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Sunday, April 15, 2018

Carpentry and Socketry for the uBITX


Yesterday I decided to spend some time at the bench -- I wanted to get the uBITX boxed up.  My basswood box had arrived from Amazon on Friday.  It was time for what George Dobbs G3RJV called "socketry."  

First, the back.  I figured I would need five connectors back there.   Connectors for 12V DC, speaker, and antenna would be needed right away (it is my preference to have the speaker connector on the back of the BITX).  Looking ahead, I might want to also have a jack for T/R control of my linear amplifier, and a jack for 24 VDC if I want to go wild and put more voltage on the drains of the IRF510s. So I put two extra holes in there.  


Basswood is SO easy to cut.  I put the LCD in the center of the front panel, and opted to put the board close to the front of the board.  This avoids the need for jumpers to connect the Raduino to the LCD, and it keeps the lines to the front panel controls and connectors very short. I mounted the board on the spacers that came with the BITX, drilling holes the bottom of the basswood box.  It all fit quite nicely. 


I would need to put two jacks on the front panels:  key jack and mic jack.  And I'd need two controls: main tuning and AF gain.  I used hole saws to cut holes big enough to accommodate the four items. 


The controls and jacks were then placed on two small pieces of copper clad board.  These then went on the front panel.  

Wiring up the uBITX was  easy.  I just followed Farhan's instructions.  I did the wiring AFTER placing the boards and controls in the box -- this helped me keep all the wires at their optimum length (not too long, and more important -- not too short!).  If you do it this way, put a cloth over the boards so you don't drop solder blobs on the uBITX. 

Farhan's uBITX fired up nicely as soon as I applied power.   The receiver really sounds nice.  I hope to make some contacts with it today. 

Three cheers for Farhan! 


3 comments:

  1. Once the carpentry is deemed complete, you need to stain the wood as a tip of the hat to the early days of radio where finely finished wooden cabinets were the norm. The copper clad boards need to be aged to have a nice patina like the old radios or painted. I recommend painting the copper Juliano Blue as a tip of the hat to the new technologies. As a finishing touch, use some appropriate decals that you can make to identify everything.

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  2. From Allison KB1GMX:

    Bill,

    Unless the heat sinks have good airflow they are largely ineffective. The heat must not be tapped inside.
    They will keep heating hotter till something bad happens. A fan helps but only if there is external circulation.

    Wood boxes are cool and I use them. For cooling when required I make an opening in the back and
    obtain A finned heat sink of substance and arrange it so the fins are flush to the outside and put the
    devices against the inside surface. Works for aluminum or wood boxes.

    I like wood as the cost is low and I can finish it as I desire without metalworking tools.

    Doing that with one large heatsink means for the uBitx using insulators and shoulder washers to keep
    the MOSFETS from shorting to the heatsink, which should be also grounded to the main board ground
    with very short leads.

    I feel the the heat sinks used are marginal even for SSB only.

    I buy heat sink by the foot from places like MPJA.com. It makes it easy to take a hacksaw and cut off
    something that dimensionally fits my needs. That and I often build for high power too and a 8" x4" X2"
    is never too large for that. ;)

    Some notes. The TDA2822 tends to blow up when run at 12V or higher, there seems to be a lot of reports
    about this. My advice is run it on a 8 volt regulator (7808).

    Long leads on things with lots of digital activity like LCD or other may radiate noise into the receiver.
    Short as possible is still the best bet, if you need long try it first and see how it goes then box it.

    Current projects in wood boxes include the kits and parts (DIz) 1Watter for 40M as the box was big enough
    for battery, Key, and headphone. I'm in the midst of putting the KD1JV Slop Bucket 20M SSB/CW rig
    in a wood box, again large enough for key, mic, speaker battery, antenna tuner too. I've put test gear
    in them to make it more durable or portable.

    If you need to: MPJA.com also sells adhesive copper tape to make a shielded area if needed.
    Aluminum tape work but tough to connect to.

    Keep building.

    Regards,
    Allison KB1GMX

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