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Old 5th Oct 2013, 11:57 am   #48
SteveCG
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Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
Default Re: 405-Line VHF Aerials in 2013

Re: post no 44.

I tried modelling an Antex X design using the computer modelling programme MININEC quite a few years ago. I found that the gain at the sound frequency was about 0 dBD relative to a vertical dipole, whilst the gain at the vision frequency was about 1-2 dBD. Bear in mind with 405 line System A, in its B channel allocations the sound was below vision in terms of the the carrier frequencies - eg CH B1 41.5 Mc/s sound, 45 Mc/s vision.

Note that all these yagi modelling programmes like MININEC produce results that need to be treated with a little caution.

The Antex X would have been successful in the UK in somewhat reducing the ghosting component spectral lines with the most energy, which are comparatively close in to the vision carrier. The use of an Antex X design on other TV systems where sound was above vision seems far more debateable.

P.S. I believe that an Antex X was a modified director-dipole design and not a dipole-reflector design.
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