Fat Shark
3
Overview on how the system operates:
-‐ Due to the nature of digital, the occupied portion of the band is very precise and thus
adjacent channels can be stacked very close to each other with no cross talk. Pilots can fly
maximum power in close proximity to each other.
-‐ The system is not a bi-‐directional link. Missing or multipath canceled information is not
resent. The receiver has two fully independent receiver circuits from which an FPGA rebuilds
the signal.
-‐ The left and right two SMA are dedicated to the two independent receivers and each of the
two SMAs are diversity switched based on RSSI (well, much more complicated that that but
this explanation will suffice). So essentially using only two antenna (one each RX) will be
similar to using 4 similar antennas. Likely best performance will be achieved with a
combination of omni and directional antenna on both receivers (left and right side will chose
strongest signal, FPGA will stitch information).
-‐ The camera is Analog HD but the system is fully digital. The AHD signal is only
communicated from the camera to the TX, which is equipped with an AHD RX, that converts to
digital prior to being transmitted. This allows the system to be used with conventional
cameras as well. Using AHD between the camera and TX reduces wire count and increases
system robustness.
-‐ The camera has a Divimath hand shake key IC which is supplied to qualified camera vendors.
The purpose is to ensure camera compatibility and performance quality.
-‐ The OSD information for recording and scanning only shows on the receiver monitor and not
on the HDMI out. This is because the graphic OSD utilizes the DVR chipset which also directly
drives the panel. The HDMI out is split out via an FPGA so that the DVR latency isn’t added.
This also allows the system to output either 16:9 or 4:3 to HDMI while the DVR is dedicated to
displaying and recording 16:9 (4:3 mode crops sides of HDMI image and is thus lower
resolution).
Antenna recommendation
Circular polarized antennas are recommended to minimize breakup as they naturally attenuate multi path
reflections. Omni on the TX is a must, combination of Omni and directional on receiver is suggested (one of
each on left and right side of RX).
VTX User Guide
Channel setup (small LED dot off)
Short press right button, LED indicator will light up. Additional short presses will increment the cycle the
channels 1-‐4 if in HQ mode and 1-‐6 if in LQ mode.
After 7s of not pressing, channel will be saved and LED will turn off.
Both HQ and LQ channels are evenly distributed between 5725 ~ 5850MHz.
