Finding radio broadcasts in a complex terrain, such as the famous seven hills, is always a challenge of engineering. The radio wave signal, propagating in space, is subjected to multiple reflections from natural obstacles, which creates interference zones and "dead" reception zones. That is why the question of which wave dominates the seven hills requires not just a knowledge of frequency, but also an understanding of the physics of radio transmission in rough terrain.
In hilly terrain, direct visibility of the transmitter is often absent, and the reflected or envelope signal begins to play a major role. Ultrashort waves (VHF) that are used for high-quality FM broadcasts behave like light: they do not skirt obstacles well and are easily blocked by elevations. If you are in a lowland between hills, reception may not be possible without an external directional antenna, even if the repeater is relatively close.
The situation is aggravated by the fact that in different locations, called “seven hills” (whether historical centers of cities or specific residential areas), the frequency plan can differ significantly. There is no universal frequency that works equally well everywhere. You need to consider the local features of the building and relief, as they dictate which range will receive your receiver most consistently.
Physics of radio wave propagation in hilly terrain
FM radio waves (frequency from 87.5 to 108.0 MHz) are ultrashortwave. Their key feature is the distribution within line of sight. When a hill or mountain stands in the path of a signal, either the signal is shielded (the formation of a radio shadow) or its reflection occurs. In conditions of seven hills, the effect of multipath propagation often occurs, when the receiver catches both a direct signal and a reflected one from the slope.
This leads to phase distortions, which the listener perceives as crackling, hissing, or periodic loss of sound. Wavelength The FM range is about 3 meters, which makes the signal sensitive to even small irregularities of the terrain relative to the point of reception. If you are on top of one of the hills, the reception will be great, but it is worth going down into the hollow - the signal may disappear completely.
⚠️ Note: Using indoor antennas in the deep lowlands between the hills is practically useless. For high-quality reception in such conditions, it is necessary to install an external antenna at a height exceeding the level of surrounding obstacles.
In addition, air humidity and atmospheric phenomena can affect the refractive index of radio waves in the ground layer. In clear weather, the reception range may be higher than in fog or rain, when the absorption of the signal by the atmosphere is enhanced. Understanding these processes helps you choose the right place to install antenna equipment.
Broadcasting ranges: FM and VHF
The main broadcasting standards that are relevant for most regions are bands. FM Frequency Modulation and the Obsolete, but Still Founding Range OCD (65.9–74.0 MHz). The seven hills are generally dominated by FM bands, as it provides better stereo sound quality and is less prone to static interference.
However, in some remote or specific locations, older VHF transmitters can operate more stable due to a longer wavelength that better skirts obstacles. If your receiver supports both ranges, it makes sense to scan both. It often happens that on the FM-band the signal “floats” due to re-reflections, and on VHF it is kept more confident, albeit in mono-mode.
It is important to distinguish between frequency and range. Frequency is a specific value (e.g. 101.2 MHz), and range is a frequency band. The table below compares the main characteristics of the ranges relevant for setting in difficult conditions:
| Parameter | FM range (87.5-108.0 MHz) | VHF range (65.9-74.0 MHz) |
|---|---|---|
| Sound quality | High (stereo) | Medium (often mono) |
| Obstacle obliviousness | Low. | Medium |
| Level of interference | Low. | High (man-made) |
| Reception range | Depends on line of sight | A little higher due to the wavelength |
When choosing equipment, make sure your tuner supports the standard. OIRT (Old Soviet VHF Standard) or CCIR (European standard FM). Modern car radios and portable receivers often have a 50 kHz or 100 kHz grid pitch, which also affects the accuracy of the setup.
How to set up an antenna for reception on rough terrain
Setting up an antenna in seven hills is a process that requires patience and precision. The first step should always be a visual inspection of the area and search for a direction to the nearest repeater. If direct visibility is closed, you need to focus on slopes that may reflect a signal in your direction. Directional antennas ("wave channel") works most effectively here.
The adjustment process is as follows:
Install antenna → Direct to the intended source → Smoothly rotate → Record the maximum signal.
Do not rely only on the signal level indicator on the receiver display, since it often has a great inertia. It is best to assess the sound quality by ear, paying attention to the level of noise in the pauses between tracks.
If you use an aerial car, remember that the body of the car is part of the antenna system. The antennas work better when the car is in open areas. In garages or in dense buildings between hills, the signal will be shielded by metal and concrete.
☑️ Testing of the antenna system
For stationary reception in a house located in the lowlands, it may be necessary to install an antenna amplifier. However, there is a danger: the amplifier enhances not only the useful signal, but also noise. If there is no signal at all, the amplifier will only make the noise louder. So first achieve at least some reception with the passive antenna, raising it higher.
