Based on an idea from daniel sandu yo3gjc inrad has taken their stock series of 9mhz filters and fitted them to a daughter card allowing drop in use in the yaesu ft dx5000 series rigs.
Rf roofing filter.
The cut off frequency of the filter is defined as the point at which the output level from the filter falls to 50 3 db of the in band level assuming a constant input level.
The narrow band sdr receiver removes strong out of band signals by using a superheterodyne method with narrow band roofing filters which significantly attenuates unwanted out of band frequency components and the wanted signals within the passband are converted to digital by a high resolution 18 bit a d converter and sent to an fpga field programmable gate array for signal processing.
Agc rf or af chain overload shack noise etc.
Reducing the bandwidth at this point in the radio helps to keep strong off frequency signals out of the second mixer where they can cause intermodulation.
The roofing filter mod inserts a narrow band crystal filter between the rf assembly and the if board.
Used sinclair bandpass filter low power n connectors 720 980mhz.
109 00 12 1 0 mh ferrite inductor.
The goal of a roofing filter is to limit the passband of the first intermediate frequency if stage.
Rugged radios audio choke electric static clamp on rf noise reducer filter.
The narrow band sdr receiver removes strong out of band signals by using a superheterodyne method with narrow band roofing filters which significantly attenuates unwanted out of band frequency components and the wanted signals within the passband are converted to digital by a high resolution 18 bit a d converter and sent to an fpga field programmable gate array for signal processing.
Bench results and observations.
This is the band of frequencies below the cut off frequency for the filter.
Inrad roofing filter kit for icom 781 transceivers.
Inrad roofing filters for the ft dx5000.
Rf filter characteristics a filter allows signals through in what is termed the pass band.
Anritsu ma410a low pass filter.
O needs vhf roofing filters wide cheap or narrow expensive o excellent image rejection o close in dr varies down conversion architecture 9 mhz typical 1 st if o performance near if is not uniform o image rejection near ham bands requires design attention o needs only hf roofing filters narrow cheap.
The down conversion method attenuates unwanted frequency mixer components outside the band and cleaner signal is input to the following a d converter.
Transmission is not changed as it does not pass through the roofing filter.
A roofing filter is a type of filter used in a hf radio receiver.
It is usually found after the first receiver mixer.
