Umbrella Antenna.

[KA5PIU]

Hello.

I have several Umbrella Antennas, umbrellas that have been adapted to work as antennas.
The trouble sometimes is finding the right umbrella.
Well, this one works nice but is a bit pricey.
http://www.smith-wesson.com/webapp/wcs/stores/servlet/Product4_750001_750051_765708_-1_757876_757837_757837_ProductDisplayErrorView_N#
The ones that have the silver lining are the best as the silver acts as an RF reflector.
Finding an umbrella with a torn fabric but otherwise fine is always an option, simply replace the fabric.
Carbon fiber fabric or silver impregnated fiber will work, the same stuff used for TASER proof clothing.
An antenna can be mounted on the tip, providing a elevated feed for your talkie.
An/or you can place a dipole at the focal point and use it as a parabolic dish, it is all good.
At least this gives you an idea of what kind of umbrella is preferred.

[NQ6U]

http://www.youtube.com/watch?v=LkqsD3crD1g

[NA4BH]

Hello.

I have several Umbrella Antennas, umbrellas that have been adapted to work as antennas.
The trouble sometimes is finding the right umbrella.
Well, this one works nice but is a bit pricey.
http://www.smith-wesson.com/webapp/wcs/stores/servlet/Product4_750001_750051_765708_-1_757876_757837_757837_ProductDisplayErrorView_N#
The ones that have the silver lining are the best as the silver acts as an RF reflector.
Finding an umbrella with a torn fabric but otherwise fine is always an option, simply replace the fabric.
Carbon fiber fabric or silver impregnated fiber will work, the same stuff used for TASER proof clothing.
An antenna can be mounted on the tip, providing a elevated feed for your talkie.
An/or you can place a dipole at the focal point and use it as a parabolic dish, it is all good.
At least this gives you an idea of what kind of umbrella is preferred.

I've heard about those. What I have read is that you need to go through the umbrella and remove all nylon/plastic parts and solder the joints. It really concentrates the signal.

[kb2vxa]

Just because it looks like an umbrella or is made from one doesn't say it's an umbrella antenna.

[K7SGJ]

I womder if Mary Poppins was a ham?

[KA5PIU]

Hello.

Mary Poppins was a master of the airwaves, that chick could fly!
If the umbrella is of non conductive fabric construction and you plan on using the ribs and perhaps the shaft for the ground plane, yes, properly grounded metal is solution.
But some umbrellas come with a UV liner.
http://www.coolibar.com/04106.html
This is not only good for UV protection, it makes an excellent RF reflector.
I think that an umbrella with the silver looks a bit geek but it is whatever makes you happy.
The umbrellas that were common on heavy equipment make excellent antenna mounts for anything above about 40 MHz, more so than a simple flat surface, as this is part of a discone antenna, and the fact that there are no folding joints and the overall size helps.
Remember, you can work the entire 6 meter band with a large umbrella antenna.
A golf sized umbrella antenna with a dual band element in the monopole configuration will be flat across all of 2 meters and do at least a 15 MHz spread across 440 that is flat.
I like something that is cheap and useful so I would not buy the expensive antennas I have referred to, this is to give you an idea of what is good and easy to work with.

[NA4BH]

Yeah but if you do it like that you get resonant blurring of the primary wave. You'd be all over the place.

[NQ6U]

Here's my umbrella antenna for 40m:

http://search.it.online.fr/BIGart/wp-content/99142-004-f3f137b3-2006.jpg

[N7RJD]

I've heard about those. What I have read is that you need to go through the umbrella and remove all nylon/plastic parts and solder the joints. It really concentrates the signal.

Don't forget the super glue and tin foil.

[w6tmi]

I've heard they have some pretty advanced science, and make some amazing... Things..

3838

[KG4CGC]

Lumpy is the one to talk to about umbrella antennas there, Rudy.

[KA5PIU]

Yeah but if you do it like that you get resonant blurring of the primary wave. You'd be all over the place.

Hello.

This is why I prefer the conductive fabric idea.
Since this would be one RF sheet it acts very much like the counterpoise portion of a discone with a monopole if fed from the top.
But, if fed as a parabolic dish it matters little as having the feedpoint in the apex is more important than anything.
It is not perfect but it works well and is cheap.
And 2 matched duck type antennas work well for the feedpoint dipole.

[W1GUH]

I need an umbrella policy.

[W3WN]

I need an umbrella policy.

I'll have one of our Commercial Lines folks call you on Monday.

[K7SGJ]

AFLAC

3843





Third base

[NA4BH]

Hello.

This is why I prefer the conductive fabric idea.
Since this would be one RF sheet it acts very much like the counterpoise portion of a discone with a monopole if fed from the top.
But, if fed as a parabolic dish it matters little as having the feedpoint in the apex is more important than anything.
It is not perfect but it works well and is cheap.
And 2 matched duck type antennas work well for the feedpoint dipole.

