• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Beams...yagi or quad

  • Thread starter Icom 706 King Cobra
  • Start date
I

Icom 706 King Cobra

Guest
What beam works best...



many use typical yagi type..

(my understanding is the power is driven via a half wave)



still many use a quad..

(my understanding a full wave)..





also in regards to circular beams...

any advantages to which it is (right or left radiating)




</p>
 

Then again some use Quagi's. On HF the TX polarization dosent matter as it changes by the time it gets to the RX station. Most Have their beams horizontal since the RX is a little quieter on QRN. On VHF and above it depends on the mode. Vert for FM and Horiz for SSB. About the only thing I know where folks use circular is for sattelites and maybe some EME. Which direction I dont know. Never tried it yet. Here is a little write up on Quagi Antennas. It's much easier to build on the higher freq.s since the antenna is much smaller. I've always wondered about a 10 element 40M Quagi.<img src=http://www.ezboard.com/intl/aenglish/images/emoticons/eek.gif ALT=":eek">


<hr />73, Mike
photo.thumb.jpeg
</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=kd5vhf>KD5VHF</A> at: 6/30/04 12:43 pm
 
To understand the characteristics of the antenna, it is convenient to borrow the description of the Quad element given by W9LZX - "a pulled-open folded dipole."



Quads provide more gain per element when compared to yagis with identical boom lengths and number of elements.



Quads are lighter than yagis when the spreaders are constructed of fiberglas.



Quads demonstrate better front-to-back and front-to-side rejection than yagis.



Quads have a smaller turning radius.



Quads operate more efficiently than yagis do at lower elevations.



Quads are much less susceptible to precipitation static than yagis.



Quads experience less wind loading effect than yagis requiring less support and rotor torque.



"Circular polarization is worthless at HF. Certainly not true at VHF/UHF, but for HF, there's no benifit."



blah, blah, blah.



here's an example of a worthless hf antenna using right-handed circular polarization. just one of many.



RHCP



a little history of the cubical quad


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 7/1/04 10:33 am
 
On the CP antenna,The only TX advantage I see is that they can change the radiation angle. Heck you can do that by raising and lowering a antenna. It may work OK for RX since the polorization of a HF signal can be verticle, horizontal or anywhere in between by the time it reaches the RX station. It dosent say but I'm betting it is also a noisey RX antenna.


<hr />73, Mike
photo.thumb.jpeg
</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=kd5vhf>KD5VHF</A> at: 7/1/04 8:50 pm
 
Sorry i left the part out about CP<img src=http://www.ezboard.com/intl/aenglish/images/emoticons/embarassed.gif ALT=":eek:">


<hr />73, Mike
photo.thumb.jpeg
</p>
 
did you read post 205?



if vertically polarized noise sources are up to -20 db. down on a horizontally polarized antenna that results in less noise, not more.



other contributing factors to lower noise levels in the quad design

are the absence of corona / end effect noise present at the element ends or tips in the yagi along with the quads comparitive immunity to precipitation static. (regardless of polarization) both of these advantages are specifically attributed to the quads closed-loop ("a pulled-open folded dipole") design.


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 7/1/04 11:05 pm
 
QUAD VS. YAGI



Why should you choose a Quad antenna over a Yagi? Well lets see! More gain, lighter weight, smaller turning radius, better front to back ratio, better side rejection, less QRN (static), better reception, lower radiation angle,and will work efficiently at a lower elevation than a Yagi.



1. More gain. Numerous tests over the years have shown the Quad to have 2 to 3 db more gain for antennas on the same length boom with the same amount of elements over the Yagi (2 el Quad = 3 el Yagi).

2. Lighter weight. Due to the use of light weight fiberglass spreader arms Quads are typically lighter in weight than Yagi's of similar gain.

3. Smaller turning radius. A two element quad with a gain of 8-10 dbi has a turning radius of only 10.1 ft. You won't find a Yagi with that much gain that will turn in that little space.

4. Better front to back ratio. When a Quad antenna is properly tuned the lobes off the back of the Quad can be brought to a smaller magnitude then is normally found in a Yagi array.

5. Better side rejection, less QRN, better reception. The design of the Quad is such that the top half of the vertical element is 180 degrees out of phase with the bottom half which causes any signal striking the vertical portion of the driven element to be canceled. This is also believed to be the reason that a Quad is so outstanding at being a low noise antenna for reception.

6. Lower radiation angle; operates efficiently at a lower elevation. The Yagi halfwave elements are more affected by their proximity to the ground because of the presence of high voltage at the element tips - 'tip to ground capacity' One effect is to lower the arrays frequency as it approaches the ground. The Quad loop on the other hand is essentially a stacked two-element array of very low proximity effect, and this "stacking effect" results in an inherent gain and a lower angle of radiation. This is why the Quad will be efficient at an elevation as low as 35 ft. The low angle of radiation also means less skips to any distant station which results in a stronger signal on the other end where it counts. the lower heights above ground also contribute to the lessening of the wind loading forces on the tower or support structure itself.

7. A Quad loop, when compared to an equivalent yagi has lower Q, wider frequency response, flatter SWR curve, wider bandwidth.



