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

    Hello guys!

    I really hope one of you will be able to help me out. i am building an micro 40dsb transciever by vk3ye (using schematics from aa7ee).

    This is my first try at homebrewing rf equipment and im facing some problems...

    I have build it in stages..so currently i have: - VXO stage - Buffer stage - Mixer stage - Antenna stage - Audio amp stage

    so basically this is the receiver part of the radio - and i think i should be able to hear some of the frequencies when i turn it on. But when i turn it on i get absolutely nothing - not even some noise or something.

    I have tested the audio amp stage and it works when attached to an audio source.

    I have no idea how to test the vxo or the buffer stage..?Also im using an crystal oscillator not an ceramic oscillator.

    I have attached the pictures of my built stages below:

    https://s29.postimg.org/j5mldgc07/15778528_10207854968996920_1804651650_o.jpghttps://s29.postimg.org/cgg1xfqo7/15776222_10207854968916918_122200636_o.jpghttps://s29.postimg.org/ht4wbkekn/15776380_10207854968596910_1173295796_o.jpghttps://s29.postimg.org/z7p4jubpj/15785516_10207854968436906_188456801_o_1.jpghttps://s29.postimg.org/i8g64l0hz/15785516_10207854968436906_188456801_o.jpghttps://s29.postimg.org/bj9mokf5z/15748849_10207854968236901_1452626444_o.jpghttps://s29.postimg.org/v2e7xxdxj/15748211_10207854966956869_1491052090_o.jpg

    schematics: https://i0.wp.com/www.pbase.com/daverichards/image/153184118/original.jpg

    transciever webpage: https://aa7ee.wordpress.com/2013/10/19/the-vk3ye-micro-40-dsb-transceiver/

    I really cant figure this out.. this is my second build of this transciever ..first one also didnt work.. :(

    My problem is probably lack of knowledge and understanding of schematics as i am a carpenter by profession, but fallen in love with electronics..

    please help!

    73, pampi_
     
    KB4QAA and AF6LJ like this.
  2. KK9JEF

    KK9JEF Ham Member QRZ Page

    Hi Pampi,

    What a great project, I love working off of AA7EE's schematics. There's something great about working from a really tidy hand-drawn schematic that makes homebrewinf really special.

    Do you have, or have access to, an oscilloscope? For troubleshooting RF circuits, it's tremendously helpful. But a simple RF probe might be enough.

    It's odd that the audio amp works when fed with an audio source, but that you get nothing at all when it's hooked up to the mixer and other parts of this circuit. With the audio amp in circuit, if you touch one of the input pins on the LM386 with a metal screwdriver, you should get a fair amount of noise out of the speaker or headphones - the screwdriver (and you touching it) will couple noise into the audio amp. If you don't hear anything in that case, i'd look into confirming that the LM386 is getting power and that the input isn't accidentally grounded.

    Keep us posted!
    73, de KK9JEF
     
    AF6LJ likes this.
  3. N7EKU

    N7EKU Ham Member QRZ Page

    Hi Pampi,

    It's great that you've done so much already! I'm sure you can get it going soon.

    A couple observations:

    Quite a few of the joints on the ground plane look like the copper on the PCB never got hot enough. For PCB connections on large areas of continuous copper, you need to first heat the copper layer until it will melt solder near the tip of the iron -- not on the tip of the iron. I have an adjustable heat solder iron and turn it up quite high, then clean the iron tip, put a bit of fresh solder on the iron and place it on the PCB. Now hold the solder onto the board near, but not touching, the tip and wait. It may take 30s or more until the flux and solder start to melt. When it does, the solder should spread out on the PCB and not ball up. When it does this, then add the component lead or wire and in just a second or two, the joint should be done. A few of your PCB joints look like the copper layer got hot enough, but only a few.

    One of the biggest problems beginners have is soldering the magnet wire used on transformers. Make sure you clean the wire well by scraping with a knife and then give it a good solder coating before making the main joint. The coating should be shiney and clean all the way around. Sometimes I scrape a bit more after first trying to tin the wire, just to get off the bits of burnt insulation. Also, make sure you are using the proper cores -- recovered ones from computer circuit boards, light bulbs, or switching power supplies won't work well at RF.

    The VXO should be easy to check if you have another rig. Tune the rig to the same frequency as the crystal and using a clip lead to the rig's antenna socket, bring the free end a few inches away from the VXO. Now tune around with the rig a bit to see if you can hear your oscillator. You can confirm the is the signal you are picking up on the rig by turning the VXO on and off rapidly to make a pulsating signal.

    Checking the VXO would be a good first step. Also re-doing the PCB connections too, and checking your magnet wire connections.

    73,

    Mark.
     
    Last edited: Dec 28, 2016
  4. N7EKU

    N7EKU Ham Member QRZ Page

    Here's how PCB connections should look:

    [​IMG]

    73,


    Mark
     
  5. S52Y

    S52Y Ham Member QRZ Page

    Thanks for the answer KK9JEF,

    I love his work also..simply amazing...

    About the LM386; i have touched the input pin as you described but i couldnt detect any noise or buzzing on touch. I have once again tested it with an audio source and it works... I have also checked the pins of the lm386 and they are not grounded.. only pin 2 and 4 are grounded..

    Interesting.. from the audio source it works great..

    Note; i have remove some resistors and capacitors from aa7ee schematics.. i got far much better results without those.. there was alot of noise with them...
     
  6. S52Y

    S52Y Ham Member QRZ Page

    Hey Mark! Thank you too very much for your answer.

    To answer your questions:

    - I will resolder the "poor" joint on the boards! Thanks for the notice!!

    - i bought the ferrite cores online so they should probably be ok? I have also make double sure that i removed the coating from the magnet wire. I scraped it off as much as i could have and tested the wire with an multimeter.

    - Hum, i will try to check the VXO as you said and will get back to you with answers!

    Thank you very very much!

    73 de S52Y
     
  7. S52Y

    S52Y Ham Member QRZ Page

    Ok, resolder the connections, no difference.. i will test the VXO and get back.

    thanks for now.
     
  8. S52Y

    S52Y Ham Member QRZ Page

    Mark,

    I have clipped on the inside and outside part of my antenna and went near the VXO with the other side of the clip..and nothing.. i couldnt detect if its working or not..
     
    Last edited: Dec 28, 2016
  9. N7EKU

    N7EKU Ham Member QRZ Page

    Hi,

    Just connect a clip lead to the inside socket pin of the antenna connector, and nothing on the outside part. A banana plug fits perfectly, or you can stuff a bent wire in the hole. Otherwise you are shorting the antenna connection.

    You may need to bring the other end of the antenna lead quite close to the VXO (just lay it across the top if you want). Just don't have headphones on, in case the VXO is working well as then the signal will be quite strong.

    Remember, the VXO frequency won't be exactly that of the crystal, so tune around with your rig some ten or twenty kHz below and above.

    I can try to compare you VXO to the schematic and see if I can notice anything. What transistor are you using?

    73,


    Mark.
     
  10. N7EKU

    N7EKU Ham Member QRZ Page

    Hi,

    Just a reminder, the rig used to pick up the VXO signal will need to be able to receive CW or SSB (not just a plain AM shortwave).

    Cheers,


    Mark.
     

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