2 Element Quad Construction

[Island_0860]

Hey !
Journal on my 2 element quad
Well.. seems like this section has been quiet for too long ..so here we go

The Plan : 2 element quad (inspired by HomerBB)
Center Freq : 27.405
Mast : 6ft 1 5/8 OD Galvanized steel pipe
Element Wire : 10 Ga single strand copper
Spreaders : 1/2 inch PVC ..reinforced inside with wood dowels
Reflector to Driven Element Spacing : 5.38 FT

This is what we have so far

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Since I live in a 3rd world country ..everything has to be "fabricated"..which will make this even more challenging
The Quad Hubs got finished yesterday..and fit nice and snug to the boom.
They are both open ended ..the idea being to adjust them in + out for front to back and gain adjustments.

[HomerBB]

Sweet! Looking great so far.
Thanks for the by-line, but it will be all you in the long run, and you're off to a great start.

[Island_0860]

Need to pickup the PVC for the spreaders today..along with the inside wooded dowels for support (thanks Homer)

For me.. looking at all the Quad pics on the web.. I never really appreciated just how BIG ..this S.O.B will be !!

Thinking to myself today.. how much easier this project would have been.. if the founding fathers at the FCC moved us on up to 49 MHZ !

Some Concerns ...
Like Gunny..I have this Super Heavy Duty syndrome ..so while normal people design Quads using #12 or #14 ga. wire ...mine MUST be #10.
Reading about how this should positively affect the bandwidth ..with less of a dropoff in gain.. and I was convinced.
Just how well the PVC Spreaders will hold true to form will be the next up and coming adventure !

More later ...

[626]

HAHAHAHA Its a syndrome?

Hey man Im looking forward to watching the progress on this bad boy. Keep up the good work.

[Island_0860]

Thanks for all the goodwill Homer and Gunny.. I'm staying motavated here.

Had some setbacks today ..seems that the wooden support dowels for inside the spreader arms are not available.
I'm kind of worried that my 1/2 PVC spreader arms wont be up to the task.

So i'm attacking the support issue a couple of different ways.
I noticed something interesting today in the #10 wire.
Because its one strand and so large it does a great job of supporting itself.
I straightened out a 4 ft section by hand ..and it stood perefectly ..no bending !
Now my thought process is that maybe all that tension wont be needed by the spreader arms to keep us in a nice tight cubical form.
I'll try my theory out on that tomorrow.

Need to buy a new ladder tomorrow .. as my 6ft folding one wont get it done.
This will help me to elavate the boom on the ground and continue working.

Also need to find a good process for stretching the wire..as this will be critical in getting all the tiny dips and rises resolved so we have a nice straight 1/4 wave copper wire elements.

A fine tip sharpie works great in marking off the 1/4 wave sections
When dry.. it adheres to copper very well and wont rub off.

Overall a good day !

[HomerBB]

Keep us posted.

[Island_0860]

Made some decisions today.

Since i'm not able to source material (wooden dowels) in order to reinforce the spreaders..I have decided to go with 3/4 PVC instead of the 1/2 .
Off to the Fabricators tomorrow with wholesale changes ...heheheh

Saw a website where someone ingenious enough got the smaller diam. PVC to support ...but involved connecting both the driven and reflector with additional PVC and ropes to compensate for the sag.

So we go with the 3/4 for spreaders ...and also decided to modify the tubes that connect the spreaders to the hub by extending the length from the now 5 inches to 12...should help out leaps and bounds better than the current config.

Have to be carefull here as anymore length would start to influence the RF properties of the quad.


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Got the new 20 ft folding ladder this morning ..and proceeded to trim back some of the tree limbs...but there is still more to go .

I having trouble understanding the support connections from the element wire to the spreaders.
Know it sounds like a simple thing ..but need to search more for some better pics or drawings .

Ill post some pics tomorrow of the site location along with the modded hubs

[HomerBB]

I did this:

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[yamaha]

Its not just 3rd word but the git-real world. Who can realy dish out 1000$ on a antenna that is at tops 100 bucks in material and could be assembled by a cave man.

[Island_0860]

Hey Homer ...
Yes I saw you mentioned the PVC "T" ...but that T is only at your feed point ?

It didnt look like to me that you used the T's for all the spreaders ..but maybe i'm wrong ?

Thanks !

[HomerBB]

I put PVC caps on the ends of the spreaders, drilled holes through them, and ran the wire through those holes.

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[Island_0860]

LOL ..dosent get much clearer than that

Thanks for your time and help my friend !

A note to anyone actually trying to build one of these.
While "Googling" dont just necessarily skip over a home made quad because its not in the same band as 10 or 11 meters.
I was doing this ..."skipping over" anything that was not described for 10 or 11 meters.
Really the only things that change are the wire length ...nothing more.

