Cubicle Quad Antenna Info request

[KJ4LNB]

Hello, I am new to this site and hope I have the correct forum to discuss this.

I read an old thread from 2005 but still need help ...

I am going to build a 4 Element Cubicle Quad Antenna and I am looking for someone with knowledge they could share about some technical questions I have, so here goes:

My Background -
In 1971 I built a 4 Element Cubicle Quad ( Not the same type as a Moonraker that is fed from the elements ) the type that is fed on the outer copper wire; so all my questions will be about that type of Base Antenna. I had a book that gave me specs and I had to order a Balun coil about the size of a silver dollar coin with a hole in it that I ran the coax around twice. It was a long time ago, I served in the Army 23 years, moved a lot, lost the book and now that I am semi-retired would like to build another antenna.
I ordered the book by Wm Orr about Cubicle Quad Antennas and will receive it soon; in the mean time I read online about the 11 meter Antenna builders info and remembered 85% of it from 40 years ago, but some things I need help with:

1. In the diagrams on the 11 meter antennas for Cubicle Quad it shows the driven element wires being fed at the coax with the inner part of the coax ( Pos ) on one end of the outer wire - and the other end of the same driven element wire being attached to the outer part of the coax shielded mesh ( - ) OR
the two ends being attached to a fancy Balun cone shaped thing that looks pretty nice ( instead of the silver dollar sized balun thing I originally used ) //// I don't really remember how I fed the antenna 40 years ago but thought I put inner coax on one end of outer element wire and ground side of coax to metal horizontal boom pole which was grounded to the mast.
Help !! Which way to feed it....

2. Rather than make a Balun - I guess I will buy one of those cone shaped ones with the eyelets .... man do they have a lot of choices.... See item # 5

3. Since the radiation is fed on the outer wire, the middle horizontal boom pole that supports the 4 elements would not necessarily need to be grounded would it?
The reason I ask is - I considered making the boom out of PVC Schedule 40 and supporting it with one center pole sticking up and non-conductive rope lines going down to the boom pole. Years ago I used a chain link fence pole as the main boom pole which was grounded, but PVC is lighter.

4. If I use PVC sched 40 do you think I would cause more noise due to static on the PVC boom pole / Antenna?

5. I have a Ranger RCI 10/11 meter radio and would probably not use any more than 500 watts on the Ham side and of course 4 watts on CB ..... but would like to build the Antenna to last; not sure about 50 ohm or 75 ohm coax; probably run about 120 feet of coax and be approx 60 feet above structure or ground.

I appreciate any help you can give me specifically concerning the old style Cubicle Quad Antenna -

IF you want to tell me about how a Moonraker type would be a better option - I Loved the old Moonrakers but can only build one at a time so I am going to build a Cubicle Quad this time. I also don't want to get a Quad that has a brass matching plate built into it.

Thanks
Jessey

 

[vkrules]

cubical quad

hi, feed the driven element with one end of the wire to coax center and the other end to the braid. Balun can be used but should not be required at 27 mhz. 4 element quad should be about 50 ohms so use the 50 ohm cable.This will depend on your spacing between elements,close spacing will give you a lower impedance ,wider spacing will give you a higher impedance. A metal boom will change your element lengths. Best to go with a non metalic boom. Fiber glass boom and speaders is the way to go, if you can find and afford it.The William Orr book on quads is a great book, might pay to read that before you start construction. Download a program called yagi cad 6.1 and have play (free download and does quads as well) There are quite a few variables that I don't have time to go into here. ..... Mark

 

[wavrider]

Many sites online for quads.

Take a look at Cebik's site

I would recommend a 1:1 current balun at the feed point. This will evenly distribute the current and make a cleaner signal from the Quad.

 

[KJ4LNB]

Even though the elements are a non-conductive - the antenna ( outer wire lengths ) would be affected with a metal boom ??

