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QRP Transciever

The learning experience of trying to make your own QRP radio for Amateur Radio

DelDel
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After passing my Tech and General exam i figured while I wait for my license to show up in the database, i figured why not try to design a transceiver. This is the beginning of my journey.

Requirements

Operate on at least 80M band

at least CW operation, Ideally i would have some kind of modular approach to adding modulators / de-modulators.

keep this an Open Source Hardware project,, I would like to make this as a resource for other beginners to learn from.


When I get there, source code and schematics will be posted to GitHub.

KiCad will be used for schematic capture and board layout.

Freecad will be used for enclosure design if the end result enclosure gets 3D printed. Freecad file will also be posted to github.

  • Would like to improve on this one

    Del02/11/2019 at 04:15 0 comments

    Found what I'd like to accomplish but with more bands:

    QCX 5W Transceiver

    a little radio with great reviews, and I can even understand most of its schematic, It uses that Quadrature mixer that we seen earlier. and it can be driven with a square wave. 

    Ultimately i would like to expand this design to work on multiple bands. which looks like it could be done by adding different sets of band pass filters, and having some mechanism to switch between them. 

    Adding some additional types of modulation / demodulation. AM FM SSB ... others?

    I think the switching could be done with Relays, as I see antenna switches work with those, however I imagine once you get into high frequencies they probably start acting like little antennas themselves. 

    I would like to hear anyone's opinion on this one. 

  • Mixers and Such

    Del02/08/2019 at 14:04 0 comments

    after some research I've learned the following:

    mixer's don't seem overly difficult to make, there are a handful of designs.

    they generally use a sine wave which makes sense to mix the RF Input with.

    finding tuning capacitors ( the kind you would hook a VFO knob to ) from the usual suspects (Digikey, Newark, Mouser, Arrow) are unobtainium, my guess is these went out of style and/or are special use, so even if you do find them, i bet they are expensive (new stock). 

    I Stumbled upon the QRP-Labs QCX transceiver. this item is pretty close to what I wanted to build in the first place. except it is CW only, and is single band., But because its a kit, I can/have learned a bunch from it. I like the Tayloe mixer it uses, especially since it is driven by a square wave, which in my world is much easier to generate, and I no longer have to look at high speed DDS chips which can get expensive quick.

    check out this video:

    plus this spits out both the upper and lower sidebands which will make adding SSB support much easier.

    This video is also really informative:

  • The search for recievers

    Del02/03/2019 at 21:32 4 comments

    found another simple reciever.

    https://www.qsl.net/pa2ohh/05simrx.htm


    I like the simplicity of this one. looks like it requires high impedance headphones, but im sure I could hack an audio amplifier in there with an lm386 or the like.

    this is a transciever

    http://py2ohh.w2c.com.br/trx/curumim/curumim.htm


    I really like the simplicity of this one. does not look tunable though.

  • found a pretty simple design to learn from

    Del02/03/2019 at 15:55 0 comments

    found a simple design for one I can pick apart and study

    https://groups.io/g/BITX20/topic/80m_hexfet_power_amplifier_by/5455337?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,5455337


    See this is what happens when you don't read, this is actually a Power amplifier, while not a radio per-say this or something like it will probably be useful in a transceiver.

    found another interesting power amplifier

  • Research and Development

    Del02/02/2019 at 20:52 0 comments

    I have a lot of learning and research to do.

    What Band, I already know a guy that works 80m band, and Holds slow morse practice, so I think I want to start there

    so somewhere around 3MHz which my O-Scope can handle with ease, this will make the long road of debugging easier. or so I think.

    Direct conversion or superhet?

    Still looking through circuit diagrams for both. I have some experience in digital design but this analog stuff is kind of new to me. 

    SuperHeterodyne Reciever

    I don't seem to be able to find (quicly) a block diagram of a direct conversion reciever.

    Antenna, I'm thinking a half wave inverted V strung up from somewhere on my property.

    Power. Well for simplicities sake probably keep it under 10W, I know that far exceeds QRP territory, but I'll set the bar somewhere around there for now.

    I welcome any feedback.

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Dan Maloney wrote 02/04/2019 at 21:43 point

I've got the QRP bug myself. I'd really like to build something to do WSPR one of these days.

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