432 MHz ("70cm") Amateur TV

Ulsterman 1690

I have recently bought a DVD recorder which has channel tuning in Megahertz and covers everything from 47-864 Megs

Presumably if I were to tune it into 432 (aprox) MHz Id be able to watch ATV transmissions (although Id probably need to change my Group C/D aerial/amp)

Am I likely to see anything (given that I live in a crap reception area to the North of Belfast) ?

watty

No.
I do have a licence extension for 430 .. 440 MHz for Fast Scan / ATV. But no-one in Ireland to my knowledge is doing it.

WE do have plans to try COFDM MPEG4 TV using maybe 4MHz bandwidth. Vistigial Sideband ATV (like regular TV) needs about 7MHz. The IRTS would not be happy with that.

All ATV in Ireland currently uses FM video standard, between 12MHz and 25MHz bandwidth. Currently Cavan, Cork, Dungarvan and possibly Dublin have 23cm band repeaters typically about 1260MHZ and 1310MHz or so.

An analog satellite reciever with a DC isolated 1.3GHz aerial colse to repeater, or with LNA instead of LNB (Low Noise Amplifier) powered as the LNB would be, will work as the Satellite IF frequency even on very old boxes is tunable from 950MHz to 1700MHz. Newer analog receivers can tune 750MHz to 2100MHz.

A Video sender's receiver will work too if you have a convertor (transvertor) to convert from 1.2 or 1.3 GHz to 2.4Ghz.

There is also an ATV repeater some place in N.I. but I don't know if it is near Carrickfergus or Bangor. It is also likely to be 23cm band.

Ulsterman 1690

The repeater is in Carrickfegus

Ive read about ATV'ers using 432-440 on the UK mainland (Its not allowed on 430-432) although the higher bands are generally preferred because on 70cms

1) The limited bandwidth means that unless one uses a vestigal sideband filter they are restricted to black and white and (usually) no sound
2) No video repeaters are allowed on 70cms (no room for them)
3) Other hams complain about ATV interfering with their voice repeaters (why dont they move the repeaters below 432 )

watty

Ulsterman 1690 wrote:

The repeater is in Carrickfegus

Ive read about ATV'ers using 432-440 on the UK mainland (Its not allowed on 430-432) although the higher bands are generally preferred because on 70cms

1) The limited bandwidth means that unless one uses a vestigal sideband filter they are restricted to black and white and (usually) no sound
2) No video repeaters are allowed on 70cms (no room for them)
3) Other hams complain about ATV interfering with their voice repeaters (why dont they move the repeaters below 432 )

1) We could use true SSB video
2) Agreed. That is why I'm doing a DVB-t proposal using MPEG4. Then a repeater will work and maybe soon (next year) DVB-t boxes that have MPEG4 (used for HD, but should work 544 x 576 pixels). One of the DVB resolutions is similar to SVCD resolution, which is slightly better than S-VHS and the same roughtly as 4:3 "window boxed" in a 16:9 animorphic 720 x576 frame.

3) The repeaters Tx and RX at the same time. Ones using cavities can work with 1.6MHz split. Three are now running without cavities with a 7.6MHz split. I have complained to IRTS but no-one regards it as a problem!

The lower part of band is for simplex SSB DX working 433.xxx is repeater outputs and 1.6MHz higher is repeater inputs.

Limerick repeater input is 433.125
Most Wireless Temp sensors, IR remote back channels on Video senders or Sky Gnome are 433.085!

I think hardly any ATV is on 430 .. 440 anywhere. Mostly 23cm FM. There is some QPSK digital ATV in Germany and one Repeater in England. (Sat Digital receiver with LNA will receive it on 23cm).

Ulsterman 1690

Problem with "true SSB video" is maintaining an accurate low frequency response

Digital sounds interesting though although it will probably a while before affordable modulators will be available

watty

Add a pilot carrier. Much Marine SSB has this. Then a PLL / Syncronous detector (many modern normal TV IFs) will lock and detect.

Well two years ago I got a quote of $3000 (Bench Test set). Which could be afforded by a radio club for the club, or by a repeater group for a Hybrid Analog & Digital in and Digital out Repeater.

Have you seen what some people are paying for IF DSP HF Transcievers? From 1,000 Euro to 10,000 Euro!

Rlogue was saying the advantage of DAB listening for him in London was that the Pirates only messed up FM listening.

IF DAB was more popular, there would be DAB pirates. Compared with Studio and Decent FM transmitter an adapted DAB bench test set is not much extra!


P.S. I'm from Carrickfergus area. Some my folks live Whitehead. I must find out more about the ATV repeater before my next trip to Norn Iron.

Richard

Sorry to butt in folks, but I'm never heard of Amateur TV. What is it? Can someone please explain it to me in layman's terms?

Thanks.

