FULL SIZE 75M LOOP..

[W3SLK]

Tom said,

Mike: I know what ya mean about the snow static. Though
I hear popping on all of my antennas usually. The loops
sound as loud as the dipoles when it snows, BUT, it could
simply be that they are all coupling to one another... ie,
when the dipole pops it gets picked up on the loop when
I'm listening on the loop - Even though they are all separated
by at least 150' apart.

I don't have near the aerials that you have so I wouldn't be able to do the side-by-side comparison. However, whenever I had my 'doublet style' (dipole, G5RV, or any reasonable facsimile thereof), I had snap, crackle, and pop in the antenna tuner. I never heard any kind of arcing with the loops.

[K1JJ]

Mike,

Does your loop use an ant tuner/openwire like the dipole
or directly coax fed?

T

[W3SLK]

Does your loop use an ant tuner/openwire like the dipole
or directly coax fed?

It is fed with COAX. My buddy, WB4VVI (SK), Eric, told me to feed it with coax since it would be a DC short. I never had problems with it. You made an interesting statement a few replies ago with refrence to antenna height VS take-off angle. I wish I had the modeling to check that out but unfortunately, anything I put up will be low angle due to inability to find tall enough (and cheap) supports.  I will be putting up a extremely large loop for the new QTH.

[K1JJ]

Mike,

Yep, dipoles at 30'-50' high are excellent for local stuff out to
maybe 300 miles. Rest assured you can't do better than that
for high angle propagation.

I was told that the stuff in the shack, like ant tuners, relays,
PL-259's are much of the cause of pops during snow static.
Capacitors charging up and arcing, etc. I've had my share
with ant tuners too.  That's why I axed about the coax. I
wonder if you hooked that coax fed loop to the ant tuner
wud it have the same amount of pops as the dipole during
storms, despite it being a closed system..
T

[W3SLK]

Tom said,

I wonder if you hooked that coax fed loop to the ant tuner wud it have the same amount of pops as the dipole during
storms, despite it being a closed system..

Nope! It was very quite from a snow static/low humidity perspective. Also, I don't know if it makes a difference, but I guess from a lightning perspective its OK, (at least it makes me feel that way) I disconnect the antenna from tuna anyway.

[Glenn K2KL]

Hi Tom, Found this explain online....

"There are two fundamental types of antennas. The first type couples to the electric field of an electromagnetic wave, and usually consists of a
length of wire in which an electric charge moves back and forth (electric dipole) ("E-field") The second type couples to the magnetic field of an
electromagnetic wave, and is usually a coil or loop of wire (magnetic dipole) ("H-field"). "

Apparently locally generated noises contain primarily "e-field" energy which would probably explain why an H-field loop would be less susceptible to local crud.

(nice photo!)  :p  :p  :p

[WA1GFZ]

Nicw picture tom vu. flip up the cloth and plug your 1X6 into her
transoceaniac

[Glenn K2KL]

Hi Tom,

I'm also interested in the antenna modeling software you're using. Is that a freeware program? is it difficult to learn? I'm already getting into the antenna plans for the new QTH and takeoff angle modeling would probably be helpful in maximizing an array to blast a signal from NC up to New England way, caw mawn!!  

[K1JJ]

My 1X6, Frank?   :lol:    Where do you come up with this
stuff?  :lol:


Glenn:  I use an older DOS pair of programs from Brian
Beezley called Antenna Optimizer (AO)  and Yagi Optimizer (YO).

I use them cuz I am familiar with their workings and have made
old files I reuse. Obsolete, but still work theory-wise.

But today, go out and search for YagiMax or many of the other
NEC4 Windows versions. I think most are cheap and some are
free. But, everyone needs to get familiar with ant modeling, as
it gives a whole new perspective upon what's going on with
ant patterns. And, you can try things like, "what would happen
if I tied my dipole and G5RV together... or put up a 5,000 ft long
wire at 200' high, etc...  

Thanks for the E/H field explanation above.

73,
T

[wavebourn]

Hi again,
I am still suffering from unanswered question... What means "full size" loop, and what is a physical meaning of such a fullness?
Don't let me die ignorant, please!!!

