RF Low Pass Filter 1.8-145 MHz

This lowpass filter circuit is a very basic filter. It required to remove the harmonic frequency content of the transmitter and can be used on frequency 1.8 - 145 MHz.

The cut off frequency of the filter can be achieved by making C2 and C4 variable trimmer acurate filtering. All coils are 22 SWG wound on 10mm Air former spaced at 2mm.

For making coils of the lowpass filter, download this RF Calculation Software and the list of Wire Gauge below.

Source: Ajpotts

See more: FM Transmitter

read more "RF Low Pass Filter 1.8-145 MHz"

RF Filter Types

An RF filter is an electrical circuit configuration (network) designed to have specific characteristics with respect to the transmission or attenuation of various frequencies that may be applied to it. There are three general types of RF filters:

A high pass filter similarly has a cut-off frequency, above which there is little or no loss in transmission, but below which there is considerable attenuation. Its behavior is the opposite of that of the low-pass filter.



A low pass filter is one that will permit all frequencies below a specified one called the cut-off frequency to be transmitted with little or no loss, but that will attenuate all frequencies above the cut-off frequency. High-pass and low-pass filters can be difficult to construct properly. Whenever possible, many amateurs simply buy them.


A band pass filter is one that will transmit a selected band of frequencies with substantially no loss, but that will attenuate all frequencies either higher or lower than the desired band.

read more "RF Filter Types"