As part of
the FCC’s Revitalization of the AM Radio Service efforts, the FCC directed its
Media Bureau to “…open two FM translator modification application windows for
AM stations to modify and/or relocate FM translator stations.” This allows an
AM broadcaster an opportunity to acquire and relocate one authorized
non-reserved band (92.1 MHz–107.9 MHz) FM translator station up to 250 miles.
The “First Modification Window,” for Class C and D AM stations, is from
January 29, 2016 to 11:59 EDT July 28, 2016. The “Second Modification Window,”
for all AM stations, begins July 29, 2016 and ends at 5:59 PM EDT October 31,
2016. The FCC Public Notice DA 1491 describing the process and scope can be
read at: https://apps.fcc.gov/edocs_public/attachmatch/DA-15-1491A1.pdf
Cris Alexander writes
about his experiences preparing his station’s applications for the First
Modification Window, which readers may find useful for their preparation.
This year marks my 41st year in this business, and until
this January, I had never had any direct dealings with translators.
That might seem a little strange, but the fact is that neither the opportunity
nor the need existed until then.
As a result, I had to get up to speed fast. The FCC released
its order announcing the AM translator windows late in 2015, and because of the
way they had set up the translator filing “windows,” they were actually more
like derbies – first come, first processed. That meant the race was on, with a
January 29 window opening that really amounted to a deadline.
I had for decades been doing allocations work for
commercial, full-power FM, so I am no stranger to the principles of contour protection
that we use for translators. I quickly learned, however, that there are a lot
of ins, outs, policies and somewhat obscure rules that are very familiar to
engineers who do translator work, but of which I had little or no knowledge.
For example, in full-power FM work, contour overlap must be
considered in both directions – interfering contours of both proposed and
protected stations cannot overlap protected contours of protected and proposed
stations. In the translator world, because there is no “protected” contour of a
translator, overlap of what would be the protected contour by an interfering
contour is not considered.
Translators are, however, protected from other translators.
If I want to put a translator near a licensed translator, a translator CP or
application on file on the same or an adjacent channel, the “protected” contour
very much comes into play just as it would with a full-power FM.
And then there are second-/third-adjacent protections. Under
the translator rules, if there is no population within the +40 dB overlap area,
you can ignore second- and third-adjacent channel protections. (This is also
true of other translator overlap situations, but it mostly comes into play in
Quite often, the +40 dB interfering signal value won’t reach
the ground, and since it’s highly unlikely that anyone lives in a point in
space up inside that “contour,” that means zero population. The net effect of
this rule is that the closer a translator’s site is to a second- or
third-adjacent channel station’s site, the better. Someone once told me the
best place for a second-adjacent translator is collocated with the other station.
I didn’t understand that then, but now I get it.
To further confuse things (in a good way), 10.6/10.8 MHz IF
short spacings can be ignored if the proposed ERP of the translator is “less
than 100 watts.” That’s why you find so many 99-watt translators.
1: Yagi antennas such as this Scala HDCA-5H are
used for translators.
Working in the Canadian and Mexican border zones, things get
really interesting. You’d better have a good copy of the treaties and read them
carefully before you start trying to site a translator in one of these areas.
There are different rules for each country that must be complied with.
Translator antennas are a whole new world. There are many
more options than we are used to in the full-power FM realm. In addition to run-of-the-mill
single- and multi-bay dipole arrays, you can use yagis (as in Fig. 1), log periodics, and phased/offset
arrays of multiple yagis and log periodics. The 15 dB maximum-to-minimum ratio
and 2 dB/10 degree rules do not apply.
The FCC database contains many “stock” antenna patterns that
you can use and specify the rotation that fits your situation, or you can “roll
your own” and key in a custom composite pattern.
You can pretty much do what you want with regard to antennas
in the translator world, but there is one caveat: The antenna is specified on
the station license, so you can’t simply replace one with another, even with a
non-directional antenna, without further FCC authorization, as you can in the
full-power FM world. You have to file a modification application and get a CP
first. Based on what I’ve seen out there, I’m certain a lot of licensees don’t
observe this requirement.
