DAB hardware

Revision as of 19:39, 23 July 2018

EasyDAB

A recent solution to generate a DAB signal has been developed by Sergiy from Kyiv, Ukraine. It is called EasyDAB v2, see http://tipok.org.ua/node/46 . The DAB modulation has been programmed in an FPGA, such that just the multiplexing and audio/PAD encoding needs to be added. A 'cookbook' description of a complete DAB transmission chain based on this board and a Raspberry Pi can be found on the RaspDAB page.

Ettus USRP

The Ettus [1] USRP devices are used to transmit DAB signals generated by ODR-DabMod. We are mostly using the B200 model.

There are several devices on the market:

USRP B200

It is the cheapest USRP, and is probably the best choice for both experimentation and transmissions with the ODR-mmbTools. It lacks shielding, but the Hammond enclosure 1455L1601 (Farnell product number 427-2882) fits well. Host connection: USB 2.0 or 3.0. Luckily, the native DAB sample-rate of 2048000 does not require USB 3.0 speeds.

Be wary about USB 3.0: some host controllers are not very well supported. Ettus Benchmarks

Some USRP B200 Measurements are available.

The original USRP, a.k.a. USRP1

This is the one that has been used in the beginning, before the UHD driver replaced libusrp, and is still on the market today because it's the only usrp that supports two daughterboards. While it's been used a lot, it's lack of 1PPS and 10MHz reference clock inputs, and less flexible clock generation requiring resampling on the host makes it less attractive than it's successors. They connect to the host using USB 2.0.

USRP2 and USRP N2xx

The networked series connect to the PC using 1Gbps Ethernet. They can be used successfully with ODR-DabMod through the UHD driver.

USRP B100 (product is end of life)

The successor of the USRP1. The kit with the WBX daughterboard was a perfect starting point, but it's not available anymore. The B200 is a good replacement.

USRP E1xx

Contains an embedded ARM processor that cannot be taken advantage of by the ODR-mmbTools. Call for volunteers: If you want to port ODR-DabMod to the USRP E100, doing the modulation on the ARM and the FPGA, please get in touch with us !

HackRF One

The HackRF One is an SDR platform by Great Scott Gadgets which can be used to transmit DAB signals generated by ODR-DabMod. It can be used both for the VHF III band and the L-Band.

Note that the format should be signed 8 bit (s8), not unsigned (u8) which is commonly used by RTLSDR dongles.

For more information see https://greatscottgadgets.com/hackrf/

Daughterboards for USRP and Analog Parts

Find in this section some hardware experiment done with USRP RF front end like daughterboards or external devices (filters, power amplifiers).

The following Ettus daughterboards can be used for transmission in VHF band III:

Basic TX, RFX400 (after modification) or preferably the new WBX daughterboard.

• Example of RF amplifier for DAB for VHF band III (never connect to an antenna without a license !)
• RFX400 daughterboard modification to operate in VHF Band III (around 200MHz)
• WBX daughterboard wide band coverage
• DAB in L Band test with the WBX daughterboard
• Filter to kill harmonics
• Carrier Shaping Mask
• Antenna for digital radio broadcasting

Fighting USRP-related problems

While the USRP devices can be used for stable operation in many situations, it is sometimes tricky to find the right configuration and system settings to achieve good results. Here are some hints and remarks to increase reliability.

• Make sure you use released versions of UHD and GNURadio, and not just the latest git checkout
• Compile the mmbTools with the correct ./configure options
• Monitor for USRP Underruns [2]
• Disable all useless services on your machine
• Disable CPU frequency scaling
• Try different USB ports, or even USB controllers for bus-connected USRPs
• Try to change the num_send_frame=128,send_frame_size=1024 UHD options