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WWV & WWVB Ground Wave!

Discussion in 'Amateur Radio News' started by KA0KA, Oct 1, 2019.

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  1. KA0KA

    KA0KA Ham Member QRZ Page

    Yes I know! I saw the HEX beam, when I was on site I saw that and shook my head!!! Great video clip, there are probably some people who have no idea what we keep talking about! What do you think runs my amp, "this sucker is electrical"!
     
  2. KI6PMD

    KI6PMD Ham Member QRZ Page

    They should use Dimension 4# great time keeping app. 73' Phil ..
     
  3. W0PV

    W0PV Ham Member QRZ Page

    Dimension 4 would certainly be good for setting off the internet. But this special event station WW0WWV is doing a Field Day type operation. See the photo album. So, despite cell phones, etc, they may not have a reliable direct connection to the web.

    However, they do have RADIOS :rolleyes: and are in close proximity of a really strong NIST time standard transmitter :D. So I was expecting that in the SPIRIT of celebrating WWV they would have made provisions to decode their commemorative stations time signal off-the-air for setting their FT8 PC clocks.

    Like using this LINUX demod/decoder perhaps to set up a local NTP server for all the Windows PC's, or spending the 30 bucks for the F6CTE Clock program for Windows.

    If there are other WWV time signal decoders, I would like to learn about them.
     
  4. KL7AJ

    KL7AJ Ham Member QRZ Page

  5. KA9Q

    KA9Q Ham Member QRZ Page

    Sure. Go to http://www.ka9q.net/wwv. You'll see a list of screen shots I made with the Kiwisdr at N6GN in Fort Collins. I grabbed IQ plots of all six HF transmitters. Look at 10 MHz; it looks like a banana! An AM signal should be a flat line exactly on the +I axis, with a dot in the middle of the +I axis for the unmodulated carrier. This one has so much phase modulation you can easily hear it in FM mode.

    It's no coincidence that the best-sounding transmitters are 2.5, 20 and 25 MHz. They're linear amplifiers. 5, 10 and 15 use high level audio plate modulation of a class-C final amplifier. Unfortunately, the linear transmitters only produce 2.5 kW; the high level ones produce 10 kW.

    I think this explains the difference. I need to brush up on my vacuum tube physics, but I think the change in plate voltage in a plate-modulated AM transmitter changes the electron density and distribution within the tube. This changes the plate/grid capacitance, which in turn changes the phase shift in the tube. There's really no other explanation since the low-level input to the transmitter is a continuous, unmodulated 5, 10 or 15 MHz sine wave. Anybody out there with SDR equipment and a plate-modulated (tube type) AM transmitter could test this, though I suspect these are distinct sets of people. :)

    Here in San Diego, 5 is pretty reliable at night and 10 during the day. Unfortunately, 2.5, 20 and 25 aren't as good; I can usually hear 2.5 at night but my old PV inverter produces a lot of RFI. (Yeah, it should shut down automatically at night but it's very old and the manufacturer never bothered with any firmware improvements.) I rarely hear 20 and 25 on what is probably sporadic E in the early evening.

    Synchronous AM detection provides several benefits. First, it avoids the distortion you hear on an AM detector when frequency-selective fading notches out the carrier. Second, you get a theoretical 3 dB SNR improvement because you're looking only at the signal in phase with the carrier; you ignore the in-quadrature phase that's noise only. (That's why an AM signal is a line on the +I axis.)

    This is how I discovered the distortion on WWV's transmitters. I've been working on my own SDR, including a synchronous AM mode, and noticed that their signals (especially 10 MHz) sounded noticeably more distorted in the synchronous mode than in the simple envelope mode. So I added a feature that put the I channel on the left earphone and Q on the right earphone. (I think this was once tried as an AM stereo technique.) On local broadcast stations I got the expected result: the audio was completely on the left channel; just noise and a very tiny amount of program audio on the right. On WWV the modulation seemed spread across the stereo image. Eventually I realized the problem was at WWV, not in my receiver. The audio distortion in synchronous AM mode is because it's designed to ignore signals in the Q channel, and because of the AM-to-PM conversion this resulted in a very nonlinear transfer curve when looking at only the I channel. Lots of harmonics on the audio tones and intermod between the 100 Hz subcarrier and those tones.
     
    W0PV and N0TZU like this.
  6. AJ4LN

    AJ4LN Ham Member QRZ Page

    I would also be interested. I've used the free limited version of the Clock program. I think I once saw someone mention another app in another forum post about WWVB.
     
  7. KA9Q

    KA9Q Ham Member QRZ Page

  8. KA9Q

    KA9Q Ham Member QRZ Page

    I just looked at all six HF frequencies again with N6GN's WebSDR. All are essentially the same as in my plots made several months ago. 10 MHz is the worst, as before.
     
  9. KA0KA

    KA0KA Ham Member QRZ Page

    You can also see this on the WWV Splatter Video quite clearly in the spectrum analyzer and waterfall I posted of the 10 MHz signal!
     
  10. K6CLS

    K6CLS Ham Member QRZ Page

    thanks so much for this... and the rest of your detailed, informative, excellent post. greatly appreciated.
     

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