The British Amateur Television Club (BATC)

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Many readers will have heard of DX-TV – the activity of receiving TV broadcast stations from outside your area.

 

 

Many readers will have heard of DX-TV – the activity of receiving TV broadcast stations from outside your area. This magazine is running columns on both general DXTV reception and special topics.

Well, there are other TV signals that you can look out for in the amateur radio bands.

The normal amateur radio licence allows the transmission of television on those bands, where there is sufficient frequency space. There are a few hundred radio amateurs in the UK who have built equipment to transmit amateur TV (ATV) and a number of always-on amateur TV repeaters.

 

A Little History

Amateur television started in the late 1940s, using 405-line black and white pictures on the 70 cm band.  Much of the equipment was built using ex-War Department kit, and early pictures were generated by flying spot scanners, with the staticon tubes then required to build TV cameras not being available (at ‘amateur’- prices) until 1952.

Fig. 1 shows Ian Waters G6KKD/T, transmitting TV in 1964.

Amateur TV thrived on 70cm and on the higher bands, using the 405-line standard in the 1950s and 1960s. In the mid-70s, it followed the BBC and ITV in adopting the 625-line standard.

It was not long before regular amateur colour transmissions started. These used false-colour images generated from black and white pictures (think: Top of The Pops special effects) or homebuilt colour TV cameras.

As frequency space in the 70cm band for colour AM ATV transmissions became more restricted (the band used to be 420–450 MHz but was reduced to 432–440 MHz to be shared between all amateur users), FM ATV transmissions on 23cm (1240–1325 MHz) became more popular, especially as they could be received on the Satellite TV receivers of the day.

Now that satellite and terrestrial broadcast TV have moved to digital, amateur TV has followed. Initial tests conducted in 2002 proved that the DVB-S standard, initially intended to be used for satellite broadcasting, was robust enough for terrestrial ATV. It was also much easier to transmit and receive than DVB-T using ex-broadcast equipment. And it had the added advantage that colour TV with sound could once-again be squeezed into the 70cm band.

 

Recent Developments

Using modified satellite receiving equipment, and custom-built computer-based transmitters, it has become possible to develop a lower-bandwidth version of the DVB-S standard, known as Reduced-Bandwidth TV (RB-TV). It can squeeze a good colour picture into 500KHz of spectrum.

This technology has allowed UK radio amateurs to transmit colour TV in the experimental bands of 146–147 MHz and, more recently, from 70.5 to 71.5MHz.

There has also been a lot of ATV activity on the 6cm band recently. Many of the ‘first-person-view’ transmitters and receivers sold for use on drones will tune to 5665MHz, which is within the 6cm amateur band.

These transmit analogue FM and are a really cheap way to get on the air with ATV.

 

What Can You Expect To See?

As with voice transmissions, there is a requirement that the station callsign must be transmitted every 15 minutes; that, combined with the fact that many constructors want to make technical adjustments, means that a lot of test cards are transmitted.

Once the contact is established (usually after making contact on the ATV voice calling channel of 144.75MHz FM), most operators will switch to the camera in their shack and show the receiving station and the progress of their latest construction project.

If the station is operating from a portable location, views of the portable station and the countryside are popular. Fig. 2 shows a typical, electronically-produced amateur test card.

Some stations show recordings of events they have attended. However, as with all amateur radio transmissions (except GB2RS), broadcasting is not permitted. Therefore, the content is very much on a one-to-one basis, and normal copyright and decency rules apply.

 

Where and When to Look

The most common frequencies and modes for simplex operation are listed in Table 1.

The best starting point to listen to – or call for – activity is on 144.75MHz, which is the NBFM Voice ATV talkback channel.

Most amateurs equipped for TV are monitoring this channel, and a number of ATV repeaters transmit the audio from this channel on one of their audio carriers.

Although ATV activity can happen at any time, once a month the BATC organises activity weekends. These generally take place on the first or second weekend of the month and provide an incentive for ATV operators to go out portable, or to make a special effort to get on the air from home.

Fig. 3 shows 24GHz portable digital ATV operation during such an activity weekend.

