QUAD Beams - Are they better than Yagis? Are thicker 'wires' better?

Summary

Justin G0KSC from Innova Antennas discusses his Quad Yagi Antenna (LFAQ) design, inspired by Yu7XL's work. The LFAQ features adjustable elements for precision and a twin boom design for rigidity and high power handling. Justin covers the antenna's design parameters, benefits like high gain and broadbanding, and its comparison to traditional Yagi antennas. He also addresses the limitations of NEC-based modeling for curved elements and the practicality of the LFAQ for various power levels and frequencies.

Takeaways

• 🌐 Justin G0KSC is the creator of Innova Antennas and shares his designs on his website g0ksc.co.uk.
• 📚 His work is featured in the ARRL Antenna Book and in the DUBUS magazine.
• 📅 In 2021, he covered quad Yagis in DUBUS magazine, which is part of the discussion in the video.
• ⏰ The video might be split into two parts due to YouTube's time limit for videos from channels with fewer than a thousand subscribers.
• 🎯 The main topic is the design and inspiration behind Justin's quad or LF Quad (LFAQ) antenna.
• 🔍 The inspiration for the LFAQ came from YU7XL's antenna designs, particularly the use of solid rods clamped onto a boom.
• 🛠️ Justin wanted to make the quad elements adjustable to fine-tune the antenna's performance.
• 📡 The LFAQ features twin booms, which allow for easy adjustment and better performance stability.
• 🔩 The antenna design includes a break at the bottom of the driven element for feeding and an insulator for the coaxial cable.
• 🔗 The LFAQ is designed to be simple to maintain and can handle high power levels, making it suitable for various conditions.
• 📊 The video discusses the trade-offs between the number of elements in a Yagi or Quad antenna and their performance, including gain and bandwidth.
• 📈 Justin uses a slide to illustrate the effective gain per foot of boom and how it compares between Yagi and Quad antennas with similar bandwidths.

Q & A

Who is Justin G0KSC and what is his association with Innova Antennas?

Justin G0KSC is associated with Innova Antennas and also operates the website g0ksc.co.uk where he publishes his antenna designs.

Where can one find Justin G0KSC's work published?

Justin G0KSC's work can be found in the ARRL Antenna Book, D-STAR magazine, and his website g0ksc.co.uk.

What is the subject of the first part of Justin's discussion in the video?

The first part of the discussion focuses on Quad Yagis and their design aspects.

What is the potential limitation of YouTube's video length for Justin's channel?

YouTube limits the video length for channels with less than a thousand subscribers to around 15 minutes.

What is the inspiration behind Justin's LF Quad antenna design?

The inspiration for Justin's LF Quad antenna design comes from Yu7XL's website, specifically the use of tubes or solid rods clamped onto a boom.

What is the main issue Justin has with the curved elements of the antenna design he mentions?

The main issue is that curved elements reduce the accuracy of NEC-based antenna modeling, which could result in the antenna not performing as expected.

What is the purpose of making the tip lamps of the antenna adjustable?

Making the tip lamps adjustable allows for fine-tuning the size of the elements to position the antenna exactly where needed.

What is the benefit of having twin booms in Justin's LF Quad antenna design?

Twin booms allow for a single through-the-boom U-bolt on each side, providing stability and making the antenna easier to assemble and adjust.

How does the design of the LF Quad antenna help with static build-up and protecting the transceiver?

The design includes an insulator running through the boom, which helps to remove static build-up and protect the transceiver by preventing electrical discharge.

What is the advantage of using larger diameter elements in a Quad antenna?

Larger diameter elements can achieve higher gain and help to broadband the antenna, making it more efficient and stable.

Why did Clarence Moore W9LZX develop the Quad antenna?

Clarence Moore W9LZX developed the Quad antenna to help remove higher altitude issues and prevent coronal discharge from melting the element tips of Yagi antennas.

What is the trade-off Justin considers when deciding the number of elements for a Quad antenna?

Justin considers the balance between performance and the additional hardware, weight, and complexity. He finds that beyond seven elements, the performance benefit does not warrant the increase in these factors.