Interference problems and methods of their solution
In an area with a large number of hills, interference often occurs - the addition of waves from one source, which came in different ways, or from different sources at the same frequency. This phenomenon manifests itself as a "double" of sound or a characteristic metallic sound. Multibeam propagation The main enemy of high-quality FM reception in the mountains and hills.
There are several technical solutions to combat this effect. The first is the use of antennas with a narrow directional diagram. The narrower the antenna’s “beam”, the less reflected signals it will receive from the side directions. The second solution is to change polarization. Most radio stations broadcast horizontally, but in difficult conditions, sometimes a vertical antenna (pin) gives a more stable, albeit less loud signal.
⚠️ Note: When using antenna amplifiers with adjustable gain, do not twist the regulator to the maximum. Overloading the receiver’s input path with a strong reflected signal will lead to complete loss of sound.
Also worth mentioning is the effect of "fading" signal (Feding). When moving between hills, the signal level can drop sharply and recover. Modern digital tuners cope with this better than analog, using anti-aliasing algorithms, but in the analog FM-band, the only salvation is the RDS system, which can switch the frequency to an alternative one when reception deteriorates.
What is RDS and how does it help?
Radio Data System (RDS) allows you to transmit digital information with an audio signal. The first is AF (Alternative Frequency). If you listen to the station and the signal begins to disappear, the tuner will automatically find the same station on a different frequency, which is currently better received, and switch without breaking the sound.
The influence of weather conditions and time of day
Atmospheric conditions have a huge impact on the propagation of VHF/FM radio waves. In hot sunny weather, upward air flows with different temperatures and humidity form over the heated hillsides. This creates inhomogeneities in the atmosphere that can both focus the signal, increasing the range of reception, and dissipate it.
In rainy weather or high humidity, the absorption of radio waves by water molecules in the air increases, resulting in a lower signal level. In winter, when the hills are covered with snow, the situation can change dramatically. Snow cover perfectly reflects radio waves, which sometimes allows you to receive a signal due to a single or double reflection from snowy slopes, where in winter a direct path is closed.
The time of day also plays a role, though less so than for short waves. At night, the level of man-made noise (from industry, transport, electric lines) usually decreases, which subjectively improves the quality of reception of weak stations. However, temperature inversions at night can create distribution channels that do not work during the day, allowing stations to be caught from very distant regions, creating interference with local broadcasting.
Modern alternatives: Internet radio and DAB+
In the digital age, the question of “what wave” is gradually losing its relevance due to the emergence of alternative ways to deliver audio content. Where traditional FM signals on seven hills are jammed by shadows and reflections, a stable 4G/5G internet can provide crystal clear sound without noise or echo. Streaming It does not depend on the terrain, the coverage of the cellular network.
Technology DAB+ (Digital audio broadcasting) is also designed to solve the problems of analog ether. The digital signal is either perfectly received or not at all (the “digital cliff” effect), which saves the listener from background noise and hissing. However, DAB+ also requires direct transmitter visibility, and in the deep lowlands between the hills, reception problems may persist, albeit to a lesser extent.
Use hybrid car radios that can seamlessly switch between FM radio and Internet stream. When you enter the shade zone between the hills, the tape will pick up the stream from the net and the music will not be interrupted.
However, it is too early to completely abandon the knowledge of frequencies and the ability to configure the antenna. In remote areas, in forests and with the jamming of cellular communication (or lack of tariffing), good old radio remains the only source of information and entertainment. Knowing the frequency plan of your area is a skill that will always come in handy.
Digital technology and internet radio solve most of the problems with sound quality, but the traditional FM antenna remains the most reliable and free source of information in emergency situations and areas without cellular coverage.
Why do different stations catch on different hills?
This is due to the terrain and location of the transmitters. Each hill can screen the signal from some towers and, conversely, open direct visibility to others. In addition, repeaters are often installed at different altitudes and operate at different frequencies to avoid interference.
Can a storm damage the radio antenna?
Yes, direct lightning strikes or induced currents from close discharges can disable the receiver's incoming cascades. During severe thunderstorms, it is recommended to disconnect external antennas from receiving equipment or use special lightning-protective devices.
How often should the antenna be reconfigured?
If the antenna is fixed rigidly and it is not blown away by the wind, reconfiguration is not required. However, over time, the contacts may become oxidized and the cable may lose its properties. Preventive checks of the quality of the contacts and the integrity of the cable are recommended once a season, especially after winter.