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Help with KGNU's FM signal
Help receiving with an FM radio
KGNU's main FM signal covers Boulder County and a little beyond.
Due to the low power of KGNU's main FM signal, many people outside of our main coverage areas find it difficult to tune in.
Therefore, we would like to suggest some options for improving KGNU FM reception at home.
Turn the antenna:
KGNU's main FM transmitter is at the top of Davidson Mesa, off South Boulder Road, in Louisville.
Turn the radio's FM antennas so that it faces our transmitter.
Buy an FM directional antenna:
Radio Shack and hardware stores carry antennas and information, as do a number of independent antenna suppliers and installers.
Radio Shack's best directional FM-only antenna costs only $17.
Radio Shack has a booklet titled "Antennas: Selection and Installation" which is a good resource for any questions on private installation.
Adding an amplifier ($20-$60) may be helpful, but can't do much if it doesn't have a decent signal to amplify in the first place.
Make your own FM antenna:
If you want, you can make your own FM antenna.
Listen in your car.
Not only are car radios better radios, but they get a better signal just by virtue of being outdoors.
Use a car radio in your home.
Some listeners have converted car radios for home use.
For those of you who have attempted to get a listenable signal through antenna and antenna amplifier modifications to no avail, there is another potential solution which may succeed.
Obtain an automobile FM receiver, speakers and antenna which have been designed, built and intended for automobile installation, plus a 12 volt DC power supply.
The last item converts household electric current from 120 volts AC to 12 volts DC.
The power converter makes it possible to use the automobile receiver inside your home without having an attached auto taking up all the room in your kitchen or bedroom.
The reason for using an automobile receiver is that they are usually built with more sensitive radio receiving capabilities.
Although the receiver would be installed inside your home along with the power converter, the antenna should be outside your home, as high as the top of your roof if possible.
If a television and FM radio antenna is already installed on your roof, it can be connected to the automobile receiver.
WARNING! Roof top antennas of any sort should have lightning protection.
Those with basic mechanical and electrical skills and knowledge should find this project familiar and easy to accomplish.
Those likely to achieve success with this plan are those who are able to receive a listenable signal while in their automobile as it's parked their driveway, street or parking lot adjacent to their dwelling or workplace.
Some sources of automobile receivers are the typical auto stereo retailers and auto salvage yards, the latter being a potential source of very inexpensive receivers.
Power converters are available from Radio Shack.
Hook your radio to your CATV cable:
If you have cable TV, contact your cable company to see if they carry KGNU.
If so, ask at what frequency, and connect your radio to the TV cable, using a splitter.
If not, please ask them why not, and also please let us know what they tell you.
(KGNU does not receive any funding from any cable operators.)
Reduce interference from electronic devices
Over the years, KGNU's FM signal has been battered by background noise from more and more devices such as computers.
Try reducing that intereference.
- Try moving the radio's antenna.
- To identify which device causes the intereference, turn off each electronic device in your home, one at a time. After turning it back on, reposition it or its cables to see if it makes a difference. Radio Shack sells clamp-on ferrite filters; place themon the cables of the offending device.
- If the interference comes from your neighbors, their equipment may be in violation of FCC rules. Talk to your neigbhors first.
Recognizing interference from other radio stations
Over the years, other radio stations have encroached on KGNU's FM signal.
New stations have gone on the air, others have increased their power, and even pirate stations have gone on the air with sloppy signals
- Listeners in South Denver may get interference from KJME (88.7 MHz) in Manitou Springs, since they increased they power (which is totally legal)
- Cheap radios in Central Boulder may get overwhelmed by KRKX (94.7 MHz) which dumps a whopping 100 KW of Xtian programming, concentrated in a very narrow beam, from Lee Hill towards Denver (this is also legal).
- On occasion, listeners in the mountains have received 88.5 MHz from Dove FM, a Xtian station in Michigan! This can only be due to really freaky enviromental conditions.
- Please identify the station. If it's a legal station, there's nothing we can do. If it's a pirate, please let us know as soon as possible, so we may deal with it
Dealing with changes in the signal strength
We often get calls from listeners who no longer get a clean signal.
The strength of our signal is kept very constant, so we don't believe that's the reason.
- Changes in the weather do make a difference: snow or even wet Flatirons. These should be self-correcting
- If the quality of your signal is reduced and remains reduced, it may be because something changed in your immediate surroundings: a new source of interference (see elsewhere in this page) or your antenna changed (connections or orientation).
Alternatives
KGNU streams its signal on the Worldwide Web
An alternative to our broadcast signal is our internet streaming.
Please check the Listen page.
KGNU broadcasts at 1390 AM as well
The quality of the sound in our AM signal is not as good as our FM signal, but in the daytime the AM signal's coverage is wider.
We want to meet your needs as our listeners, and involve you in this unique form of independent media and communication that KGNU is.
We hope these options provide you with viable solutions to your present reception difficulty.
Please Call us or email us if we can be of further assistance.
Dealing with intereference from our FM signal
Premise.
KGNU broadcasts legally as authorized by the FCC.
Any interference to your equipment from KGNU is your responsibility, not KGNU's.
However, as a gesture of good will, KGNU may help you mitigate such interference to your equipment.
The frequency of 88.5 MHz is adjacent to the frequency of the audio of TV channel 6.
Normally, this is not a problem.
However, in the '70s, TV sets were manufactured with reduced selectivity (the ability to reject undesired signals near the desired one).
