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161 posts

Master Geek


Topic # 95109 28-Dec-2011 02:53
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Was looking to change my old Yagi aerial for a new one when I came across articles describing possible improvements by using a Log Periodic aerial. Seem to be easily available in the UK but here only Yagi aerials of one form or another seem to be sold! Any one using one or know who sells them. Compatibility problems?

Thanks

Robin

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Uber Geek
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  Reply # 562048 28-Dec-2011 08:12
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NZRobin: Was looking to change my old Yagi aerial for a new one when I came across articles describing possible improvements by using a Log Periodic aerial. Seem to be easily available in the UK but here only Yagi aerials of one form or another seem to be sold! Any one using one or know who sells them. Compatibility problems?

Thanks

Robin


Not much point at UHF as there's unlikely to be any significant improvement.
Maybe useful where there in areas such as rural Auckland (like really long distance fringe areas) trying to pull in a signal of Waiatarua on Channels 29, 33, 45 (538 - 666mhz). Most other areas have a narrower spread of frequencies (e.g. ChCh is only 682 - 706mhz).
More important is whether your location needs a narrow or wide beam width antenna which is dependant on the signal path (direct or obstructed).


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Ultimate Geek
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  Reply # 562297 28-Dec-2011 22:33
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I always used a log periodic in Auckland for channel 2 (TV1) which helped reduce ghosting.

The integrated band 3 portion of the aerial was a standard yagi setup.

I never had any trouble finding one. Hills certainly made one, but demand has probably reduced their availability with the imminent demise of analogue Tx.

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  Reply # 562340 29-Dec-2011 07:39
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PimpMyMagic: I always used a log periodic in Auckland for channel 2 (TV1) which helped reduce ghosting.

The integrated band 3 portion of the aerial was a standard yagi setup.
.

A log periodic is of no use at all for a single frequency/channel as it is intended to cover a wide frequency range. The reason it works well on Low Band VHF (Ch1 -3) is that the resonant element lengths required for each channel are significantly different.
The difference in required element lengths reduces significantly the higher you go in frequency. Hence the use of the standard yagi setup on the High Band VHF part of the antenna. At UHF they are of little practical use unless you have a very wide spread of frequency/channels.

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