AM Frequency of the Week: 530

[rfry]

...The tallest monopole in the US is for WRDT 560 for its 13.9 watt nondirectional PSSA, and is 992 feet high according to my calculations.

I'm way out of date on how this was implemented. Presumably WRDT nighttime operation uses one of the tall TV towers NNW of Detroit, but how did they do that? Normally such towers have no base insulator, not much of an r-f ground system (as in 120 x 1/4-wave buried radials), and their guys are uninsulated — a configuration not too useful as a normal, series-fed monopole for the AM broadcast band.

 

[Schroedingers Cat]

Though I have been to the tower site, I couldn't get that close and the tower is very "busy" with antennas and transmission lines. We went there to pick up a prize my wife won in a contest. I think that Cris Alexander from Crawford may have done an article about this in Radio World. I may be confusing it with another, but I seem to remember that it is three skirted wires, one mounted on each tower leg. I'll see if I can find the article online. It seems like after this PSSA was located far from the City of License, the FCC cracked down. After the 1460 in Racine tried to put a PSSA in Milwaukee, they wouldn't grant it, and they ended up changing the COL and moving the entire operation to near Milwaukee. Another time they cracked down was after WNZK pulled a "CHYR" with another split frequency operation on 690 Days and 680 Nights. The FCC said no more like these. They don't seem to like it when you get too clever. But from my experience, it is competitors who try to stop these kinds of things, and complain to the FCC when they do.

 

[DXBob]

WNZK appears to still have this split frequency operation, 690 kHz day and 680 kHz night:

WNZK-AM 690 kHz - Dearborn Heights, MI

6 Towers day and night.

Bob

 

[Schroedingers Cat]

It's 6 towers in each pattern, 8 towers total. One row has three towers, the other row has five towers. it uses the 3 Northern most towers of the 5 for the Day pattern, which steers the maximum to the NNW. They use the 3 Southern most towers of the 5 for the Night pattern, which steers the maximum to the NNE.

It gets too much interference from CFTR to operate on 680 Days, and on 690 Nights it would not adequately protect the CINF 690 in Montreal Class A Skywave. So that was the only way to do it.

 

[cyberdad]

Do you remember when WSUI 910 was 5 kW directional Day and Night? They then went nondirectional Day. They later moved further South, and had to decrease 20% the Night power from 5 kW to 4 kW to reduce the field toward KCJB 910 by 10%.

Did you ever see the "American Gothic' house in Eldon, IA? It was once owned by early AM DA developer and CIE Founder and Owner Carl E. Smith. He inherited it from relatives by paying the taxes as I recall. He owned it for a number of years and then donated it. Smith was from the Eldon area.

At my college location, about 45 miles due south of Iowa City, WSUI had a good signal night and day. The only diference was you could sometimes hear other signals in the background This was in the late 60s. I don't know if the pattern was similar to today, but I'm almost certain they were 5kw fulltime in those days.