DAB + Transmitter Home Made.

Here's a quick view how i made my dab+ lowcost transmitter.

After playing around with  the hack RF i decided to upgrade a bit an get a real dab+ transmitter, i got me one from Sergiy.

I filed for a licence, and got one for 150 watts ERP on channel 7B, the first licence in Holland for a local radio station !!  ( :-) )

I disassembeld an old FM  transmitter , wich i had for 25 years in service, but giving problems and by now its replaced.

So now i could use the housing of that 100 watt oldie.

After taking the thing apart, i got 2 levels in the housing, upper and lower.

On the front there's the on/off switch, control leds for 12 and 50 volt and the network connection.

The back side is fully heatsink, with 2 fans on it.

On the lower level i placed the dc power units, consiting of a 50 volt, 12 volt an 5 volt one.

The upper level would become the rf deck.

Exiter is the EasyDABv2  running on 5 volt.

Pre-power stage, is the RA30H1721M, low band because i filed for a lower channel e.g. 7X or lower.

This amp can make 8 watt with 45 db shoulder steepness.

I need only 800 mwatt ......

On the left there's rf input, variable resistor is for input drive,  its 200 ohms with 68 ohms in parr.

Final stage is made of a powerfet ,DIY kit, running at 50 volt.

Stage needs 800 mw for 60 watt output, still ,having 45 db shoulder steepness.

Its a diy kit, 300 watt ham amplifier ( 145 mhz ) , but its a broadband version.

I changed the input section, by removing the ferrite en shortend the output transformer by 5 mm.

Bias is set to 2.5 amp at 50 volt ( 125 watt ) !!!

This runs through a low pass filter ( 5 elements ) and straight to a 2 x 2 element antenna bay at 40 meter high.

 

Jan de Vries

Radio Westerwolde

Vlagtwedde ( Holland )