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My Very Most Complex HomeBrew!

Discussion in 'Homebrew and Kit Projects' started by K6BSU, Jun 25, 2016.

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  1. K6BSU

    K6BSU Ham Member QRZ Page

    Boy! I would never go through this again. After doing some research and experimentation with the Vackar VFO circuit, I wanted to put into something. Well, the more I designed/built, the more "stuff" just had to go into this receiver. It ended up quite complex.

    Instead of a multi-pole bandswitch, I used plug-in boards for the ham bands. The plug-in tunes the RF amps, has a xtal-controlled mixer for the VFO. The whole thing is double-conversion, with AGC, separate BFO, and a decent audio chain.

    Floyd K6BSU rcvr 001.jpg
     

    Attached Files:

    W1GCI likes this.
  2. K6BSU

    K6BSU Ham Member QRZ Page

    filter 006.jpg I found a better shot of the plug-in units.

    F.C.
     
    KC8YLT likes this.
  3. N7EKU

    N7EKU Ham Member QRZ Page

    Bravo!

    Very nice contruction. I really like how everything is laid out so well! How's the performance? Are you happy with the results?

    Cheers and 73,


    Mark.
     
  4. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    WOW! Very nice indeed. Can you tell us the "full story"? Is it your design or did you follow a found schematic? As EKU added, how's the performance?

    I'd love to hear all about this. Very nice work

    Dave
    W7UUU
     
  5. WR2E

    WR2E Ham Member QRZ Page

    Much awesomeness Floyd!

    Tell us more!
     
  6. K9STH

    K9STH Ham Member QRZ Page

    My most complex home brew item was a 17-tube receiver that I built as a junior in high school in early 1961.

    It can partially be seen in the lower left-hand corner in the photograph in the second page at

    http://nebula.wsimg.com/556bb7e9fed...C3F25F0398F58962E&disposition=0&alloworigin=1

    I would not attempt that large of a project these days! But, when one is 17-years old . . .

    It was my main receiver for several years until I got a Heath MR-1 Comanche receiver and then a Collins 75A-1.

    I still build a fair amount of equipment. But nothing as complex as a receiver that covers 550 kHz to 34 MHz and then the 6-meter and 2-meter bands with variable bandpass tuning, calibrated band spread, etc.

    Glen, K9STH
     
    W7UUU and KC8YLT like this.
  7. KL7AJ

    KL7AJ Ham Member QRZ Page

    Boy...the term Vackar sure wobbles some nostalgia glands! It was WAY ahead of its time when it came out.
    Congratulations. Excellent project.
     
  8. K6BSU

    K6BSU Ham Member QRZ Page

    Let's see. How can I describe receiver performance? Maybe compare it with another of my radios? Not as quiet as my Kenwood transceiver, but just as sensitive and selective. I have only two plug-in tuning units, so I'm limited to just the 40 and 20 Meter bands.

    The Vackar VFO is truly remarkable! My work with this circuit resulted in a super-stable unit, which nearly approaches crystal stability. I wrote two articles on this circuit published in QST magazine. This resulted in many inquiries, and I think a new appreciation of this unique circuit.

    The receiver is of conventional circuit layout, although it is entirely of my own design. Double conversion with three commercial Xtal I.F. filters from a Harris military receiver. Xtal bandwidth can go down to 0.2 KHz without excessive "ringing", which is super for copying CW.

    It also has amplified and delayed AGC, variable notch filter, a manually peaked RF preamplifier, and a 6 Watt audio amp (copied from a commercial Hi-Fi).

    You can see by the construction that the circuit is arranged in "modules" with connectors. This allows testing of individual "blocks", and permits modifications with the modules out of the receiver and easy to access on the workbench. The blocks are labelled.

    Floyd K6BSU
     
  9. W0RIO

    W0RIO Ham Member QRZ Page

    Nice project, the plug in modules remind me of the TenTec Argo and Scout transceivers.

    Have you ever considered building plug-ins for other bands? Seems like it would
    be relatively easy to do since you have the base unit working.

    - another F.C.
     
  10. VU2NAN

    VU2NAN Ham Member QRZ Page

    Hi OM Floyd,

    Wow!

    73,

    Nandu.
     

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