@ -143,6 +143,7 @@ The following setups assume the host is compiled with the setup TUI mode (if ava
- When using a repeater/modem board attached to an appropriate FM repeater/radio, it *may* be necessary to "de-tune" the repeater/radio slightly, most commercial grade equipment operating within a 12.5khz channel may impose a strict 2.5khz (and no greater) maximum *analog* FM deviation, this is well below what is required for good digital operation. It may be necessary using whatever tuning/alignment tools to "de-tune" or adjust the equipments alignment to allow for a wider *analog* FM deviation, as close to 2.80khz as possible.
- In some situations, it may be necessary to adjust the symbol levels directly. Normally this isn't required as the DVM will just work, but some radios require some fine adjustment of the symbol levels, this is exposed in the calibration mode. It is however recommended, that these adjustments *not* be made unless appropriate RF test equipment is available.
- Unusually high BER >10% and other various receive problems may be due to the radio/hotspot being off frequency and requiring some adjustment. Even a slight frequency drift can be catastrophic for proper digital modulation. The recommendation is to ensure the interfaced radio does not have an overall reference frequency drift > +/- 150hz. An unusually high BER can also be explained by DC level offsets in the signal paths, or issues with the FM deviation levels on the interfaced radio being too high or too low.
- For hotspot operation, it may be necessary to enable/disable the AFC (automatic frequency correction) or change the gain mode. Both of these options can be altered using the setup TUI or directly in the `config.yml` file. In some cases when operating in trunking mode, for example, it may be necessary to change the orientation of the transmit antenna by using a 90 degree adapter as well as changing the gain mode to "Low" to prevent Rx desense.
Bryan Biedenkapp
2 years ago