If you didn't feed it as a parabolic and placed your duck antennas in copper tubing, you would have better control over your polarization and with a 90 degree turn you could change it. Simple. I've found that a mylar type backing works the best, but only in dry conditions.

[K7SGJ]

For wet days with heavy electrical activity, get that sky hook vertical driver way way up there. We will be able to copy you from DC to light.

[NA4BH]

There you go, use the available static electricity to help your propagation.

[K7SGJ]

And minimize procreation.

[NA4BH]

It's a win/win situation.

[KG4CGC]

acts very much like the counterpoise portion of a discone with a monopole if fed from the top.Yeah, uh, no. It would act like a ground plane antenna.
A discone relies on the phase and angle of the elements to produce a vertical omni pattern. In order to take advantage of the parabolic design of the umbrella for anything near a discone design, you will still need a a driven element much like in a corner reflector design. It must be mounted much closer to the reflector plane, like a couple of inches. Then you will need a cone at 90 degrees mounted 1 to 1.5 wave lengths with the point facing down, away from the center. It 2 dimensional terms, it would like a "V" over a "U" ...
In an actual discone ...........

...........At a 30 degree angle,
the diameter of the
base of the cone is equal to the length
of the side, although
not critical.

[W3WN]

AFLAC

Third base
AFLAC doesn't sell Umbrella... policies. I can get you a stuffed duck though.

[KA5PIU]

Yeah, uh, no. It would act like a ground plane antenna.
A discone relies on the phase and angle of the elements to produce a vertical omni pattern. In order to take advantage of the parabolic design of the umbrella for anything near a discone design, you will still need a a driven element much like in a corner reflector design. It must be mounted much closer to the reflector plane, like a couple of inches. Then you will need a cone at 90 degrees mounted 1 to 1.5 wave lengths with the point facing down, away from the center. It 2 dimensional terms, it would like a "V" over a "U" ...
In an actual discone ...........

...........At a 30 degree angle,
the diameter of the
base of the cone is equal to the length
of the side, although
not critical.

Hello.

2 applications, one umbrella.
To do the semi discone the monopole is mounted to the tip of the umbrella.
The umbrella is unfolded and the entire assembly is held from the handle at whatever angle desired.
The umbrella has the element on the outside.
In the second application the radiating element and a counterpoise is placed in the focal point of the umbrella.
This is why there are 2 antennas, one is the counterpoise if used as a parabolic dish.
A pair of straps are used to hold the antennas in place along the shaft and the entire thing is folded up when not in use and it looks like any other umbrella.
This can be strapped to a briefcase as is the custom and a talkie with an extra battery and a charger and you have the dork free go kit.
Things like the VX-3r can be placed in a shirt pocket, larger radios will fit in a gentleman's coat pocket.
The entire point of this exercise is to have the ability to work OSCAR (AMSAT) as well as enhanced terrestrial communications while at no time looking like a ham.
The Arrow antenna Yagi works a bit better but is a dead giveaway.

[W7XF]

AFLAC

3843



Third base

SHUT THE DUCK UP!! :rofl: :rofl: :yes: :clap:

[W7XF]

AFLAC doesn't sell Umbrella... policies. I can get you a stuffed duck though.

Ron... doesn't AFQUACK serve Beijing Duck as a main course?? :lol:

[KG4CGC]

o do the semi discone the monopole is mounted to the tip of the umbrella.
I believe that this is still a ground plane.

[K7SGJ]

No more wise quacks.

[W7XF]

That means you can't play with your Drake.

[K7SGJ]

So much for chokin' the mallard.

[W7XF]

You and your ruddy complexion..... :lol:

[KG4CGC]

You and your ruddy complexion..... :lol:
Spotted dick?
When I worked for a plastics company years ago, the one with the sweatshop reputation, our plant manager was a redheaded, freckle covered man. One day he was using the restroom on the plant floor. He was quietly sitting in a stall when one of the foremen accidentally opened the stall door. Apolized and walked backed out he did. The story got out on the floor and in a group of several guys circled around, one smartass just had to through this little ditty out into the conversation. "Did he have freckles on his dick?"
<groan> Oh that was bad. We laughed ... eventually.

[KA5PIU]

I believe that this is still a ground plane.

