First homebrew transciever - not working

Discussion in 'Homebrew and Kit Projects' started by S52Y, Dec 28, 2016.

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  1. S52Y

    S52Y Ham Member QRZ Page

    Hey Mark, thats great to hear! I cant thank you enough!

    My lm386 was working great with an mp3 player too.. really loud and great quality audio..

    Im really interested to see what will we figure out on finding out wheres my problem.

  2. KH2G

    KH2G Ham Member QRZ Page

    You should be able to get noise as in buzzing by touching the wiper of the volume control. If your running audio into it at high level you may be jus tblasting through. I would take the audio board by itself and get it going then the next board etc. Make it like a block diagram and get each block going then tie them together,. It will work. Enjoy!!
    S52Y likes this.
  3. S52Y

    S52Y Ham Member QRZ Page

    Hey! Thanks for the answer.

    I get a buzzing sound when touching. I have it done as you proposed but with no results :( i have all the "blocks" tightly togehter.

    When viewing the vk3ye and aa7ee youtube videos those guys get such good audio quality.. iv probably made a mistake somewhere but it beyond my knowledge where it is..

    thank you for your input.

  4. VK4FFAB

    VK4FFAB Subscriber QRZ Page

    Do you have a signal generator and oscilloscope? When something does not work right I do the following.

    1. make sure the oscillator/s is working, I trace that signal to the input of the mixer and make sure that the level of drive is enough for that type of mixer.
    2. inject a weak signal at the frequency design frequency 7mhz? 0.1v p-p or less into the antenna port, and trace that to the mixer inputs.
    3. with 7mhz injected into the antenna port, and the oscillator set to 7.000.600 check for the 600hz on the mixer output.
    4. Inject 600hz into the AF amp and listen on the speaker for a nice tome.

    That will show you at what stage things are failing. A signal generator is a must, inject 600hz into the input of the LM386 bypass everything, and just put the signal right into pin2 and then pin3, if you do not have a cw tone in the speaker, you will know either you build the circuit wrong or you just have a faulty chip.
  5. S52Y

    S52Y Ham Member QRZ Page

    Yeah that is a problem, dont own a oscilloscope nor a signal generator...

    i will try to find someone with an oscilloscope and check the things you said!
  6. VK4FFAB

    VK4FFAB Subscriber QRZ Page

    the signal gen is something you can build yourself, it does not need to be fancy, though fancy can help. A code practice oscillator used for learning CW makes a 600hz audio tone, rather than putting its output into a speaker, you can feed it into your audio amp and see if you hear anything on the audio amps speaker.

    Pretty much anything that is audio can be attenuated down some and fed into the input of the audio amp, mp3 player, headphone out on your main rig, you name it.
  7. N7EKU

    N7EKU Ham Member QRZ Page

    Hi Pampi,

    How are you? I've been busy and it slowed me down on building. Sorry for the delay...

    Anyway I got the rig about half finished. I have the audio amp done plus now the VXO, and the mic amp finished. I only have left to build the TX/switching end and the antenna input filter.

    On my first test with the rig hooked up to my 40M dipole, I noticed right away that the receiver is being badly swamped by strong signals from medium and shortwave broadcasters. I guess this is what happens on the 40M band when you have no band pass filter and an active mixer :-/ Later I will add the antenna band pass filter and see how that improves reception on the frequency I actually want to hear!

    But without the antenna, I compared it to another rig by hooking a clip lead to the rig's antenna input and another to the Micro40's antenna input (pin2), then sweeping back and forth with an antenna analyzer around the crystal frequency. Both receivers picked up the signal from the analyzer fine.

    I'm not sure how much of your transceiver is finished? If you didn't build the antenna input filter, it could be that there is nothing wrong with your construction. Without the filter, the receiver is pretty useless because it is so overloaded. Also, since there are so many strong shortwave broadcasters on your side of the globe, it would probably be important to install the AM BC filter as shown in AA7EE's drawing too.

    I've had little time to work on website stuff though, so I will post a few pictures here if you want me to. But more important will be to see about your input filter, and then to think about what measurements you can do if things are still wrong. I did happen to have a 7.055MHz crystal which is the freqency used here in Canada for their trans-provincial SSB net and with that I was able to pick up strong stations OK with my Micro 40 receiver section.

    I have built a classic RF probe as shown for decades in ARRL's Radio Handbook. A good construction article for this is N5ESE's website, so go there if you don't have a probe built yet. If you build one, I can make some measurements on this set using my probe and we can compare the values we get.


  8. S52Y

    S52Y Ham Member QRZ Page

    Hey Mark! Sorry for the late answer.

    I have build the input antenna filter but not the AM bandpass filter. Should i build it?

    And bout the rf probe, i have built it and measured the voltages across the circuit, 2 pages back on this thread. I would love to compare the values!

    Thank you again Mark!

    Best regards,
  9. N7EKU

    N7EKU Ham Member QRZ Page


    Hmm, maybe don't worry about the AM filter yet. I saw only one or two measurements from two pages back. Anyway, I just finished a big list of measurements, and right at the end found that I had a zener mis-marked and need to change it (it was a 12V one so it wasn't doing anything!) and then redo the measurements. I should get them done tomorrow.


  10. N7EKU

    N7EKU Ham Member QRZ Page


    I got them done. To save time, I just snapped a picture of my notes -- I hope they are readable.



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