Some will know I intend to launch a new DATV repeater in a part of Spain where DATV is virtually unheard of - despite there being pleny of licenced amatuers. With this in mind, there are a few things I'd like to hear your views and the pros & conns for each.
1. Should I choose DVBS2 or DVBT2?
2. Vertical polarisation or horizontal?
3. In/out frequencies in same band or not?
I imagine these questions must have been discussed at length in the past, but I'd like to hear what people think today.
New Repeater Questions
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This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
Re: New Repeater Questions
1. I would do DVB-S2 as equipment is more readily available and you can run narrow band widths to improve S/N.
2. In the UK horizontal was mandated for repeaters many years ago, the logic was to make it compatible with yagis used for narrow band. Going vertical does have advantages in that the repeater aerials are simpler (getting a true omni horizontal polarised antenna is not easy) and stations near by can use a white stick to access.
3. Cross band is much easier as you don't have so many problems with defense so the filters can be much simpler.
73
Noel
2. In the UK horizontal was mandated for repeaters many years ago, the logic was to make it compatible with yagis used for narrow band. Going vertical does have advantages in that the repeater aerials are simpler (getting a true omni horizontal polarised antenna is not easy) and stations near by can use a white stick to access.
3. Cross band is much easier as you don't have so many problems with defense so the filters can be much simpler.
73
Noel
Re: New Repeater Questions
Michael
In addition to Noel's comments,
1. DVB-T needs better linearity in the RF power amplifiers implying lower power output than DVB-S2. USA ATV stations use DVB-T, but the reasons appear to be more to do with the availability of plug-in appliances to transmit and receive with than any performance advantage. Being an ex-broadcast engineer you will know that DVB-T was chosen for commercial terrestrial use in Europe because of its resilience to multi-path signal corruption, but in practice the low symbol rate DVB-S2 transmissions and high rates of FEC used by ATV negates any problem caused by multi-path signals.
2. There's no readily available omni-directional vertical antenna for 23cm that has more gain than an Alford Slot gives in horizontal polarization. The Slot is easy to make too. Few 23cm stations have vertical antennas in the UK as there is very little FM repeater operation on the band. That probably holds for Spain too.
3. Same band operation at 23cm needs two frequencies at least 30MHz apart; this is set by the performance of the duplex filters if using a single antenna. Single antenna systems need over 110dB isolation between the TX and RX from the filtering. You can reduced this by up to 30dB if using vertical separation between TX and RX antennas at the cost of having different coverages because of the height difference. This isn't a problem if the antennas are 25m above ground level usually.
Crossband repeaters are much easier and cheaper to get going, but users need dual-band antenna TX/RX systems.
73
Clive
In addition to Noel's comments,
1. DVB-T needs better linearity in the RF power amplifiers implying lower power output than DVB-S2. USA ATV stations use DVB-T, but the reasons appear to be more to do with the availability of plug-in appliances to transmit and receive with than any performance advantage. Being an ex-broadcast engineer you will know that DVB-T was chosen for commercial terrestrial use in Europe because of its resilience to multi-path signal corruption, but in practice the low symbol rate DVB-S2 transmissions and high rates of FEC used by ATV negates any problem caused by multi-path signals.
2. There's no readily available omni-directional vertical antenna for 23cm that has more gain than an Alford Slot gives in horizontal polarization. The Slot is easy to make too. Few 23cm stations have vertical antennas in the UK as there is very little FM repeater operation on the band. That probably holds for Spain too.
3. Same band operation at 23cm needs two frequencies at least 30MHz apart; this is set by the performance of the duplex filters if using a single antenna. Single antenna systems need over 110dB isolation between the TX and RX from the filtering. You can reduced this by up to 30dB if using vertical separation between TX and RX antennas at the cost of having different coverages because of the height difference. This isn't a problem if the antennas are 25m above ground level usually.
Crossband repeaters are much easier and cheaper to get going, but users need dual-band antenna TX/RX systems.
73
Clive
Re: New Repeater Questions
Hello Michael,
I agree with the previous commenters. We also operate all ATV inputs and outputs horizontally.
Inputs: 70cm DVBS, 23cm, 13cm, 3cm FM analog
Outputs: 13cm DVBS, 5.7GHz, and 10GHz FM analog
On the 13cm band, we operate two antennas, each with filters in front of them.
If you want to operate in-band, you have to keep in mind that all receivers also require duplex filters.
Good luck.
73 Thomas DL5BCA
I agree with the previous commenters. We also operate all ATV inputs and outputs horizontally.
Inputs: 70cm DVBS, 23cm, 13cm, 3cm FM analog
Outputs: 13cm DVBS, 5.7GHz, and 10GHz FM analog
On the 13cm band, we operate two antennas, each with filters in front of them.
If you want to operate in-band, you have to keep in mind that all receivers also require duplex filters.
Good luck.
73 Thomas DL5BCA
I always have crazy ideas.
Please don't be surprised.
Please don't be surprised.
Re: New Repeater Questions
Hi , To add some thoughts..
Use DVBS or DVBS2 and multiple bandwidth for receiving.
DVBT is better but local test showed not good results using a Knucker Receiver comparing to dvbs2 Minitiouner..
We got severe problems with power windmills with tend to grow higher every year.
They cause multipath problems witch might be a reason to reinvestigate DVBT.
Get internet on repeater site to monitor/control/and stream in/out.
This makes a more flexible repeater where RX or TX problems can be overcome by internet stream.
Also look in good backchannel as digital repeater easy takes upto 10 sec delay witch makes full duplex difficult.
Benno
Use DVBS or DVBS2 and multiple bandwidth for receiving.
DVBT is better but local test showed not good results using a Knucker Receiver comparing to dvbs2 Minitiouner..
We got severe problems with power windmills with tend to grow higher every year.
They cause multipath problems witch might be a reason to reinvestigate DVBT.
Get internet on repeater site to monitor/control/and stream in/out.
This makes a more flexible repeater where RX or TX problems can be overcome by internet stream.
Also look in good backchannel as digital repeater easy takes upto 10 sec delay witch makes full duplex difficult.
Benno
Re: New Repeater Questions
After many years of using the first Repeater HB9TV analog FM relay, we switch to DVB-S for 20 years.
With the proliferation of modes, we opted for a transponder that works similarly to the QO-100.
It accepts all digital and analog formats : Video DVB, SSB, FM, phone FM wide FM, AM, and DATA !
The implementation is simple, and the results of my measurements are breathtaking!
You can find a description on the website SwissATV.ch
https://home.swiswissATVtv.ch/2024/12/u ... -mondiale/
73's from Pierre HB9IAM = F8BXA
With the proliferation of modes, we opted for a transponder that works similarly to the QO-100.
It accepts all digital and analog formats : Video DVB, SSB, FM, phone FM wide FM, AM, and DATA !
The implementation is simple, and the results of my measurements are breathtaking!
You can find a description on the website SwissATV.ch
https://home.swiswissATVtv.ch/2024/12/u ... -mondiale/
73's from Pierre HB9IAM = F8BXA
Re: New Repeater Questions
Pierre, the URL is mangled.
Best regards,
Chris, 2E0ILY in rural Shropshire.
It was a lot more fun being 20 in the 70's than being 70 in the 20's
Chris, 2E0ILY in rural Shropshire.
It was a lot more fun being 20 in the 70's than being 70 in the 20's
Re: New Repeater Questions
You can find a description on the website SwissATV.ch ......the right link .... 
https://home.swissatv.ch/2024/12/une-premiere-mondiale/
73's From ON1RC
Chris
https://home.swissatv.ch/2024/12/une-premiere-mondiale/
73's From ON1RC
Chris