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WWTC Moves in with KKMS by Mark Persons |
Radio
World Article April 10, 2019 |
| Sharing AM towers makes sense for these stations It is
happening more and more with property values going up. AM stations are
sharing transmitter sites with other stations for the benefit of both.
Case in point; Salem Media Group just combined two of its stations in
the Twin Cities market of Minneapolis and St. Paul. Salem is a Christian
based network of 115 stations nationwide with four signals in the Twin
Cities. |
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Fig. 1: The KKMS radio towers point north into the metro. |
| The Site Fig. 1 shows towers at the 980 KHz KKMS site in Eagan, a south suberb of the Twin Cities. It was a prime candidate for diplexing two AM signals. All four towers are now used for both stations. No new towers were added and no changes were made. Tower lighting power is via Austin brand isolation/lighting transformers, commonly called Austin Rings. Lighting chokes can change tower impedance a bit. Ring transformers don’t have that problem. All patterns point north-northeast. The study showed WWTC would lose a little coverage to the west, but would gain in high population areas. For perspective, most AM directional patterns in Minnesota point north with nulls to the east, south, and west, protecting existing stations in the U.S. This site, on the south side of the market, makes a lot of sense. Tight Schedule Steve Smit, engineer at Salem in the Twin Cities, was a busy man on this project. First there was a year of planning. Then construction started in late summer of 2018. There were 95 degree days in September, followed by 40 degrees two weeks later. This is Minnesota! Steve had to manage this new work while doing all the necessary engineer duties required to keep four stations running. |
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Fig. 2: Water half-filled trenches to the towers |
| Slip Sliding Trenches were dug to each of the four towers at a depth of 4-1/2 feet. Fig. 2 All was going well until three inches of rain drenched the site causing trench bank cave ins. The top layer of coushioning sand was washed away in places. They had to dig to recover the transmission lines, sample lines, control lines and power cables by clearing away debris and rocks. Sand was then put in again before final trench closure. The soil is a mixture of clay, field stone and sand that was very greasy and slippery after the rain. What a mess, but they got it done. |
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Fig. 3: One of the three-bay tower cabinets |
| The Phasor Kurt Gorman and crew at Phasetek, Inc. in Quakertown, PA, rebuilt a used phasor from Salem’s 1300 KHz KKOL in Seattle, WA. They were also able to reuse some parts from other Salem network stations. Fig. 3 The antenna coupling unit/filter cabinets were new, but again benfited from some used components inside. Concrete pads were poured at each of the four towers to support the 4 ft. x 3 ft. x 12 ft. cabinets containing antenna coupling networks and filters for the two stations. Fences had to be rebuilt to accommodate the change. Fig. 4 shows the newly
constructed antenna coupling network for KKMS. You will note there is no
RF contactor to change from day to night patterns. That station has just
one pattern with the same 5 KW power for day and night. That is very
convenient! Fig. 5 is an antenna coupling network for WWTC. The center
bay, of each 12-foot cabinet, is a combining network, which is seen in
Fig. 6. All nicely done. |
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Fig. 4: The KKMS antenna coupling network |
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Fig. 5: WWTC’s coupling network |
| The Building The station was built in the 1960s for one AM with the possibility of an FM in the future. All equipment was on the main level. No thought was given to expanding. Fortunately there is a basement, as is the custom in almost all Minnesota buildings. The basement area was rebuilt to accommodate two transmitters and the WWTC phasor system. Wiring had to be bored through cast concrete walls and air conditioning was installed. The Transmitters A used Harris 3DX50 Transmitter was brought in from KKOL, 1300 KHz in Seattle, WA, then tuned to run on 1280 KHz at 10 KW day and 15 KW night. It is loafing along in this application. Interestingly, Steve had helped install that transmitter, back in 2005, when he worked out there. This transmitter was built to run on 480 volt three-phase power. So, new electrical service was added for it. The list of items to be completed went on and on. |
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Fig. 6: The combiner network just before final hookup |
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Fig. 7 shows Steve Smit checking the WWTC common point impedance on the
newly rebuilt and operational phasor. To his back are a Nautel ND-5
backup transmitter, from WWTC’s original transmitter site. There is also
an equipment rack and the Harris 3DX50. |
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Fig. 7: WWTC transmitters and phasor |
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Fig. 8: The KKMS transmitter room |
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Fig. 8, The KKMS transmitter and phasor room remained the same. Steve is
seen checking readings, at the phasor, with two Gates 5 Transmitters as
alternate mains. This is a good arrangement with two equally-capable
transmitters that substitute for each other on a regular basis. |
| MOM RF Method of Moment proofs were performed several years ago by Tom Jones and this time were proofed by Kurt Gorman. MOMs, as you know, avoid frequent monitor point measurments on the pattern for KKMS, along with day and night monitor point readings at WWTC. Of particular importance were monitor points on the somewhat restrictive WWTC night pattern. They had to be read during the day, resulting in some listener complaints. Kurt Gorman filed the FCC paperwork. Approval was granted in early January 2019. The stations are 100% operational and the staff is happy to have this project completed. The timing was good. Temperatures dropped to 30 degrees below zero (actual temperature) for several days later in January. You wouldn’t want to work on an AM under those condtions! Programming It is not all automated or from a bird. About 25% of aired material is locally producted for the four Salem stations in the Twin Cities. They find it is important to be connected with listeners, via live talk, in the market. There’s More KDIZ, the 1570 KHz non-directional station, moved from the west site, to KYCR’s three-tower transmitter location in Golden Valley, MN, in March 2019. Salem owns that one too. It was just one more combining project for Steve Smit. Michael Patton of Michael Patton & Associates in Baton Rouge, LA, was hired to retune the 3DX50 transmitter for WWTC and a Nautel ND-5 transmitter for KDIZ. In the end, Salem consolidated three transmitter sites down to just two, each with two stations. Studios are all at the KKMS/WWTC site where Steve’s office is. Very convenient. Comment on this or any article. Write to
radioworld@futurenet.com.
We're always looking for good facility project stories to share. |
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This is a reprint of the article which appeared in the online version of Radio World at: https://www.radioworld.com/tech-and-gear/tech-tips/wwtc-moves-in-with-kkms |
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Questions? Email Mark Persons: teki@mwpersons.com |
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