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The Development of the Directional AM Broadcast Antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WA7ARK, Apr 4, 2020.

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  1. WA7ARK

    WA7ARK Ham Member QRZ Page

  2. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Thanks, Mike.

    Who doesn't love a Blaw-Knox?
    KA0GKT likes this.
  3. N1OOQ

    N1OOQ Ham Member QRZ Page

    The elevated cage radials was interesting. For broadbanding?
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    Not likely, since they never move off their assigned frequency. I count 8 elevated radials per tower.

    Not sure why they thought they needed the parallel wires in the radials. Even if they feed the entire 10kW into one tower (which they didn't because the array is directional), the feed current is abt 17A. Divided between 8 radials, that is only ~2A per radial.

    An antenna designer in the 1930s would have thought that they died and went to heaven if they had EzNec....

    I think it was the "if a little bit is good, more is better" syndrome...
  5. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    From the aritcle:
    The radials had to be elevated in consequence of raising the feedpoint. However, I do not know why the cage configuration was chosen; Mike's explanation makes sense.
    Last edited: Apr 4, 2020
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I knew a guy (everyone knows a guy), and wish he was still around to comment here: W2EPQ, Jim Cosman, who built and owned AM radio stations in the NYC area and owned WPAT-AM. He also built it and designed it.

    Jim was a sorta-neighbor (about 10 miles away) and he was in my radio club, SARA, when I was president of that club in the early 80s. Great guy. Rich guy.:p

    Anyway, he had a lot of interesting stories, all of which can be verified if you have access to old radio institute proceedings, most of which are on line but you have to be a member to access them.

    When he first put WPAT on the air it was on the same frequency as WBEN in the Buffalo, NY area about 350 miles away and the FCC insisted his skywave signal was too strong and caused co-channel interference (this was in the late 40s or early 50s). They insisted he change something to reduce the skywave signal.

    So...he rented a helicopter and FCC field strength monitoring gear, and took a trip or two. He collected real-time F/S data at various elevations above ground and presented that to the FCC to verify his radiation pattern strongly favored groundwave coverage and an insignificant radiation was at any elevation to create a powerful skywave signal.

    He won his case and was allowed to continue.

    I believe his "top hat loaded" towers are still there, close to the Garden State Parkway near Paterson. Station's changed ownership over the years of course; Jim died in the mid-80s.

    He had a hell of a hamshack in his enormous basement; he also had the first "fully heated driveway," about 700 feet long, I had ever seen. That prevented the necessity to ever shovel snow off the very long driveway. Interesting guy.

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