Gonset GSB-100 Modulation Transformer

Discussion in 'Amplitude Modulation' started by KD4HLV, Apr 20, 2021.

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  1. KD4HLV

    KD4HLV XML Subscriber QRZ Page

    I am working on a Gonset GSB-100 and has a open winding and looking for a Modulation Transformer for this to finish a repair I am doing. I have attached a picture of the transformer and a diagram of the outline.
    Let me know if you can help out.

    Thanks,
    Marty
     

    Attached Files:

  2. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Are you referring to T1, the transformer after the Low-Pass audio filter and before the Phase Shift network?


    Pheel
     
  3. WB2GCR

    WB2GCR Ham Member QRZ Page

    I think Pheel is trying to say that the GSB-100 is not a plate modulated rig?
    So, it's not a "modulation transformer"!
    You may need the transformer anyhow...
     
  4. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    The reason I ask is I have an HT-37 "parts" rig that has a similar transformer, called T101 which feeds the 90 degree phase-shift network and follows the speech amp. It's yours for 5 bucks + shipping.

    https://bama.edebris.com/download/hallicra/ht37/ht37.pdf

    This rig and the Gonset GSB-100 have similar circuitry as they both use the "Phasing" method to generate LSB, USB, and AM. Where the HT-37 uses two 6146's as the 'linear' amp, the Gonset uses a single 6DQ5. Neither rig has a "modulation" transformer. They do have two separate transformers in the 'modulation stage' that feeds the Balanced Modulator circuit.


    https://bama.edebris.com/manuals/gonset/gsb100/


    Pheel


     
  5. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    A couple of nights ago I was talking with a newcomer to AM, who told me his Swan transceiver (that he was not using at the time) was "plate modulated", then he went on to say that it transmitted one sideband plus carrier.

    One sideband plus carrier is not AM. It's SSB with poor (or no) carrier suppression. I explained to him what "plate modulation" is, but not sure it got through to him.
     
  6. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    The HT-37 does transmit a full DSB plus carrier AM signal at a max output of 25 Watts. N4RXV has an HT-37 with good AM audio.

    The HT-37 had a remarkably good design but poor implementation in terms of it's electro-mechanical components, specifically, the BandSwitch setup. I would not recommend ever purchasing an HT-37 because of that.


    On the Swans and Gonsets, in sideband mode, the carrier is suppressed at a level of about -45dB, but it is not "zero."


    Pheel

     
    Last edited: Apr 21, 2021
  7. KD4HLV

    KD4HLV XML Subscriber QRZ Page

    Referring to T2, T3 Modulation Transformer where the 90deg phase shift happens to suppress the opposite carrier.
    One of the Transformers Plate winding is open.
     

    Attached Files:

  8. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Okay, I have those as well.

    This stage is simply amplifying the quadrature phases and providing the proper impedance matching. The actual carrier suppression and the generation of SSB is taking place in the Balanced Modulator.

    Pheel
     
    Last edited: Apr 23, 2021
  9. KD4HLV

    KD4HLV XML Subscriber QRZ Page

     
  10. KD4HLV

    KD4HLV XML Subscriber QRZ Page

    Yes, This is a "modulation transformer" 'Balanced Modulator'
     
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