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.
Rf roofing filter.
Have technology from space aliens nsa yet i still can t filter the guy up the band.
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.
It is also the only other rig besides the ftdx 5000 that has down conversion crystal roofing filters.
A four position dip switch is used to set up the roofing filter function.
Filter insertion loss plus a few db.
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.
It is usually found after the first receiver mixer.
The n1 n2 switching cable gets extended and plugged into the inrad board.
Why your filter is not working.
Two coax cables insert the roofing filter between the rf board and the 9 mhz if board.
It is usually found after the first receiver mixer.
A roofing filter is a type of filter used in a hf radio receiver.
A look at filtering and drift on a classic yg 455c 1 for the ts 830s adopting the yg 455c 1 for use in the kenwood ts 830s 2nd if kenwood ts 820s.
The plot below shows the sweep frequency response of the rf board in an ic 775 radio.
The improvement in first if selectivity is dramatic.
My 1977 dream rig now joining the shack lineup.
Transmission is not changed as it does not pass through the roofing filter.
A two screw terminal board connects to 12v and ground.
The goal of a roofing filter is to limit the passband of the first intermediate frequency if stage.
A supplied jumper cable connects back to the if board.
The roofing filter mod inserts a narrow band crystal filter between the rf assembly and the if board.
The rf amplifier has optimized nf points and the over sized wide range rf transformer exhibits minimum saturation in strong signal processing.
A couple of sx 101a plots.