So you might say, why isn't everybody using a Quad antenna? Well I don't know for sure but I think its because the early Quads were built with bamboo spreader arms, and make shift, wood arm-to-boom supports. Although quick and easy, these materials were rather fragile. The quads that Cubex builds today use nothing but best fiberglass spreader arms available. And let me tell you these Quads are tough. When Hurricane Andrew came through Florida there were a lot of towers that came down with the Quads still intact (until they hit the ground!). We have unsolicited reports of Cubex Quads withstanding over 100 M.P.H. winds with no damage.



Some of this information is from the Crown Manual written by Clarence C. Moore W9LZX the inventor of the Cubical Quad Antenna.



here's the Delta Loop / V Quad in use presently at NAO911.

it's been in the air for going on 10 years, desert winds, dust storms and all....



www.firecommunications.co...image9.jpg





BTW, the "argument" has only been going on for less than 65 years and it has only been conceded recently that the 2 el quad is equivalent to the 3 el yagi for gain. let's not forget the experience related by Clarence C. Moore at HCJB in Quito Ecuador. (for all of you high power buffs) if you read the article linked to in my previous post/s, you don't want to be using 10K+ power levels with the yagi antennas, especially at the higher altitudes.



post 205 / a little history of the cubical quad....


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 7/2/04 2:28 pm
 
Icom 706 K.C.



here are a few questions for you........



* What is the operating frequency range of the system ?

* How much gain is required ?

* What kind of radiation pattern is desired ?

* What is the maximum allowable VSWR ?

* What polarization is required ?

* How much power will the antenna have to handle ?

* Where will the antenna be mounted ?

* What is the lifetime of the antenna ?


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 7/2/04 12:01 pm
 
for those of you who worry about the effect of high winds on large multielement parasitic arrays, be they yagi or quad, here's a little tip that will come in handy the next time you are confronted with this situation.



except for rare, turbulent weather scenarios, wind usually blows from one direction to another. let's say for examples' sake that the wind is blowing out of the north and headed south. if you will turn the array so that it points east-west placing the boom of the array perpendicular to the direction of the wind, loading will be minimized. in most circles this is referred to as "parking" or "stationkeeping" the array.



the other point i was trying to get across by mentioning the quads superior performance at lower elevations when compared to the higher elevations in the case of the yagi is that wind-loading is also a function of height, both of the tower / support structure and the wind-load area of the array combined. the total wind load and the effective moment in foot pounds is significantly reduced at the lower elevations.



in this particular case the quad exhibits less total loading than the yagi at their respective differing elevations.



no one can properly instruct you as to which antenna would suit you best until the questions are answered. when they are, your specific application comes into proper view and perspective and then and only then can the pros and cons of the differing designs be weighed to determine which would provide the best performance according to your unique situation.



what works for one does not necesssarily work for the other.



what is necessary is that due consideration be given to all the aspects of not only antenna design, but also the trade-offs between two or more designs along with all the antenna and tower / structure wind-loading data and taking advantage of the design and structure combination that will accomodate the purpose to which the antenna is to be put to. the difference is between taking down the antenna when you want to vs. picking it all up when you have to. in the case of the antenna pic of the deltal loop pictured earlier, wind-loading at gusts of up tp 100 mph is not a concern, for obvious reasons.



for those of you not intimidated by numbers, here's a file that might be helpful in assessing your own situation and needs.



www.firecommunications.co...height.pdf


</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=freecell>freecell</A> at: 7/2/04 1:34 pm
 
And some folks will argue that a Quagi is better than both.<blockquote>Quote:<hr>After many experiments, it was determined that Yagi-style directors delivered better gain than quad loops when the antenna was extended beyond four or five elements. But the use of a quad-style driven element and reflector offered several advantages, including good gain, good immunity to noise resulting from static buildup, and extreme ease of construction and impedance matching. <hr></blockquote> My 2 cents on the "extreme ease of construction and impedance matching" It depends on what freq. you are building the antenna for. I built a 8el Quagi for UHF and used copper tubing for the driven element and reflector and didn't need any spreaders. The boom and element supports were made with 1/2"od PVC pipe and a few fittings so this was easy but ya just can't build them that easy for HF freq.s. <img src=http://www.ezboard.com/intl/aenglish/images/emoticons/wink.gif ALT=";)">


<hr />73, Mike
photo.thumb.jpeg
</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=kd5vhf>KD5VHF</A> at: 7/2/04 9:40 pm
 
For 2 meter and 220 you wont have to worry much about weather since the antennas are small. Remember Vert for FM and Horiz for SSB and since it is mostly "line of sight" the higher the antenna the better. Check the home brew section for some links to sites with plans to build whatever you decide on.The quagis I've built were easy BUT you need to make sure you measure right. Sometimes a 1/8" difference will throw it way off. Just FYI, here is a neat rotor with memories and remote control that would work well with the small antennas,www.warrenelectronics.com/antennas/9521A.htm


<hr />73, Mike
photo.thumb.jpeg
</p>Edited by: <A HREF=http://p067.ezboard.com/bworldwidecbradioclub.showUserPublicProfile?gid=kd5vhf>KD5VHF</A> at: 7/2/04 11:33 pm
 

dxChat
Help Users
  • No one is chatting at the moment.
  • dxBot:
    Tucker442 has left the room.
  • @ BJ radionut:
    LIVE 10:00 AM EST :cool:
  • @ Charles Edwards:
    I'm looking for factory settings 1 through 59 for a AT 5555 n2 or AT500 M2 I only wrote down half the values feel like a idiot I need help will be appreciated