Ulsterman 1690

Its basically Amateur radio with pictures

Basically radio (or in this case TV) enthusiasts who have gone through a process of sitting an exam. Obtaining a licence (usually ) and using equipment that theyve either built/modified themselves or bought in specialist shops (£££$$$€€€) communicate with fellow amatuers (depending on what frequency theyre using and their specialised field of interest) on the other side of town or the other side of the world.

In the Republic they are officially known (rather quaintly) as "radio experimenters"

British Amateur TV club
UK radio amateurs
Irish Radio Experimenters
US radio amateurs
"Dissident" radio amateurs (controversial one this)

watty

The only class of Radio & TV operators world wide allowed to modify or build transmitter equipment and use it without type approval.

Most of course simply buy ready made equipment.

Frequencies allowed (some variations between countries):
136KHz
1.8 .. 2.0 MHz
3.5 .. 3.8 MHz
7.0 .. 7.2 MHz
10MHz
14, 18, 24 & 28 MHz bands
50MHz / 6m, 144MHz/2m 430..440MHz/70cm
Also bands around:
1.3GHz
2.4 GHz
5.6GHz
10GHz
20GHz

Voice transmissions include
AM, SSB, FM. NBFM and DRM

Data
CW (Morse), RTTY, PSK31, Packet modes, DRM, WSJT and others. Speeds from a fraction of a baud to 200Mbits.
Irish Packet Network = 1200 Baud, Slovenia Packet Network 1.2M bps and 10Mbps.

Still Pictures
Slow Scan TV (like Wireless fax, in B&W or Colour), DRM,

Fast Scan or ATV
AM vestigial sideband, FM, DVB QSK etc.

Amateurs/Radio Hams/Wireless Experimenter also organise, staff and supply Emergency Communications networks as the normal phone and internet systems colapse during disasters and also Police/Garda/Fire/Ambulance/Marine /Civil defence rely on base stations for inter -operation or operation at all.

Usually the only stations running after a disaster are Military and Radio Hams.

Raynet in UK and AREN in Republic.

US emergency radio by US Hams was only communication for nearly a week in many hurricane hit areas last year. Indian goverment gave Hams special permits to go to some areas to provide communication services.

You can sometimes chat to International Space Station as many of the Astronaunts/Cosminauts have Amateur Radio licences and there is equipment for that on ISS.

stylers

Is that 23cm beacon in cork running at the moment ? - i think its shown on the irts repeater map, and someone runs one in the cavan area too. I heard some lads on the limerick 2m repeater about a year ago, sounded as if they were doing ATV trials, and had pictures too..

Owen..

watty

The Cork Repeater is running on 23cm. Also has an ouput on Channel C of video senders possibly.

Located Spur Hill.

AFAIK the only ATV in Limerick has been my transmissions. Off the air.

There may be tests again this summer on 1.2 .. 1.3GHz band (analog, receivable with Analog Sat receiver connected direct to aerial with no LNB ) and 10Ghz (Digital. Possibly receivable with PC Satellite Card and LNB).

Though there is an Allocation on 2.4GHz, Comreg will only permit voice and data. They won't explain why even low power TV is forbiden.

DMC

Its such a pity that the original meaning of ATV has been overtaken with time by this term and off-road buggies.

Lew must be spinning somewhere....

watty

ROFL ...

Interestly Baird is frequently credited with inventing TV. The first ATV transmission may have been by:

Paul Nipkow (1860 - 1940)

One of the earliest proposals for a mechanical television system was put forward by German researcher Paul Nipkow in 1883. When he developed patent No. 30,105, he was an unknown twenty-three-year-old student living in Berlin. It proved to be the basis for most early television schemes in the world, although he never built the apparatus.

In Nipkow's patent, which he called an 'electric telescope', a disc was punched with holes in a spiral near the outer edge. When the disc revolved, each hole vertically scanned a line of the image, allowing variations in light to reach a selenium cell. As one hole swept over a segment of the picture, the next in sequence tackled the portion next to it, until the complete subject had been scanned. The selenium cell transferred the light variations to an electronic signal. Pictures were reconstituted at the receiver by a similar disc which was synchronized with the transmitter.

Baird's doomed 1930's system was a copy of this. The UK 405line electronically scanned system, the forerunner modern TV systems was developed also in the 1930's in EMI. The idea of a scanned CRT display and a similar smaller tube with a phoconductive target as Camera (used up til 1980s) was first proposed in 1905.

So between 1883 and start of the ATV company a lot of Amatuers were involved in TV.

EMI may have only been copying the work started on Electronic Television by
Russian émigré Vladimir Zworkin, working for Westinghouse (in 1923) and later RCA, others say That is an RCA ploy and Philo Farnsworth really invented it in 1927.

