Butterfly Dipole for DVB-T: Simple and economical DIY indoor antennas 1

Published:2011/8/23 21:43:00 Author:Amy From:SeekIC

Rolf Badenhausen

Digital terrestrial television (DVB-T) is now available in many parts of the country. Of course, you need a DVB-T receiver and a (new) UHF TV antenna. If you don’t have a suitable antenna, the small indoor DIY alternative described here is a simple and economical solution.

Terrestrial digital video broadcasting is now available in many pans of the country, and there are plans to eventu­ally switch off existing PAL analogue broadcasts altogether; in some parts of Europe this is already happening.

If you currently receive television by satellite or cable and. for reasons of cost, wish to switch over to DVB-T, a DVB-compatible antenna is required Of course, this is not connected directly to the television, but rather via a DVB-T receiver, or so-called ’set-top box’.

Only a few of the DVB-T receivers have a simple indoor antenna available as an accessory. Figure 1 shows an example of a basic rod antenna. The main disadvantages of this type of antenna are its sometimes unsightly appearance and its narrow-band sen­sitivity compared to the width of the UHF band over which the digital chan­nels are spread.



More appropriate for indoor DVB-T use is the patch antenna known as a ’but­terfly dipole’ after its striking shape. As well as demonstrating a better broad-band performance in field trials. this comparatively discreet antenna can easily be hidden, for example behind a modestly-sized picture frame.

DVB-T

Thanks to the data compression offered by MPEG-2 it is possible to transmit four digital channels in the same bandwidth as that occupied by a single analogue channel. This is partic­ularly impressive when you consider that a modern television signal with 62S lines and a 50 Hz field frequency would give a raw digitized data rate of around 216 Mbit/s. The bandwidth required for that would be prohibitive for terrestrial or satellite transmissions. MPEG-2 is a significant advance on the MPEG-1 video compression stan­dard. It can reduce the digital data rate to 13.27 Mbit/s. just 6 % of its original value. Also, a sophisticated modula­tion scheme, known as COFDM (Coded Orthogonal Frequency Division Multiplex), ensures that the available bandwidth and transmit power are used optimally. Very early article on DVB-T may be found in [1].

Reprinted Url Of This Article: http://www.seekic.com/blog/project_solutions/2011/08/23/Butterfly_Dipole_for_DVB_T__Simple_and_economical_DIY_indoor_antennas_1.html

Print this Page | Comments | Reading(2031)