[Towertalk] Quad vs Yagi

[Steve Katz]

The actual article to which ZL1DD refers is in the May 1979 issue of Ham
Radio magazine, and entitled, "Quads vs. Yagis Revisited," by Dr. Wayne
Overbeck, N6NB.  A photo from that article, and a little writeup about it
can be found at:

http://commfaculty.fullerton.edu/woverbeck/antgain.htm

(scroll down, the reference is near the bottom of this section)

I knew Wayne well (still do) at the time he did this research and wrote the
article, and he traveled all over southern California with an LM470
motorized tower trailer (70' tower) and TH2 Hy-Gain 2L trapped yagi, not
known for its stellar performance.  He would park in the driveways of, or in
front of the homes of, noted DXers using cubical quad antennas, typically
also up about 70 feet, and do one-on-one, on-air comparisons in real time.
In virtually every case, the station/quad owner was shocked to find his quad
worked no better (and normally no worse) than the little 2L yagi, on short
paths, long paths, and all paths.  It was a very good article, since it was
well documented with lots of photographs and the callsigns of the DXers who
participated in the research.  -WB2WIK/6

"If everything seems under control, you're just not going fast enough." -
Mario Andretti

> -----Original Message-----
> From:	Barry Kirkwood [SMTP:bjk@ihug.co.nz]
> Sent:	Monday, November 18, 2002 1:49 AM
> To:	Tower Talk
> Subject:	[Towertalk] Quad vs Yagi
> 
> I know of but one comparative study of quads and yagis in the field that
> 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 mounted
> telescoping tower.
> Comparison antenna could be used at same height on same site as test
> antenna.
> Criterion was forward gain.
> Across the bands the trap tribanders looked rather bad. Away from optimum
> frequency the larger trap antennas often did worse than the reference
> 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
> monoband 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 witness
> some exercises reported in QEX in recent years.
> (ii) The larger tribanders would have given better f/b and narrower
> beamwidth compared to the smaller tribander even though forward gain was
> mediocre. This would give advantage on receive and if ample TX power was
> available the overall communication capability of a staion so equipped
> would be satisfactory to most users.
> (iii) The case Force 12 makes for horizontally stacked full length element
> tribanders is based on sound science.
> (iv) Data published in RSGB Radio Communication suggests that the
> Cushcraft triband yagi with a log cell driven element is underperforming
> on 28mHz. 
> (v) Speaking generally, as the good Dr Cebik shows, modern modelling
> programs have good success in matching real world antennas of the sort
> under discussion. 
> (vi) Claims of x% loss for various configurations should at least be
> supported 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
> 
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