D-104 loading...

Discussion in 'Amplitude Modulation' started by W1BR, Jan 27, 2021.

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  1. WZ5Q

    WZ5Q Ham Member QRZ Page

    The way I read Jay's post is that he knows the OP has a Kobitone element, and that he was suggesting that the OP look up the frequency response of the D104 element and EQ the Kobitone element response to match the D104 element response.

    I have personally tried the Kobetone element and was very disappointed in it's sonics even after EQ'ing. A purely subjective opinion of course.
    KW6LA and KA0HCP like this.
  2. W1BR

    W1BR Ham Member QRZ Page

    That maybe, but others have been more enthusiastic about the Kobytone vs. any other available replacement

    The problem is not midrange presence, it apparently is excessive low end response. Transmitter is heavily
    modified Ranger I, and that contributes to to low end response.
  3. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    What does the Speech amp circuitry in the ranger look like?

  4. W1BR

    W1BR Ham Member QRZ Page

    I'd have to dig for it... I posted the changes here several month's ago.

    Frank, WA1GFZ lives a mile or so from me... I asked him for a critical report and he
    suggested, being critical, that reducing the "mud" frequencies might give some
    improvement. I probably should get some 75 M reports on the BW5100 before
    getting the dikes out.
    Last edited: Jan 27, 2021
  5. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    K1LKP likes this.
  6. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    oops silly me put all the blame on this guy.jpg

  7. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    And don't forget that many if not most older gentlemen have major high frequency hearing losses.

    I would get some more opinions from people with different receivers.

  8. KE0ZU

    KE0ZU Ham Member QRZ Page

    My understanding is that the Kobitone cartridge is also a crystal mic, so therefore I'd think the response would react similarly to the D104 element. Here is a graph of the 104 with differing load resistances.

  9. WZ5Q

    WZ5Q Ham Member QRZ Page

    It depends upon the type of crystal and how it's mounted. The older D-104 element uses a rather large Rochelle Salt Crystal that is mounted to the element base. It has a "stirrup" that is mounted to opposing corners of the crystal and then connected to the metal diaphragm with a dob of wax. Sound pressure from the diaphragm flexed the crystal between the mounts. I have attached some pictures of one that I have repaired.

    Unfortunately I have no information on the Kobitone element as I have not opened it up to know what is inside of it.

    1 - D-104 Element opened .JPG

    3 - D-104 Element repaired.JPG

    4 - D-104 Element repaired.JPG

    5 - D-104 Element diaphram.JPG

    6 - D-104 Element waxed.JPG
    KD2ACO, KW6LA and KA0HCP like this.
  10. N1BCG

    N1BCG Ham Member QRZ Page

    You can certainly load it down with a parallel resistor according to the Astatic frequency response vs load chart that KE0ZU posted. A series cap could also be added.

    The simplest solution is to not close-talk the mic (if you are) since the “proximity effect” will dramatically emphasize lower frequencies.
    K0OKS and AC0OB like this.

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