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Author Topic: V or Inverted V - Whats the difference?  (Read 3699 times)
KD2CJJ
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Posts: 368




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« on: August 15, 2012, 12:58:56 PM »

I can find a ton of info on an Inverted V config... but what about a V config?

Any takers?

Thanks
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73

Mike
KD2CJJ
W5DXP
Member

Posts: 3532


WWW

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« Reply #1 on: August 15, 2012, 01:08:15 PM »

I can find a ton of info on an Inverted V config... but what about a V config?

A V-antenna or V-beam is generally considered to be a multi-wavelength traveling wave antenna akin to half a rhombic antenna.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
WB6BYU
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Posts: 12986




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« Reply #2 on: August 15, 2012, 02:02:15 PM »

For a half wave dipole, maximum radiation is from the center portion of the antenna.
Usually we want to get this up in the air as much as possible, so the inverted vee
configuration is preferred over the upright vee.  There may be occasions where you
want to lower the feedpoint of a low band dipole to enhance radiation straight up
for local work, resulting in an upright vee.  It still works, but it doesn't take optimum
advantage of the available height, which is why it isn't as popular.

I'm using the term "upright vee" to differentiate it from a "vee beam", which is
generally in a horizontal plane with 1 wavelength or more of wire on each side.
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KD2CJJ
Member

Posts: 368




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« Reply #3 on: August 15, 2012, 02:59:41 PM »

Assuming the apex (ie feed point) of the dipole is at the same height does the radiation pattern or gain change for an upright V vs.  an Inverted V or even a horizontal dipole?

Thanks...



For a half wave dipole, maximum radiation is from the center portion of the antenna.
Usually we want to get this up in the air as much as possible, so the inverted vee
configuration is preferred over the upright vee.  There may be occasions where you
want to lower the feedpoint of a low band dipole to enhance radiation straight up
for local work, resulting in an upright vee.  It still works, but it doesn't take optimum
advantage of the available height, which is why it isn't as popular.

I'm using the term "upright vee" to differentiate it from a "vee beam", which is
generally in a horizontal plane with 1 wavelength or more of wire on each side.
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73

Mike
KD2CJJ
W8JI
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Posts: 9304


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« Reply #4 on: August 15, 2012, 04:21:39 PM »

Assuming the apex (ie feed point) of the dipole is at the same height does the radiation pattern or gain change for an upright V vs.  an Inverted V or even a horizontal dipole?


An Inverted V is really a longwire array, but people call droopy dipoles inverted V's.

The **primary** effect of a droopy dipole, or inverted V dipole, is to reduce the effective height a little bit.

If you install a dipole in V configuration, it really lowers effective height. This is because radiation comes from current, and maximum current is near the feedpoint in a 1/2 wave dipole antenna.

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WB6BYU
Member

Posts: 12986




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« Reply #5 on: August 15, 2012, 04:28:38 PM »

Quote from: KD2CJJ

Assuming the apex (ie feed point) of the dipole is at the same height does the radiation pattern or gain change for an upright V vs.  an Inverted V or even a horizontal dipole?


There is a small increase in effective height when the ends are bent up instead of down
while keeping the feedpoint height the same.  The effect on radiation is a slightly lower
angle of radiation.

Usually, if you can get the ends up that high, it makes more sense to try to get the
feedpoint up higher also.


For the same feedpoint height, there probably is a break even point where bending the legs
up further no longer makes any improvement because the vee angle is too sharp.  That
would be an interesting study...
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KD2CJJ
Member

Posts: 368




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« Reply #6 on: August 16, 2012, 06:39:45 AM »

I ask because I am considering supplementing or even augmenting my fan dipole which is along side my house and putting up above my house about 30 feet or so a rotatable dipole for 20 meters - the extra 10 feet or so plus getting above my house should considerably improve my signal especially since my V config now is about 65 degrees and literally against my house (so I am not getting anything North completely deaf, East and West dont hear all that much --- I get plenty of booming signals from the south - which is what the antenna is facing now)

My strategy is to have a rotatable dipole (I know I know there are better options but the wife is against it... this is just phase 1 until I can convince her my hex beam doesnt look all that ugly - but thats next summer he he) for 6 - 20m and an end fed for mono-bander 40 meter...

