Is a DAB tx possible?

Iv seen a few threads talking about cheap dab gear. obviously the range is no where near as good as FM, but is it possible ?

It's possible, but probably not worth doing. There are six "bouquet" frequencies possible at present. In most bigger cities, all six are in use, so there's nowhere to add an additional bouquet. Each bouquet is 6 MHz wide - the width of an old analogue TV channel - and can convey several stations (the number is decided by the bandwidth / data rate that each station wants to use). If you're going to do it, you need to get together with a bunch of other stations to provide the content.

The "open source" DAB solution that's freely available requires multiplexer hardware, good quality sound cards, a pile of Raspberry Pis, and a moderately powered PC to assemble the data stream to be conveyed to the transmitter. The cheap transmitters that are available are in the region of £600 for 50mW, and amplifying it requires a highly linear amplifier with a very precisely defined RF bandwidth and precise filtering. Your average rig-building solder-jockey wouldn't have a clue.

To be honest, DAB should stand for "Dead And Buried". It's a 40-year-old technology, using MP2, and it's surpassed in coverage and quality by simple web streams. You can put your station on the 'net, using one of the "unlimited" services (about £30 - £40 per month), and get listeners all over the world. If you broadcast live, and have a means of the listeners getting in touch with the studio, you can generate quite a following.

My 'net station has huge audience figures, globally, and isn't illegal - we even pay the Performing Rights fees. If someone chooses to put our web stream into a transmitter, that's fine by us - it's nothing to do with us, so we can't be touched for it! We also provide content for a couple of American radio networks (and charge them for it), and it's still fun to do!

Albert H wrote: ↑Thu Oct 29, 2020 12:05 pm My 'net station has huge audience figures, globally, and isn't illegal - we even pay the Performing Rights fees. If someone chooses to put our web stream into a transmitter, that's fine by us - it's nothing to do with us, so we can't be touched for it! We also provide content for a couple of American radio networks (and charge them for it), and it's still fun to do!

Link?

100%

FreeDAB did this, so it's possible if you have the effort to do it. Hit up http://wiki.opendigitalradio.org/Main_Page for some information, it's an open-source DAB project. But like Albert said, it's only really worth it for tinkering value, since a) covering a wide area isn't as simple as FM and b) no-one re-tunes their DAB that often, if at all, so next to no-one would pick you up.

Yeh Albert what’s the link for your radio ?

XXL wrote: ↑Fri Oct 30, 2020 9:27 pm Yeh Albert what’s the link for your radio ?

It's not mine - I just make it work!

Albert H wrote: ↑Thu Oct 29, 2020 12:05 pm My 'net station

Albert H wrote: ↑Sat Oct 31, 2020 3:06 am It's not mine

I've done it to show another forum, but as was said I only tinkered.

Albert H wrote: ↑Sat Oct 31, 2020 3:06 am

XXL wrote: ↑Fri Oct 30, 2020 9:27 pm Yeh Albert what’s the link for your radio ?

It's not mine - I just make it work!

Ok then. What’s it called. I’ll have a listen.

Albert H wrote: ↑Sat Oct 31, 2020 3:06 am

XXL wrote: ↑Fri Oct 30, 2020 9:27 pm Yeh Albert what’s the link for your radio ?

It's not mine - I just make it work!

D0nt you also present an album show on it?
Yes, what’s the link, either way.

Undercover Neckz wrote: ↑Sat Oct 31, 2020 3:28 am

Albert H wrote: ↑Thu Oct 29, 2020 12:05 pm My 'net station

Albert H wrote: ↑Sat Oct 31, 2020 3:06 am It's not mine

hhhhhhh

It's partially mine!

My voice appears occasionally......

Can I add it to the internet stations list we have?

It can be done easily - all you need is an EasyDAB modulator, Raspberry pi with MMB tools installed.
An simple amplifier can be build with for example an Aliexpress board and a mitsubishi mosfet

Is a bandpass filter between the EasyDAB modulator and the amplifier not used due to the low power final output?

You need a decent cavity filter to ensure there’s a clean output


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The signal of an DAB exiter / transmitter always has shoulders. Depending on the quality of the setup, these shoulders can be very large - or very small. When they are large, you can interfere on the "neighbour" channels. Also, the reception distance will decrease.
For filtering of these shoulders, a spectrum mask / helical filter is used.

In my test setup a EasyDAB modulator is used, with shoulders at -70Db - so a filter between the modulator and amp is not needed.

Maximus wrote: ↑Wed Aug 25, 2021 6:15 pm You need a decent cavity filter to ensure there’s a clean output

The small scale DAB trial muxes have been doing without cavity filters by using massively overrated amps. Basically if you use a really high power amp but under run it, you'll stay way below the intermodulation point and the output will be pretty clean even without the filter. I think they were running 250w amps for something like 20-50w output. Idea being that big amps are still cheaper than filters.

We build home made cavity filters. They're not too difficult if you have a network analyser!