Does anyone have any experience of these? The plots I've seen seem to
have very variable gain/frequency responses.

On 05/04/2015 20:30, Capitol wrote:

Does anyone have any experience of these? The plots I've seen seem
to have very variable gain/frequency responses.

The devil is in the detail. Mostly it is all buzzword induced hype.

Unless you transmit is astonishing what you can get away with.
(RF power amps take exception to mismatched antennae)

--
Regards,
Martin Brown

On Sunday, 5 April 2015 20:44:22 UTC+1, Martin Brown wrote:
On 05/04/2015 20:30, Capitol wrote:

Does anyone have any experience of these? The plots I've seen seem
to have very variable gain/frequency responses.

The devil is in the detail. Mostly it is all buzzword induced hype.

Unless you transmit is astonishing what you can get away with.
(RF power amps take exception to mismatched antennae)

check in the mirror that your antennae are matched


NT

Well its not a black art, all aerials still obey the same rules, its just
the compromises made in the design. I recall these were used in millimetric
radar systems and the main reason was that they needed to be able to steer
them electronically. Not tried the scaled up versions, I have to say.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Capitol" wrote in message
o.uk...

Does anyone have any experience of these? The plots I've seen seem to have
very variable gain/frequency responses.

On 06/04/2015 10:07, Brian Gaff wrote:

Well its not a black art, all aerials still obey the same rules, its just
the compromises made in the design. I recall these were used in millimetric
radar systems and the main reason was that they needed to be able to steer
them electronically. Not tried the scaled up versions, I have to say.
Brian


Although they obey the same rules the complex shape of a finite depth
fractal does produce interesting resonance characteristics that may
sometimes be useful - but there is a lot trendy snake oil being sold.

Some old TV aerials were (unrecognised at the time) fractal array
designs. The Wiki article isn't bad for the OP as an intro.

http://en.wikipedia.org/wiki/Fractal_antenna

Some of the deeper theory of serious fractal antenna designs has only
been relatively recently understood (around 2000). Some very odd novel
metamaterials are based on this sort of approach too.

My money would be on log periodic though for practicality.

--
Regards,
Martin Brown

Martin Brown wrote:
On 06/04/2015 10:07, Brian Gaff wrote:

Well its not a black art, all aerials still obey the same rules, its just
the compromises made in the design. I recall these were used in
millimetric
radar systems and the main reason was that they needed to be able to
steer
them electronically. Not tried the scaled up versions, I have to say.
Brian


Although they obey the same rules the complex shape of a finite depth
fractal does produce interesting resonance characteristics that may
sometimes be useful - but there is a lot trendy snake oil being sold.

Some old TV aerials were (unrecognised at the time) fractal array
designs. The Wiki article isn't bad for the OP as an intro.

http://en.wikipedia.org/wiki/Fractal_antenna

Some of the deeper theory of serious fractal antenna designs has only
been relatively recently understood (around 2000). Some very odd novel
metamaterials are based on this sort of approach too.

My money would be on log periodic though for practicality.


I'm not convinced that fractals are understood. Log periodic is a form
of fractal. The problem as I see it is that there doesn't seem to be a
calculating procedure for fractals which can optimise a design. You seem
to have to pick a geometry, then calculate a possible set of results.
Testing can be quite close to the calculation, but gain figures are
never posted. Fractals seem to suffer from lots of notches in the
response curves as a result of repeating one fixed shape. I was hoping
someone here had some hands on experience of performance.

On Monday, 6 April 2015 11:45:01 UTC+1, Capitol wrote:
Testing can be quite close to the calculation, but gain figures are
never posted. Fractals seem to suffer from lots of notches in the
response curves as a result of repeating one fixed shape. I was hoping
someone here had some hands on experience of performance.

I tried designing one a few years ago when I needed a wide bandwidth.
In the end the results were disappointing and I gave up and used a
more "conventional" structure where it is more obvious how any particular
adjustment will influence the characteristics.

I used EM simulation followed by testing prototypes with a VNA.

One of the biggest problems is that an antenna design that needs
to fit in an enclosure with nearby circuitry is difficult to
simulate accurately and therefore requires trimming. If you
can't predict what effect a particular adjustment will have,
the process becomes painful.

