Difference between revisions of "FrSky DHT RSSI configuration"

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To get an idea of how well the different set of antennas would perform, I swapped the antennas one by one and recorded the Tx and Rx values from the configuration application.
To get an idea of how well the different set of antennas would perform, I swapped the antennas one by one and recorded the Tx and Rx values from the configuration application.


All the tests where performed with a FPV VTX 1180 MHz running next to the receiver and everything was done indoors with antennas about 10 meters apart in separate rooms.
All the tests where performed with a FPV VTX 1180 MHz without low pass filter running 20 cm away from the receiver and everything was done indoors with antennas about 12 meters apart in separate rooms.


* Transmitter:  FrSky 2dbi rubber duck antenna
* Transmitter:  FrSky 2dbi rubber duck antenna
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''37''' - RSSI Rx: '''66'''
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''37''' - RSSI Rx: '''66''' - ''Without VTX Tx 62 Rx 70''
** Receiver: Generic Alfa 5dbi rubber duck antenna - RSSI Tx: '''52''' - RSSI Rx: '''71'''
** Receiver: Generic Alfa 5dbi rubber duck antenna - RSSI Tx: '''52''' - RSSI Rx: '''71''' - ''Without VTX Tx 67 Rx 71''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''41''' - RSSI Rx: '''74'''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''41''' - RSSI Rx: '''74'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''49''' - RSSI Rx: '''73'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''49''' - RSSI Rx: '''73'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''62''' - RSSI Rx: '''78'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''62''' - RSSI Rx: '''78''' - ''Without VTX Tx 59 Rx 70''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''54''' - RSSI Rx: '''74'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''54''' - RSSI Rx: '''74'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''54''' - RSSI Rx: '''74'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''54''' - RSSI Rx: '''74'''
Line 33: Line 33:


* Transmitter: Generic Alfa 5dbi rubber duck antenna
* Transmitter: Generic Alfa 5dbi rubber duck antenna
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''37''' - RSSI Rx: '''54'''
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''37''' - RSSI Rx: '''54''' - ''Without VTX Tx 62 Rx 71''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''52''' - RSSI Rx: '''78'''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''52''' - RSSI Rx: '''78'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''41''' - RSSI Rx: '''74'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''41''' - RSSI Rx: '''74'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''57''' - RSSI Rx: '''77'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''57''' - RSSI Rx: '''77''' - ''Without VTX Tx 64 Rx 73''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''49''' - RSSI Rx: '''74'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''49''' - RSSI Rx: '''74'''
** Receiver: Dipole 27 mm wire antenna - RSSI Tx: '''54''' - RSSI Rx: '''68'''
** Receiver: Dipole 27 mm wire antenna - RSSI Tx: '''54''' - RSSI Rx: '''68'''


* Transmitter: Generic Alfa 2.4 GHz 14 dBi patch antenna
* Transmitter: Generic Alfa 2.4 GHz 14 dBi patch antenna
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''73''' - RSSI Rx: '''83'''
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''73''' - RSSI Rx: '''83''' - ''Without VTX Tx 75 Rx 82''
** Receiver: Generic 5dbi rubber duck antenna - RSSI Tx: '''78''' - RSSI Rx: '''87'''
** Receiver: Generic 5dbi rubber duck antenna - RSSI Tx: '''78''' - RSSI Rx: '''87''' - ''Without VTX Tx 79 Rx 82''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''83'''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''83'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''73''' - RSSI Rx: '''82'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''73''' - RSSI Rx: '''82'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''81'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''81'' - ''Without VTX Tx 67 Rx 77'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''82'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''82'''
** Receiver: Dipole 27 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''82'''
** Receiver: Dipole 27 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''82'''


* Transmitter: Generic Dealextreme 2.4 GHz 14 dBi flat panel antenna
* Transmitter: Generic Dealextreme 2.4 GHz 14 dBi flat panel antenna
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''73''' - RSSI Rx: '''82'''
** Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: '''73''' - RSSI Rx: '''82''' - ''Without VTX Tx 76 Rx 82''
** Receiver: Generic 5dbi rubber duck antenna - RSSI Tx: '''78''' - RSSI Rx: '''85'''
** Receiver: Generic 5dbi rubber duck antenna - RSSI Tx: '''78''' - RSSI Rx: '''85''' - ''Without VTX Tx 79 Rx 85''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''73''' - RSSI Rx: '''81''' - ''holding the panel 90 degrees to the side to match the vertical dipole polarity''
** Receiver: Dipole 33 mm wire antenna - RSSI Tx: '''73''' - RSSI Rx: '''81''' - ''holding the panel 90 degrees to the side to match the vertical dipole polarity''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''73''' - RSSI Rx: '''82'''
** Receiver: Dipole 32 mm wire antenna - RSSI Tx: '''73''' - RSSI Rx: '''82'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''72''' - RSSI Rx: '''80'''
** Receiver: Dipole 30 mm wire antenna - RSSI Tx: '''72''' - RSSI Rx: '''80''' - ''Without VTX Tx 75 Rx 82''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''76''' - RSSI Rx: '''83'''
** Receiver: Dipole 29 mm wire antenna - RSSI Tx: '''76''' - RSSI Rx: '''83'''
** Receiver: Dipole 27 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''82'''
** Receiver: Dipole 27 mm wire antenna - RSSI Tx: '''74''' - RSSI Rx: '''82'''

Revision as of 22:41, 12 August 2012

The FrSky DHT is a flexible and relatively powerful 2.4 GHz transmitter. The kit comes as a DIY package with an RP-SMA connector which makes it easy to switch antennas. The communication is two-way allowing for both Tx and Rx signal strength indication (RSSI). The ACCST system shifts 80 channels around hundred times per second in the 2.4GHz band, similar to FSK.

