Whitestick V DISCONE?

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paulears
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Re: Whitestick V DISCONE?

Post by paulears »

You're getting confused between E plan and H plane. White sticks have similar distortions to the E plane plot - but you have to picture these graphs as what you would get looking at your antenna from the side. So little goes straight up, and most goes out at right angles to the antenna on it's pole. The white sticks do similar things but they have more 'spikes' and odd angles, called lobes. So parallel with the ground you might get the most output, but as the angle goes up, it gets less, then a sudden increase, then a pull back, then another null, etc etc until you get to the very deep null at the very top.

The horizontal radiation pattern of omnis is in effect, as circle. In 3D it's a torroid shape, that gets a bit thicker at the bottom or top at certain frequencies. The white sticks look more like a donut with layers of icing, then a big hole.

The more gain, the more lobes - which can sometimes be handy, other times destructive. With mil airband being so huge - they stay away from any kind of resonant antenna design, because it always seems to mean less gain somewhere else - which they don't want!
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thedeerhunter270
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Re: Whitestick V DISCONE?

Post by thedeerhunter270 »

paulears wrote:You're getting confused between E plan and H plane.
Yes, possibly. Although, as I pointed out, radiation pattern of a discone does change with frequency over its 10:1 range. Something to be taken in to consideration when using this type of antenna.
paulears wrote:The horizontal radiation pattern of omnis is in effect, as circle. In 3D it's a torroid shape, that gets a bit thicker at the bottom or top at certain frequencies. The white sticks look more like a donut with layers of icing, then a big hole.
I find it easier to visualise.

This seems interesting: http://www.urel.feec.vutbr.cz/~raida/mu ... -A&lang=en
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thedeerhunter270
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Re: Whitestick V DISCONE?

Post by thedeerhunter270 »

Vertical Radiation pattern. As I've been trying to point out - as the frequency increases, the max radiation pattern is actually pointed down. At 100 MHz fairly standard doughnut, but at 500 MHz the lobes are definitely pointing down.

http://www.radiohaus.com.br/produto/471 ... hz-3000mhz
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paulears
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Re: Whitestick V DISCONE?

Post by paulears »

Take your point, but the critical fact is they're not wasted by pointing up! the primary energy distribution is still in the useful direction at unity gain, or a bit more according to the graph??, and the two lobes up at 45 degrees are unlikely to bring in very much, and a -5dB not very important. What would be good is to see E plane graphs for the dual white sticks.
As soon as you introduce gain, then the lobes start to emerge, this is the pattern for a single band Jaybeam
Image
More gain = more lobes and the dual band ones then interact and get even stranger. I suppose it really depends on the arrival angle of your important sources - if they're coming in at the right angle, performance seems even better, but a few degrees either way and it's poorer.
In practice, I doubt it matters too much.

The downwards emphasis can even be useful - one of the questions OFCOM ask on a technically assigned licence is about down focussing to give better site coverage but with less spill. I'd not considered discones as useful for this, but perhaps so?
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thedeerhunter270
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Re: Whitestick V DISCONE?

Post by thedeerhunter270 »

paulears wrote:Take your point, but the critical fact is they're not wasted by pointing up!
I agree.

But from my own anecdotal findings, for aircraft reception a 1/4 wave ground plane may work better than a discone. Due to the radiation pattern of a 1/4 wave being 45 degrees upwards. (Always surprised me that the military use discone's so much)

If you want a do-it-all antenna for a wide range of frequencies a discone is a good choice. But I think it all depends on where and what you want it for. On the other hand if you want an antenna for 150 - 200 MHz and 400 - 500 MHz and you don't need the military airband; a X30 or x50 will work better I feel.

I have used a discone before, but I don't think it would work do well where I live now due to topography (very hilly).

This is all part of the fun of the hobby.
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paulears
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Re: Whitestick V DISCONE?

Post by paulears »

I think it's simply because the discone works OK everywhere - across a huge bandwidth, and dipoles don't. Great for on frequency, but if you run a discone through an analyser you get a whole swath of up and down troughs and peaks and the dipole just curves away quite quickly. Marine band is a good example - a narrow band where a dipole is so useful, while air band including the low section is over 20 MHz wide, military band is over 100MHz wide.
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