Boulder is one of the few areas in the country where the FCC allowed both a radio station at 88.5 MHz (KGNU) and a TV station on channel 6 (KRMA).
In the '70s many KRMA viewers using new TV receivers, in outlying areas, received interference from KGNU.
As a solution, KRMA installed a translator in Boulder on Channel 11, and KGNU reduced its power from 3500 W to 1300 W.
In addition, KGNU offered filters to KRMA viewers who requested them.
Today, the issue is pretty much gone, thanks to better TV receivers, the KRMA translator, and people's use of cable TV.
Should you experiece interference from KGNU while tuned to KRMA Channel 6, please install an "FM trap" filter, available from Radio Shack.
If you experience interference in some other way, and you are in Englewood, then it's interference from our AM transmitter.
Making your own antenna
There is a simple, homemade antenna that can pull-in your favorite station.
(excerpted from an article by Harry Roach)
FM (frequency modulation) stations broadcast between 88 and 108 MHz (MegaHertz), the same numbers printed on your FM dial.
This 20 MHz spread is a fairly narrow "window" in the spectrum of available radio frequencies.
To receive it well, try a T-shaped antenna made of 300-ohm lead-in wire.
The critical segment of this antenna is the crossbar of the T.
The vertical tail of the T is not important.
For your antenna to pick up the full width of the FM band the crossbar of the T should be 4 feet , 9 inches long.
That length will give good reception across the FM dial.
If you wish to zero in on a particularly weak station, however, you must resort to a little math to alter the length of the crossbar.
The formula is simple: divide 468 by the frequency of the station in MHz.
The result is the length of the crossbar in feet.
For 88.5 MHz, that length is 5' - 3.5".
For 89.1 MHz, that length is 5' - 3".
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Were did the number 468 come from? It is a mathematical constant and used by engineers to design television antennas.
It is based on the relationship between a signal's frequency, its wavelength and the velocity of light (frequency x wavelength=velocity of light).
A dipole antenna works the best if its length is about 5% shorter than the wavelength of the signal is designed to receive.
For the ease of construction and other practical reasons, antennas are more commonly made to measure half the wavelength of the signal (minus 5%), and that's the length you get when you divide the frequency in 468.
What we are making is called a half-wave, folded dipole antenna.
Designing your antenna to zero in on a particular FM station will not exclude other stations.
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Making your own antenna is simple.
You will need the following materials: small wire cutters, plastic electrical tape, magnetic compass, road map, hammer and tacks, soldering iron (helpful but not essential), 300-ohm lead-in wire (this is standard FM radio and TV wire, available in radio supply stores for 30 cents a yard) and 6 feet of 1/2 by 2 inch wood lath.
The 300-ohm wire consist of two stands of copper wire held parallel
to each other by the plastic body of insulation (Figure 2).
Cut the horizontal crossbar of your antenna to the desired length, but with an extra inch at either end.
Use the wire cutters to strip the plastic away from the extra inch at either end, exposing the wire.
Twist the exposed wires together at each en, solder them if you wish, then wrap each end in plastic electrical tape.
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Find the center of the horizontal crossbar just above the lower wire, cut a 3 inch slit with a sharp knife (Figure 3).
Be careful.
Now use the wire cutters to cut the lower wire in the middle of the slit you made with the knife.
Bend the wire down and strip off the plastic (Figure 4).
Now you are ready to attach the vertical tail of the T to the horizontal crossbar.
Strip an inch of plastic off one end of the vertical tail as you did with the ends of the crossbar.
Then twist each wire together with its corresponding exposed wire in the middle of the crossbar (Figure 5).
I solder each twist for added strength, but you needn't bother with this if you make sure the wires are securely fastened together.
The left and right wires should not touch.
Carefully wrap each wire with electrical tape.
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Now tack or nail the horizontal crossbar to a thin strip of wood to give it rigidity.
I used an old 6 foot length of 1/2 by 2 inch wood lath.
A long pole will do just as well.
The length of the tail is determined by the location of your horizontal crossbar.
If you want to attach the crossbar to the ceiling above your FM receiver, the tail will be 8 to 10 feet long, depending on the height of your ceiling.
The higher you put the antenna, the better your reception will be.
I put mine on the roof, so I used about 10 yards of tail.
The wire runs down the outside of my house and in a window to my receiver.
Any antenna placed on a roof should be equipped with a lightning arrester.
At the FM receiver end of the tail, strip off an inch or two of plastic and attach one wire to each of the two FM antenna terminals on the back of the receiver.
I use spring clips, but you can simply twist each wire around each terminal.
Be sure the wires do not touch.
In placing your antenna, it is important that the horizontal crossbar be perpendicular to the line of broadcast from the FM station you wish to receive.
Determine the line of broadcast on a road map.
Maximum range for an FM antenna varies depending on the power of the station, the intervening topography and the orientation of the antenna.
Mountains cam make radio waves bounce around, setting up echoes that interfere with reception, and they can also block FM waves entirely.
But radio waves are unpredictable: the antenna might work wonders.
Specific data for 88.5 Mhz: Full wavelength= 321.8111318cm, or 10 feet, 6.697 inches.
This would make the half wavelength 5 feet, 3.348648 inches or about 5 feet, 3 1/3 inches.
Specific data for 99.9 Mhz: The full wavelength is equal to 300.092568cm.
Subtracting the recommended 5%, this becomes 285.0879396cm or 9 feet, 4.2393463 inches.
The half wavelength is 4 feet, 7.11967315 inches, about 4 feet 7 1/8 inches.
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