There are always discussions about who is going where, and at what time, on the BATC Forum beforehand.

https://forum.batc.org.uk

 

ATV Repeaters

Another interesting starting point is to look for your local ATV repeater. Most of these transmit 24/7, with a ‘carousel’ of information, and with pictures being displayed when there are no incoming images to be relayed.

Table 2 shows some of the more active repeaters. In Fig. 4, you can see the ATV Repeater GB3VL, which has its aerials on Lincoln Cathedral.

Repeaters such as this one can be also be viewed on the internet. They are streamed by the BATC on their streaming page at this URL:

https://batc.org.uk/live

 

What Equipment Do I Need?

The most important parts of the receiving station are the aerial and preamplifier. There is no difference here between the equipment that you would require for voice operation and that required for TV. Just make sure that it covers the right frequency and that you can point the aerial directly at the transmitting station.

For 2m, 70cms, 23cms and 13cms, a Yagi aerial is best. For the higher microwave bands, a dish will be required.

The image in Fig. 5 is of some typical ATV Aerials for 2m, 70, 23 and 3cm.

In terms of the receiver, you can use an old FM satellite receiver to receive FM TV transmissions on 23cm directly. Similarly, you can use a free-to-air digital satellite receiver (not a Sky receiver) to receive the digital transmissions on 23 cm.

For the higher bands, you will need a downconverter. Normal C-band LNBs work well for receiving 9cm, and modified Ku-band LNBs can be used for 3cm.

To operate on 6 cm, the best option is to purchase a cheap first-person-view transmitter and receiver from eBay; make sure that they can be tuned to 5665MHz (generally, the 32-channel and 48-channel ones can).

Using very small aerials, some 10km line-of-sight paths can easily be covered.

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Using dish aerials, a range of more than 100km has been achieved.

 

Receiving and Transmitting Reduced-Bandwidth TV

Reduced-bandwidth TV (RB-TV) is an extension of the commercial DVB-S and DVB-S2 standards to enable lower symbol rates and narrower bandwidth transmissions. The commercial standards specify a minimum symbol rate of 1 million symbols/second (1MS); amateur experiments have proved that pictures can still be transmitted at symbol rates as low as 66,000 symbols/second (66KS).

Reducing the bandwidth allows the transmissions to be fitted into crowded or narrow bands and increases the signal-to-noise ratio, allowing contacts over longer distances, or the use of reduced power.

Picture quality does reduce at lower symbol rates – but it is better than no picture at all.

To receive RB-TV, Jean-Pierre F6DZP has designed some software to be used with a satellite tuner and a USB interface with a PC; it is called MiniTioune.

Fig. 6 shows a homebuilt MiniTiouner digital TV receiver with a PC interface.

In Fig. 7, you can see the author, as received (on 10GHz) using a MiniTiouner and the MiniTioune software. Full details of the system, which can also receive normal DVB-S and DVB-S2 signals, are here: https://wiki.batc.org.uk/MiniTioune

ATV transmission is normally accomplished by generating the transmitted signal at a low power level, and simply using a linear amplifier to boost the signal up to the required level, or by feeding it to a transverter and linear amplifier for the higher microwave bands.

Digital  ATV signals can be generated by SDRs or by using specialist (homebuilt) hardware.

There are 2 options currently available: First, you can use a PC with the DATV Express software to drive a Lime SDR or a Pluto SDR. Full details of this option are at this URL:

https://www.datv-express.com/CustomPage/Downloads

Second, you can use a Raspberry Pi 3B with a touchscreen and the Portsdown software to drive a ‘Portsdown Filter Modulator Board’ or a Lime SDR. Again, more details can be found at this website:

https://wiki.batc.org.uk/The_Portsdown_Transmitter

The image in Fig. 8 is a Lime SDR Mini Transmitting TV, driven by a Raspberry-Pi Portsdown.

The picture source can be a Webcam, Pi Camera or a normal video camera. Software-generated test cards are also available.

