Dab+ In House Reception

[stewartjm]

Thought I would share. Live about 90km from Brisbane transmitters on the Sunny Coast. As such DAB+ works on the window sill sometimes, but plugged into the main tv antenna which faces Brisbane for the VHF digital TV, it works fine. I know its horizontal and needs to be vertical, but it works.

Used this idea, http://www.digitalradioplus.com.au/files/u...20repeaters.pdf

I took the TV signal off the existing antenna that gives a signal error of 0-10 at worst and fed it into a 44dB VHF only narrow masthead amp, I used a Kingray

http://www.kingray.net.au/products/matv/ma...lifier/MHV44HLG

I then took the output into a length of coax with 37cm of centre copper core exposed and then another 37cm of braid exposed to make a simple coaxial ¼ wave dipole at 204MHz, mid band 9B DAB.

Have to say it works exceptionally well, I now just use the telescopic antenna on two portables around the house with no dropout or issues.

Cheers

Stew

[alanh]

J,

Congratulations, you have made an inband repeater of a lower power than the one in Collins St Melbourne.

Whilst your horizontal receiving antenna is less sensitive to the signal from Mt Cooth-tha, it is also less sensitive to your amplified output. This would reduce the possibility of feedback provided you received signal is adequate.

AlanH

[stewartjm]

J,

Congratulations, you have made an inband repeater of a lower power than the one in Collins St Melbourne.

Whilst your horizontal receiving antenna is less sensitive to the signal from Mt Cooth-tha, it is also less sensitive to your amplified output. This would reduce the possibility of feedback provided you received signal is adequate.

AlanH

Thanks Alan, in more testing I get about 50-100m coverage from the antenna which is fine for my needs. The amp cost me about $60 which is worth it to get the range of DAB radio choice. I understand the quality arguments on FM vs low bit rate DAB+ etc etc, but what digital gives me is a much broader choice of Genre. As most people dont turn on a TV and watch one channel all evening, so it is with radio, different stations for different times of the day.

Cheers

Stew

[RF Burns]

Thanks Alan, in more testing I get about 50-100m coverage from the antenna which is fine for my needs. The amp cost me about $60 which is worth it to get the range of DAB radio choice. I understand the quality arguments on FM vs low bit rate DAB+ etc etc, but what digital gives me is a much broader choice of Genre. As most people dont turn on a TV and watch one channel all evening, so it is with radio, different stations for different times of the day.

Cheers

Stew

That's all good, but be careful. Despite what Alanh may tell you, you are operating an illegal & unlicensed transmitter. Those in building shop ones you based it on, in most cases don't/won't reach outside the building, but even if they do they are still within the licence & service area. Even with only 50-100m coverage range, you are operating it at frequencies outside the licence area & intended reach of the signals, if you cause interference to others, &/or neighbours don't agree with your DAB+ thoughts for choice & make a complaint, you are in big trouble & face large fines or gaol (if ACMA decide to make an example out of you). Micro transmitters with a reach of 5-10m range are permissible, but what you have a small radio station could transmit with.

[andrewlace]

Simple solution a) run a vertically polarised band 3 antenna into the back of your radios using an f connector if at all possible.

feed a vertically polarised antenna into a single channel 9A amplifier. This will reduce noise, overload and feedback on other channels. Use another band 3 antenna to retransmit. Polarising the antenna horizontally may help to isolate the two antennas as alanH has suggested.

It is a possible consideration that by running it off the tv antenna and then amplifying by 44dB and then retransmitting you will create a feedback loop on tv signals. You may also overdrive the amplifier. The diagram that was included seems to think that retransmitting the other FTA channels is a good idea when in fact it may create interference and become a licensing issue.

Using a two way splitter backwards is not a great way of mixing signals, always recommend against mixing lots of signals together to use a big wideband amp when all you need is one low noise signal, this introduces noise.

Used a turned down K120 channel 9A amplifier.

If you have any dramas be prepared to turn the thing down. This was my suggested alternative and it did work well.

Always be aware of potential issues with retransmission particularly interference issues for your neighbours in the area.

There are other single channel amplifiers on the market that other installers may have had experience with.

[andrewlace]

Excellent statement GlennP; I missed the 100m range. Wow, look at a smaller amp for sure. Also try to get a vertically polarised antenna feeding your amp if you're amping tv signals. You may end up with ACMA issues.

QUOTE (stewartjm @ Jan 3 2012, 12:31 PM)

Thanks Alan, in more testing I get about 50-100m coverage from the antenna which is fine for my needs. The amp cost me about $60 which is worth it to get the range of DAB radio choice. I understand the quality arguments on FM vs low bit rate DAB+ etc etc, but what digital gives me is a much broader choice of Genre. As most people dont turn on a TV and watch one channel all evening, so it is with radio, different stations for different times of the day.

Cheers

Stew

That's all good, but be careful. Despite what Alanh may tell you, you are operating an illegal & unlicensed transmitter. Those in building shop ones you based it on, in most cases don't/won't reach outside the building, but even if they do they are still within the licence & service area. Even with only 50-100m coverage range, you are operating it at frequencies outside the licence area & intended reach of the signals, if you cause interference to others, &/or neighbours don't agree with your DAB+ thoughts for choice & make a complaint, you are in big trouble & face large fines or gaol (if ACMA decide to make an example out of you). Micro transmitters with a reach of 5-10m range are permissible, but what you have a small radio station could transmit with.

[alanh]

Firstly when the receiver is outside the house is it receiving Mt Cootha-tha or its amplified version? The signal strength will not be absorbed by the building.

Secondly the signal strength can be reduced by turning the gain down within the masthead amplifier or use an attenuator on the output.

AlanH

[stewartjm]

You are right Alan, the reception outside is Mt Cootha, as when I turn off the amp I still get it outside in places. It was to fill in within the house which is does well. I have turned the amp back to just above where it drops out in the house. Kind of regret sharing my efforts with the comments about ACMA. Talked with the TV installer I got the booster off and he said that he did not believe that it would rate as a transmitter. Anyhow last post here.

Have fun folk's I like the music anyhow, be glad when the Government allows the start of rural DAB+

Cheers

[alanh]

JM,

The report from the Department on which technology to use for regional and remote areas was inconclusive. Legislation is yet to be presented to parliament.

The choices are DAB+ or DRM+/DRM30. DRM covers much larger areas than DAB+. DRM radios are not too far away.

AlanH