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Sunday, September 15, 2013

BITX Build Update # 7


As you can see (above) I've made lots of progress on the BITX-17.  Going counter-clockwise from the lower right, you can see the mic amp, the BFO/carrier oscillator, the first mixer, the first and second bi-directional amplifiers, the diode ring VXO mixer and the VXO.

I plan on building the whole rig (including the power amplifier stages) on this wonderful piece of PC board (thanks to Jim, W8NSA).

I had what I thought was the brilliant idea of using LEDs for  all the T/R switching diodes.  I thought I'd use red for receive and blue for transmit.  I consulted with the BITX yahoo group and cooler heads prevailed.

The design has an LM-386 as the speaker amp.  I'm kind of bothered by this -- I'd prefer an all-discrete component rig, so I am thinking of building an AF amp with discrete transistors instead, perhaps the circuit from Roger Hayward's RX for the Ugly Weekender.  What do you all think about this? 

I'm having a lot of fun building this rig.  If anyone out there is looking for a fall/winter project, build one of these.

I have to order some 5 MHz crystals for the filter and oscillator.  Mouser has them at about 70 cents each.   


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2 comments:

  1. A few years ago, Jim Kortge K8IQY built an entire Tx/Rx using just 2N2222's. http://www.k8iqy.com/qrprigs/2n240/2n240page.html

    Maybe you could use some of this Bill?

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  2. K4ICY describes a simple three-transistor audio amp here:

    http://www.k4icy.com/weekend_radio_3tr-audio-amp.html

    I built it using two 2N3904s and one 2N3906. Works fine, with plenty of audio.

    Jerry AA6KI
    Tucson

    ReplyDelete

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