Obtaining a good return loss for transmitter matching is easy if
you use the procedure favoured by some manufacturers: just use
several metres of lossy coax between the antenna and the analyzer.

John

In article , Capitol
scribeth thus
Martin Brown wrote:
On 06/04/2015 10:07, Brian Gaff wrote:

Well its not a black art, all aerials still obey the same rules, its just
the compromises made in the design. I recall these were used in
millimetric
radar systems and the main reason was that they needed to be able to
steer
them electronically. Not tried the scaled up versions, I have to say.
Brian


Although they obey the same rules the complex shape of a finite depth
fractal does produce interesting resonance characteristics that may
sometimes be useful - but there is a lot trendy snake oil being sold.

Some old TV aerials were (unrecognised at the time) fractal array
designs. The Wiki article isn't bad for the OP as an intro.

http://en.wikipedia.org/wiki/Fractal_antenna

Some of the deeper theory of serious fractal antenna designs has only
been relatively recently understood (around 2000). Some very odd novel
metamaterials are based on this sort of approach too.

My money would be on log periodic though for practicality.




I'm not convinced that fractals are understood. Log periodic is a form
of fractal. The problem as I see it is that there doesn't seem to be a
calculating procedure for fractals which can optimise a design. You seem
to have to pick a geometry, then calculate a possible set of results.
Testing can be quite close to the calculation, but gain figures are
never posted. Fractals seem to suffer from lots of notches in the
response curves as a result of repeating one fixed shape. I was hoping
someone here had some hands on experience of performance.

Tried a "NEC" program at all?...
--
Tony Sayer

In article , Capitol
scribeth thus

Does anyone have any experience of these? The plots I've seen seem to
have very variable gain/frequency responses.

Whatever are you up to with that sort of thing?..
--
Tony Sayer

On 06/04/2015 23:59, tony sayer wrote:
In article , Capitol
scribeth thus

Does anyone have any experience of these? The plots I've seen seem to
have very variable gain/frequency responses.

Whatever are you up to with that sort of thing?..

A difficult to manufacture DIY aerial?

--
Regards,
Martin Brown

Martin Brown wrote:
On 06/04/2015 23:59, tony sayer wrote:
In article , Capitol
scribeth thus

Does anyone have any experience of these? The plots I've seen seem to
have very variable gain/frequency responses.

Whatever are you up to with that sort of thing?..

A difficult to manufacture DIY aerial?


I am currently building a pigeon proof TV aerial, a double biquad. I
can mount this under the eaves so the bloody pigeons can't perch on it
and fight. Our pigeons IMO resemble small turkeys which I blame on the
deranged neighbour who feeds them. They destroyed the last new log
periodic TV aerial in 3 months and next doors a few months later. I give
next doors weedy looking replacement 6 months at the outside. I pigeon
proofed the original Yagi with spikes, this worked within limits until
they destroyed the feeder cable at Xmas. They also crap all over the
roof causing more moss growth and the patio, which she complains about.
Preliminary tests on the double biquad are promising. I haven't
attempted to measure the gain bandwidth yet but may get round to it this
week in a very crude manner. I came across fractal antennae so
investigated the theory and discovered there really wasn't a predictive
one. As this group has a wide range if interests, I thought I'd ask here
to see if there was any hands on experience. NEC programs require that
you start with an empirical geometry and then you can calculate the
performance. On fractals the geometric limits are infinite, so you end
up doing the calculations for ever. Aerials always end up as cut and try
IME, it's just like trying to lay out frequency synthesisers in UHF radios.

On 07/04/2015 10:33, Capitol wrote:
Martin Brown wrote:
On 06/04/2015 23:59, tony sayer wrote:
In article , Capitol
scribeth thus

Does anyone have any experience of these? The plots I've seen seem to
have very variable gain/frequency responses.

Whatever are you up to with that sort of thing?..

A difficult to manufacture DIY aerial?


I am currently building a pigeon proof TV aerial, a double biquad.
I can mount this under the eaves so the bloody pigeons can't perch on it
and fight. Our pigeons IMO resemble small turkeys which I blame on the
deranged neighbour who feeds them. They destroyed the last new log
periodic TV aerial in 3 months and next doors a few months later.