Hello.

t is not a true ground plane, there is an adjustable angle.
The easy way to adjust the angle is to run out and buy a pair of shaft collars the size to fit the shaft, a touch oversize is fine.
This is also sometimes sold as a "drill stop", same thing.
Frequently you can buy a package with several sizes in a package on sale at harbour freight on sale that are cheaper than trying to find one the right size.
Take the set screw out and replace it with a thumb screw on each.
Put one on the upper side of the slide at the maximum angle you want and the other you slide up and lock both in place.
You can always readjust them.
I do not want or need that much of an angle, and the top one will prevent it from fully opening as well as requiring more disassembly than I prefer, so I only use one on the bottom.
I broke the latching mechanism on an umbrella running the coax through the shaft and came up with this as a fix for that when I discovered the adjustable angle feature.
The springiness of the fabric will help keep it in position from around 80% to fully open.
Remember that an umbrella even fully open has an angle, it does not present a flat plane.
I thought that this was a ground plane and nothing more, but the bandwidth of the antenna is greater by a factor of 2+ over a simple ground plane and the radiation angle is increased.
At a 70 degree angle the bandwidth is well over 5 times that of a monopole on a ground plane.
An antenna with a good SWR across 143 to 149 on a ground plane is now 90 to 170+
I am using an MFJ antenna analyzer so I am at a loss much over 170 MHz.
And to measure radiation angle I use a field strength meter with a monopole, not perfect but it does work.
I also of course simply do on the air testing into a repeater and the like.
But, this is very cheap.
You do not even need to alter an umbrella to conduct the experiments.
Get a bit of coax with the correct ends and your talkie antenna along with a few rubber bands.
Attach the talkie antenna to the tip of your umbrella with the rubber bands and connect to your talkie, unfold your umbrella and hold it at angles up to fully open.
See what you can find.
You can also use a large table umbrella, most have a bit of a hole in the canter of the fabric that works well as a route for the coax.
An excellent mount is the big truck mirror mount with whatever style of connector you need, be it a mobile antenna or talkie.
Remember that a larger umbrella, such as a golf or table umbrella, will provide you with protection from the elements as well.

[KG4CGC]

I found this. I knew I've seen it before. This, will be your best bet at an umbrella discone.
3844
I found this on Eham.
y= x2 / ( 4 * focus distance) ==> y= x2 / ( 4 * 3) ==> y= x2 / ( 12 ) This results in (x, y) values of (1, .083), (2, .333), (3, .75), (4, 1.333), (5, 2.083), (6, 3), (7, 4.083), (8, 5.333), (9, 6.75), (10, 8.333), (11, 10.083), and (12,12).

http://www.eham.net/articles/13789




Discone vectors in a curved umbrella frame need to work within the desired parameters of 30 degree physics. This means calculating for high forced current vs just looking for an impedance solution. That is if you are going to try to go with the traditional configuration. This can be tricky as you could easily result in an unintentional ground plane.

[KA5PIU]

Hello.

That is one way to produce a discone antenna but remember that the direction of the cone is not critical.
http://en.wikipedia.org/wiki/Discone_antenna
As is pointed out, at lower frequencies this may be a ground plane or coaxial dipole.
This is why I suggest a larger umbrella for the lower frequencies and even for VHF high I prefer something the size of a golf umbrella.
But none of this is all that critical.
Take an antenna that you already know works, usually a talkie antenna, add umbrella, adjust angles as needed, experiment, see what you come up with.
I like the gain I get over a monopole on the talkie without any geek factor.
Even as a ground plane on 6 meters I get at least 20 decibels of gain over that of the same antenna on the talkie.
Remember that this is now an elevated feed with a ground plane.
The thin flexible antennas for talkies work best with this for dual band use, not only does the thin wire not show up but there is a longer antenna for the counterpoise to work against.
Again, experiment, see what you can find.
The radio in question is the VX-7r.
The antennas are the stock job as well as several others, with the longest thin antenna being the most preferred, Diamond, MFJ, whoever, they all work about the same.

[KG4CGC]

I think your talking about experimental configurations without theoretical basis in documented formulations.

[KA5PIU]

I think your talking about experimental configurations without theoretical basis in documented formulations.

Hello.

No, you can do the math, or even buy such an antenna pre made.
http://www.eham.net/reviews/detail/2873
This is the "cheap" Radio Shack version.
There are dozens of true discone antennas out there and you can always make your own.
Remember that the design is not critical, and with an umbrella and a shaft collar you can change the angle at any time.
If you want more than a simple monopole you can add radials but I have never found any advantage and it starts to look like something other than a simple umbrella.
But, experiment, try and disprove the theory and come up with one of your own.
I do not call this a true discone as it only has the monopole as an active element but the fact that bandwidth will increase with an increase of angle makes me think.
There is no question that the radiation angle does change.

[KG4CGC]

You've completely lost me now.

[NA4BH]

You've completely lost me now.

I don't think you are the one that is lost.

[NQ6U]

You've completely lost me now.

That was by design, I suspect.

[KA5PIU]

Hello.

