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Friday, March 5, 2021

Over the Waterfall into the Dark Side: Hodgepodge SDR


This one's for Pete. My effort to add features and modes to my Hodgepodge transceiver took a dramatic turn when I connected the rig to my computer via an RTL-SDR dongle. Woohoo! A Hodgepodge waterfall! Check it out.
The dongle was modified for direct sampling at HF. In the box with the dongle I have one amplifier stage, consisting of a 40673 dual gate MOSFET and one parallel tuned circuit, now tuned to the Hodgepodge IF of 11.998 MHz. I tap the the Hodgepodge's BITX40Module at the output of the first mixer, just before the crystal filter. This was a lot of fun. I can even check my own signal on transmit! This is like having the best of both worlds.

11 comments:

  1. There has been a great disturbance in the Force...

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  2. Yes, I feel it too. I fear that the Radio Gods are not pleased.

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  3. Your soul is lost forever. Only through sincere searching and noble deeds can it possibly be reclaimed. Repent!

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  4. I may have to sacrifice a chicken to placate Papa Legba.

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  5. Bill,
    Finally, it's time for SolderSmoke - Digital Edition. We're ready for a paradigm shift! I feel it coming.

    KB3SII ... .. ..

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  6. No way Steve. I now see the error of my ways. I blame the pandemic. Many people did things in isolation that they regret. This was just a fling, a digital dalliance. It doesn't mean anything. I'll soon be back to analog VFOs and discrete components.

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    Replies
    1. Bill
      Hopefully, you have not had any permanent damage due to the isolation required by the pandemic. So if it's just a fling, you can prove that to us by making a stable PTO based on Collins technology of the 1950's with 21st century parts.
      Steve KB3SII

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    2. Steve: At Pete's suggestion I recently bought (on ebay) the 9 MHz VFO from an FT-101. It is completely analog. I plan on using it as the heart of an 80/20 transceiver with a 5.2 MHz IF. No chips, no menus, no USB ports. OK?

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  7. From total ignorance (mine) that strip of 'whitewash' looks like an incorrectly terminated (Open?) port of a mixer letting noise in. Can arithmetic on the centre frequency reveal the source? It might even be a (very) strong image.
    ...and to me Digital is not 'the dark side', it's just another window (a Ranchslider'?) to the electronics world.
    73 :)

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  8. You may have a great troubleshooting tool with the SDR receiver. You may be able to look outside the 40 meter band and find the source. I'm wondering is some LED lamp is the source. Could you have any LED lamps in or near the shack?

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  9. David: I followed your suggestion. I used the RTL-SDR dongle to look at 40 meters. There were the tell-tale spikes, spaced neatly every 50 kHz. ARRL Handbook says this is typical of a switched power supply. Before I started patrolling the neighborhood with a portable receiver, I decided to check my own house for any recently installed electronic devices. It didn't take long -- when I unplugged the new (mid-pandemic) treadmill the spikes disappeared. Mystery solved. Thanks. 73 Bill

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