Outlines

00:00

📡 Introduction to Quad Yagi Antennas

Justin G0KSC from InnovA Antennas introduces himself and his work published on g0ksc.co.uk and in ARRL's antenna book and DUBUS magazine. He discusses the Quad Yagi antennas, also known as LFAs, which he will cover in depth in a potential two-part video due to YouTube's time limit for channels with fewer than a thousand subscribers. The inspiration for his design comes from optimizing Yagi antennas and the influence of YU7XL's designs, particularly the use of solid rods clamped onto a boom. Justin addresses the issue of model accuracy with curved elements and his solution of making the tips of the elements adjustable to fine-tune the antenna's performance. He introduces his design, the LFA Quad, which features twin booms for rigidity and the ability to adjust element sizes uniformly.

05:00

🔩 Design Features and Benefits of the LFA Quad

The LFA Quad design by Justin G0KSC includes a twin boom setup that allows for easy adjustment of the antenna's elements using U-bolts and insulators for secure coax feeding. The design helps to prevent static buildup and protect the transceiver while also providing a bandpass filter property. The antenna is robust and can handle high power levels, making it suitable for various environments, including icy conditions. The use of larger diameter elements contributes to higher potential gain and broader bandwidth compared to traditional quads made with thin wires. The historical context of the quad antenna's development by Clarence Moore W9LZX is also mentioned, highlighting its advantage in preventing coronal discharge issues that can damage Yagi antennas.

10:01

📊 Performance Considerations of Quad Antennas

Justin discusses the trade-offs between the performance benefits and the physical requirements of Quad antennas compared to Yagi antennas. He explains that while Quad antennas can offer higher gain, the need for more materials and the complexity of their construction must be weighed against the performance advantages. He mentions that he produces the LFA Quad up to seven elements and declines to go longer due to the diminishing returns on performance and the potential for narrow bandwidth issues. A slide is presented to illustrate the effective gain per foot of boom and the optimal number of elements for both Yagi and Quad antennas, suggesting that beyond seven elements, the performance difference is not significant enough to justify the additional hardware and weight.

15:01

🛠 Practical Aspects of Quad Antenna Design

In the final paragraph, Justin touches on the practical aspects of designing Quad antennas, including the challenges of feeding them with 50 ohm coax and the need to manage power handling and radiation. He presents an EasyNEC model of a short two-element Quad antenna for 144 MHz, which offers a compact design with good gain and front-to-back ratio. The discussion highlights the simplicity of direct 50 ohm feed compared to older designs that required matching networks, and the importance of considering the velocity factor of the coax when designing the feed point. The summary ends with a note on the continuation of the discussion in a second part of the video.

Keywords

💡Innova Antennas

Innova Antennas is the company run by Justin G0KSC, where he designs and publishes antenna designs. It's central to the video's theme as it represents the source of the expertise being shared. The website g0ksc.co.uk is mentioned as a place where his designs are published for free, indicating the company's role in providing resources for amateur radio enthusiasts.

💡ARRL Antenna Book

The ARRL Antenna Book is a comprehensive guide to antenna design and performance, published by the American Radio Relay League (ARRL). It's mentioned in the script as a place where Justin's work appears, indicating the recognition his designs have within the amateur radio community.

💡Dubus Magazine

Dubus Magazine is a publication that covers topics related to amateur radio. Justin mentions that his work has been featured in Dubus Magazine, and specifically in 2021, which underscores the ongoing relevance of his antenna designs to the broader community.

💡Quad Yagi

A Quad Yagi is a type of antenna that combines elements of both quad and Yagi antennas. The video discusses this design extensively, with Justin explaining the Quad Yagi he has designed, known as the LFAQ. It represents an innovation in antenna technology being presented.

💡Design Parameters

Design parameters refer to the specific characteristics that define an antenna's performance, such as frequency range, gain, and impedance. The script discusses these in the context of the LFAQ antenna, emphasizing the importance of understanding these parameters to optimize antenna performance.

💡Yu7XL

Yu7XL is mentioned as a source of inspiration for Justin's LFAQ antenna design. Yu7XL's website is referenced for detailed antenna designs, indicating the collaborative and knowledge-sharing nature of the amateur radio community.

💡NEC-based Antenna Modelers

NEC (Numerical Electromagnetics Code) based antenna modelers are software tools used to simulate antenna designs. The script mentions that using NEC-based modelers can reduce the accuracy of models with curved elements, which is a technical challenge addressed in the development of the LFAQ.

💡Twin Booms

Twin booms refer to the physical structure of the LFAQ antenna, which uses two booms instead of the traditional single boom. This design choice is discussed in the script as a way to allow for adjustable elements and improve the antenna's performance.

