Fractal antenna orientation

A while back I had a slightly OT discussion regarding the practicalities of fractal antennas for HDTV.

I subsequently made an 8 element version and it works very well in areas of no line of sight/poor reception.

I don't use a reflector on this and it's interesting that the antenna works well on both the horizontal and vertical plane indoors.

See below using on the horizontal.

http://users.tpg.com.au/agnet/unknown.jpg

So any insight into which plane is optimum for this type of design ?

I was quite surprised that it works in the alignment seen in the picture.

Could it be used as a beam antenna with a suitable reflector at one end ?

Maybe it's just picking up a reflected/multipath signal from the metal roof ?

On 1/09/2011 9:43 AM, Dr Who wrote:
>
> A while back I had a slightly OT discussion regarding the practicalities of fractal antennas for HDTV.
>
> I subsequently made an 8 element version and it works very well in areas of no line of sight/poor reception.
>
> I don't use a reflector on this and it's interesting that the antenna works well on both the horizontal and vertical plane indoors.
>
> See below using on the horizontal.
>
> http://users.tpg.com.au/agnet/unknown.jpg
>
> So any insight into which plane is optimum for this type of design ?
>
> I was quite surprised that it works in the alignment seen in the picture.
>
> Could it be used as a beam antenna with a suitable reflector at one end ?
>
> Maybe it's just picking up a reflected/multipath signal from the metal roof ?
>
>
>
>
>
Have you fiddled with it near an rf source watching signal ??

--
X-No-Archive: Yes

atec77 wrote:

> On 1/09/2011 9:43 AM, Dr Who wrote:
> >
> > A while back I had a slightly OT discussion regarding the practicalities of fractal antennas for HDTV.
> >
> > I subsequently made an 8 element version and it works very well in areas of no line of sight/poor reception.
> >
> > I don't use a reflector on this and it's interesting that the antenna works well on both the horizontal and vertical plane indoors.
> >
> > See below using on the horizontal.
> >
> > http://users.tpg.com.au/agnet/unknown.jpg
> >
> > So any insight into which plane is optimum for this type of design ?
> >
> > I was quite surprised that it works in the alignment seen in the picture.
> >
> > Could it be used as a beam antenna with a suitable reflector at one end ?
> >
> > Maybe it's just picking up a reflected/multipath signal from the metal roof ?
> >
> >
> >
> >
> >
> Have you fiddled with it near an rf source watching signal ??

If I go outside it gets swamped with signal and there's no discernable difference between antenna orientation.

But using it indoors with no line of site and very bad reception conditions it's interesting that it works better on the horizontal plane than the vertical.

So getting back to my original question, could this type of array be used as a beam antenna ?

On Aug 31, 4:43*pm, "Dr Who" <dead_letter_off...@hotmail.com> wrote:
> A while back I had a slightly OT discussion regarding the practicalities of fractal antennas for HDTV.
>
> I subsequently made an 8 element version and it works very well in areas of no line of sight/poor reception.
>
> I don't use a reflector on this and it's interesting that the antenna works well on both the horizontal and vertical plane indoors.
>
> See below using on the horizontal.
>
> http://users.tpg.com.au/agnet/unknown.jpg
>
> So any insight into which plane is optimum for this type of design ?
>
> I was quite surprised that it works in the alignment seen in the picture.
>
> Could it be used as a beam antenna with a suitable reflector at one end ?
>
> Maybe it's just picking up a reflected/multipath signal from the metal roof ?

You should model it in NEC2.

(E-Mail Removed) wrote:

> On Aug 31, 4:43*pm, "Dr Who" <dead_letter_off...@hotmail.com> wrote:
> > A while back I had a slightly OT discussion regarding the practicalities of fractal antennas for HDTV.
> >
> > I subsequently made an 8 element version and it works very well in areas of no line of sight/poor reception.
> >
> > I don't use a reflector on this and it's interesting that the antenna works well on both the horizontal and vertical plane indoors.
> >
> > See below using on the horizontal.
> >
> > http://users.tpg.com.au/agnet/unknown.jpg
> >
> > So any insight into which plane is optimum for this type of design ?
> >
> > I was quite surprised that it works in the alignment seen in the picture.
> >
> > Could it be used as a beam antenna with a suitable reflector at one end ?
> >
> > Maybe it's just picking up a reflected/multipath signal from the metal roof ?
>
> You should model it in NEC2.

Good thinking.

I will have a go tonight.

On 4 Sep 2011 08:13:23 +1000, "Dr Who"
<(E-Mail Removed)> wrote:

>(E-Mail Removed) wrote:

>> > http://users.tpg.com.au/agnet/unknown.jpg

>> You should model it in NEC2.

>Good thinking.
>I will have a go tonight.

Common commercial HDTV antenna models:
<http://www.hdtvprimer.com/SimData/SimData.html>
<http://www.hdtvprimer.com/ANTENNAS/comparing.html>
<http://www.hdtvprimer.com/SIMS/>

Note: You're really asking this in the wrong newsgroup. Look for
something that discusses TV antenna. www.avsforums.com would
probably be a good place to start.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

> On 4 Sep 2011 08:13:23 +1000, "Dr Who"
> <(E-Mail Removed)> wrote:
>
> > (E-Mail Removed) wrote:
>
> >> > http://users.tpg.com.au/agnet/unknown.jpg
>
> >> You should model it in NEC2.
>
> > Good thinking.
> > I will have a go tonight.
>
> Common commercial HDTV antenna models:
> <http://www.hdtvprimer.com/SimData/SimData.html>
> <http://www.hdtvprimer.com/ANTENNAS/comparing.html>
> <http://www.hdtvprimer.com/SIMS/>
>
> Note: You're really asking this in the wrong newsgroup. Look for
> something that discusses TV antenna. www.avsforums.com would
> probably be a good place to start.