THE REAL WORLD
2: Many translators operate from shared sites
as this one on
Lookout Mountain. Can you spot all the translator
Once I got a stack of construction permits (CPs) and started
working on actually building the translators out, I learned a lot more. In a
lot of ways, translator installations are much simpler than full-power station
installations, but there are site considerations and rules that must be taken
Many translators will be located at a shared site, and if
the shared site is home to other FM translators or full-power stations, some
filtering will almost certainly be required to prevent IM products from being
generated and transmitted. Fig.
2 shows a potpourri of translator antennas on Denver’s Lookout Mountain.
A lot of translator power amplifiers are broadband for frequency agility, and
this makes filtering all that much more important. Better check with the
manufacturer to find out what kind of rejection is needed to keep from
producing and transmitting unwanted signals.
The “newcomer doctrine” is a longstanding FCC policy that says
the newcomer to a site is responsible for fixing all the interference issues
that arise as a result of the newcomer’s operation. That means that you may
have to buy filters for some of the other site users as well as for your own
transmitter. It’s definitely something to pay attention to, especially if your
antenna will be in close proximity to another station’s antenna. Many site
lease agreements also contain a requirement as such. Fig. 3 is an example of a filter isolating
a high power FM from a low power translator.
3: Filters are often required at multi-user
if there are full-power FM stations at the site or
filter provides 70 dB of rejection at 1.6 MHz to take care of a
kW station on one side and a 100-watt translator on the other.
Of course, getting to the people responsible for operating
and maintaining other translators at a shared site can be a challenge in itself.
The FCC rules require that a posted sign, like one in Fig. 4, to be mounted on the antenna
support structure. The sign identifies
the translator and provides the name, address and phone number of the licensee
or local representative. That rule is not always followed, and even when it is,
signs can fade or be blown off the tower. The landlord or site manager may be
the best source of contact information on other site users.
In my travels of late, I have seen all kinds of “funny
business” with translator installations, such as directional antennas going the
wrong way and unlicensed antennas. While in most cases this kind of thing won’t
significantly impact other site users, sometimes it can. The FCC’s database and
online FM Query search tool is an excellent way to pull up information on other
licensees, including copies of their licenses or other authorizations. It
doesn’t take long to figure out what antenna, ERP, height and location a
translator station is supposed to have.
4. FCC rules require signage identifying the
and providing local contact information.
One other thing I have learned is that open frequencies are
a breeding ground for pirate stations. Naturally, pirates and even legitimate
Part 15 broadcasters want a clear frequency, and if there is an unused channel
in a community, that’s where they’ll be. It’s a good idea to begin listening to
a frequency weeks before putting a new translator on the air to make sure that
there aren’t other signals there, authorized or otherwise, that will cause
As I was preparing to put a new translator on the air on an
empty channel in Denver, I started listening to the channel and heard a very
strong signal airing a very eclectic music mix complete with time and
temperature announcements. The signal was listenable for miles in any
direction, suggesting something other than Part 15 power. We DFed the signal to
a house in a neighborhood and could clearly see the ten-foot vertical whip
antenna in the back yard.
Some neighbors saw me walking up and down the sidewalk in
front of the house with a spectrum analyzer and yagi antenna pointed at the
house. I called the local FCC office and they sent an agent out the next day.
He confirmed the pirate’s location, but by then, undoubtedly alerted by
neighbors, the operator had powered down to Part 15 limits. I sent a
politely-worded letter to the resident advising him that a licensed translator
would soon be coming on the air on the frequency he was using and I asked him
to find another spot. A couple of days later the signal went away and hasn’t
A couple of weeks after that we began getting reports of a
strong pirate signal on our frequency up near Boulder – we knew it was a pirate
signal because a voice identified the station as “Pirate Radio!” We DFed that
one to a one square mile area in the densely populated hilly neighborhoods on
the west side of Boulder and handed it off to the FCC. As of this writing we
are still waiting on remedial action.
Translators and boosters can be a wonderful means of
providing a quality 24-hour signal for an AM station or filling in coverage
gaps caused by terrain shielding. They broadcast a signal just like full-power
stations, but the arena in which they operate is completely different. It pays
to become familiar with Subpart L of Part 74 of the FCC rules and spend some
time with folks that are very familiar with translator installation, operation
and maintenance. You’ll be up to speed in no time.
“Cris” Alexander is director of engineering at Crawford Broadcasting Co. and a
longtime Radio World contributor. He is an SBE Fellow and past recipient of the
Robert W. Flanders SBE Engineer of the Year award.