Though the HRO-60 has a crystal filter, the easiest way to add modern seletivity is
to add a mechanical filter.
We chose to add a prepackaged solution, the Collins 353-A mechanical filter adapter. It simply plugs into the first IF tube socket. These adapters were manuafactured by Collins for a number of receivers, including our HRO.
They contain a Collins mechanical filter of a specific bandwidth, in our case 3.1 KHz.
To install it, the 1st IF tube is removed and the adapter installed in its place. Then the second IF (455 KHz) is realigned to the center of the filter's passband.
We chose to add a prepackaged solution, the Collins 353-A mechanical filter adapter. It simply plugs into the first IF tube socket. These adapters were manuafactured by Collins for a number of receivers, including our HRO.
They contain a Collins mechanical filter of a specific bandwidth, in our case 3.1 KHz.
To install it, the 1st IF tube is removed and the adapter installed in its place. Then the second IF (455 KHz) is realigned to the center of the filter's passband.
Click on any picture to enlarge it
Collins manual
Installed Collins filter adapter