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5.6GHz - 5.8GHz Information Page

 

     This page is currently under construction and will eventually offer our findings and advice with regard to transmitters, receivers and antennas for analogue ATV in the 6cm band.

    Introduction

     Welcome to the KTG 6cm page. The sections below are based on our own experiences over several years experimenting and learning about the band. 6cm offers an easy entry to ATV, particularly analogue (which is our preferred mode), with a plentiful supply of FPV equipment cheaply available on the web, particularly Ebay and Banggood. Very low power levels with simple antennas enable operation over useful distances if the path is clear and even if not so clear it's surprising what can be achieved. Tiny antennas can produce amazing results, are easy to intall, and be quite inconspicuous when high up. Such small antennas also make portable working less of a chore. My thanks to Brian, G6PKS (Herne Bay), for devoting much time and effort to testing and constructing, the other end of the link between us, which has been and continues to be, invaluable. Chris, G4AYT (Whitstable).

    Transmitters

 

     Above: The 2W TX at G4AYT located in the loft. Layout: Top left - Tone generator, Bottom left - Mic pre-amp for local mic, Centre under fan - Tarot 600mW driver TX, Right under fan - 2W PA module.

     Above: The neatly constructed, as ever, 6cm ATV transceiver by G6PKS. The unit is based on the Tarot TX and RX but has the addition of a tone generator for antenna alignment, a microphone pre-amplifier, a Raspberry Pi computer for testcard generation and an RX audio amp to drive the internal LS. As is, the antenna has to be manually changed between RX and TX N-sockets as required, however, a microwave changeover relay is planned to be fitted shortly.

     Opposite right: Andy's, 2E0BAY (Gillingham), Tarot TX and RX on the bench with double diamond antennas fitted. The Tarots usually come as a combo and don't appear to be available separately. Unlike most FPV TX and RXs these units have two sound channels, 6.00MHz and 6.50MHz, which can be very useful. They are a bit more expensive than other options. Another drawback is the RX is not as sensitive as some others with a single sound channel, by as much as -6dBm or more. The antennas Andy is using here are linear polarised (vertical, as in the picture, or horizontal when the 'diamonds' are one above the other). More usually FPV antennas are designed for circular polarisation and are omnidirectional with little gain, with the exception of the circularly polarised helicals. These double diamond antennas have some gain and directivity, and like the Tarots, are available on Ebay. Important note - Some of the leads supplied with the Tarot RXs have been found to have the video out on the red RCA connector, not the expected yellow one!

     Antennas

     

     Above left is the G6PKS end of the link, clearly showing the flat 'Gibeon' antenna on its own 2" mast. This antenna is fed with S400 cable which goes straight through the wall near the mast lower bracket and into the radio room directly the other side.

     Above right shows the two 6cm antennas, one for transmit and one for receive at G4AYT, below the 23cm yagi. These flat 'Gibeon' antennas have very high gain and narrow beamwidth and are available on Ebay or direct from the manufacturer, yagi.pl in Poland (cheaper direct from the manufacturer but payment is more complicated and there is obviously a delay with delivery). However, highly recommended. They are made using weather and sun resistant materials to a very high standard and can be mounted for horizontal or vertical polarisation. The connector is a gold plated 'N' type socket. With any antenna at this frequency very good quality low loss cable and the shortest of runs is essential, S400 is particularly good although cables like Westflex103 are satisfactory, but really only for a few metres. Better still, connect the RX/TX directly to the antenna - easier with the RX as the TX can get very hot and usually requires a fan, weatherproofing is then an issue. The same antenna can, of course, the used for TX and RX, but then either physical changeover or a relay is required, and the latter can be quite lossy at these frequencies.

     These antennas at G4AYT are used for the link to G6PKS (and soon, G8NAV), but are rotatable within a few minutes by arrangement and can comfortably reach a range of 20km or more over a good path with a few hundred milliwatts TX power using analogue ATV.

      Regarding loss mentioned above, we all know connectors and adapters introduce loss, even more so at 6cm, so use as few as possible. Some will be inevitable, for instance the antenna N-type female to the RX/TX which will probably be SMA. But beware, confusion can arise with the two types of SMA connector: there is the standard type and the RP type. 

    Activity /P and /M on 6cm 

     We have started putting together a collection of photos of Kent Television Group friends 5GHz ATV activities out and about portable and mobile around the County and beyond. To view these to date take a look HERE and feel free to submit any of your own for inclusion if you've been out /P or /M, via the address at the top of the Home Page.

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