| Roofing filter mod boards and filters can now be ordered for the Omni series radios. Installation in the Omni VI and VI+ is very easy and requires soldering +12V and ground as well as extending a 2 wire cable by 5 inches. (This unit will also work in the Omni V, but the customer must splice two coax cables due to the different pc board connectors.) All parts and instructions are supplied.
The PC board is mounted on two standoffs which fasten to the final amplifier shield can. Two coax cables insert the roofing filter between the RF board and the 9 MHz IF board. A two screw terminal board connects to +12V and ground. The N1/N2 switching cable gets extended and plugged into the Inrad board. A supplied jumper cable connects back to the IF board. A four position DIP switch is used to set up the roofing filter function. It may be selected with either N1 or N2, or both. The actual OEM filter positions N1 and N2 may be populated or not.
The table below shows the measured third order IMD dynamic range of the Omni VI+ for its unmodified (OEM) condition, modified with the 600 Hz filter and modified with the 2400 Hz filter. The improvement is quite dramatic and places the Omni VI into the group of today’s top performing radios.
| Tone Spacing
| OEM
| 600 Hz filter
| 2400Hz filter
|
| 2 kHz |
79 dB |
94 dB |
85.5 dB |
| 5 kHz |
82.5 |
97 |
95.5 |
| 10 kHz |
86.5 |
98 |
96.5 |
| 20 kHz |
95 |
97.5 |
97.5 |
Full installation instructions are available here:
Please see our document titled "A Few Words About Roofing Filters" for more details.
You may order the Roofing Filter mod for CW or SSB, or you may simply order the mod kit including associated cables and parts but no filter. Only one filter will fit on the board; you choose the filter, depending upon how you will use the mod. ***SSB FILTER DISCONTINUED. 763 AND 765 FOR CW ONLY ARE AVAILABLE.
The available filters are:
- #764 – for SSB -- 2400 Hz. *DISCONTINUED* - CW FILTERS ONLY AVAILABLE
- #763 – CW normal pitch, 750 Hz. (Use with N1 or N2 filters centered on 9000.75 kHz.) This is the usual CW choice.
- #765 – CW low pitch, 500 Hz. (Use with N1 or N2 filters centered on 9000.5 or 9000.6 kHz.)
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