TV contacts over distances between 50 and 100km can easily be achieved. During the recent tropospheric propagation enhancement, ATV pictures were exchanged between Devon and the North York Moors on 2m and 3cm, at a distance of 407km.

 

Finding Out More About Amateur Television

The British Amateur Television Club (BATC) was formed in 1949 by a group of enthusiasts to encourage amateur television, and it currently has over 1,100 members worldwide.

Not only does the club produce a quarterly magazine (CQ-DATV).

[At the time of writing, the February 2019 issue of CQ-DATV was available to download – Ed.].

The BATC also hosts a website:

https://batc.org.uk

Furthermore, there is a forum and some further resources for helping to distribute information about the hobby.

The BATC also runs a video streamer service for members and ATV repeaters.

Fig. 9 is an image of the BATC logo.

Additionally, the BATC represents the needs of amateur TV enthusiasts to OFCOM and the RSGB. This representation has been key to the release of the new 146MHz and 71MHz bands for amateur use.

The club runs a small online shop selling hard-to-get parts and printed circuit boards for ATV projects.

Our members also run stands at major radio rallies, demonstrating amateur TV and answering questions.

You can join online or at a rally, which gives you access to the latest issues of CQ-DATV, as well as the shop items.

Fig. 10 shows the BATC stand at the Friedrichshafen Show in June 2018.

 

What Next?

The geostationary Es’hail-2 satellite, which was launched on 15 November 2018, carries a dedicated transponder for digital amateur TV. This should be capable of being received on a 90cm dish anywhere in the UK; transmissions will require a slightly larger dish.

More details will be published on the BATC Forum once testing has started. Exciting times!

 

[if you run a similar, or otherwise radio-related club, association or hobby-group, I would like to hear from you for a possible future profile in the pages of RadioUser – Ed.].

 

 

Table 1: The most common frequencies and modes for simplex operation in ATV

 

Band

Frequencies

Modes

2 Metres

144.75MHz

NBFM Amateur TV Voice Talkback

2 Metres

146.5MHz

RB-TV 333 KS, RB-TV 125 KS

70 cm

437.0MHz

DVB-S 1MS, DVB-S 2 MS

23 cm

1255.0MHz

FM-TV, DVB-S 1 MS, 2 MS and 4MS

6 cm

5665.0MHz

FM-TV

 

Table 2: Active ATV repeaters

 

Location

Callsign

Frequency

Mode

NW London

GB3BH

10.065 GHz

FM

8 km NW Leicester

GB3GV

1318.5 MHz

DVB-S 4 MS 1/2 FEC

Kirk Merrington, Co Durham

GB3KM

3406 MHz

DVB-S 2 MS 7/8 FEC

Norwich

GB3NV

3406 MHz

DVB-S 2 MS 5/6 FEC

Anglesey

GB3TM

1316 MHz

DVB-S 4.167 MS

Tacolneston, Norfolk

GB3TN

1316 MHz

DVB-S

Sheffield

GB3TT

1310 MHz

FM

Dunstable Downs

GB3TV

1318.5 MHz

FM

Dunstable

GB3TZ

2326 MHz

DVB-S 4 MS 3/4 FEC

Mow Cop

GB3UD

1319 MHz

DVB-S 4.167 MS FEC 1/2

Bath

GB3UT

1311.5 MHz

FM

Lincoln

GB3VL

1310 MHz

DVB-S 4MS 1/2 FEC

Mirfield, West Yorkshire

GB3YT

1316 MHz

DVB-S 4MS 1/2 FEC

Bristol

GB3ZZ

1316 MHz

DVB-S 4MS 1/2 FEC

 

Addendum: BATC Offering Free Membership for Students (31 January 2019)

The BATC  is pleased to announce a new Student membership category, open to anyone in full-time education. This membership is being offered for 5 years, free of charge, to students, with the aim of attracting younger members to learn about amateur Television, one of the fastest-growing technical areas of amateur radio. Students should apply using the online form at the URL below. Once your application is approved, you will be sent details of how to obtain the free-of-charge membership from the BATC on-line shop.

https://batc.org.uk/student-membership.

 

 

This article was featured in the March 2019 issue of Radio User