quad reflector versus yagi reflector

[PLUTO]

"3- Be real careful with the Moonraker Hubs, that attach the elements to the Boom. As their are around 40 years old, they are fragile and will eaisly crack and break. If you don't have to unbolt them, I wouldn't" I agree 100%, what I have done (and still do) is drill a small hole in the hubs at an angle into the boom, then put a small self tapping screw through the hub into the boom (snug but don't overtighten). It keeps the hubs from spinning on the boom and you don't have to risk overtightening and cracking the hub. And remember....measure twice and drill once

 

[cdx304]

I would go will a yagi reflector and not the quad reflector the front to back is real poor .With the yagi reflector and spacing and element lengths you can get over 50db front to back and 100db front to side .
I built a 3 element beam put it up with a 1:1 swr and i had a guy 7 house down from me and his signal would be 60db over s9 pointed at him and i would barely know he was there when the back of the antenna was pointed at him .
High forward gain is ok but i prefer not to hear off the back end.
I put a moonraker 4 and that antenna was horrible front to back .
The moonraker will come down and get a yagi reflector and re-spaced and element lengths changed including removing the wire tips with tubing .
Thats my two cents .

 

[Captain Kilowatt]

I would go will a yagi reflector and not the quad reflector the front to back is real poor .With the yagi reflector and spacing and element lengths you can get over 50db front to back and 100db front to side .
I built a 3 element beam put it up with a 1:1 swr and i had a guy 7 house down from me and his signal would be 60db over s9 pointed at him and i would barely know he was there when the back of the antenna was pointed at him .
High forward gain is ok but i prefer not to hear off the back end.
I put a moonraker 4 and that antenna was horrible front to back .
The moonraker will come down and get a yagi reflector and re-spaced and element lengths changed including removing the wire tips with tubing .
Thats my two cents .

You should patent your design. No commercial antenna manufacturer has yet to design a three element yagi that performs like that nor have they ever designed an antenna with 50 dB F/B ratio or 100 dB F/S ratio. You could make millions.

 

[Jay Mojave]

Hello CDX204 and all: Have to agree with Captain KW there. I think you may have got the dB values misunderstood or you have a earth shattering 3 element antenna.
I am impressed that you can measure 100 dB that's almost pushing the dynamic range of my Network Analyzer!

Suggest you rethink or remeasure those dB values.

Jay in the Great Mojave Desert

 

[n8fgb]

Hello CDX204 and all: Have to agree with Captain KW there. I think you may have got the dB values misunderstood or you have a earth shattering 3 element antenna.
I am impressed that you can measure 100 dB that's almost pushing the dynamic range of my Network Analyzer!

Suggest you rethink or remeasure those dB values.

Jay in the Great Mojave Desert

You have heard on dBd, gain over dipole, and dBi, gain over isotropic. He is using dBdl, gain over dummy load.
Rich

 

[Captain Kilowatt]

You have heard on dBd, gain over dipole, and dBi, gain over isotropic. He is using dBdl, gain over dummy load.
Rich

I could see that if talking forward gain but front to back or front to side is a simple ratio with no other reference than the antenna itself. The big issue is using a signal meter and assuming it is calibrated at 6 dB per S-unit linearly accross the scale. I don't know of any radio that truly is.

 

[Marconi]

Here is what my Eznec models predict for the Maco 104C the conventional yagi vs. the Moonraker 4 with the quad reflector. I added overlays for each in Free Space and over Real Earth.

Sorry for the light color in the overlays.

Note the difference in the Moonrakers 1* degree lower angle. This angle difference may be due to the quad reflector, or it could be due to the balance boom design.

Maybe these models jive with the reported idea that quads make maximum gain at a lower angle, but the idea they show more gain is not evident here.

What do you think?

Edit: Btw, without checking the specs these were old models from my file, but I think there were probably to specs.

 

[Marconi]

Just to be fair on the difference in a quad vs. yagi here is a full 4 element quad with and overlay of all three antenna included.

So, this does show the quad making a bit more gain at a lower angle vs. the Maco or the Moonraker.

 

[vkrules]

Very little difference, if any, with a quad reflector and a yagi reflector on a 3 el quagi.
Both can be tuned for high F to B or forward gain. The lower radiation angle ( and maybe slightly higher gain) seems to be a function of the driven el . In use the quagi and quad seem slightly less directive than the yagi but with similar F to B and gain.Computer modeling seems to confirm this With the H and E plane graphs.

Here is the BUT. You cant just replace one with the other ,the spacing and length has to be changed.for optimum results Yagi quagi and quad all require different spacing.( something to do with the coupling of loop elements)

There is many different variables,and you can configure the said 3 el thousands of different ways, giving different results .

When I build a 3el quagi I like to use a quad driven with yagi parasitics mainly because you get a nice physically balanced ant .

It's easy to build a 3 el and get good gain But to get high F to B takes a lot of careful tuning and testing ( more than most builders are prepared to do)

Yagi design software is very good these days .I can design a yagi, build it and get the predicted results with only minimal tuning to the driven el for match.
However I always have to adjust the reflector on a quad or quagi to get the predicted F to B !

 

[Needle Bender]

Most of the people I've spoken with, whom have had both a Yagi & a Quad, will never go back to a Yagi.
...probably because, as Tom W8JI has clearly stated, they're basically the same.

 

[cdx304]

You have heard on dBd, gain over dipole, and dBi, gain over isotropic. He is using dBdl, gain over dummy load.
Rich

Most antenna designs are made with max gain not front to back or front to side .The old three element i made was the best performing antenna i have ever used .You could hear of the front and that's it the side and back were very silent .

 

[cdx304]

Most of the people I've spoken with, whom have had both a Yagi & a Quad, will never go back to a Yagi.
...probably because, as Tom W8JI has clearly stated, they're basically the same.

A quad antenna would great in Canada but the weather we have here would break the wire .

 

[Captain Kilowatt]

A quad antenna would great in Canada but the weather we have here would break the wire .

The cold weather is not so much a factor as the heavy ice loads in some areas breaking the spreaders. If properly tensioned the wires should not be affected by the cold at all. I used to run a quad reflector element for years and years with no problem. It never broke once.I knew guys running quads in Winnipeg and Fort McMurray and it doesn't get much colder than those places. Neither place has heavy ice however. Several guys down here ran/run quads and we have lots of ice but not that severe cold. The wind is the greatest enemy of a quad. just too much in that three dimensional space to shake and move around, and we do indeed get a lot of wind here on the coast.

 

[w9cll]

The wind is the greatest enemy of a quad

I agree, when I had the PDL2 up I used to watch that thing shake, rattle and roll in the wind. It never came apart though.

 

[Road Squawker]

... and if you install the quad as a "diamond" and not a "square", then the water runs off (most of the time) instead of freezing on the wire.