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LF Receiver

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by AC0OB, Nov 10, 2019.

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  1. AC0OB

    AC0OB Subscriber QRZ Page

    I have been contemplating a simple homebrew receiver for some time that covers about 130kHz to 480 kHz.

    I wanted to source most parts from my stock on hand using discrete components; no PICs, just SS analog circuitry. I will add one of those Chinese frequency counters later.

    I think the varactor tuning at the mixer will provide more tuning resolution than would an open air mechanical variable.

    I am leaning toward the page 2 mixer which simply winds the antenna coil around L2.

    I have bread boarded only the LF Detector thus far so component values on the mixer and IF Amp may change.

    Some of the circuit ideas were adapted/adopted from a friend's 5W 75m transceiver design.

    So I am just throwing this out there and wondering if anyone else has homebuilt an LF receiver.


    Attached Files:

    Last edited: Nov 10, 2019
  2. KL7AJ

    KL7AJ Ham Member QRZ Page

    I have a homebrew direct conversion receiver, using a function generator as the local oscillator. Very clean and stable. I'm using a minicircuits DBM, but you can easily build one with a couple of toroidal transformers and some germanium diodes. The AF amp is three cascaded FET voltage amplifiers...very simple...and sensitive. My next phase is to build a front end preselector, but so far I haven't had any overload problems.
    DC receivers have the definite advantage of no internally generated birdies....kind of an important thing at LF.
  3. K1LKP

    K1LKP Premium Subscriber QRZ Page

  4. N0UU

    N0UU Ham Member QRZ Page

    You are in for an adventure. Start simple from you junk box. It will work. Filters are easy down there. Low noise devices are handy, but you might not need. Switching mixers are handy as most IM happens on the rise and fall of the LO so digital signal to the mixer is a must.While the DSP front ends are now the rage, you can get really good results with analog. Build modular and have fun. N0UU
  5. KL7AJ

    KL7AJ Ham Member QRZ Page

    That Ham Up looks interesting, but it converts up to VHF which wouldn't do me any good. If the thing converted to HF somewhere, I'd jump right on it.

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