Updated Band Switching
The Portsdown band switching was updated in July 2021 to enable the selection of 16 bands.
By default, 7 of these bands are for direct transmission (without a transverter), and 9 are allocated for transverter use.
Against each of the 16 bands, the following settings are stored:
- A Label that is displayed on the band select button and the Contest card for that band.
- A transverter (transmit) local oscillator frequency, so that both the IF drive frequency and the final transmitted frequency can be displayed on the Portsdown Menus.
- Settings for the 4 GPIO lines, which are available on the Raspberry Pi GPIO header, the LimeSDR FPGA GPIO and the DATV Express GPIO pins.
- An attenuation level for an external attenuator to set the transmit drive level.
- The transmit power level for a DATV Express card
- The Lime Gain for a LimeSDR
- The Pluto output power level
- The Contest numbers for the band
- The receive LO frequency for an ADF4351-based receive converter (primarily for 50 and 70 MHz operation)
- Enable/disable for a LimeRFE PA
- The TX port to be used for a LimeRFE (not yet implemented)
- The Receive Attenuation for a LimeRFE (not yet implemented)
Factory Default Settings
The factory default settings are shown below. Note that the d0 to t8 designation and the band index are both used internally in the Portsdown and cannot be changed.
| Usage | Band name | LO Frequency | GPIO Binary | GPIO Decimal | (Band Desig) | (Index) |
|---|---|---|---|---|---|---|
| 50 MHz Direct | 50_MHz | 0 | 1 0 0 0 | 8 | (d0) | (14) |
| 71 MHz Direct | 71_MHz | 0 | 0 0 0 0 | 0 | (d1) | (0) |
| 146 MHz Direct | 146_MHz | 0 | 0 0 0 1 | 1 | (d2) | (1) |
| 437 MHz Direct | 70_cm | 0 | 0 0 1 0 | 2 | (d3) | (2) |
| 1255 MHz Direct | 23_cm | 0 | 0 0 1 1 | 3 | (d4) | (3) |
| 13 cm Direct | 13_cm | 0 | 1 0 1 1 | 11 | (d5) | (4) |
| 9 cm Direct | 9_cm | 0 | 1 1 0 1 | 13 | (d6) | (15) |
| 50 MHz Transverter | 50_MHz_T | -94.8 | 1 1 0 0 | 12 | (t0) | (9) |
| 13 cm Transverter | 13_cm_T | 2248.5 | 1 1 1 1 | 15 | (t5) | (10) |
| 9 cm Transverter | 9_cm_T | 2970 | 0 1 0 0 | 4 | (t1) | (5) |
| 6 cm Transverter | 6_cm_T | 5330 | 0 1 0 1 | 5 | (t2) | (6) |
| 3 cm Transverter | 3_cm_T | 9930 | 0 1 1 0 | 6 | (t3) | (7) |
| 24 GHz Tranverter | 24_GHz_T | 23610 | 0 1 1 1 | 7 | (t4) | (8) |
| 47 GHz Tranverter | 47_GHz_T | 46944 | 1 0 0 1 | 9 | (t6) | (11) |
| 76 GHz Tranverter | 76_GHz_T | 75832 | 1 0 1 0 | 10 | (t7) | (12) |
| Spare | Spare | 0 | 1 1 1 0 | 14 | (t8) | (13) |
GPIO Lines
The 4 GPIO lines used are listed below. Note that the MSB is only available on a Portsdown 2020 if a 7 inch screen or the SSH console is being used to control the system. The pin is used by smaller touchscreens, and so it cannot be used for band switching.
| Function | Portsdown 4 Pin Number | Portsdown 2020 Pin Number |
|---|---|---|
| D0 LSB | 32 | 28 |
| D1 | 35 | 35 |
| D2 | 7 | 7 |
| D3 MSB | 22 | 22 |
The GPIO values can be duplicated between bands if more than one band needs the same switchuing arrangement.
Changing the settings for a Band
The settings for each band can be changed by selecting Menu3, Set Band Details and then selecting the appropriate band. The system will then request that you enter settings for each of the parameters above except the LimeRFE and Receive LO values. The LimeRFE values are entered from the Lime Config Menu whilst the appropriate band is selected.
The receive LO values (for driving and ADF4351-based up-converter) are entered by selecting Menu 3, Set RX LOs; note that this menu is not yet fully functional.
The contest numbers for the bands can also be managed in sets related to their locator from Menu 3, Set Call Loc & PIDs, Set Contest Codes.
Selecting a Band for Use
By default, the band is selected automatically based on the transmit frequency selected. So anything under 60 MHz is assumed to be 50 MHz, anything between 50 and 100 MHz is assumed to be 71 MHz and so on. To overide this and use a transverter, select the Band/Tvtr button on the main menu, and then select the transverter band that you want. Alternatively, you can select "Direct" to resume automatic selection of bands where no transverter is used.
Backwards Compatibility
The settings above have been carefully chosen so that the default settings are backwards compatible with the 4-band and 8-band RF switch designs.