Persons writes: It all started in 1963, when Herb Hoppe signed on
with a 250 watt AM daytimer on 800 kHz at Sauk Rapids, Minn., some 60
miles northwest of Minneapolis, in a market of 100,000 people. WVAL,
as he called it, was named after his wife, Val.
forward to 1982, when the FCC opened up the AM “clear channels,”
allowing additional nighttime service applications on those otherwise
sacred frequencies. Herb moved the station over to 660 kHz at 10 kW
by day and 250 watts by night, with four towers using a Harris
transmitter and phasor system.
had to let go of the 800 kHz frequency due to FCC ownership rules at
FCC rule change in the 1990s allowed broadcasters to have more than
one AM station in the same town. Herb applied, with the help of
Mueller Broadcast Design, to get 800 kHz back and built a 2,600 watt
daytime/850 watt nighttime facility in 1996, using a new Nautel
transmitter and phasor from Kintronic Labs, this time with two towers
during the day and three towers at night, “diplexed” to share the
same towers as 660.
right: Two AM stations feeding the same towers at once.
practice is becoming more commonplace nowadays, as real estate values
and construction costs have risen, but at the time it was not as
widely done by owners and station engineers. The 660 kHz became
WBHR(AM) sports talk, and 800 kHz got its original WVAL call sign.
country fiddle music, as it was broadcast in the 1960s, was heard
again on 800, to the delight of listeners and the station’s
son, Gary, became involved and saw an opportunity in the 2004 AM
Auction 84 filing window to add to the mix. He applied for 540 and
1010 kHz during the window and got approval for 1010 first. This
required building three more towers and “triplexing” three
stations into most of the same towers with two patterns. (It’s 1.7
kW into three towers daytime and 240 watts into four towers
one is WMIN(AM), a great call for a Minnesota station that had been
used on 1010 in the Twin Cities prior to its move to 1030 and then
again with the help of Mark Mueller, they added 540 kHz with 250
watts using four towers by day and three towers at night. This one is
WXYG(AM) and now it is “quadplexing.” Engineering got more
complicated, but still workable. With such a low frequency, the
coverage is phenomenal. Did you know that 250 watts on 540 is almost
equal to the coverage of 50 kW on 1600 kHz in areas of low ground
made all of this economically feasible was that no more land was
needed to add three towers and three stations to the first one. The
original 40 acres of land was enough. A new and much larger
transmitter building was constructed to hold the additional
transmitters and phasing systems, but that was an interesting project
was involved in most of the onsite engineering work, but most credit
should be given to Mark Mueller for the design and tuning of this
masterpiece of a system.
original WVAL ITA AM-250A Transmitter was converted from 800 kHz to
be used as a backup on 660 kHz and then converted again as a backup
for 1010 kHz. Each time, it performed flawlessly and is still working
after more than 50 years.
because it is a tube transmitter, it was able to handle huge amounts
of reflected power while each new directional array was tuned. Only
after the tune-up were solid-state transmitters brought online.
Mueller continues: In 1995 the client asked if he could have his
old frequency back now that the FCC allowed broadcasters to have more
than one AM station in the same town. After a bit of analysis, I
determined that the answer was a big yes.
had moved to 660 kHz in the 1980s but was originally on 800 kHz with
250 watts non-directional day but no night authority. My study showed
that 2,600 watts day and 850 watts night was possible, but both would
need to be directional. Hmmm, where could the transmitter site be
the client already had four towers on a huge piece of property, just
outside of town, that was being used for 660 kHz, and the ground
system was more than large enough, plus the tower heights and
spacings would work fine on 800 kHz. FCC filing windows were still in
the future so an application for a new station on 800 kHz was
tendered in January 1996 and granted by the FCC in 1997.
Labs built the phasor, antenna coupling networks and diplexing
filters to keep 800 from interfering with 660 kHz and vice versa.
Mark Persons did the installation and I tuned and proofed the system
with both stations happily running into the same set of towers.
can be a great solution for where to locate a station. No new land
was required and the transmitter building was just (barely) large
enough to house two phasors along with main and auxiliary
transmitters for each. WVAL returned to 800 kHz in March of 1999
while 660 kHz became WBHR.
as often happens, clients see opportunity in expansion and with the
WVAL addition to WBHR proving that it could be economically done, the
question of whether additional frequencies were usable from the site
came up. Two were found, and the story continued with the 2004
Auction 84 AM filing window and the addition of the two stations.
more towers were built on the same piece of land to optimize the
patterns and make it all work out right. 1010 was granted first in
2005 and implemented in 2008, while 540 was granted in 2007 and
constructed in 2010.
was an interesting challenge keeping up with this unique project, as
there are no other four-station directional antenna arrays to compare
it with. Having three of the four stations on the lower end of the
band helped in some respects, like keeping stray inductive reactances
from the interconnecting tubing under control, and hindered in
others, as when low drive-point impedances were encountered on WXYG.
order to minimize the potential for unpleasant surprises, the tower
houses were rebuilt to hold all of the equipment, which was then
installed as a unit instead of piecemeal additions to each existing
array. Close attention to grounding and component layout minimized
interaction between stations and allowed the system to perform with
no significant interaction or cross products.
are more than 50 pass-reject filters in this system, since none of
the stations use all seven of the unused towers, which are detuned
through the filters.
entire system had already been modeled for the design, and
development around the site was affecting existing monitor points, so
MoM (Method of Moments) antenna proofs were done on all four
stations. It has been well over a year since the last station was
added and there have been very few maintenance problems, not bad
considering four stations are sharing the same site.
client is happy and I am also very pleased that this kind of setup
can and will work.
Persons, WØMH, is a professional broadcast engineer
certified by the Society of Broadcast Engineers. He has more than 30
years of experience and has written numerous articles for industry
publications. His website is www.mwpersons.com.
Mueller has been a broadcast technical consultant specializing in AM
directional arrays for 30 years and can be reached at Mueller
Broadcast Design, in La Grange, Ill., by visiting the website