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Kenwood TS-830S Deafened Receive Repair!

Discussion in 'Radio Circuits, Repair & Performance' started by N9PCT, Mar 20, 2019.

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  1. N9PCT

    N9PCT Ham Member QRZ Page


    I have 3/4 of a syringe of Chipquik flux left. That's typically what I use when soldering anything on a board. A lot of the guys in the club just use rosin core no-clean solder but I like the manually applied stuff as I think it makes the joints better / easier to solder and the stuff just comes off with isopropanol and a q-tip.
     
    KA9JLM likes this.
  2. N3KO

    N3KO Ham Member QRZ Page

    Thanks for sharing this, I have a sizable Kenwood Hybrid collection and knowing the way around surgery very helpful.
     
  3. W9BRD

    W9BRD Ham Member QRZ Page

    AME stands for "AM equivalent." AME is what CHU is transmitting at 3330, 7850 and 14670 kHz: a carrier plus one sideband. It's done so receivers without beat-frequency oscillators can demodulate the signal.

    "Exalted carrier" is a a mushily named approach to receiving AM in which the carrier in the incoming signal is amplified relative to the sideband(s) and re-inserted for demodulation. "Tuning AM like it's SSB" with the carrier at zero beat with the receiver beat-frequency oscillator (BFO) is the essentially the same thing; phase-locking the BFO to the incoming carrier--synchronous detection--is the gold-plated, best approach to doing this, but is unnecessary for communications-quality audio.
     
  4. N8YX

    N8YX Ham Member QRZ Page

    Which is how Kenwood and a number of other manufacturers implement what they call "AM" in their transceivers.

    In the focus of this discussion, it's also done because bean counters. Easier to unbalance the balanced modulator with a bit of carrier - cost-wise - than it is to amplitude-modulate the carrier closer to the antenna.

    And we're back to the crux of the matter, a mushy-sounding "AM" signal...
     
  5. W9BRD

    W9BRD Ham Member QRZ Page

    No, it's done because full-on AM was clearly not a TS-830 design goal, making unbalancing the balanced modulator, low level AM, the only kind of AM one can do without drastic system-diagram and physical change in a radio mainly designed for SSB. Even screen modulation, which requires no modulation iron, would be a challenge to design into a system largely designed for linear amplification from signal source to antenna. (I'm also leaving out such iron-free approaches as PDM, implementing which would stray even farther from the block diagram of the TS-830.)

    The presence of the sideband filter alone will make the 830's unbalance-the-balanced-modulator approach to generating AME sound muffled compared to AM band-limited only by plate/screen bypass and plate blocking capacitors, and modulator frequency response.

    Not knowing for sure the reason for existence of the TS-830M, I'll guess that AME was included for non-ham use of the transceiver. (AME itself was a stopgap; its heyday spanned the transition from classical full-carrier DSB AM to SSB among maritime, aeronautical, and similar communicators. Oh, for the days when New York Radio [VOLMET] transmitted a big AM signal at 3001 kHz and real people read the aviation weather live, background noise and all...)

    BTW, I get a kick out of the relatively modern use of the adjective hybrid for such radios. The Drake 2 and 4 lines were using transistors for key functions before 1970.

    I wonder how many AM enthusiasts have built the exciter described in Campbell, Hayward and Larkin's Experimental Methods in RF Design? In the approach used there, a diode DBM is used to generate high-quality DSB, and then the carrier is summed back into the DSBSC signal in a combiner. Very cool.
     
    Last edited: Jun 14, 2019
  6. N8YX

    N8YX Ham Member QRZ Page

    You may directly modulate the RF predriver and get out of the business of using the SSB filtering/balanced modulator portion of the radio for AM generation. Manufacturers have done this...it's more expensive - component-wise - than simply unbalancing the modulator with a carrier and transmitting it along with one sideband. But it makes for a cleaner-sounding signal.
     

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