

    Hey, Also a real time clock with a push button that would QSY you to WWV and then sync your clock with the NIST: http://forum.arduino.cc/index.php/topic,14946.0.html

    Man, so much you could do with this. I'm very excited.


  8. 100K pot for tuning a general coverage radio with a digital first LO? What is that? It would be much better IMHO to use a quadrature encoder. If you can source the parts for this radio, then you can source a quadrature encoder for a couple of bucks too. I have an Si570 working on USB via I2C, let me dig it up and see what I can do by patching in the Arduino and downloading Farhan's source. David


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