💡Gain

Gain in the context of antennas refers to the antenna's ability to direct radio waves in a specific direction and improve signal strength. The script discusses how the LFAQ's design can achieve higher gain, particularly when using larger diameter elements.

💡Bandwidth

Bandwidth is the range of frequencies over which an antenna operates effectively. The script mentions that the LFAQ is designed to have a good bandwidth, which is crucial for its versatility and performance across different frequencies.

💡Coronal Discharge

Coronal discharge is a phenomenon where high voltages can cause electrical discharge in the air, which can damage antenna elements. The script explains how the closed loop design of the quad antenna helps mitigate issues associated with coronal discharge, thus enhancing the antenna's durability.

💡Stacking

Stacking refers to the practice of mounting multiple antennas vertically to improve their performance. The script mentions the ability to stack quad antennas as a benefit, highlighting the flexibility in array configurations that quad antennas offer.

Highlights

Introduction to Innova Antennas and g0ksc.co.uk website for antenna designs.

Justin g0ksc's work featured in ARRL antenna book and D-STAR magazine.

Discussion on Quad Yagi antennas and aspects to be covered.

Potential need for the presentation to be split into two parts due to YouTube's time limit for less than a thousand subscribers.

Design inspiration for the LFA Quad came from YU7XL's website and his antenna designs.

Challenges with NEC-based antenna modelers when dealing with curved elements.

Introduction of the LFA Quad with twin booms for better adjustability and performance.

Explanation of how the LFA Quad's design helps to remove static build-up and protect the transceiver.

Advantages of larger diameter elements for higher gain and broadband capabilities.

The Quad antenna's ability to handle very high levels of power.

Historical context of the Quad antenna's development by Clarence Moore W9LZX.

Comparison of the Quad antenna's performance to a Yagi antenna with similar bandwidth.

Practical considerations for the length of Quad antennas and their performance benefits.

Ability to stack Quad antennas for increased performance.

Introduction to EasyNEC and its role in antenna modeling.

Details on a short two-element Quad antenna model with a direct 50-ohm feed point.

Advantages of a 50-ohm direct feed for simpler antenna setup and power handling.

Performance metrics of a 144 MHz two-element Quad antenna model.

Conclusion and预告 of part two of the presentation.