Fiberglass Boom - I guess I will take another trip to Lowe's and see if I can find such an animal there....
They are probably starting to wonder about me walking up and down the aisles at Lowe's and back and forth ..... lol

I hope the Wm Orr book will be here today and I will read it thoroughly.

Thanks

 

[Captain Kilowatt]

Nothing wrong whatsoever with a metal boom on a quad. All the major commercial quads have a metal boom. The thing NOT to have metal is the spreaders that support the loops. The price of a fiberglass boom to handle a four element quad and be sturdy enough in high winds and ice loading as well as be rigid enough so as to not flop all around would be VERY pricey.

 

[HomerBB]

I used metal boom and spreaders On a Quad. The metal spreaders were terminated 18" short of reaching the wire loops. I detected no compromise in performance over the previous Quad I had that had non-conductive spreaders throughout. Neither of the spreaders were of resonant lengths for the band in use, so I theorized that was why no problems appeared in my case.

 

[project]

http://www.cubex.com/hard.htm#ELE

Here is a one source for parts

 

[Captain Kilowatt]

I used metal boom and spreaders On a Quad. The metal spreaders were terminated 18" short of reaching the wire loops. I detected no compromise in performance over the previous Quad I had that had non-conductive spreaders throughout. Neither of the spreaders were of resonant lengths for the band in use, so I theorized that was why no problems appeared in my case.

Exactly, The quad loops on the Moonraker, Shooting Star and a few other yagi/quads all had metal spreaders with fiberglass ends about three or four feet long. Minimal amount of non-resonant metal won't hurt a thing. I figure the multimillion dollar companies probably spent a few dollars in R&D first.

 

[Captain Kilowatt]

CUBEX HARDWARE & PARTS

Here is a one source for parts

Here is another good one.


MAX-GAIN SYSTEMS, INC.

 

[KJ4LNB]

Checked both parts places - thanks

I checked both sites ....
Cubex seemed to make more sense to me, but it is 2:30 in the morning here, so I am headed to bed ...... zzzzz

 

[Mudfoot]

I believe quads would have been more popular in the old days, had amateurs had access to more durable construction materials.

Most quads were built with flimsy materials that couldn't withstand the elements. Now, with superior materials, quads are more popular. Just wish I had the ability to deploy a few big quads.

 

[Wire Dawg]

I recently assembled a 4 element quad from Cubex. After some research, I WAS ready to install a 1:1 current balum that I bought from dxengineering. However, after connecting RG-213 directly to the bottom of the driven element (braided to one side and inner to the other/ horizontal polarization) I determined that there was no need for the balum. SWR was at 1.2:1 for nearly a full Mhz bandwidth from center freq (which turned out to be chan. 30). Tests with a field strength meter lead me to believe that the projection of the main beam was well-aligned (not lobe-sided). QSO's confirmed that the antenna radiated well in the direction that was pointed. Like you, I'm returning to this hobby that I embraced prior to my 15 years in the AF as a 361 (antenna/cable) and 304 (ground radio). Your decision to build is commendable, as it adds to the enjoyment, and because Quads are (IMO) superior in the functions of what an antenna is supposed to do. Good luck!

 

[KJ4LNB]

Just curious - why did the center freq turn out to be channel 30?

Were the outer wire sizes not calculated for 27.185 or there abouts?
Or
Were the spreaders made a longer length, which also changes the outer wire lengths?

 

[wavrider]

Without a balun at the feed point the coax probably had some effect on the resonant frequency.

A balun is for connecting a balanced antenna to unbalanced transmission line I.E. coax.

Are they necessary? I use them but they are not necessary to make an antenna work, the antenna just works better with a balun, 1:1 current balun.

If a balun is not in the budget then an RF choke AKA ugly balun will be the next best thing.

 

[KJ4LNB]

1:1 Balun

Well then I make the budget include a 1:1 Balun .....

I would rather get it right the first time than have to take it down and do something else to it.