QUAD versus YAGI
47DX117 
19AT091
This subject has been covered by many in the past and lots of information is availible on aditional antenna sites.
All in mind taken the answer is simple: both have theire own ups and downs.
And it is your personal OPINION wich will fit you the best.
There are some basic rules to keep in mind though:
- A Quad has a smaller turning radius then a Yagi with the same boomlenght
- A Quad has a slight higher Gain than a Yagi with the same boomlenght (1dB not 2!)
- A Yagi is overall cheaper to build (aluminium./ fiberglass)
- There are still stories of Quads breaking up !
- A Quad has a slight lower noise level, this comes because the
radiating element is a closed circuit (a yagi with a folded dipool or a
quagi will show you the same)
- A Yagi is easier to handle / construct / maintain /
- A Quad is NOT always lighter, just imagine if ice sticks at those
wires and fiberglass poles! It becomes quite a windcathcer then aswell!
- A few meters above ground the quad has a lower take-off angle, when both antennas are placed high there is no difference.
- The Bandwith of a yagi is wider,
- A quad well tuned has a better F/B.
- There is an old ham saying wich is : "with a Quad the band opens 15 minutes earlier"
Overall im not in favour for the yagi nor the Quad.
I never have noticed a big difference. Those wo did probarbly didnt buildt one of the antennas right, or didnt compare correct.
It depends for me only on Physical size what to build (for stacking yagis are easier)
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