Further note:
i may be in error with exact figure of quad loop gain over dipole. have
loaned my w4pv book.
sorry about all lower case but typing one hand as large cat insists on being
cuddled.
73
end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
ph/fax 64-9-372-5161
www.waiheke.co.nz/signal.htm
----- Original Message -----
From: "Barry Kirkwood" <bjk@ihug.co.nz>
To: <i4jmy@iol.it>
Sent: Tuesday, November 19, 2002 7:16 AM
Subject: Re: [Towertalk] Quad vs Yagi
> 1. What do you mean by significant? If 2 el quad is consistently better in
> forward gain by order of 1 dB then this is significant.
> 2. The 2 el quad can be analysed as two stacked two element yagis with
> quarter wave spacing. Theory predicts and measurment confirms that this
will
> give up to but no more than 1.8 dB over one such yagi alone.
> 3. I would agree that 1-1.8 dB makes no great difference on a single
> contact. Over a large number of contacts under contest conditions it will
> make a difference.
> 4. Like stacked yagis the quad will show better f/b and and front-side
than
> a single two element yagi.
> 5. Generally loops are less affected by rain static on receive than dipole
> elements.
> 4. I have no special investment in quads and in fact run a yagi. The
> structural problems of quads are usually greater than those of yagis.
> 73
> Barry
>
> end
> Barry Kirkwood PhD ZL1DD
> Signal Hill Homestay
> 66 Cory Road
> Palm Beach
> Waiheke Island 1240
> NEW ZEALAND
> ph/fax 64-9-372-5161
> www.waiheke.co.nz/signal.htm
> ----- Original Message -----
> From: <i4jmy@iol.it>
> To: "bjk" <bjk@ihug.co.nz>
> Cc: "towertalk" <towertalk@contesting.com>
> Sent: Monday, November 18, 2002 11:27 PM
> Subject: Re: [Towertalk] Quad vs Yagi
>
>
> Comparing apples with oranges may lead that a banana is longer.
> Differrent modeling software converge that gain of a 2 elements
> optimized quad is not significatively different than gain of a two
> element optimized yagi, more or less one dB. Moreover, there is no
> reason why it should be different.
>
> 73,
> Mauri I4JMY
>
>
>
> ---------- Initial Header -----------
>
> From : towertalk-admin@contesting.com
> To : "Tower Talk" <towertalk@contesting.com>
> Cc :
> Date : Mon, 18 Nov 2002 22:48:55 +1300
> Subject : [Towertalk] Quad vs Yagi
>
> > I know of but one comparative study of quads and yagis in the field th
> at seems to me to meet scientific standards.
> > Cannot remember the reference, but it was in Ham Radio a long time ago
> .
> > Method:
> > Two element trap tribander used as comparison antenna with truck mount
> ed telescoping tower.
> > Comparison antenna could be used at same height on same site as test a
> ntenna.
> > Criterion was forward gain.
> > Across the bands the trap tribanders looked rather bad. Away from opti
> mum frequency the larger trap antennas often did worse than the referenc
> e antenna.
> > Two element quads did better than monoband yagis of same boom length,
> in line with theory which predicts ca 1.8 dB better.
> > Longer multielement quads tended to underperform by comparison with mo
> noband yagis of the same boom length.
> > Note:
> > (i) This was before antenna modelling programs were widely available.
> It may be possible to optimise the performance of longer quads, as witne
> ss some exercises reported in QEX in recent years.
> > (ii) The larger tribanders would have given better f/b and narrower be
> amwidth compared to the smaller tribander even though forward gain was m
> ediocre. This would give advantage on receive and if ample TX power was
> available the overall communication capability of a staion so equipped w
> ould be satisfactory to most users.
> > (iii) The case Force 12 makes for horizontally stacked full length ele
> ment tribanders is based on sound science.
> > (iv) Data published in RSGB Radio Communication suggests that the Cush
> craft triband yagi with a log cell driven element is underperforming on
> 28mHz.
> > (v) Speaking generally, as the good Dr Cebik shows, modern modelling p
> rograms have good success in matching real world antennas of the sort un
> der discussion.
> > (vi) Claims of x% loss for various configurations should at least be s
> upported by data from modelling if they are to be taken seriously.
> > 73
> > Barry
> >
> > end
> > Barry Kirkwood PhD ZL1DD
> > Signal Hill Homestay
> > 66 Cory Road
> > Palm Beach
> > Waiheke Island 1240
> > NEW ZEALAND
> > ph/fax 64-9-372-5161
> > www.waiheke.co.nz/signal.htm
> >
> > --- StripMime Report -- processed MIME parts ---
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> > text/plain (text body -- kept)
> > text/html
> > ---
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