I want to avoid traps and utilize my LDG tuner to tune up the frequencies for the dipole..

Here is what I am looking at:
http://www.zerofive-antennas.com/6-20-meter-multiband-vee-ladder-line-fed-dipole

I was curious as to why this was in a V config if only just to reduce the size....

Quote from: KD2CJJ

Assuming the apex (ie feed point) of the dipole is at the same height does the radiation pattern or gain change for an upright V vs.  an Inverted V or even a horizontal dipole?


There is a small increase in effective height when the ends are bent up instead of down
while keeping the feedpoint height the same.  The effect on radiation is a slightly lower
angle of radiation.

Usually, if you can get the ends up that high, it makes more sense to try to get the
feedpoint up higher also.


For the same feedpoint height, there probably is a break even point where bending the legs
up further no longer makes any improvement because the vee angle is too sharp.  That
would be an interesting study...
Logged

73

Mike
KD2CJJ
K9IUQ
Member

Posts: 1622




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« Reply #7 on: August 16, 2012, 07:55:21 AM »

Here is what I am looking at:
http://www.zerofive-antennas.com/6-20-meter-multiband-vee-ladder-line-fed-dipole

I was curious as to why this was in a V config if only just to reduce the size....

Note that the antenna has 17.8 ft legs. To make it an inverted V would mean it would have to be mounted on at least a 18 ft mast - so it would clear your roof. By making it a V, you could mount it on your roof with only a 1ft mast.  Cheesy

This is probably the reason....

Stan K9IUQ
« Last Edit: August 16, 2012, 07:57:38 AM by K9IUQ » Logged
W5DXP
Member

Posts: 3532


WWW

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« Reply #8 on: August 16, 2012, 08:02:19 AM »

By making it a V, you could mount it on your roof with only a 1ft mast.  Cheesy

Which is not a lot better than a horizontal 1/2WL dipole mounted on a 1ft mast. I can't find in the The ARRL Antenna Book where it even describes an HF rabbit-ears antenna.Smiley
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
WB2WIK
Member

Posts: 20540




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« Reply #9 on: August 16, 2012, 08:13:09 AM »



My strategy is to have a rotatable dipole (I know I know there are better options but the wife is against it... this is just phase 1 until I can convince her my hex beam doesnt look all that ugly - but thats next summer he he) for 6 - 20m and an end fed for mono-bander 40 meter...

I want to avoid traps and utilize my LDG tuner to tune up the frequencies for the dipole..

Here is what I am looking at:
http://www.zerofive-antennas.com/6-20-meter-multiband-vee-ladder-line-fed-dipole

I was curious as to why this was in a V config if only just to reduce the size....

That is why.  That Zero Five antenna should really be on a rotator (sounds like you do have that planned) and as high above ground as you can install it.  Making it a "vee" configuration reduces the turning radius so it takes less space to rotate.

Comet makes a 4-band rotatable dipole for 10-15-20-40 meters which is about the same size and uses traps, so it can be fed with coax instead of ladder line like the Zero Five (which uses no traps, so with your tuner you're tuning the whole "system" including the antenna and its balanced line): http://www.universal-radio.com/catalog/hamants/4778.html



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WB6BYU
Member

Posts: 12986




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« Reply #10 on: August 16, 2012, 08:20:44 AM »

Quote from: W5DXP

Which is not a lot better than a horizontal 1/2WL dipole mounted on a 1ft mast.



Except that it keeps the ends of the elements higher above the roof so they aren't detuned
as much a they rotate past vent pipes, metal flashing, etc.

Using the same model as before, but tilting the arms upwards, the dipole has 0.1dB more gain
at 25 degrees, and the vee has 0.2dB more gain at 20 degrees.  So a slight lowering of the
angle of radiation, but nothing that you'd notice in normal operation.  It will vary somewhat
on different bands.
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K3VAT
Member

Posts: 699




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« Reply #11 on: August 16, 2012, 03:47:37 PM »

...
I want to avoid traps and utilize my LDG tuner to tune up the frequencies for the dipole..
...

May I inquire why it is that you want to avoid a trap antenna?

