I have recently bought a portable radio receiver called Dual DAB 4. It supports DAB (MP2), DAB+ (AAC) and the analog FM. It is equipped with a monophonic speaker and a telescopic antenna (although it is too short for the FM reception). Frontier Silicon Verona FS2052 tuner module contains Apollo 2 RF front-end IC and Kino 3 DSP. It is possible to use an included external 7.5V switching power supply or 6x AA batteries. 

According to the datasheet, the FM sensitivity (for 40dB SNR) is typically -106dBm (1.4µV) and -97dBm (3.9µV) for DAB. Unfortunately there is no stereo de-noising or blending, but mono sensitivity is fine. There are no conventional analog IF filters, signal is filtered on the DSP. Sometimes there is an audible sound gap during a switch between filters. ±100kHz selectivity is poor, but ±200kHz is quite good – it performs better than my old JVC KS-833R car-radio with 2×180 & 1×110 kHz filters, but of course the performance is not like a famous XDR-F1HD. Nevertheless I have to admit that results are excellent for such price. I paid only 15€ for a refurbished unit!

dual

Now let’s see what could be improved in Dual DAB 4. I have removed the telescopic antenna and soldered a BNC connector for an external 75Ω antenna input. Stereo noise decreases noticeably with an external preamp. I haven’t heard any intermodulations, even using a 18dB preamp, so the AGC performs very well. Audio quality is very poor with the stock speaker. I replaced it with another one which was advertised as a neodymium speaker, but I’m not 100% sure about that. It is somewhat bigger (see photos below) but thankfully it fits inside the receiver case. :-) Now I can enjoy sound with much more bass and treble.

The battery life is a noticeable issue. It is caused by a 3.3V linear voltage regulator. The input voltage varies depending on a supply. 6xAA batteries give 9V, so the losses are the worst. 6×1.2V rechargeables give 7.2V, so losses are somewhat lower. According to the datasheet, tuner module has the highest power consumption in FM/RDS mode (317mW). Listening to DAB/DAB+ takes respectively 227mW and 245mW. I have replaced the stock regulator with a step-down power switching module based on a L5973D. I can’t hear any interferences coming from the switching supply, but there are some coming from the tuner itself. Just try to keep the antenna a bit away.

dab4modified

speaker2 speaker1  tuner dab4outdoors

For some real-world tests I connected Körner 19.3 to Dual DAB 4 with an external wideband preamp PAR-825U (25dB gain, 47-862MHz range, 2dB noise figure). I recorded some aircraft scatters, mostly reflections via Airbus A380. RDS decoder seems to be sensitive enough on weak signals!

  • 89.9 Ö2 – Radio Wien 537km RDS
  • 97.0 Ö1 & 89.4 Ö3 568km RDS 
  • 96.3 SRo 1 535km RDS
  • 88.8 Hitradio Antena 486km RDS
  • 94.1 F1 & 102.9 Impuls 566km RDS
  • 89.1 CRo 1 546km RDS
  • 99.4 Bayern 3 & 90.7 Bayern 1 621km
  • 89.5 hr3 & 101.7 hr4 700km

What about DAB? Polish broadcast operators, Emitel and INFO-TV, are testing the DAB+ emissions. In Warsaw, the capital of Poland, there are 3 transmitters:

Ch. Pol. Name Location ERP  
7B H EMITEL Warszawa – PKiN 1.1kW  
12D V INFO-TV DAB+ Warszawa – Komin EC Kawęczyn 10kW SFN
12D V INFO-TV DAB+ Warszawa – Hotel Mariott 3.5kW SFN

I don’t have any 174–240 MHz antenna, but the reception is possible all the time with Körner 19.3 (Emitel, H) and 2x 5-el (INFO-TV, V) at about 100km distance.

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