You had referred to a parabolic discone and the math.
http://www.hamdomain.com/para-discone/
I am referring to one device and 2 uses.
As a discone.
http://www.northcountryradio.com/Articles/discone.htm
Look at figure one and think umbrella, the tip of the umbrella having a monopole with a small ring at the base.
3846
This is the other portion of this umbrella, the parabolic dish.
http://www.w1ghz.org/antbook/app-6b.pdf
Now look at the first figure and think of an umbrella with the handle in the air, this is the parabolic dish function with a simple dipole at the apex of the dish, somewhere around the handle.
2 functions with one device.
I decided to skip the ring at the base of the antenna and try it as a simple ground plane but soon discovered that the angle of the ribs of the umbrella have a profound effect on how the antenna behaves.
But at this point this is only my findings.
This is based on a British product intended only for extending the range of a marine talkie, something it does very well.
But they have no need to extend the bandwidth, in fact marine radios are very limited anyway, so anything else but a ground plane makes no sense.
Hopefully with the pictures and extra text this will make sense.

[KG4CGC]

I'm not following you.

[NA4BH]

I'm not following you.

As your legal counsel (today), I advise you to not make further comments about this. ;)

[KA5PIU]

Hello.

Sorry but I can not make it more clear.
Go to a large table umbrella and mount an antenna on the tip that sticks past the outside of the fabric.
Now move the umbrella up and down while testing.
See what you can come up with.
As you move the umbrella down you increase the angle from the ground plane, not exact science but it need not be.
If you have concerns over the rib joints simply run some hookup wire along the ribs and all of them in the center, a bit of tape and a wirenut will work wonders.
From there, and looking at the British thing, I decided to make a portable version.

[NA4BH]

Hello.

Sorry but I can not make it more clear.
Go to a large table umbrella and mount an antenna on the tip that sticks past the outside of the fabric.
Now move the umbrella up and down while testing.
See what you can come up with.
As you move the umbrella down you increase the angle from the ground plane, not exact science but it need not be.
If you have concerns over the rib joints simply run some hookup wire along the ribs and all of them in the center, a bit of tape and a wirenut will work wonders.
From there, and looking at the British thing, I decided to make a portable version.

I've found that not only using the conductive cloth, attach copper wire around the joints of the umbrella. Taking an alligator clip and moving it from strand to strand, you can fine tune your lowest Vswr and not lose signal strength.

[KG4CGC]

Be careful with your gauge. If you experiment with thin gauge wire, it will throw your measurements by up to .15% should you do your first hard prototype with heavier wire.

[NA4BH]

Be careful with your gauge. If you experiment with thin gauge wire, it will throw your measurements by up to .15% should you do your first hard prototype with heavier wire.

OOPs. I'm glad you brought that up. 18ga or larger, anything smaller and there is a good chance of the whole thing going up in a flash of light. Actually the figures, per my calculations is .1524% distortion on a nominal power insertion.

[KG4CGC]

OOPs. I'm glad you brought that up. 18ga or larger, anything smaller and there is a good chance of the whole thing going up in a flash of light. Actually the figures, per my calculations is .1524% distortion on a nominal power insertion.
Look at your voltage at the feed point (gap between inner and outer elements) keeping in mind that it is the current that is of interest and not the impedance. If you go with impedance alone you can get false readings all over the map.

[NQ6U]

Make sure you're using a wattmeter that reads true RMS, too, otherwise your power calculations could be off by as much as 30%.

[NA4BH]

Look at your voltage at the feed point (gap between inner and outer elements) keeping in mind that it is the current that is of interest and not the impedance. If you go with impedance alone you can get false readings all over the map.

OK, I stand corrected. I was not going from the feed point. OOPs again. They way I was doing it made the graph look like a rollercoaster ride at Six Flags.


Make sure you're using a wattmeter that reads true RMS, too, otherwise your power calculations could be off by as much as 30%.

Very true.

[W7XF]

Someone just design a taco discone for Rudy!!!!!!!

[KA5PIU]

Hello.

Found this after talking about the Chinese vs Japanese on HF.
http://www.tele-satellite.us/TELE-satellite-1007/eng/umbrella.pdf

[N2NH]

Hello.

Found this after talking about the Chinese vs Japanese on HF.


I can't tell you how disappointed I am that I missed that QSO.

[KA5PIU]

Hello.

It was that or the Geritol net!
I can't wait for construction to pick up!
You can put me back on the blade, I will be good! I promise!
Hell, put me on a roller, right now I will take something with a detroit 2 stroke and crap muffler!
Anything but that hamster dance!

http://www.youtube.com/watch?v=p3G5IXn0K7A

[NQ6U]

WART

[KG4CGC]

X2
WART

[VE7DCW]

The WART challenge