class e rigs

Discussion in 'Amplitude Modulation' started by N2DTS, Oct 23, 2017.

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    I think he says he CAN, not that he operates it that way.
    Maybe some guys just bypass the low pass filter?
    Or don't include it?
     
  2. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    The first response in my mind is WHY? And, what does it matter to have that kind of bandwidth?
    My transmitter produces up to 20K but I certainly never run it like that. I never boost any
    frequency band below 1 kHz and normally, I use cut and shelve techniques to tailor audio
    in order to maximize the quality, not the bandwidth. In essence, my bandwidth hovers around
    10 kHz. I dump all frequencies below 100 Hz which we don't need for speech anyway.
    Some guys want to sound super Basso by boosting the low end which sounds like ass and just
    ruins the transmission quality. Evidently, the previously mentioned operator practices this
    sort of thing. If so, he's an idiot.
    Period.
     
  3. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    I don't cut frequencies below 100~, but add emphasis to the 800~-4K range, letting the lows cut themselves off naturally, around 80~. The problem is not the lows below 100~, but intentionally boosting the lows to the point of sounding like the speaker is in a barrel, allowing readability to be lost in the noise and QRM if the signal isn't perfectly full quieting. The frequency response capability of my audio measures flat down to at least 40~, limited mostly by the transformers, which are all broadcast quality units. The low frequencies transmitted must be balanced by the highs, and vice versa. The same applies, whether the transmitter/modulator system is class-E which is inherently flat across the audio spectrum, or class-C hollow state plate modulated which is limited by the capabilities of the transformers.

    In order to preserve the voice waveform and avoid undesirable frequency shift, the system should be capable of flat response at least one octave above and one octave below the intended range of the transmitted audio. For example, if you intend to transmit a frequency range of 100-4000~, the transformers and speech amplifier stages should be flat at least to 50-8000~.
     
  4. WZ5Q

    WZ5Q Ham Member QRZ Page

    That is the key.
     
  5. K5UJ

    K5UJ Ham Member QRZ Page

    A lot of the ESSB guys are all in with that low frequency bass audio, and I went there too for a while, but in AM, it is a very inefficient use of transmitted audio power because there is little or no intelligibility in voice audio below ~120 cycles and for some reason it has a negative impact on reception of skywave AM. I can have some guy with a lot of low frequency audio and if I cut off everything below 200 cps his intelligibility goes way up. Some guys have naturally deep voices and I think they need to attenuate their transmitted low frequency response.
     
  6. N2DTS

    N2DTS Ham Member QRZ Page

    With the response curve of my ears, anyone with a lot of low end can not be understood and I have to cut the bass.
    The Marantz has a low cut button and I turn the bass down.

    I DO like it to be in there, the Icom 7300 cuts the lows off at 200 Hz on AM rx and it just sounds poor that way.
    Sometimes its easier to copy someone with all the lows removed, but it does not sound very good.

    On the other hand, who cares about modulator power? A good rig should have plenty of extra.
    You can have a very nice AM signal with 100 to 4000 Hz passband if the EQ is good.
    It can roll off below and above that, or brick wall.
    I think many receivers people use do not pass audio below 200 or 150 Hz as I have reported on the globe king hum (60 and or 120 Hz) that others could not hear.
    I tend to think it sounds cool, a power hum in the background.

    I just think its bad practice to be on 3873 and trash out past 3885 during prime time.
    But now I suspect its not the class E rigs causing the problem, although many of them do it.
    Steve (QIX) puts out a strong signal with one but does not have the artifacts...
     
    KA0HCP likes this.
  7. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    A properly functioning class E rig potentially has a flat audio response with minimal distortion from DC to daylight (unlikely, but at least up beyond the limits of human hearing, based on the capabilities of the modulator). With PWM, high frequency response is inherently limited by the clock frequency. The audio curve must be shaped in earlier stages of the audio chain, since there needn't be any transformers to limit upper frequency response.

    Barring malfunction, extreme bandwidth with these signals is deliberate. Certain class E operators have been heard to boast over the air that their audio frequency response reaches up to 20 kHz or beyond. How many hams do you think actually listen to these signals with receiver selectivity set to 40 kHz bandwidth?
     
    KA0HCP, WB2CAU and WA3VJB like this.
  8. K6CLS

    K6CLS Ham Member QRZ Page

    That's the best thing about ham radio, nobody knows I am really a dog!! Wag wag bark.
     
  9. WA3QGD

    WA3QGD Ham Member QRZ Page

    Really? the distortion products and imd tend to catch the attention of other Operators,some whom then feel the need to exact their revenge upon anyone using the AM mode.One either wants to operate as a gentleman or chooses to operate outside the defined parameters of courtesy and respect.Some seem to like the Bridges burning approach.
     
  10. WZ5Q

    WZ5Q Ham Member QRZ Page

    "Damn the torpedoes, full speed ahead!" ;)
     
    AC0OB likes this.
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