Modern radios

Discussion in 'Amplitude Modulation' started by N2DTS, Nov 21, 2019.

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  1. KL7AJ

    KL7AJ Ham Member QRZ Page

    Absolutely flat to 4Khz (8khz RF bandwidth) and then cuts off like a brick wall.
     
  2. KL7AJ

    KL7AJ Ham Member QRZ Page

    PS...I never run it that wide, though.
     
  3. K4KYV

    K4KYV Subscriber QRZ Page

    Nothing wrong with running it that wide or wider if there are no closely adjacent QSOs in progress that you would interfere with. I normally run mine flat to 5 kHz (10 kHz rf bandwidth) but under congested condx, flat to 3400~ (6800 Hz rf bandwidth). The bands are seldom that congested these days, often swathes of unused spectrum either side of the frequency even during peak hours on 160, 75 and 40.

    Few transmitters cut off cleanly like a brick wall; most have more gradual skirts. Remember, even if you cut off to -40 dB beyond the nominal cut-off frequency (considered by the FCC to be "good engineering practice"), if you are coming in to someone's receiver at 40 dB over S9, you still may have artefacts at S9 signal strength out beyond your nominal bandwidth.
     
    AC0OB, WZ5Q and WD4IGX like this.
  4. N2DTS

    N2DTS Ham Member QRZ Page

    There had been a lot of hash about bandwidth in the past.
    Its not all the same, if you have a class E rig and run a multi band processor out to 100% modulation to 10 KHz
    you will be very annoying to people if you have a good antenna and run a kilowatt of AM as some have done.

    If you run a T368 or a Johnson kilowatt or a kw-1, with a D104 or such, you will roll off the high end and it will not be dense,
    nearby qso's will hear a wisp now and then, big difference!

    Modern radios can pack the audio spectrum out to whatever cutoff is set (if any) and that is the problem, not the people
    running tube rigs with normal audio.

    4 Khz audio is fine, so is 5 or more if its low duty cycle and rolled off somewhat.
    It all depends on how you run your gear.
    I tend to think some want to be broadcast on the ham bands where it does not really belong.
    Its voice, not music and I think voice can sound great restricted to 5000 Hz and rolling off.
    I bet 3/4 of the people listening do not have hearing or filters that go much wider.
     
  5. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    What the heck is an "R928?" Do you mean the RS-928 like this?

    http://hamradiotransceiver.biz/category/rs-928/
     
  6. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    I agree - which is why I love my DX-100 and boat anchors in general.

    I can still get tubes, and in the next year I am going to stock up on a lifetime supply for myself.

    That much said, I have sometimes thought about what I would do if I wanted to set up the best possible, highest fidelity audio, AM setup, but not using anything like a converted BC transmitter. I'd want to avoid those because this house is not where I expect to live in retirement in maybe 10 more years and I wouldn't want to move one of the darned things twice!

    I've thought maybe a K7DYY transmitter, or both of them (until and unless he comes out with the tri-band version) and any number of receivers, anything that allows a wider than 6kc filter to also receive really high quality audio. But even that won't get you on the higher than 40m bands though, to be fair, neither will a converted BC transmitter.

    So what's the best selection for all bands? Much as I favor boat anchors it may well be a Flex plus an amp that can handle decent carrier power key down for a fairly extended time.
     
  7. KA4KOE

    KA4KOE Ham Member QRZ Page

    My R390 beats the pants off my Flex 6300.
     
  8. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    Sure, but that's only a receiver. Nothing says you can't use the Flex to transmit and the R-390 to receive.
     
  9. N2DTS

    N2DTS Ham Member QRZ Page

  10. K5UJ

    K5UJ Ham Member QRZ Page

    Then SDRs are not "superior in every aspect" because being able to repair your own equipment is a desirable attribute. You don't get to simply dismiss anything that's a negative by saying it "is not valid." Repairing our equipment is an important and significant part of ham radio. The throw away business model is for non-technical appliance consumers. not hams, however certain vendors exacerbate and enable consumer ham behavior by making it difficult to perform repairs, usually by not making schematics available. Support the right to repair. Insist on getting a schematic from a manufacturer for his product as a condition of sale. By performing your own repairs, you help to slow the descent of ham radio into a black box consumer market segment.
    https://en.wikipedia.org/wiki/Electronics_right_to_repair
     
    N2EY, K4KYV, AC0OB and 1 other person like this.

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