How wide is wide?

Discussion in 'Amplitude Modulation' started by W8AAZ, Jun 11, 2020.

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  1. K4KYV

    K4KYV Subscriber QRZ Page

    An old rule that has been around for ages: The weaker they are, the longer they talk.

    My other gripe is "breakers" that pop up off frequency. I receive with the synchronous detector 99% of the time, and it takes a second or two for it to lock onto an off-frequency carrier. Usually, by the time the PLL locks onto the carrier, the breaker has already given his call and stood by, so I missed it completely. Except when one is crystal controlled, the is absolutely no reason to break in without first zero-beating your VFO to the carrier of the most recent station that just finished transmitting.

    If you are crystal controlled, perhaps it would be best to call CQ on your xtal frequency, rather than trying to break into an ongoing QSO that is not on or very close to your crystal frequency.
  2. WB2CAU

    WB2CAU Ham Member QRZ Page

    I see no valid reason to be purposely wider than the passband of a typical AM receiver. That's not being a good neighbor on the band if it's busy. And if your receiver bandwidth is open to 10 KHz or wider during times when the band is busy, you're hearing more QRM than the sizzling highs of the station you're in QSO with anyway. If the band is empty, well, that's a different story... except at my age I can't hear anything of consequence above 8 KHz anyway. And most of you are old like me!
  3. N2DTS

    N2DTS Ham Member QRZ Page

    From casual listening, this (being wide) does not seem as much of a problem as it used to be.
    There was one station who always ran 10 KHz audio with multi band compression to keep it 100%
    all the way out, but that person seems to have changed things.

    In normal operation, without multiband compression far out, its not normally much of a bother.
    Maybe if the signal is 40 over S 9 and only 5 KHz from your frequency.

    And the bands have had big holes with no one on lately, filled with lightning crashes mostly.

    I find the sync detector worthless 99% of the time, with one station being 1 kHz low, another two being spot on, and
    another being 2 KHz high.

    Who cares really (except the sync detector users) but often that one person is 2 KHz closer to another qso
    (AM or ssb).

    You would think, in this day and age of dds, $10.00 freq counters, inexpensive sdr receivers, and even dds vfo kits,
    people would have some idea where they are on the band.
  4. WZ5Q

    WZ5Q Ham Member QRZ Page

    Yea, you would think...
    but if one doesn't even know how to zero beat an ongoing QSO before making a transmission or even know what zero beating is, then they probably don't know how to operate all that fancy equipment you mentioned much less be able to hook it up.
    K8PG and AG5CK like this.
  5. AG5CK

    AG5CK Ham Member QRZ Page

    Good point. I've came across plenty of goobers running modern and vintage rigs. Never assume someone is or isn't an appliance operator based on what rig they use. If you have enough money someone will homebrew something for you.
    KA4KOE likes this.
  6. KA4KOE

    KA4KOE Ham Member QRZ Page

    I run no wider than 5 KC; as low as this 223 will go.
  7. KA4KOE

    KA4KOE Ham Member QRZ Page

    Yes, I ran across that recently.
  8. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    You are only as old as you to admit to being! :D

    Some of you may have seen my various speech amps and there are reasons for those component values in the circuits.

    The first stage includes a pre-emphasis circuit in the cathode with a 3 db emphasis starting at approx. 650 Hz to make the signal more intelligent during noisy periods; the pre-emphasis tends to make the audio rise above the noise levels.

    The integrator in the second stage starts to limit audio to about 5.5kHz with a -3dB rolloff. I feel these values allow enough "presence" to make it through the background noise and lightning crashes while keeping the transmitted bandwidth within a 10Khz bandpass. But that's just me.

    I also modify the cathode and plate load resistor values in order place the speech amplifiers into their linear operating curves in order to reduce distortion. Any distortion products can contribute to excess bandwidth, something which many people forget when discussing occupied bandwidth.

    Any modulation method, where it be Plate modulation, screen modulation, or cathode modulation can only sound as good as the audio presented to it. Once the speech amp has been modified, then one can go to modifying the modulator.



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