FM Reception Tips
Use the right equipment-- the right way.
From time to time, we receive a request from a listener asking what can be done to improve their reception of WHFC's signal. While the specific recommendations will vary, the following are some generalizations which may help if you are experiencing reception difficulty.
It must be remembered that the process of delivering sound from a radio studio to your ears involves a complete system. This includes the station's transmitter and antenna, the listener's receiver and antenna and the transmission path between the two. This last is important because if there is a large hill between the transmitter and receiver, there is nothing that can be done to provide good reception.
At FM frequencies, reliable reception does not extend far beyond the horizon line as viewed from the transmitter. This is why FM and TV transmitters have very tall towers or are located on mountaintops. It is also why FM and TV receiving antennas are best situated on tall masts.
Steps to improving your reception should start with the antenna. If your receiver is a stereo component or console, there should be a pair of screw terminals on the back marked "FM antenna" or something similar. If nothing is connected to these terminals, you need an antenna.
A word about impedance: FM receivers (except most portables) have provisions for connecting an external antenna. The screw terminals mentioned above are intended for 300-ohm impedance twinlead and 300-ohm antennas. Another type of antenna connection might be a 75-ohm F-type connector jack, which requires that 75-ohm coaxial cable and a 75-ohm antenna be used. It is important to remember that maximum signal strength is passed from the antenna to the receiver when all impedances are matched. If the antenna, cable and receiver impedances are not matched, the received signal will be degraded. If you must use a 75-ohm antenna with a 300-ohm radio, you must insert a small matching transformer (called a balun) between the coax cable and the radio screw terminals. Matching transformers are readily available at your local Radio Shack, Home Depot, Circuit City or other electronics stores.
An antenna may be as simple as an inexpensive "twin-lead dipole" which can be purchased at most electronic or builders supply stores. This will only be effective in the primary coverage area of the station, about 20 miles or so from the transmitter. Ordinary TV "rabbit ears" will work reasonably well in this area as well, with the rods extended out to 31 inches from each side of center.
Non-directional (omni-directional) outdoor antennas, such as "turnstiles" and "S-shaped" may be helpful in many instances and usually give better results than any type of indoor antenna. But if eliminating multipath and/or interfering stations is the goal, an omni-directional antenna may not help. Only directional antennas can attenuate signals from unwanted directions, such as reflections from nearby hills or buildings, or an adjacent frequency or same-channel interfering station.
For fringe-area reception, an outside antenna similar to a TV antenna is required. In fact, some TV antennas can be used for FM reception. If your VHF TV antenna is equipped with a rotator, you may experiment by connecting it to the antenna input of the FM receiver and aiming it at the WHFC transmitter site located at Harford Community College about 5 miles east of Bel Air on Route 22.
If this experiment works satisfactorily, a splitter can be purchased to connect both the TV and FM receivers. If the trial does not produce improvement, it is possible that the TV antenna is of the type designed to reject signals in the FM band.
For simultaneous reception of TV and FM, a good outside FM antenna (called a Yagi, after its inventor) can be purchased at most consumer electronic stores. This should be mounted on a mast as high as practical. If there is an existing TV antenna, an FM Yagi antenna may be mounted on the same mast, a few feet away from the TV antenna.
In extreme fringe areas it may be necessary to use more than one Yagi antenna, vertically or horizontally stacked, for more signal pickup.
One type of FM antenna that is especially unobtrusive and easy to mount on a house is a wavelength vertical. The vertical antenna consists of a 56-inch stainless steel rod with an impedance-matching coil and mounting clamp at the base. A vertical antenna is non-directional and should be mounted up in the clear, away from obstructions. With the vertical antenna, reception should be satisfactory for local and regional stations, but keep in mind that it cannot attenuate signals from unwanted directions.
Antennas should not be placed near or behind metal of any type, including gutters, aluminum siding, metal furniture, electrical wiring, the "guy" wiring that secures an outdoor antenna mast, etc. Metal objects can reflect signals and create unwanted multipath distortion problems or detune the antenna by their proximity, reducing its efficiency.
Apartment dwellers that cannot erect a mast and antenna may wish to purchase an indoor amplified antenna. Hint: for new home construction in areas with antenna restriction covenants, you might consider placing a twinlead dipole antenna on the sheathing of an outside wall before vinyl siding is applied. The lead-in from the dipole may be passed through a hole in the sheathing and can be any length. After the vinyl siding is up, no one will be the wiser.
Before purchasing any antenna or receiver, it would be a good idea to make sure that it can be returned to the dealer if it doesn't perform well at your particular location. If you have any questions, I will be happy to discuss them with you. Send an email or snailmail to me at WHFC and I promise to respond. Happy listening!
David May, Host of Desert Island Jazz