|
Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
|
Thread Tools |
9th Feb 2021, 6:46 pm | #1 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
|
23cm ATV receiver
There is local to me an amateur television repeater that transmits on 1316MHz since I have always been interested in ATV I thought I would try and receive it as cheaply as possible.
Some research on the BATC website told me that a Comag satellite receiver would work. The FTA receivers are used as the IF from the LNB is in the middle of the 23cm amateur band. So I purchased one from eBay. When it arrived I discovered that there were several faults with it. Firstly the display kept flashing on and off, secondly when the screen was displayed it was in Russian (Cyrillic alphabet) thirdly the remote didn't work. To sort the flashing I assumed that it would be a duff cap so I went round all of them and heated each one with a soldering iron. I found that one ,when hot stabilised the picture. It was changed and I had a stable picture in Russian. I put a scope on the receiver photo diode and there were pulses corresponding to button presses on the remote, but no actual function. A search on the net showed that the remote bore no resemblance to the one supplied which was why it didn't work. I tried several TV remotes I had and one for a UMC TV made the receiver do things. By making a note of which button caused which function I could get menus up. So button marked A-B made the menu select go down 2 entered the menu P-MODE select etc Luckily the setup menus were icons not words so by trial and error I found the menu to change language to English. I now had a working receiver but no aerial. In the attic I had an old TV aerial, using that and dimensions from the VHF/UHF handbook (RSGB) I cut the elements down to size and created a folded dipole from a length of brass rod. A balun was made from a length of coax and soldered to the dipole along with a BNC socket. With this hung in the window and a length of coax into the receiver I did an auto search for any signals. As it tuned it found GB3ZZ the repeater. Talkback is on 144.750MHz so I put out a call and spoke to G4BVK and old friend who helps run the repeater. He powered up his TX and I contact was made. The main problem was that when I transmitted on 2M it killed the receiver due to the close proximity of the two aerials. The receiver has been sitting on the bench for several hours working as it should and the monitor is displaying the repeater test card. Last edited by Malcolm G6ANZ; 9th Feb 2021 at 6:52 pm. |
9th Feb 2021, 7:42 pm | #2 |
Heptode
Join Date: Apr 2003
Location: Newton Abbot, Devon, UK.
Posts: 761
|
Re: 23cm ATV receiver
Most impressive Malcolm!
I'd probably have given up with it, even as a sat RX... |
9th Feb 2021, 7:54 pm | #3 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
|
Re: 23cm ATV receiver
Thanks Colin. Yes I could have binned the receiver and got another, but where's the fun in that?
I should explain that my amateur licence is G8KGH and the G6ANZ is left over from when I had a TV transmitting licence the full call is G6ANZ/T |
9th Feb 2021, 8:34 pm | #4 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,009
|
Re: 23cm ATV receiver
Fascinating! I only ever did SSTV-receive on 14MHz.
What modulation is the 23cm ATV stuff using these days? I presume they've migrated to digital like the broadcast-TV peeps. |
10th Feb 2021, 10:17 am | #5 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
|
Re: 23cm ATV receiver
ATV uses the same digital encoding as used by the broadcast companies. This is why a satellite receiver can ve used. For transmission the BATC has developed an encoder that runs on a Raspberry Pi, the Pi also controls software defined radio transmitter. This setup enables you to transmit digital TV on any band from 70cm up, since it's digital the bandwidth is quite narrow. It makes a change from when I used to transmit analogue TV on 70cm the signal tended to fill the band even in black and white!
|
10th Feb 2021, 7:19 pm | #6 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,935
|
Re: 23cm ATV receiver
I am guessing my Fortop rx/tx on 70 cm is now obsolete ? Sadly.
__________________
G8JET BVWS Archivist and Member V.M.A.R.S |
11th Feb 2021, 11:12 am | #7 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
|
Re: 23cm ATV receiver
Not necessarily, You can still transmit digital TV on 70cm. Here is the copied data for GB3ZZ ,my local repeater:
OUTPUT - 1316MHz DVB-S 4ms/s mpeg2 FEC1/2 dual channel multiplex 23cm INPUT primary available 24/7 - 1249MHz DVB-S 4ms/s mpeg2 23cm INPUT secondary available 06.00am to 22.00pm - 1249MHz DVB-S/S2, 2ms, 1ms or 333ks, mpeg2/H264/H265 70cm INPUT primary available 24/7 - 437MHz DVB-S 2ms/s mpeg2 70cm INPUT secondary available 06.00am to 22.00pm - 437MHz DVB-S/S2 1ms or 333k, mpeg2/H264/H265 Inputs & outputs horizontally polarised LOCAL TALKBACK - 144.750MHz FM usually vertically polarised You can transmit into it on 70cm and watch on 23 cm. There may be an ATV repeater near you which has the same capabilities. |
11th Feb 2021, 1:16 pm | #8 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,935
|
Re: 23cm ATV receiver
Thank you Malcolm.
__________________
G8JET BVWS Archivist and Member V.M.A.R.S |