Wide-band interference in the vicinity of 3875-3900 kc/s

Discussion in 'Amplitude Modulation' started by K4KYV, Apr 27, 2020.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: FBNews-1
ad: Left-2
ad: L-MFJ
ad: Subscribe
  1. K4KYV

    K4KYV Subscriber QRZ Page

    Some kind of propagated buzzing/arcing type interference has been reported in the range of 3875 to 3900Kc. It is pretty wide banded and moves around somewhat, showing up pretty regularly when the band goes long. Apparently this has been going on for quite a while, sometimes quite strong in signal strength.

    "Tonight the interference signal was VERY strong allowing me to hear some very weak/distorted bible beater audio artifacts in the signal. I was able to match the artifacts to WWCR on 3215Kc. The WWCR audio content was identical to the severely distorted artifacts I was hearing in the interference. This was confirmed with both voice and music content. The same type of buzzing/arcing noise heard in the 3885Kc area could just be heard in the low level audio when the modulation on the 3215Kc transmitter would drop down and the audio content was minimal. Looking at the 3215Kc AM signal with the spectrum analyzer revealed the same type of pulses and interference peaks embedded in their sidebands as shown in the 3885Kc area... Every one around here has been hearing it for months on end. Even Tim has complained about it at times. At last I found out what is causing it now."

    I haven't heard it, but haven't listened on 75 past few nights due to lightning QRN. Map shows vast swathes of thunderstorms, and tornadoes reported to the south. I'll make it a point to listen the next few evenings, but if propagation goes long as usual lately, it's less than 50 miles away and may be skipping over me.

    Has anyone else heard this?
     
    W8KHK likes this.
  2. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I haven't heard that.

    What I have heard are some new Slopbucekteers on 3.878 who insist on skinnying up right against 3.880 many nights with what sounds like ESSB operation. They are always screwing around with their equipment and apparently they set their plastic radio receiver bandwidths to about 2kHz.

    More AM operation is needed on 3.875 to 3.876.

    Pheel
     
  3. W8KHK

    W8KHK Ham Member QRZ Page

    Seems like these "Bible Beaters" are a pretty rough crowd, potentially almost as radical as the "SlopBucketteers"!

    https://www.splcenter.org/fighting-...mists-use-technology-broadcast-hate-worldwide

    Excerpt from above link entitled: Powerful, U.S.-based shortwave radio stations are broadcasting extremist propaganda around the world.....

    " Turn the tuning knob once or twice. Coming in clearly from WWCR in Nashville, Tenn., anti-Semitic Colorado preacher Pete Peters is shouting. "The Bible," Peters thunders, "says it's okay to kill homosexuals." ".

    I wonder if they take pleasure in turning up the wick and splaTTTTering all over other services just to get attention? Being a supposedly licensed broadcast station, albeit short-wave, are they immune and exempt from FCC regulations and enforcement? Is their content above censure? Multiple 100 KW emanators will probably not run under the radar forever. Time will tell...
     
    Last edited: Apr 27, 2020
    KD0DQZ likes this.
  4. WZ5Q

    WZ5Q Ham Member QRZ Page

    I can hear the interference signal whenever the 3215Kc Transmitter is broadcasting and the band is long. The signal strength varies but I have been hearing it every night/morning to some extent or another, but it usually gets very loud after about 04:00 UTC. This morning the interfering signal has drifted down the band and has centered around 3854Kc as of 07:00 UTC. I can just make out the distorted audio cadence of Brother R.G. Stair.
     
  5. ND6M

    ND6M Ham Member QRZ Page

    FWIW,.................I believe their Chief Engineer is a licensed Amateur.
     
  6. K4KYV

    K4KYV Subscriber QRZ Page

    Actually, 3878 would be a more appropriate frequency for AM operation when it's open, but there is a QSO in progress on 3885. Five kc/s apart is too close for comfort for two AM signals, even when the audio response is cut to ~3 kc/s to limit signal bandwidth. Very often, I'll call CQ on 3878, but stations still come back to me on 3880. I usually ask them to QSY and zero-beat my signal, although occasionally I run into someone who is xtal controlled.

    Wonder if the slopbucketeers still land on 3878 if someone else is using it. Remember back in the days when Richard, Wally & co. were parking on '78 explicitly and admittedly to run AMers off 3880? They would land right on top of an ongoing QSO and wouldn't move. I remember once when I ignored them and stayed put, they threatened to come with a crew to pay me a "visit".

    This may be the same ESSB group that I occasionally hear; they seem to move around between 3870 and 3880, but so far I have never heard them land right on top of an ongoing QSO. It seems kind of silly to transmit ESSB and receive with 2 kc/s bandwidth.
     
  7. N8FVJ

    N8FVJ Ham Member QRZ Page

    At times SSB operators transmit at the edge of 3880 and at edge of 3890 AM frequencies and it is disrespectful. The 75 meter band is wide open frequency wise unlike 20 years ago, so these operators can go elsewhere. So, perhaps it is malicious interference. My receiver only selects one side band on AM so I can usually tune the SSB operators out by selecting the sideband furthest away from their interfering signal.
     
  8. K4KYV

    K4KYV Subscriber QRZ Page

    I think you are just getting started on AM. Do you plan to acquire capability to receive both sidebands (DSB)? Copying only one sideband is a poor way to receive AM, unless QRM is covering up the other. I would highly recommend synchronous detection; it makes the interference transparent enough that you can often listen right through and ignore it.

    Copying one sideband, you inherently lose 3 dB of the transmitted signal, but you also reject 3 dB of random band noise due to halving the bandwidth, so far breaking even on signal/noise ratio. But the vectorial addition of both sidebands working together doubles the recovered signal voltage at the detector, giving you a boost of 6 dB. However, the doubled bandwidth also doubles the noise, so you end up with a net gain of 3 dB s/n ratio when copying both sidebands, or conversely, you lose 3 dB s/n ratio when copying only one sideband.

    The above assumes uniform noise distributed over the entire pass-band with no QRM covering either sideband. Bottom line: when there is no interference near the frequency, you lose 3 dB signal to band-noise ratio when receiving only one of the sidebands. This can make a difference between copy/no copy under weak signal conditions even if there are no nearby interfering signals.
     
    N0TZU likes this.
  9. N8FVJ

    N8FVJ Ham Member QRZ Page

    I use an AM COM DNR speaker that allows copy right at the band noise. So, the 3dB loss likely does not apply. You cannot hear signals IMO into the band noise.
     
  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Sounds like that post belongs in the Political Forum.

    What I have been hearing is some sick dude going up and down the band (you can hear his carrier slowing sweeping up and down) and then parking near or on a QSO and rebroadcasting SW BC stations. I have heard him maliciously interfere with both SSBer's and AMer's.

    Now that's one psycho I would like to be able locate!

    Pheel
     
    Last edited: Apr 28, 2020

Share This Page