1. Everett

    Everett New Member

    Looks like a sunset spike, at first. Conspiracy theorists, take note: the screenshot includes data that is useful. (I like weather underground)

    Looks like a sunset spike at first. But, a few oddities. First, it was taken, according to the data, at 4:17 PM, sunset is at 4:41 PM. More importantly, shouldn't a sunset spike be facing to the southwest?

    Perhaps a "picking up another radar" spike?

    Since at least one poster here is a NWS radar technician, perhaps the experts here could enlighten me?
    Woud "Vol. cov. pattern 32" be of use?
    (Can sunset spikes be in the opposite direction as the sun?)

    Attached Files:

  2. solrey

    solrey Senior Member

    I believe that spike on the St. Louis radar has been rather persistent for several weeks, over the past couple of months a youtuber has made quite a few videos of interference spikes from St. Louis and Houston. The interference is probably from cell phone towers. I contacted the NWS office in Houston about the spikes on their radar and the contact person said it was probably interference from nearby cell towers and they had contacted the FCC to begin resolving the issue. I think the St. Louis radar has the same issue.

    The central Illinois radar has had a problem with 4G cell tower interference in the past.


    A March 2012 NEXRAD Program Update states...


    4G tower interference has been an ongoing problem.

    The only way a sunspike could point in the opposite direction from the sun is if there were a mirror like reflection off of a nearby building or something like that, so it could be possible but highly unlikely.

    And nearby radars do occasionally interfere with one another.
  3. scombrid

    scombrid Senior Member

    That spike is a communications tower that is in the line of sight of that radar unit. Basically as the base scan sweeps the sky it briefly points at the radio tower and since it is receiving a continuous signal from that direction the radar draws a line pointing in the direction of the radio tower out to the edge of the sweep radius. There are several towers that have been causing interference with the St. Louis radar for a few years now.

    I actually have the tower that is causing that spike marked on google earth on another computer.

    Sunrise and sunset spikes will be pointing SE and SW respectively this time of year and will only be present for one frame on a radar loop.
  4. Everett

    Everett New Member

    Ok, that makes sense. I will admit I didn't actually see more then one frame, just that one. You'd think they'd have gotten the communication tower problem fixed by now. I'm assuming it only shows up on clear air mode? During the tornadoes we had a couple of weeks ago, which were pretty much in that direction, that could have been a major problem if a storm happened to cross through the interference at an important time.

    Also, reading that link, am I the only one ticked off by the reports of poor funding?
  5. solrey

    solrey Senior Member

    Funding is always an issue. I mean, any entity always wants more funding. On the other hand there have been significant upgrades recently like dual-polarization and dynamic scanning capabilities.

    Here's some more info on 4G interference, a.k.a. WiMax.


    Known interference sites:
    Grand Rapids, MI
    Jacksonville, FL
    St. Louis, MO

    Probable interference sites:
    KOUN Dual-Pol Testbed (Norman, OK)
    Midland/Odessa, TX
    Houston, TX

    Air Traffic Control ASR-11 radars also interfere with WSR-88D's. The FAA is, or maybe already has since the document is from 2011, installing transmit filters on the applicable units. The ROC/NWS is also working with the FCC, NTIA, ORFM and the WiMax vendor to resolve the interference issues, which would consist of a transmit filter on WiMax transmitters. There are 40 WSR-88D's that operate in a frequency range <2.775 GHz that could be affected by WiMax transmitters.

    Thanks to scombrid for mentioning that interference spikes only show up on the lowest tilt angle of 0.5 deg.

    For more information check out the Radar Operations Center.


    Funny that the youtuber "planetlightforce" accuses the NWS of an "unethical use of nexrad radar" by "beaming" Grand Rapids, St. Louis and Houston. Got blocked, of course, for politely explaining the sources of interference and they are the reason I contacted the NWS in Houston to confirm what I already knew. People like that just don't want their little fantasy shattered by actual facts of any sort.