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Cheap digital readout for an old bird.

Discussion in '"Boat Anchor" & Classic Equipment' started by N3UIQ, Feb 1, 2020.

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  1. N2EY

    N2EY Premium Subscriber QRZ Page

    QST for November, 1977: "A Versatile Frequency Display" by W1DBM (Phil Rand).

    The key to how it worked was programmable, presettable up-down counters - 74192 TTL ICs. There were thumbwheel switches to set the offset and a toggle switch to choose up or down counting. The thing could be used as a plain counter by setting the offset to zero. It was a four digit design reading out in kHz and tenths of kHz - the parts were so expensive back then that displaying the band was deemed not worth the cost. The displays used were Tung-Sol Digivac fluorescent, running on 24 volts. The up-down feature is essential if the unit is to be used with rigs where the VFO tunes opposite the direction of tuning.

    A year or so before that article appeared, I designed and built a similar "digital dial" device. Mine used LED readouts, and a diode matrix for presets which permitted setting the offset and tuning direction for up to 5 bands.

    Then I discovered I liked analog dials better.

    73 de Jim, N2EY
     
  2. N2EY

    N2EY Premium Subscriber QRZ Page

    In terms of 5 band rigs, Swan was probably the only one.

    There were several three-band rigs which used the single-conversion switched-VFO scheme to cover 80/40/20. The setup was to put the IF at about 5.2 MHz and the VFO ranges at 8.7 to 9.2 for 20 and 80, and 12.2 to 12.5 for 40. This scheme gives the "correct" sideband on all three bands if the IF is set up for USB (80 and 40 invert because the VFO is higher in frequency than both the input and output signal frequencies).

    Let's see.....Eico 753, Swan 240, National NCX-3, Hallicrafters SR-160 and SR-500 all used that scheme. There may be others. Swan just took it to the next level by including two more ranges to cover 15 and 10.

    73 de Jim, N2EY
     
  3. N3UIQ

    N3UIQ Premium Subscriber QRZ Page

    That really does look Swanish, I would have picked a better font for the "KW Atlanta," makes it look like something from Harbor Freight, otherwise a tidy looking rig.
     
  4. G3YRO

    G3YRO Ham Member QRZ Page

    Yes single conversion rigs mean you really only need one Carrier Crystal, as the sideband automatically inverts.

    Some people say that's NOT why the Amateur convention of LSB on the lower bands and USB on the higher bands came about, but I've never heard a more logical explanation ! (and people who built SSB rigs in the 50s told me that was why)

    Roger G3YRO
     

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