Thanks for the links Jeff.

I posted it here just as a discussion on fractal antennas per se.

I will check out the avsforum. I wasn't aware of that one.

Cheers

On 4 Sep 2011 17:10:05 +1000, "Dr Who"
<(E-Mail Removed)> wrote:

>> Note: You're really asking this in the wrong newsgroup. Look for
>> something that discusses TV antenna. www.avsforums.com would
>> probably be a good place to start.

>I will check out the avsforum. I wasn't aware of that one.
>Cheers

Oops. Wrong URL:
<http://www.avsforum.com>
<http://www.avsforum.com/avs-vb/>
Antenna discussions usually land in HDTV technical:
<http://www.avsforum.com/avs-vb/forumdisplay.php?f=25>

I didn't find anything specific on fractal antennas, but did find this
100+ thread on UHF TV construction:
<http://www.avsforum.com/avs-vb/showthread.php?t=798265&page=1>

I can't resist offering my never humble opinion on fractal antennas.
Methinks they only make sense when dealing with a specialized
radiation pattern (i.e. cell phone SAR) in a confined area (i.e.
inside a cell phone) such as a box. When there are few limits on the
size of the antenna, such as in an outdoor antenna, fractal antennas
are not the best solution.

Basically, it's compromise between size, gain, and bandwidth. You can
have any two, at the expense of the third. For example, the gain of a
simple dipole is about 2.1dBi. If you shrink the length of each
element, the gain remains about 2dBi until you get down to about
1/10th wavelenth. Of course, the tuning also changes, so you have to
add inductance (loading coils) to tune it, and a matching circuit to
reduce losses. Both of those drastically reduce the bandwidth of the
antenna. So, you keep your gain, reduce the size, but screw up the
bandwidth. That's not a good idea for a TV antenna, which needs
plenty of bandwidth.

I suggest you use 4NEC2 to model a simple dipole. Then change it to a
simple fractal dipole per your photo and compare the results. When
you model your completed antenna, compare it with the other similar
size HD antennas that I previously posted links. At some frequency,
your fractal antenna will probably have the same gain, be smaller, and
have a narrower bandwidth, so that it only works on some partial range
of TV channels.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Can fractal antennas solve the problem of the Penrose Unilluminable
Room? [Smiley attached here]

<http://demonstrations.wolfram.com/ThePenroseUnilluminableRoom/>

Drag the little omnidirectional light bulb around inside the room.

Jeff Liebermann wrote:

> On 4 Sep 2011 17:10:05 +1000, "Dr Who"
> <(E-Mail Removed)> wrote:
>
> >> Note: You're really asking this in the wrong newsgroup. Look for
> >> something that discusses TV antenna. www.avsforums.com would
> >> probably be a good place to start.
>
> > I will check out the avsforum. I wasn't aware of that one.
> > Cheers
>
> Oops. Wrong url:
> <http://www.avsforum.com>
> <http://www.avsforum.com/avs-vb/>
> Antenna discussions usually land in HDTV technical:
> <http://www.avsforum.com/avs-vb/forumdisplay.php?f=25>
>
> I didn't find anything specific on fractal antennas, but did find this
> 100+ thread on UHF TV construction:
> <http://www.avsforum.com/avs-vb/showthread.php?t=798265&page=1>
>
> I can't resist offering my never humble opinion on fractal antennas.
> Methinks they only make sense when dealing with a specialized
> radiation pattern (i.e. cell phone SAR) in a confined area (i.e.
> inside a cell phone) such as a box. When there are few limits on the
> size of the antenna, such as in an outdoor antenna, fractal antennas
> are not the best solution.
>
> Basically, it's compromise between size, gain, and bandwidth. You can
> have any two, at the expense of the third. For example, the gain of a
> simple dipole is about 2.1dBi. If you shrink the length of each
> element, the gain remains about 2dBi until you get down to about
> 1/10th wavelenth. Of course, the tuning also changes, so you have to
> add inductance (loading coils) to tune it, and a matching circuit to
> reduce losses. Both of those drastically reduce the bandwidth of the
> antenna. So, you keep your gain, reduce the size, but screw up the
> bandwidth. That's not a good idea for a TV antenna, which needs
> plenty of bandwidth.
>
> I suggest you use 4NEC2 to model a simple dipole. Then change it to a
> simple fractal dipole per your photo and compare the results. When
> you model your completed antenna, compare it with the other similar
> size HD antennas that I previously posted links. At some frequency,
> your fractal antenna will probably have the same gain, be smaller, and
> have a narrower bandwidth, so that it only works on some partial range
> of TV channels.

Thanks again Jeff.

The thing that shocked me was that the fractal antenna worked so well laying on it's back pointing upwards towards the sky. I only discovered this by accident.

Up until then I had viewed it as a directinal panel antenna for Digital TV application and that it would be orientated on the vertical like a biquad.

Any reflector that is added seems to be also aligned in a similar fashion to a biquad. But as the fractal is used extensively as a patch antenna in mobile phones, I suppose element orientation isn't an issue.

That being the case it might be possible to use a reflector in a different alignment - eg. at the end of the array.

I will try and see if I can find a schematic of a fractal dispersion pattern.

Cheers

Cheers