[Island_0860]

Got the hubs into the shop today..they will be ready tomorrow

Picked up the 8 7ft spreaders with their end caps (Homer) ..LOL

As you can see in the pictures ..I have one tree that must be trimmed back that would affect the quads southern view.

Tonight i will be researching the choke balun in detail . ...and wire stretch techniques

I dont have any 50 ohm coax..as this will be coming in from the U.S on wedensday.

Will post better pics tomorrow when the hubs get completed


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[HomerBB]

Well, that's progress.

The choke can be as simple as five to six wraps of 50 Ohm coax around a four inch core such as a piece of PVC, etc, any non-conductive material.

Looking forward to more.

[Island_0860]

Nice when you receive parts when promised
The new hubs were ready today on time.
They came out great...perfect fit to the boom
Now the core of our work seems to be done.

Plans for tomorrow
Deciding on how the quad is going to get its support (mast or tower).
Building 7 1/2 ft saw horses that will allow me to continue working at ground level while supporting the monster !
Complete the balun construction

On Monday i will get the mast to boom tube welded in place.

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[HomerBB]

Looking great.
I supported my Quad between two step ladders.

[MDYoungblood]

Hey Island_0860,
Are you going to make your cubical quad dual polarity? You need to do a little research into the HyGain Big Gun II. it was a quad like you are building with 2 driven wires. What you have so far is excellent work, keep it up.
3's

Greg

[626]

There are so many options with quads. One of the main advantages is that they are a little less affected by height then a yagi. You still wanna get it up in the air at least a wavelength cause its not referenced to ground.

MD Youngblood brought up a good point. If you want you can have it vertically polarized, horizontally polarized, you can make it switchable. You can also make both elements driven. You can also drive them out of phase and have circular polarization. Dang they are versatile. Great choice.

[Island_0860]

Hey Homer !

The 2 folding ladders is what I was thinking ...but mine are only 5 FT of the needed 7 FT !

I'm going with this setup ..but ran out of lumber and nails on a Sunday ..heheheh


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[Island_0860]

Got some more great news..

I was thinking that I had an "Ace in the hole'' ..with the use of my R2001D and the Tracking Generator function.
Well seems that option isnt installed ..so its back to the traditional methods

I can still use it as a variable low level transmitter..as to simulate distance and this should give me something to look at in evaluating the Quad's performance.

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[Island_0860]

Hey MDYoungblood !

I plan to use the Horizontal polarity for now.

Since there is no local 11 meter activity here.. and understanding that Horizontal will be a bit easier to support on the Quad ..i'm going to go with that.

Another reason is I just have 150 ft of RG 8 coming in from the US

But the dual polarity will be a priority for the future ... when I decide to go and get a 16 ft boom for 4 elements.

I'm liking your Pierce simpson base by the way ...LOL

[drdx]

I put PVC caps on the ends of the spreaders, drilled holes through them, and ran the wire through those holes.

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Man, you are resourceful, that looks great.

Why those caps at then end of the spreaders, and just not drilling holes in the ends of the spreaders themselves? I'm guessing that's easier on assembly and probably takes care of any splitting issues at the end of a spreader, as the cap is easier to replace than the spreader arm? For that matter, you could probably also use couplers instead of caps if that's all you had. Great topic, I was just wondering and like to use as few parts as possible. Do you use pvc cement on yours homer? I'd think the tension would be enough and allow the ability for replacement later as pvc will kinda stick to itself after temperature variances.

On the wire stretching, and I've never done it, but wasn't there some old trick or wive's tale about putting the wire in an oven and cooking it to "temper" it so the stretching wouldn't be an issue?

What about the feed, maybe I missed it, but are you using anything for matching? I've had mixed luck with that on loop feeding myself and used baluns in the past.

-drdx

[HomerBB]

What about the feed, maybe I missed it, but are you using anything for matching? I've had mixed luck with that on loop feeding myself and used baluns in the past.

-drdx

For a single quad loop, or a two element Quad I use a 1/4 wave 75 Ohm matching section and a 1:1 balun. It works every time.

[Island_0860]

Exactly ..
In the perfect world.. the 2 element quad will have close to 100 ohms impedance.
To complete the choke and stepdown the impedence...I plan to coil up 1/4 wave of 75 ohm RG 11

I really attemped to calculate this info on my own ..but was unable to locate any on line or calculator program.
Some of the calculations involve knowing the cable velocity factor impedance etc.

[HomerBB]

example: 36 x .25 x VL (rg59 - .67) = 6.03' or 6'