Awesome shortcuts for Long Distance DTV reception: part one

Achieving success with weak signal tropospheric reception is attainable by utilizing your laptop, notebook or netbook computer rather than a set top box. This writer tries not to use the computer for entertainment, preferring to buy stand-alone devices. But as a wise Homer once mused to his amazement: ‘Computers can do that?’ – hell yeah! This article is an attempt to explain why a set top box may be considered redundant for weak signal purposes.

Use a tuner specifically designed for mobile DVB-T reception. Manufacturers test receiving performance at speeds approaching 150 kilometres per hour. The AF9010 DVB-T Demodulator is one such integrated circuit. The Genius TVGo (third revision) is one of the multitude of USB tuners which contains this chipset. Here up the creek, that $60 Genius consistently outperforms all the set top boxes (which cost considerably more) on both rooftop and indoor yagi antennas. Equivalent tuners that utilize the same Microsoft BDA drivers and AF9015 Demodulator are available from $20 from Hong Kong. An example.

Whilst any indoor antenna system may yield undesirable results in this country (because of the relatively low transmitter powers assigned), it is progressively-minded to consider those USB cards offering dual diversity antennas. Manufacturers claim these provide significantly better reception of weak signals. One manufacturer, Elgato claims:

EyeTV Diversity contains a Digital Signal Processor (DSP), which uses information from both tuners to generate the best signal possible…

The result of this Antenna Diversity (AD) and multi-tuner technology is superb reception deep indoors, in weak DVB-T coverage areas, and at high speeds. In tests, the technology provided good reception in 95% of locations within the home (compared with 67% for conventional receivers), and a 50% improvement in the quality of the television signal.

Once the USB DVB-T tuner is installed, command-line software will permit Viterbi decoding of weak signals. This step provides confirmation of DVB-T signal reception where signals are terribly weak! Such signals will not yield any picture nor show any indication of life on any set top box signal meter under ownership.

For Linux (above; tested under Terminal in Ubuntu 12) DVB Tune is recommended. The human translation for the above screenshot is that the ‘Tuner Front End has attained Viterbi’ from King Muzza’s favourite transmission site.

For Windows (tested under MS-DOS in Windows XP) Scan Channels BDA is recommended. In good faith, both tiny software packages are believed to be based on the GNU Library General Public License (GPL) with the Linux operating system, hence freely downloadable.

Koos van den Hout is a Systems Administrator for a department at the Utrecht University in Holland. Koos extolls Linux software such as DVB Tune on his exquisite blog concerning weak signal ‘DX’ DVB-T reception:

Some signals are very weak, to try and find out whether those are actually valid dvb-t signals I use dvbtune or zap to tune to the frequency (and either try to guess modulation, error correction and guard interval or let the automatic tuning in zap do its work), watching the signal strength and error rates and then use dvbsnoop in another window to try to get valid data from PID 0x10 which can give a hint to what services are active on that channel.

Further discussion

DVBTune in practice
Tuners with the AF9015 as ‘guts’
Installing drivers for AF9015-based tuners in Ubuntu/Linux

Postscript

Last night the writer had a play around with an old BT848 based analogue television tuner card. These cards with full Personal Video Recorder (PVR) facilities were ground breaking in the 2000’s, and notoriously popular for de-scrambling cable television, according to some anonymous sources!

One of the advantages of analogue is that noise can be readily seen in the video. And of course it is a drawback in comparison to digital! The same applies with regard to FM versus DAB Plus. RF ‘noise’ from the computer itself (in this particular instance, a desktop computer) presents some challenges which will be discussed very briefly here. Why? Because interference is the modern enemy of radio reception, in this blogger’s opinion. The more it is discussed the better we can equip ourselves with some potential defensive positions!

Laptops are often considered preferable for receiving weak or long distance television signals. The interference generated is often less problematic than what spews from desktop systems. Use of battery power is recommended. In a portable computer, mains adapters and battery rechargers are notorious sources of interference.

For further reference, the VK Logger offers a wonderful and simple dialogue here and here. The discussion is applicable to both radio and television signals.


Massive kudos to Koos van den Hout.

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