[Glenn K2KL]

I wasn't the one who made the "full size" comment but I would dare to guess they meant resonant, full wave loop, in other words, 260ft of wire for 80 meters.

Hi again,
I am still suffering from unanswered question... What means "full size" loop, and what is a physical meaning of such a fullness?
Don't let me die ignorant, please!!!

[Glenn K2KL]

Thanks Tom, I'll look into those programs. That will give me something to do while the radios are packed away!  :cry:

I almost spilled my coffee when I read your comment... ""what would happen if I tied my dipole and G5RV together... "

hmmmm.... what would happen if I tied my Gotham vertical to my Isotron antenna?

My 1X6, Frank?   :lol:    Where do you come up with this
stuff?  :lol:


Glenn:  I use an older DOS pair of programs from Brian
Beezley called Antenna Optimizer (AO)  and Yagi Optimizer (YO).

I use them cuz I am familiar with their workings and have made
old files I reuse. Obsolete, but still work theory-wise.

But today, go out and search for YagiMax or many of the other
NEC4 Windows versions. I think most are cheap and some are
free. But, everyone needs to get familiar with ant modeling, as
it gives a whole new perspective upon what's going on with
ant patterns. And, you can try things like, "what would happen
if I tied my dipole and G5RV together... or put up a 5,000 ft long
wire at 200' high, etc...  

Thanks for the E/H field explanation above.

73,
T

[wavebourn]

I still don't understand... As I know a loop of any size will be resonant, if it is loaded by a capacitor.

I wasn't the one who made the "full size" comment but I would dare to guess they meant resonant, full wave loop, in other words, 260ft of wire for 80 meters.

Hi again,
I am still suffering from unanswered question... What means "full size" loop, and what is a physical meaning of such a fullness?
Don't let me die ignorant, please!!!

[K1JJ]

"Full-sized" depends upon the antenna being discussed.

A "full sized" loop simply refers to the physical size being
a "conventional" full wave , not the method of tuning it to
resonance. There are 1/2 square loops, 1/8 wave loops, etc.  
It so happens that a full wave makes it an easy feed for
50 ohms, etc., thus it became the standard in speech.

Like wise, when you hear someone say they are running
a "full sized" Yagi on 40M, they mean that they are using
physical 1/2 wave elements that are naturally close to
50-70 ohms... as compared to running a shortie 40M Yagi with
loaded elements - using linear loading, coils, etc.

Then again, a "full sized" vertical is meant to be a 1/4
wave stick compared to a shortie that is smaller and
loaded/tuned.

So as you can see, "full-sized" is a nick name put on a
particular antenna style and is not really a technical term
to tell you anything other than the way it is run without
loading to achieve a natural ~~ 50 ohm match.. I guess...

It's also a way to say you are running a REEEEAAL
Man's antenna...

GOOD QUESTION, Tolly!!!!!

73,
Tom, K1JJ

[Steve - WB3HUZ]

A dipole at anything less than 80-100 feet height won't exhibit much, if any, directionality on 160 meters, especially for the paths/distances (and thus take-off angles) you are considering. I'd say put up the dipole and rock on.

 THE DIPOLE THING WONT FAVOUR THE DIRECTIONS I WANT...I'M NOT INTO WORKING DX ANYMORE,BEEN THEN,WORKED THAT...I ENJOY THE HIGH QUALITY AM QSOs,AND THOSE ARE GENERALLY WITHIN 300 MILES,OR SO...I DO HAVE THE END FED WIRE,THAT REALLY WORKS WELL

[WA1GFZ]

sorry Tom Vu I think the tube is actually a 1L6
things come to me

[Glenn K2KL]

Full size = full size elements (as Tom said,) no loading, (C or L)


Here we go..... "Full size" half wave antenna = 468/F in MHZ

Does that clear it up?

[K1JJ]

Full size = full size elements
(as Tom said,) no loading, (C or L)
Here we go..... "Full size" half wave antenna =
468/F in MHZ Does that clear it up?

Bingo. You said what took me two paragraphs to
puke out...  :lol:


As Steve said, the high angle components of most horizontal
antennas are almost omni directional.  When high angle signals
are coming in on 6M, sometimes rotating the Yagi makes
little or no difference. Whereas, when low angle signals are
coming in, you can barely hear them on the back of the
beam.