Electronic Colour TV was demonstrated in 1940 in the USA. Earlier colour systems demonstrated in the 1920s in Europe. But obviously not in Ireland

The Company ATV made some great TV series though.

zg3409

Hi all,

I am actively involved in Amateur Television in Ireland. I can answer any questions people may have on this thread or through private messaging.

I am involved in Dublin and Cavan and I know the guy in Belfast. (Watty if you need Belfast info I can help) I have also received the Cork TV repeater (while visiting cork) and there is a repeater near Waterford.

Regarding the topic

1) If you tune to 436Mhz analogue or so on a TV, chances are, you will see nothing. We can transmit in black and white on this frequency but it blocks the whole band for others to use and it is only black and white. If we attempted colour it would broadcast outside the limits of the band and interfere with other users.

2) There are still a few 436Mhz transmitters around Dublin but I haven't heard of anyone using them in the last 5 or 10 years.

3) The main activity is on 1240 to 1320Mhz using old analogue Satellite Receivers (the type some people watched german TV on 20 years ago)! These are hard to come by now but there are some low cost off the shelf (new)equipment that can cover the frequency.

4) Coverage at this frequency is spotty so you need to be in coverage in order to receive the repeaters. Generally they only transmit 10 or 20 watts spread over 20Mhz bandwidth.

5) Ordinary old analogue Satellite receivers are not very sensitive. We usually use pre-amps in line to boost the signal and high gain directional aerials.

Regarding digital transmission quite a bit has been done in Europe to upgrade some sites to combined analogue & digital transmit/receive. The main problem is cost. Transmitters work out around 1,000 euro , while normal free to air digital satellite receivers can be used to receive.

Regarding digital transmission on 432 to 440Mhz some work has been done. Generally this band is just used point to point (person to person) and not used by repeaters. (In some countries such as Australia they have the room for repeaters on this band).

Generally the digital format used at this frequency (in Europe) is DVB-S. It's expensive to generate, and on the receive side you need to up-convert the signal from 436Mhz to 900 ish to feed into a digital satellite receiver. Up-converters work out about 150 euro. DVB-T is not really used on this band as normal TVs are expecting a 7 or 8Mhz wide signal which is too wide for normal use.

So 99% of the digital activity in Europe is on 1240-1320Mhz.

I have been working on investigating the digital options for the past 6 Months. I have posted my findings and observations here:

http://batc.org.uk/forum/viewtopic.php?f=15&t=887

I am waiting on a digital transmitter to be manufactured, so I can start testing.

Watty and co. If you are interested in getting involved I can demonstrate, especially if you are in the Dublin area. I would like to demonstrate some digital TV transmissions when I get the gear. I might do a demo in Waterford and Cork or at some Amateur Radio rally or meeting.

It would be great if we could combine our efforts.

More info is here (mostly related to Cavan)
http://www.iatc.ie/

http://www.13cm.co.uk (some equipment) (Note we want 23CM equipment)

A lot of the information is in paper format in a pay-for magazine produced the the British Amateur Television Club. I am a subscriber.

http://batc.org.uk/

We also are using old MMDS aerials and downconverters (converted to be pre-amps) on 2300-2400.
We have links from Dublin to Cavan on 10GHz too. Rather than rushing out and buying stuff I would encourage everyone to get in touch with other interested locals and myself.

PM me or reply to this thread.

Dan EI9FHB
South Dublin Radio Club
http://www.southdublinradioclub.ie

watty

Since this thread I have done DVB-t and DVB-c on 435MHz and 10.2GHz using a PC card from Dektec

Here http://www.boards.ie/vbulletin/forumdisplay.php?f=922
or
http://www.techtir.ie/articles/amateur-radio
or
http://www.techtir.ie/forum/hobby-radio

is better than this forum.

I've reported the thread as an thread as old as this confuses people

(P.S. ages ago I've worked with people in Dungarvan and Cork doing the 23cm FM TV).

It's possible to actually run 4 channels (at low bitrate MPEG4 H.264 L3 codec) in 2MHz. It's fairly easy to reduce the TX channel width by using lower SR and to replace the IF filter in a receiver with a narrower one. I got some 2MHz wide 44MHz IF filters.
The Arris Cable modems can work on 110MHz to over 900MHz directly and have a 1.2GHz 1st IF (so you can use 1st IF as RF in on 23cm). You can fit 2MHz wide 2nd IF at 44MHz and take off feed then to Tuner (DVB-c or DVB-T) on BandI.

There are cheap solutions for 10Ghz / UHF.

Also a DOCSIS CMTS for hotels can be got cheap and used as basis of combo DATA/TV Repeater as DOCSIS downlink is 2MHz to 8MHz DVB-C (conversion to DVB-T possible) and uplink is 800KHz, 1.6MHz, 3.2MHz or 6.4MHz wide TDMA.