73, Rich, K3VAT
5BDXCC on wire
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KD2CJJ
Member

Posts: 368




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« Reply #12 on: August 16, 2012, 05:15:23 PM »

Well....  I want to be above 1/4 wave on the other bands to get additional gain....  I also want to minimize the needed to maintain the traps over time, lastly I want to minimize the amount of tuning initially - this of course is the least of the reasons but is a plus to the other two...
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73

Mike
KD2CJJ
K3VAT
Member

Posts: 699




Ignore
« Reply #13 on: August 16, 2012, 06:00:23 PM »

May I inquire why it is that you want to avoid a trap antenna?  

Well....  I want to be above 1/4 wave on the other bands to get additional gain ...

Going above 1/4 wave on other bands will not provide any substantial gain, in fact, it may produce one or more high-angle lobes that would benefit your "local" contacts and reduce the signal magnitude at lower elevation angles.  You'd have to go to sufficient lengths such as one would find in an extended double zepp (1.25 wavelengths long; see ARRL Antenna Book 8-40) to see any real gain (there are other configurations where some gain can be obtained).

 I also want to minimize the needed to maintain the traps over time,

Modern traps, whether from Mosley, Crushcraft, Hygain, Bencher (Butternut) that are found in yagis & verticals or individually manufactured traps such as those from Unadilla are high-quality components and often do not require any maintenance for several years, minimum.  Some old Mosleys from the 60s still have their original traps.  My Unadilla trap dipole shows no problem after nearly 3 years.

...lastly I want to minimize the amount of tuning initially

The nature of traps is that you Don't need to do any tuning whatsoever.  I have instant bandswitching with my WARC (12M, 17M, and 30M) trap dipole (two traps needed).  

Plus, (beneficial for a reduced space lot like my .2 acres), traps will physically shorten the required wire length as compared to a full size dipole.  My WARC trap dipole is about 85% the length of a fullsize 30M dipole.

What's the trade-off?  Bandwidth is reduced.  This will effect bands 40M and lower.  At 20M my trap dipole has < 1.5:1 SWR for all but the high part of the upper end.

You may want to do a search of this forum for trap dipoles to see some other opinions.  They're a great way to go - at least for me!

GL, 73, Rich, K3VAT

« Last Edit: August 16, 2012, 06:08:13 PM by K3VAT » Logged
KD2CJJ
Member

Posts: 368




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« Reply #14 on: August 16, 2012, 08:00:36 PM »

You raised some valid points...  Are all the bands quarter or half wave with the traps?

Can you recommend a manufacturer over one or the other?

May I inquire why it is that you want to avoid a trap antenna?  

Well....  I want to be above 1/4 wave on the other bands to get additional gain ...

Going above 1/4 wave on other bands will not provide any substantial gain, in fact, it may produce one or more high-angle lobes that would benefit your "local" contacts and reduce the signal magnitude at lower elevation angles.  You'd have to go to sufficient lengths such as one would find in an extended double zepp (1.25 wavelengths long; see ARRL Antenna Book 8-40) to see any real gain (there are other configurations where some gain can be obtained).

 I also want to minimize the needed to maintain the traps over time,

Modern traps, whether from Mosley, Crushcraft, Hygain, Bencher (Butternut) that are found in yagis & verticals or individually manufactured traps such as those from Unadilla are high-quality components and often do not require any maintenance for several years, minimum.  Some old Mosleys from the 60s still have their original traps.  My Unadilla trap dipole shows no problem after nearly 3 years.

...lastly I want to minimize the amount of tuning initially

The nature of traps is that you Don't need to do any tuning whatsoever.  I have instant bandswitching with my WARC (12M, 17M, and 30M) trap dipole (two traps needed).  

Plus, (beneficial for a reduced space lot like my .2 acres), traps will physically shorten the required wire length as compared to a full size dipole.  My WARC trap dipole is about 85% the length of a fullsize 30M dipole.

What's the trade-off?  Bandwidth is reduced.  This will effect bands 40M and lower.  At 20M my trap dipole has < 1.5:1 SWR for all but the high part of the upper end.

You may want to do a search of this forum for trap dipoles to see some other opinions.  They're a great way to go - at least for me!

GL, 73, Rich, K3VAT


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73

Mike
KD2CJJ
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