Ditmeister Vibroplex dot taming mod

Discussion in 'Straight Keys - CW Enthusiasts' started by K9NUD, Nov 21, 2021.

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  1. K9NUD

    K9NUD XML Subscriber QRZ Page

    Hey all,

    I recently went down the bug rabbit hole. I picked up a used Original (1990's vintage) and got the hang of it fairly quickly. One thing that troubled me (besides the need to slow it down) was the mushy dits. I looked around and found some mods available. I found the W0EB site helpful, though it was littered with warnings about copying his invention and being sued.

    The point of the mod is this: Pre-loading the spring contact will result in a better electrical connection. Many use dental floss. I tried that but was not satisfied. I started noodling on things I could try that were within 36 inches of my key.

    In the interests of advancing the radio art in general, and bug adoption in particular, here's the mod I came up with. Behold, the ditmeister! You'll need a paper clip (large is better, color is up to you). The tools required are needle-nose pliers and a strong cutter (don't ruin your nippers for this). You'll need to readjust the dit gap accordingly. I find the dits to be far more succinct. More tension results in shorter dits. YMMV.

    The instructions are simple: start cutting and bending. Please out-do me and post your mods. Have fun!

  2. WA3LKN

    WA3LKN Premium Subscriber QRZ Page

    What you are describing is the "dot stabilizer" (McElroy's terminology) used on McElroy bugs from 1938. See photos.

    DSCF3753.JPG DSCF3752.JPG
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  3. K9NUD

    K9NUD XML Subscriber QRZ Page

    Very nice! I was envisioning that exact design when the paper clip idea popped into my mind. I will still do it, and possibly come up with a way to make incremental adjustments. Too much tension and the dits get too short. To little and the bounce reappears. I got lucky on my first try with the paper clip
  4. WA3LKN

    WA3LKN Premium Subscriber QRZ Page

    Good luck! And the thought that somebody was threatening legal action over using 'his' design gave me a good laugh.

    And the 'vari-speed' that folks use on their bugs was actually offered in QST in 1954.

    Attached Files:

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  5. WA1GXC

    WA1GXC Ham Member QRZ Page

    Your mechanical interventions are extremely clever and smart--and evidently effective. I give you tremendous respect and acknowledgement for that.

    I don't know if you're inclined to undo it all.
    But if you want to give it a shot--

    I suspect the initial mechanical set-up of your bug is a bit off in several ways. Foremost of these is the resting (static position) of the pendulum as it
    comes to dead-rest against the damper assembly-----
    The single-most important and unforgiving adjustment on your instrument.

    If it's not J U S T-touching at rest, nothing else, no other accommodation in the standard sequence of adjustments will ever allow it to send perfect code.
    And the device is quite capable of that.

    Look through the back-pages (numbered blocks) in Straight Keys and find a few titles in the queue about bug adjustment and slowing-up the device.

    I hope you enjoy what you have, but you shouldn't need the extra stuff. A bug should look like a bug while sounding like a bug. If not, the bug
    is trying to tell you something.

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  6. DD5RK

    DD5RK Ham Member QRZ Page


    for adjusting a bug there is a .pdf document:

    originally published in QST MAGAZINE

    worked for me.

    I adjust the bug with a memory scope.
    First I measure the thresholds of the keyer of my radio, IC7300.
    If I know the thresholds of the radio, I measure the pulse-pause ratio of the bug, at this thresholds for the Dits.

    After proper adjustment I get for the Dits:

    T_on = 48,5ms
    T_off = 54,4ms

    For the length of Dahs I'm responsible by myself.
    To check these I use an audio recorder audacity.
    I send and record some code and measure the relation between Dits and Dahs.
    This should be 1 : 3.

    50ms for Dits means a basic speed of the bug of about 24 WPM
    if the relation of Dits and Dahs is ok.

    My bug has quite severe contact bouncing on the Dits, one can see on the scope.
    To damp these I connected a capacitor of 0.1uf parallel to the contacts.

    Have fun with your bug

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  7. KL7AJ

    KL7AJ Ham Member QRZ Page

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  8. K9NUD

    K9NUD XML Subscriber QRZ Page

    Thanks for the kind words and helpful tips. I saw a helpful YT video on that aspect of the setup and followed it closely. I actually applied some electrical tape to the pendulum shaft and the damper closure to quiet things down a little, being careful to readjust for that just touching effect.

    I suspect that the mod is overcoming three issues, namely, 1: poor sending technique (I've been a bug user for less than two weeks), 2: less-than-perfect contact, and 3: modern rigs with their hyper-sensitive keying. On that second point, I tweaked my contacts for a flat closure. Others have recommended a smaller contact area. On the last point, I noticed that my QCX+ transceiver has trouble decoding my sending, often showing two dits instead of one (i instead of e). The RBN has no issues, and the QSOs seem to go fine. That most likely speaks to the rig's sensitivity and the imperfect contact.

    This is definitely a hobby within a hobby...

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