Thursday, September 7, 2017

SearchResearch Challenge (9/6/17): What's that thing on the ground?

Every time I fly into San Francisco airport... 

... I see this very strange antenna on the left side of the plane as we fly west to land.  (I figured out the lat/long for you so you don't have to extract it:  37.5469956,-122.2338807)    I've seen it for years, and yet, I don't have any idea what it is or why it's there.  It's all very mysterious.  (What ARE those red letters on the ground around it?) 

It's hard to see in this aerial image, but it's an odd antenna, with a large plate-like thing at the top of the mast. I was so surprised by this oddity that after my last flight, I drove over and took a closer look after landing.  It took a while to get there, as the roads around it aren't very straight, but I managed.  

Can you see the hexagonal frame at the very top?  (Click on the image to zoom in. Or if you want to, download the image and you can zoom as much as you'd like.)  

At the fence I also found this, in case it helps: 

This is one of those everyday mysteries--things you see all the time without understanding what it is. But that's NOT what SRS is about!  When we see mysteries, we try to understand what's happening.  So.. .

Can you figure out the story here? In particular: 

1.  What IS the story behind this antenna?  (A bit of history, please.)   
2.  Why does it have that funny plate plate at the top?
3.  Who uses this antenna now, and for what purpose? 

Next week, we'll talk about what we've found (and most importantly, HOW you can use your SRS skills to answer your own questions like this).  

Leave your notes in the comments--and please tell us all HOW you found out!  Did you use any special search methods?  Did you need to use any special databases?  

Search on! 


  1. Searching for the antenna numbers gives the owner as Susquehanna Radio Corp., which I then googled and found were defunct, taken over by a new company. Either way, searching for 'Susquehanna radio corp antenna san fransisco airport' found a really nice posting about this antenna, and its pair, at

    This is an AM transmitter, and the 'top-hat' is an electrical height extender, which increases the boost for distance signal that couldn't be done because it's too close to the airport.

    It's tied to the radio station KNBR/KNBC (Depending on era), transmitting on 680 AM.

  2. Hello Dr. Russell and everyone

    [tower 1016438]

    Constructed 01/01/1937 “TOWER - Guyed Structure Used for Communication Purposes”

    There searched [1016439] Constructed 01/01/1976

    [San Mateo Susquehanna Radio Corp tower]

    Results link to Wikipedia articles about KNBR ( KTCT ) and Susquehanna Radio Corporation

    Today, the company is still active as a holding subsidiary named "Radio License Holding SRC, LLC".

    Then went to Google Maps and clicked what is here? 1410 Radio Rd.

    [1410 radio rd]

    Susquehanna Radio Corp. Cell Site

    [Redwood Susquehanna Radio Corp tower]

    KNBR - Redwood City, CA, USA - Radio and Television Transmitter Towers Site mentinos History.

    [knbr tower top]

    With the top hat, KNBR realizes an electrical equivalent of .520 wavelength. and shows an image of the top to see it perfectly.

    Also mentions a YouTube video found in the results but it is hard to understand the audio

    The "HAZ" markings throughout the antenna field are...

    More History

    Open in 1949 and shows a picture of people in the top hat.

  3. using the supplied coordinates –
    Waymarking - history fron Wiki
    meaning/purpose of HAZ signs - for aerial viewing/pilot warning
    ground level, some of the 'HAZ' letters, lower left
    closer view of antenna structure
    KNBR history
    searched ASR (Antenna Structure Registration) numbers from photo…
    FCC info on antennas
    FCC info
    FCC ASR overview
    hexagon antenna on top:
    "An anti-fading antenna (informally and often incorrectly termed a "Franklin" antenna) is a long- and medium-wave transmission antenna with a flat vertical radiation pattern. The design goal is to move the mush zone farther from the transmitter site. An anti-fading antenna will reduce radiation at elevations of more than 50 degrees as much as possible. In principle, such a radiator should be as thin as possible, although thicker radiators improve the bandwidth and contribute to a taller effective height."

