5.6 GHz

Amateur TV activity on the 6 cm band is increasing due to the availability of cheap modules intended to transmit “First Person Video” (FPV) back from drones to their operators.

Frequency choice

The UK amateur band plan is shown on the RSGB website here: https://thersgb.org/services/bandplans/html/rsgb_band_plan_2017.htm

GB3KM has a licensed input on 5665 MHz and this has been chosen as the primary ATV operating frequency.

The FPV equipment receive and transmit frequencies are set using DIP switches, and most tune to this frequency but care needs to be taken when selecting equipment to make sure it does cover this frequency.

Equipment

The FPV units are widely advertised on eBay with titles similar to “Tarot 5.8G 600MW Telemetry TX/RX Combo for FPV Image Transmission TL300N” and are available at reasonable prices. The typical units are very small but have reasonable FM-TV performance with a quoted spec of 600 milliwatts out and receiver sensitivity of -80 dBm. Amplifiers are available to raise the output power to 2 watts or more.

This units are very small but do run very hot in operation and it is suggested you provide a good heatsink for both Tx and Rx

Using dish aerials of 30 – 60 cm (such as a surplus Sky dish), line of sight ranges of 80 km can easily be achieved. P5 (noise free) FM ATV pictures have beenexchanged over an 85 km path using the equipment pictured.

Detail of G8GKQ transceiver setup is shown here (receiver unit on left & transmitter with fan on the right)

Antennas

As 5.8GHz is also used by broadband wireless networks, there is a wide choice of antennae available for use on 5.6GHz ATV. This can range from flat plates to wire mesh dishes.

It is also possible to use a satellite mini dish with a suitable feed - the picture shows a Sky mini dish fed with a WA5VJB log period PCB feed (available from G4DDK)

Antenna change over relays

The losses at 5.6GHz can be significant and care must be taken when wiring up the units to ensure RF cables are of good quality and kept to a minimum length. The surplus SMA relays often available at rallys are ideal for 5.6 GHz. If no suitable relay is available It may be cheaper to use a separate antenna for receive and transmit as shown in the picture below.

Reverse SMA

Be aware that suplus SMA relays are almost certain to be standard SMA connectors and the 5.6GHz FPV units are reverse SMA. Adapters from reverse to standard SMA are available on ebay or other suppliers.

24v relay operation

Most of these relays are often 24v coils - use a switching regulator from ebay as shown in the above picture.