Transcripts

hi

i'm justin g0ksc of innova antennas

and also the g0ksc.co.uk website

where a lot of my design work is

published or some of my older designs

are published for

free building yourself um you'll also

find some of my work in the

a r r l antenna book

and also in dubus magazine and dubus

magazine

in 2021 in the first part

i will be covering uh the quad yagis

and some of the aspects of what we will

discuss today

uh in an article there so please do take

a look at that also

um one thing i do need to to say at the

beginning is that this might need to go

over into two parts and the reason for

that

is at the moment whilst we have less

than a thousand subscribers

youtube tend to limit the time that you

can recall for so it's

it's around 15 minutes just over perhaps

but that's about the best that i can do

at the moment before we um

before we go into a position where um

they won't allow it to upload

so rather than having to try and trim

that

or cut it in half and produce two videos

it may be when it gets to that 15 minute

mark that i have to do that

okay so what we're going to be talking

about is my quad or

lfaq as i've designed it what

the design parameters were and why

and where that came from i've got some

notes here as well so i don't have to

sort of

add quite as many notations hopefully

onto the

presentation there afterwards so the

first thing really

is where did the inspiration come from

was very heavily

into optimizing yagi's and the

lfa yagi abdesyagi and so on which

you'll find on

some of the previous videos and

discussions about

but really the inspiration for this lfa

queue the the rigid

uh quad came from yu7 xl

now um bobin has a website which you can

find

at qslnet and uh he discusses

some of the various bits and pieces with

regards to his antennas

and at the bottom here he has a list or

a link where you can go to

where he discusses a great deal of the

the antennas

in detail you can click into one of

those and have a look at the details or

download the details

on that antenna and perhaps even build

yourself

so a very nice concept and if you look

it's using the tubes or

a solid rod that in this case is molded

and clamped onto a boom here

and then orientated onto a a long single

boom

now that idea is great the only issue

that i have with that is that

is that well in actual fact it's two

the first is that with easy nec or nec

based

antenna modelers mini neck modelers

marna gal when you have curved

elements as you do here that

reduces the accuracy of the model

and so what that means is that when

you're producing the antenna it might be

that you produce something as long as

this and it's not quite where you need

it to be

so you may have to either model it so

that it's very wide and lose a little

bit of the performance

or have to have a few different hits at

it

so one of the aspects that i wanted to

do was to

make these tip lamps adjustable so that

on all of those elements if the antenna

didn't sit exactly where you wanted it

to be

you could reduce the size of each of

those elements

or increase the size of each of those

elements all by the same percentage

so you could sit that antenna exactly

where you wanted it to be

the problem is with that is that when

you were to then

secure these element tips maybe with a

hose clamp or something like that

it would mean that these could easily

fold over

so what i produced is the lfaq

which would then have um twin booms

and we can see a first picture of one of

those here

this is a a 144 megahertz version

and as you can see it has twin booms in

this case

they're three-quarter inch this means

that you can just use a single

through the boom u-bolt on each side

and then the elements pass through the

top and the bottom now there is a break

at the bottom on the driven element so

that you can feed it

and there's an insulator that runs

through the boom so that the coax feeds

either side of the boom

but as far as electrically connecting at

the top that's fine at the design

frequency

that isn't seen so you've got the rf

travels around here hits this point

that's a point of

theoretical zero current come back again

just voltage

pick up the current go back with some

forward so we're going backwards and

forwards each side just like this

so at the design frequency that isn't

seen that helps

to remove the any static build up that

can

drain away and protect the the

transceiver and also

although it's not seen at the design

frequency it doesn't mean that the

antenna goes

uh high impedance very very quickly so

you have a bandpass filter that's

available filter property that's added

to the antenna too

so that's where it's at you can see then

there's just a single small bolt that's

needed to heat

up each of these to the elements here

and then the end sections uh there are

loops here with slide in trombone

sections like they are on the

lfa yagi which means that you can adjust

every one of them by the same percentage

to get exactly where you want to be

with that particular antenna so you know

it could be the case that

if you wanted to you could weld

those points once you're done or spot

world because there is the aluminium

brazing which you can use now with a hot

torch

and just simply effectively solder each

of those joints

and you're good to go the other

associated benefits with doing that

is as well i'm just looking at my notes

here to make sure i don't miss anything

this is obviously fairly simple to to

maintain

but when you have um traditional quads

they're generally made with thin wires

now one of the benefits of the quad of

course

is that per foot of boom it can be

higher than a yagi over a given if the

yagi and the quad have got the same

bandwidth associated with them

then of course it can be that there's a

higher gain figure

that does diminish and i'll show you in

a second why

um but with the

radiating element or the elements

themselves the thinner they are

the less gain there is it's very slight

but the bigger the element

generally the more gain that can be

achieved so of course when you have a

quad which lends itself to higher

gain and then you use thin wires you're

reducing potentially what gain you could

be having

so when you now get to and we can do

these on hf

but when you get these to vhf on you and

you're now using half inch elements with

3 8 inch end sections which is almost 13

millimeters

by 10 millimeters if you look at the

ends then the potential gain is much

much higher

and that also helps to broadband the

antenna as well

so what else was there um we spoke about

the gain part

um obviously it's strong and stable and

if you've got a fairly good bandwidth

which is easy to achieve with these

especially

with the larger diameter elements then

it becomes very stable as well so if you

imagine you had something like this in a

very very icy location