    from wiki - used: [purpose of hexagonal structure on top of radio antenna] looked through image results for similar…
    related to SF/GE’s short wave station KGEI: interesting to scroll through… before there was "an app for that…"
    KGEI station
    radio articles & show index schedules - page 40, GE radio broadcasting, part 1
    part 2 - page 40 - 'On Short Waves'

    related, wandering south.
    KGEI history in 60's
    VOA history in Palo Alto…
    "The last known program broadcasts from KROJ and KROU took place around November or December 1945. The war was over, and the two new and very large stations, VOA Delano and VOA Dixon, both in California, were already being phased into service. The temporary units at Palo Alto were no longer needed for broadcast service, and we would guess that they were quietly taken back into the regular communication service from Radio Palo Alto, station KFS."
    American Shortwave Panorama
    …meanwhile, south, in the central valley, north of Bakersfield, Kern County… the former VOA site
    Delano, CA
    background history there… many more antennas…

    thought I might find the current station here… but no dice… only static
    this is KZSU
    FM, SD, not an AM Sports station

    1. Remmij -- Does that last YouTube link work for you? (It's blocked to me due to copyright restrictions.) Does it work for you?

    2. Hi Dr. Russell, for me says no longer available for the same reasons you mention.

    3. … hmmmm, was working, now just a static memory courtesy of the IFPI -
      FM alt - not blocked… yet
      such is the true nature of the internet – it can all be altered/gone in the blink of a facial recognition eye… the end is near, SPJ cyclonic spinning in afterlife
      peak moji/peak iMeh $1k — X years culminating in round bunker(albeit cool)reality distortion field über powerpoint

      as for: "How did you find this? (What got you to the "Station became a church" page?)"
      finding the building address with GooMaps and searching the addresses for both buildings… (as best as I recall)
      California Historical Radio Society
      Bay Area Radio
      note the trailer…
      KPO 1933 & 2015 - 1410 & 1406 Radio RD.

      fwiw - Henk vas Ess has some material of interest…
      van Ess

  4. Searched for more about the "famous" Haz: [intext:"HAZ" radio tower signal redwood city]

    Ctrl F shows the meaning

  5. This comment has been removed by the author.

  6. I won't repeat what others have already said, except to say that the key datapoint for me for search purposes were the Tower Registration Numbers (followed by the lat long).

  7. Replies
    1. This is a fascinating side-story about the building. How did you find this? (What got you to the "Station became a church" page?)

  8. 1
    Searching the tower number 1016438 finds which shows under Obstruction NOTAMs: !SQL 07/011 San Carlos, San Carlos, CA (KSQL) Obstruction tower light (Antenna Structure Registration 1016438) 37° 32' 50.10" North 122° 13' 57.80" West (2.3 Nautical miles north-north-east SQL) 311.0 Feet (308.1 Feet above ground level) out of service Jul 21, 2017 1648Z to Sep 21, 2017 2359Z

    This notification to pilots tells them that a light on this tower is obstructed.

    Punching in your lat/long to GE Shows first that the red letters all are HAZ, a visual warning that there are two HAZardous towers they should avoid.

    3. shows owner as Susquehanna Radio Corp.
    Attention To: Gary Kline
    3280 Peachtree Road, Suite 2300
    Atlanta , GA 30305

    3. from this [radio towers redwood city] finds provides your locations and a history but here is the quicky: Quick Description: A transmitter for KNBR in Redwood City, CA

    The long of it: Long Description:
    "KNBR is an AM radio station licensed to San Francisco, broadcasting on a clear channel at 680 kHz from transmitting facilities near Belmont, California. KNBR's non-directional 50,000-watt class-A signal can be heard throughout much of the western United States and as far west as the Hawaiian Islands at night. For several decades, KNBR enjoyed a long history as the flagship station of NBC's West Coast radio operations."

    !. full history:

    2. [design of AM radio transmitting antenna] finds a pretty good Wikipedia page with image. THe funny plate on top of the radiator mast is found in Wikipedia Category:Antenna masts with capacitive top hats / This category is for radio masts with screens or radial rods attached to the top for capacitive loading. These "top hats" are sometimes used on the mast radiators employed for AM broadcasting on the MF and LF bands, to increase the current in the top of the antenna to increase radiated power, allowing a shorter antenna to be used.

    THe entire mast is electrically charged to act as the antenna, that is why the area is fenced with warning signs to keep out. tells us the two mast radiators form the desired directional pattern.