VHF-Band Band Pass Filter – The Main Importance of VHF Signals in Communication
AWG Tech has a wide range of VHF-band band pass filters. The passband frequency of our VHF-band bandpass filter can be anywhere from 30MHz to 300MHz. VHF-Band filters are typically LC filters, but we have employed other filter technologies like cavity filters for some of our VHF-band band pass filters.
The table below shows a sample of the VHF Bandpass filters that we have. This is not a complete list. Contact us if you need filters with other center frequencies and bandwidth.
| Part Number | Center Frequency (MHz) | Frequency Range (MHz) | Insertion Loss (dB) | Rejection (dB) |
|---|---|---|---|---|
| ABPF-50MBW10M-001 | 50 | 45 – 55 | 2.0 | 50 dB @ dc – 22 MHz 50 dB @ 80 – 200MHz |
| ABPF-100MBW20M-001 | 100 | 95 – 105 | 3.5 | 30 dB @ dc – 75 MHz 30 dB @ 120 -500 MHz |
Band Pass Filter: What are they?
Band pass filters can be a combination of both a low pass filter and a high pass filter. The name suggests that it permits only a particular frequency band and impedes every remaining frequency. In audio applications, there are times that it’s required to pass only a certain frequency range – this range doesn’t start at 0Hz nor does it end at a very high frequency. However, these frequencies are within a particular range, either wide or narrow. These frequency bands are commonly known as Bandwidth.
There are bandpass filters that use VHF signals to operate; these are the VHF-Band band pass filter. These filters are commonly used in FM radio and television broadcasting, for two-way land mobile radio systems and for long range data communication up to several tens of kilometers with radio modems and marine communications.
Before that, let’s first see the circuits of these filters.
Band Pass Filter Circuitry
Unlike a low pass filter that only lets low frequency signals pass through, or a high pass filter which pass higher frequency signals, a band pass filter passes signals within a particular “band” or “spread” of frequencies without disrupting the input signals or introducing extra noises. This frequency band can be of any width and is usually known as the filter’s bandwidth.
The “perfect” band pass filter can also be utilized to seclude or filter out specific frequencies that lie within a certain frequency band, noise cancellation for example. These filters are generally known as second-order filters (two-pole) due to them having two reactive components, two capacitors each located on the low pass and high pass circuits.
VHF Frequencies: What are they and what is their propagation characteristic?
VHF (very high frequency) signals is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) ranging from 30 MHz to 300 MHz, with wavelengths of ten to one meters. Frequencies below such are labelled as high frequency (HF) and above it are known to be ultra-high frequencies (UHF).
The VHFs propagation traits are suited for short-distance terrestrial communication, with a range that’s basically somewhat farther than line-of-sight from the transmitter.
- VHF waves are restrained to the local radio horizon for 100 miles or less.
- VHF is least likely to be affected by the atmospheric noise from electrical equipment than lower frequencies.
- While being impeded by land features like hills and mountains, it’s less affected by buildings and frequencies can be received indoors, although multipath television reception due to building reflections can be a huge problem in urban areas.
- Unlike high frequencies (HF), the ionosphere doesn’t usually reflect VHF waves (termed as sky wave propagation).
- VHF waves can be amplified by tropospheric ducting.
VHF Frequencies and Antennas
VHF is the first band which frequencies are small enough to make effective transmitting antennas for vehicles and handheld devices. Thus, it would result that the VHF along with the UHF wavelengths are utilized for two way radios in vehicles, aircrafts and hand-held transceivers. Portable radios usually use whips or rubber-made antennas, while base stations usually utilize bigger fiberglass whips of vertical dipoles.
VHF-Band band pass filters greatly affect the ongoing communication processes in important offices like the marine and the military. Knowing what makes them work will lead one to know what their main importance is.