I will use an D6FR receiver in this setup.

Serial adapter

To connect to the transmitter you need a USB-to-serial adapter. FrSky makes one with the necessary pin-header.

Frsky usb cable.jpg

Plug the black header into the corresponding four pins on the transmitter. Power will be provided by the USB-port.

RSSI configuration

The DHT provides a serial data port for configuration of the alarms for the RSSI and the two analog inputs. Download the 3rd-party configuration program and the required drivers.

Frsky config.png

Antenna testing

To get an idea of how well the different set of antennas would perform, I swapped the antennas one by one and recorded the Tx and Rx values from the configuration application.

All the tests where performed with a FPV VTX 1180 MHz without low pass filter running 20 cm away from the receiver and everything was done indoors with antennas about 12 meters apart in separate rooms.

  • Transmitter: FrSky 2dbi rubber duck antenna
    • Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: 37 - RSSI Rx: 66 - Without VTX Tx 62 Rx 70
    • Receiver: Generic Alfa 5dbi rubber duck antenna - RSSI Tx: 52 - RSSI Rx: 71 - Without VTX Tx 67 Rx 71
    • Receiver: Dipole 33 mm wire antenna - RSSI Tx: 41 - RSSI Rx: 74
    • Receiver: Dipole 32 mm wire antenna - RSSI Tx: 49 - RSSI Rx: 73
    • Receiver: Dipole 30 mm wire antenna - RSSI Tx: 62 - RSSI Rx: 78 - Without VTX Tx 59 Rx 70
    • Receiver: Dipole 29 mm wire antenna - RSSI Tx: 54 - RSSI Rx: 74
    • Receiver: Dipole 29 mm wire antenna - RSSI Tx: 54 - RSSI Rx: 74
    • Receiver: Dipole 27 mm wire antenna - RSSI Tx: 51 - RSSI Rx: 74
    • Receiver: Generic Alfa 2.4 GHz 14 dBi patch antenna - RSSI Tx: 73 - RSSI Rx: 79 - control
  • Transmitter: Generic Alfa 5dbi rubber duck antenna
    • Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: 37 - RSSI Rx: 54 - Without VTX Tx 62 Rx 71
    • Receiver: Dipole 33 mm wire antenna - RSSI Tx: 52 - RSSI Rx: 78
    • Receiver: Dipole 32 mm wire antenna - RSSI Tx: 41 - RSSI Rx: 74
    • Receiver: Dipole 30 mm wire antenna - RSSI Tx: 57 - RSSI Rx: 77 - Without VTX Tx 64 Rx 73
    • Receiver: Dipole 29 mm wire antenna - RSSI Tx: 49 - RSSI Rx: 74
    • Receiver: Dipole 27 mm wire antenna - RSSI Tx: 54 - RSSI Rx: 68
  • Transmitter: Generic Alfa 2.4 GHz 14 dBi patch antenna
    • Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: 73 - RSSI Rx: 83 - Without VTX Tx 75 Rx 82
    • Receiver: Generic 5dbi rubber duck antenna - RSSI Tx: 78 - RSSI Rx: 87 - Without VTX Tx 79 Rx 82
    • Receiver: Dipole 33 mm wire antenna - RSSI Tx: 74 - RSSI Rx: 83
    • Receiver: Dipole 32 mm wire antenna - RSSI Tx: 73 - RSSI Rx: 82
    • Receiver: Dipole 30 mm wire antenna - RSSI Tx: 74 - RSSI Rx: 81 - Without VTX Tx 67 Rx 77
    • Receiver: Dipole 29 mm wire antenna - RSSI Tx: 74 - RSSI Rx: 82
    • Receiver: Dipole 27 mm wire antenna - RSSI Tx: 74 - RSSI Rx: 82
  • Transmitter: Generic Dealextreme 2.4 GHz 14 dBi flat panel antenna
    • Receiver: FrSky 2dbi rubber duck antenna - RSSI Tx: 73 - RSSI Rx: 82 - Without VTX Tx 76 Rx 82
    • Receiver: Generic 5dbi rubber duck antenna - RSSI Tx: 78 - RSSI Rx: 85 - Without VTX Tx 79 Rx 85
    • Receiver: Dipole 33 mm wire antenna - RSSI Tx: 73 - RSSI Rx: 81 - holding the panel 90 degrees to the side to match the vertical dipole polarity
    • Receiver: Dipole 32 mm wire antenna - RSSI Tx: 73 - RSSI Rx: 82
    • Receiver: Dipole 30 mm wire antenna - RSSI Tx: 72 - RSSI Rx: 80 - Without VTX Tx 75 Rx 82
    • Receiver: Dipole 29 mm wire antenna - RSSI Tx: 76 - RSSI Rx: 83
    • Receiver: Dipole 27 mm wire antenna - RSSI Tx: 74 - RSSI Rx: 82
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