that can be loaded with ice and it

wouldn't be troubled at all

it's going to stay fairly rigid as well

and the other aspect is is that you can

handle very very high levels of power

now i'm just going to open up a slide

which i

delivered in a presentation and i'm

doing this rather than bringing them in

later because it feels more fluid if i

if i do these rather than overlay these

in the presentation later on

um the the the chord itself was

first introduced and developed by

clarence moore w9

lzx or w9 lzx

for our european friends and

the reason that he developed the quad

was to

help remove some of the higher altitude

issues that he had where he was

operating with the antennas

on a commercial station and coronal

discharge which you can see here on this

electricity cable

when you get very high power and that

happens on a yagi it happens at the tips

of the elements

and ultimately what that means is that

the element tips can melt and fall away

and then of course your antenna is no

longer um uh effective

frequency of operation will be on the

band where you were using it

because of course the elements would be

uh becoming shorter

so with the closed loop then

uh there isn't any tip that that can

that can be uh subjects to that

uh highest levels of coronal discharge

so you don't have the

the melting aspect that could occur as a

result

so um that was the the main reason um

for the introduction of the the quad but

of course it has other associated

disadvantages

if you look at the quad in the way that

i've produced it with the twin booms

and with the quad elements the quads

elements are

plus or minus depending on where you are

in the array

um a wavelength long whereas the yagi

elements

are a halfway vlon so when you're using

tubes you've now got twice as much tube

per element

as you would have with an equivalent

yagi

you also have two booms rather than the

one boom of the yagi

so it gets to a point where does the

performance that you're achieving

outweigh

what you're putting in so i'm going to

bring up another

slide which i made here earlier

to show you to which is very very basic

but to give you

um an indication as to where uh we are

as far as that performance

benefit is now commercially through in

of antennas we make uh the

lfaq up to around seven elements and

people on occasion say well could you do

me one longer could it be uh nine ten

twelve or or whatever it is

but i have a point of view with that and

one of the problems for me

is that um i said early on that i

wouldn't produce anything

commercially that i wouldn't be happy

with using myself

even if the the market demands it it's

like the

2 meter 70 sems yagi's on the same boom

no they're they're third harmonic

related so

if you're feeding with a single feed

point the two meter elements are going

to conduct when 70 sems is in use

which is going to flower petal the

pattern on 70 sems

so yes you can get a good swr but

you're not going to get the same

performance as you would do with other

dual band yards where you don't have

that third harmonic relationship issue

so it's a similar situation here if you

look at this scale here

we've got an effective gain per foot of

boom

in the vertical plane and then the

number of elements that you might have

on a yagi or a quad

so you can see when you've got a two

element a two element quad or two

element yagi

the difference that you would have in

gain

between the two is at its greatest as

the boom

gets longer that delta that difference

between the gain

between the yagi and the quad

starts to become closer together now for

me when you get up to sort of seven

elements

the the difference when you have an and

you can make

the game much bigger if you wanted to

but you're going to have narrow band

what i'm talking about is comparisons

between a yagi and a quad

which have similar bandwidth so

let's say 14 to 14.35

megahertz under say one point two to one

so that yagi and that quad both have one

point two to one from 14.0 to 14.35

that delta between those two points

for the additional hardware the

additional weight which is

is getting on for twice the amount in

the quad doesn't warrant

the difference in performance because

after all if i had the vertical space

i could then stack two of those yagi's

one above the other

and have a greater performance in that

single uh quad

okay so that's where we are uh on on the

quads and why i tend not to go

uh too long with these the other great

benefit with the quads

is the ability to be able to stack now

um what i'm going to do is i'm going to

open up an easy

neck version of the antenna and i'm

watching the time because we're already

up to 13.

um if you haven't got viewing

or any basic knowledge of easy neck or

some of the other modelling packages

this is available through easyneck.com

there is a free version

where you can buy and support the

developer the

the simple version and see some of these

in their fullness

and i will give some downloads to some

of these models which you can have a

look at

these will be presented on the screen

now and they'll be staying on my site

for you to be able to download

and play with now this is the a very

short

two element quad and it's a direct 50

ohm

feed point one of the things with the

older style quads is i always tended to

be around 110 112

ohm now i've come to the conclusion that

the reason it was optimized around that

figure

is you can use a quarter wave length of

75 ohm

piece of quarter wave length coax with

50 ohm coax at the end of it

that will give you a 50 0 match at the

end of that 75 ohm

length of coax but it needs to be

having the considerations of the

velocity factor of the cable so you need

to measure that to make sure it's okay

but the problem with that is of course

you reduce the power

capabilities of the antenna you need to

get it right

uh the the sizes that's involved for the

coax

and with a 50 ohm direct feed generally

you can have a shorter boom with a

similar

amount of gain perhaps in some cases

better amount of gain per foot of boom

once you get up to vhf and uhf getting

those

lengths of the coax correct and also the

power handling starts to become

a bit more of an issue and obviously

it's a great deal simpler to be able to

feed it

a quad with a 50 ohm coax and just have

to worry about a few

ferrite cores or a simple choke to stop

coax radiation

so when you look at this one this is for

2 meters 144 megahertz

and if i do the run here you can see it

gives

6.74 dbi 16

and a half db of front to back so it's

pretty reasonable

and when you look at the the boom length

it's just 14 centimeters long

i mean it's it's very very short indeed

and the reason it's that length is we

have to come in that amount

to keep the impedance fairly low i'm

going to need to chop this here

and i'll carry on in part two in just a

few seconds

you