KQWB (AM) Radio in Fargo, ND., is one of the first AM station to completely switch from the traditional AM band to the expanded band.  Actually they are licensed to West Fargo, but the transmitter is on the Minnesota side of the border.  

There is quite a story to be told here.   It all started in the summer of 2000 when Mark Borchert, Chief Engineer for KQWB Radio, owned by Triad Broadcasting, called to say that it was difficult and expensive to maintain the 1550 KHz 5 KW night 5 tower directional antenna system.  Daytime power  was 10 KW, but the system involved switching between the upper and lower sections of the center tower to connect the top of the tower for non-directional day and then disconnect the top of the tower when the station was running in the night pattern. 

Harsh Conditions

High voltage and harsh Minnesota/North Dakota winters meant frequent visits by tower climbers with the station off the air while they worked.  Anyone who has been to this area also knows that the wind blows almost all the time making it very difficult even to schedule tower climbers.

The station was deemed a significant interference contributor to the 1550 KHz frequency and was a prime candidate for the expanded band.  It was granted a construction permit for 10 KW day and 1 KW night on 1660 KHz both, non-directional.  

Because adding a 1660 KHz station to the existing 5 tower antenna system would have meant at least six RF filters and even more complication to the switching system, the decision was made to completely turn off 1550 KHz in favor of the 1660 KHz expanded band frequency. 

A new Harris DX-10 Transmitter was ordered for 1660 KHz.  It was installed and ready when I arrived in September of 2000.  

We turned off the 1550 KHz transmitter for the last time and got to work.  A tower climber used a strap to permanently bond the top and bottom sections of the center tower to make it a five-eights wave radiator on 1660 KHz.  

The other four towers were disconnected and I measured the antenna resistance on the new 1660 KHz frequency.  After a few calculations, we started moving components around in the center tower antenna coupling network.  This also involved removing the antenna pattern switching relay.  A few trial and error moves tuned the antenna coupling network for broadband performance. 

 Successful Switch

The new KQWB-AM 1660 KHz station was on the air by late in the afternoon with a great sounding signal.  It is running in Motorola AM stereo and serves the Fargo/Moorhead market well day and night.  The 1550 KHz is gone forever from this site. 

How how have things gone since the changeover?  Mark Borchert reports that maintenance has been next to zero.  The station now runs local sports involving cities that were in the night directional pattern nulls on the old frequency.  

The average market share for 35+ is almost exactly what it was prior to the change.  The format is nostalgia.  Mark reported having to spend some time with listeners getting them converted over to the new frequency.  That problem is past now,  now and the sailing appears to be clear for a station that had been facing financial disaster from engineering expenses.

Mark Persons, ham W0MH, is certified by the Society of Broadcast Engineers as a Professional Broadcast Engineer with more than 30 years experience. He has written numerous articles for Radio World over the years. His Web site is www.mwpersons.com

From the Radio World September 11, 2002  http://www.rwonline.com