Playing
about with a DAB aerial
Digital
Audio Broadcasting uses roughly the same frequencies as some of
the old 405-line VHF TV transmissions. The aerial was originally for channel 10, which was around 200Mc/s* I think. Anyway, that suggested that the elements and spacing would be about 10% too long, which is a lot really. I worked out the proper dimensions for 222MHz and the result was that I shortened the elements by 70mm. I reduced the spacing between the reflector and dipole by 25mm and between the dipole and first director by 30mm. I didn't bother altering the other directors. After that the aerial worked pretty well, with about 6dB more gain than a four element Antiference DAB aerial. The latter is wideband of course, in case the full DAB band ever gets used, so the gain isn't very good really. Although
the new home brewed aerial brought in a Winter Hill multiplex
at quite good strength according to the spectrum analyzer, reception
on the DAB tuner was little better than with the Antiference because
we have a DAB transmitter 1km away and the tuner couldn't discriminate.
Not surprising really because the local is 80dB above Winter Hill! *I did that for effect. Don't write in. |
Home | About us | What we do | Aerial Issues | Aerial Photography | Reference | Contact Us | Annexe | ||||||
Print this page | © 2003-2012, Wrights Aerials | Add to Favorites |