1 Volt QRP Transceiver

Discussion in 'Amateur Radio News' started by G4TUT, Apr 22, 2008.

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  1. G4TUT

    G4TUT Ham Member QRZ Page

    1 Volt QRP Transceiver

    Members of the DL QRP group are involved in a project to build a QRP transceiver that runs on just 1 volt.

    The goals of the project are:

    - Save the resources of our earth, save the earth
    - Reduce battery waste
    - Reduce required materials
    - As much fun as possible, so make a real useful transceiver

    Details of the project have now been made available on the web. The article says:

    "Modern solid state technologies makes it possible to design RF transmitters and receivers with a powers supply as low as 1 Volt with good efficiency. The mainly power consumpting parts, the AF end-amplifier and the RF-PA have to be designed very carefully to give good results and to meet the goals. The efficiency today would be optimal at 3 Volt. This experimental design will be the base for a 3 Volt Transceiver with an RF power of > 0.5 Watt."

    Read the full article with circuit diagram at http://www.lichtnetzwerk.de/1volttxvr_dkumentation.pdf


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  2. K8ERV

    K8ERV Ham Member QRZ Page

    Just knew if I held on to those 1v cells long enuff someone would find a use for them. I may have the market cornered. Offers?

    TOM K8ERV Montrose Colo
  3. VA7AAX

    VA7AAX Ham Member QRZ Page

    check out the August 1992 QST.It has a lemon powered(homemade lemon batteries) transmitter.Since power out and band is not specified(that was for 10m) , I guess they just found a TX.

    I think the main problem would be current.Those 1.5V AA aren't rated for a lot of current, which means they would die within a few minutes.

    Thanks to the DL-QRP for this innovative project idea.

    73 de va7aax
  4. KE4IKY

    KE4IKY Ham Member QRZ Page

    Perhaps a better goal would be a specific amount of efficiency from a transmitter.

    If the real goal is to "save the earth" (as if it can't take care of itself ), try using a hand (or foot) cranked generator for the tx and a crystal rx that doesn't need ANY batteries.

    This whole thing just sounds very unfocussed to me.

    (BTW a VX-7R can get by with 3 volts and 300mw out, at least it's nice to know the goals they are aiming for should be achievable).

    I'm all for radio projects that get people going though.

  5. K7JEM

    K7JEM Ham Member QRZ Page

    From the figures they give, a single AA alkaline cell should last for many hours of constant use. The highest current draw given is 330mA.

    At an average draw of 300mA, an AA cell should last about 8 hours of key down time, assuming it wasn't all at once. Figuring that CW is about a 25% duty cycle when actually operating, that would translate into 32 hours of operational time.

    100+ mW of CW power on 20M should garner some contacts. It is a very interesting idea, and well done.

  6. KB9BVN

    KB9BVN Ham Member QRZ Page

    I think QRP ARCI had a contest to tackle the issue of using a single 1.5v battery to power a rig as well. I'll have to dig in my back issues of QRP Quarterly. Anyone else remember that?
  7. W6EM

    W6EM Ham Member QRZ Page

    In the interest of efficiency......

    Aside from Chuckle's chuckles, have our friends thought about CE or DS efficiencies? By lowering the input voltage, the rather fixed Vce or Vds saturation drop becomes a larger percentage of the power supply. Hence lower efficiency. And, I don't care if its class A, AB1, B, or C.

    Lowering the power supply rails makes sense if all you're doing is switching, but amplification is another ball game.

    Better to have the higher voltage since you can use more of it in developing desired output power. Or, the voltage drop losses become less significant.

    That is, if the intent is to improve efficiency, save the lemon or aluminum can supply or whatever.

  8. K7JEM

    K7JEM Ham Member QRZ Page

    Thats exactly what I thought. Probably can make a more efficient radio with more output simply by using two (or three) AA cells instead of one. Would make a very small change in overall weight.

    But I think the purpose here is to show what can be done with one cell, and it accomplishes that goal.

    Transmit efficiency is .33 x 1.5 = .495 watts in to generate .18 watts out, or 40% efficiency.

  9. W6EM

    W6EM Ham Member QRZ Page

    Not to belabor the point, Joe, but input power would be 0.33 X (1.5-VceSAT)
    if a bipolar final amp stage. If VceSAT is a typical 0.1V, that's significant.

    Based on your calc above, I didn't get your result. I got 0.198W, assuming 40% efficiency and not including VceSAT. 0.18W would be 36.3%, if my calculator's right.

    If you include a VceSAT of 0.1, output is 0.185W.

    Assuming two cells, and halving the current, 0.165 X (3-0.1) = 0.4785, with the same VceSAT. And with 40% efficiency, a net of 0.191W.

    A net improvement of 0.006/0.185 or 3.2% by having the higher power supply voltage. Not much, but it might make someone grin......

    But, who knows, maybe the extra weight is a factor. Of course, not for Flying QRP Pigs.
  10. K7JEM

    K7JEM Ham Member QRZ Page

    I'm talking about overall efficiency, and it's probably more like 36%, not 40%. Don't know where I got 40% from, must have input the wrong number.

    On battery operation, the overall efficiency is really what matters most, since that is the bottom line. But it should improve dramatically as the voltage increases.

    Still, having a single AA battery power any sort of transceiver for several hours is no small feat.

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