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
Vlagtwedde ( Holland )