This is why a direction finding antenna like an Adcock sucks
when trying to DF local high angle signals, but is a killer
when signals are far away and low angle.  I found this
out when I built one here once.

That modeling program will show you this and other interesting
schtuff.

T

[ve6pg]

ON THE 160 PART,THAT WAS A DIFFERENT TOPIC,...NOT RELATED TO THE ISSUE OF THE HORIZONTAL 75 METRE LOOP. TO SAY IT AGAIN,THE IDEA WAS A LOOP,MOUNTED ON 4 POLES,APPROX 270FT TOTAL,ABT 30 FEET IN THE AIR. THIS WILL BE FED WITH LADDER LINE. HOME BREW.MY END FED WIRE,190FT LONG,OUTPERFORMS MY 75 METRE DIPOLE,SO I WAS THINKING OF PLAYING WITH THE LOOP...TNX..TIM..SK..

[K1JJ]

Never mind....

[WA1GFZ]

Where does Yaz sleep now mr. vu?

[wavebourn]

It seems to me I am too stupid...
I understand why electric antenna shoul be of 1/2 or 1/4 of a wavelength, but don't understand what magnetic antennae has to do with wavelenght at all...
Except, may be, when a loop becames both electrical and magnetic antenna, due to a big size.

"Full-sized" depends upon the antenna being discussed.

A "full sized" loop simply refers to the physical size being
a "conventional" full wave , not the method of tuning it to
resonance. There are 1/2 square loops, 1/8 wave loops, etc.  
It so happens that a full wave makes it an easy feed for
50 ohms, etc., thus it became the standard in speech.

Like wise, when you hear someone say they are running
a "full sized" Yagi on 40M, they mean that they are using
physical 1/2 wave elements that are naturally close to
50-70 ohms... as compared to running a shortie 40M Yagi with
loaded elements - using linear loading, coils, etc.

Then again, a "full sized" vertical is meant to be a 1/4
wave stick compared to a shortie that is smaller and
loaded/tuned.

So as you can see, "full-sized" is a nick name put on a
particular antenna style and is not really a technical term
to tell you anything other than the way it is run without
loading to achieve a natural ~~ 50 ohm match.. I guess...

It's also a way to say you are running a REEEEAAL
Man's antenna...

GOOD QUESTION, Tolly!!!!!

73,
Tom, K1JJ

[Glenn K2KL]

Hi Tim;

I think you'd be heating the worms with a 30ft heigh, 75m horizontal loop. My opinion is a vertical triangle loop for 75 would be a better choice. Only needs one single 60ft support (minimum). The triangle loop would be 86ft per side and even though the bottom of the ant would be close to the ground, this arrangement will probably have less ground loss than a horizontal loop at 30ft. The triangle will still have plenty of high angle component because of the less than optimum height. The triangle loop is a good direct match for Coax as well.

HI FROM TIM...I WAS OUT IN THE GARDEN THIS AFTERNOON,AND GOT THINKING ABOUT PUTTING UP A FULL SIZE 75 METRE LOOP.THIS LOOP WOULD BE FED WITH OPEN WIRE,BUT HERE IS MY QUESTION. THIS ANTENNA WOULD LIKELY BE 25-30FT OFF THE GROUND.,AND I WOULD LIKE OPINIONS AS TO THE PROS/CONS OF SUCH AN INSTALLATION. IF YOU HAVE TRIED ONE WITH 4 SUPPORTS THIS CLOSE TO THE GROUND,PLEASE LET ME KNOW...73...TIM...SK..

[Steve - WB3HUZ]

I dipole at 30 feet hieght on 75 meters will also show little or no directivity at high take-off angles (or more likely all angles except for very low take-off angles).

The extra effort in putting up a loop may not be worth whatever signal or noise improve is gained.

[Glenn K2KL]

Good point Steve. I have to get my hands on that modeling program..

I dipole at 30 feet hieght on 75 meters will also show little or no directivity at high take-off angles (or more likely all angles except for very low take-off angles).

The extra effort in putting up a loop may not be worth whatever signal or noise improve is gained.