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

next doors weedy looking replacement 6 months at the outside. I pigeon
proofed the original Yagi with spikes, this worked within limits until
they destroyed the feeder cable at Xmas. They also crap all over the
roof causing more moss growth and the patio, which she complains about.
Preliminary tests on the double biquad are promising. I haven't
attempted to measure the gain bandwidth yet but may get round to it this
week in a very crude manner. I came across fractal antennae so
investigated the theory and discovered there really wasn't a predictive
one. As this group has a wide range if interests, I thought I'd ask here
to see if there was any hands on experience. NEC programs require that
you start with an empirical geometry and then you can calculate the
performance. On fractals the geometric limits are infinite, so you end
up doing the calculations for ever. Aerials always end up as cut and try
IME, it's just like trying to lay out frequency synthesisers in UHF radios.

How well it works depends on local signal levels. Where I live a foot of
random wire will do almost as well as a real Yagi antenna.

--
Regards,
Martin Brown

Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit 8 TV receiver locations & 6 recording locations.

In article , Capitol
scribeth thus
Martin Brown wrote:
On 06/04/2015 23:59, tony sayer wrote:
In article , Capitol
scribeth thus

Does anyone have any experience of these? The plots I've seen seem to
have very variable gain/frequency responses.

Whatever are you up to with that sort of thing?..

A difficult to manufacture DIY aerial?


I am currently building a pigeon proof TV aerial, a double biquad. I
can mount this under the eaves so the bloody pigeons can't perch on it
and fight. Our pigeons IMO resemble small turkeys which I blame on the
deranged neighbour who feeds them. They destroyed the last new log
periodic TV aerial in 3 months and next doors a few months later. I give
next doors weedy looking replacement 6 months at the outside. I pigeon
proofed the original Yagi with spikes, this worked within limits until
they destroyed the feeder cable at Xmas. They also crap all over the
roof causing more moss growth and the patio, which she complains about.
Preliminary tests on the double biquad are promising. I haven't
attempted to measure the gain bandwidth yet but may get round to it this
week in a very crude manner. I came across fractal antennae so
investigated the theory and discovered there really wasn't a predictive
one. As this group has a wide range if interests, I thought I'd ask here
to see if there was any hands on experience. NEC programs require that
you start with an empirical geometry and then you can calculate the
performance. On fractals the geometric limits are infinite, so you end
up doing the calculations for ever. Aerials always end up as cut and try
IME, it's just like trying to lay out frequency synthesisers in UHF radios.

Umm .. wouldn't a decent aerial in the loft achieve what you want?.

Or perhaps an air gun;-)...

--
Tony Sayer

In article , Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit 8 TV receiver locations & 6 recording locations.

Well using a "multiswitch" does that...
--
Tony Sayer

tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit8 TV receiver locations& 6 recording locations.

Well using a "multiswitch" does that...

Can't see how that helps.

In article , Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit8 TV receiver locations& 6 recording locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..
--
Tony Sayer

tony sayer wrote:
In articleNb2dnagS9oT1crnInZ2dnUVZ8tOdnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit8 TV receiver locations& 6 recording locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..

So, you are limited to 4 channels at a time? Incidentally, loft aerials
don't work very well in this location, the additional problems of a low
pitched concrete roof and rain/snow etc rather rules one out.

On 08/04/2015 14:42, Capitol wrote:
tony sayer wrote:
In articleNb2dnagS9oT1crnInZ2dnUVZ8tOdnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric
coating".

Doesn't really suit8 TV receiver locations& 6 recording
locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..

It does require a satellite tuner on the end of each though.

So, you are limited to 4 channels at a time? Incidentally, loft
aerials don't work very well in this location, the additional problems
of a low pitched concrete roof and rain/snow etc rather rules one out.

It is hard to get a dish these days with less than two LNB outputs. Mine
has four of which only one is actually used. Splitters do exist. No idea
if they are any good since I only have one satellite tuner.

--
Regards,
Martin Brown

On 05/04/2015 20:30, Capitol wrote:

Does anyone have any experience of these? The plots I've seen seem
to have very variable gain/frequency responses.

BTW you might want to pose this question in s.e.design where there are
some folk who do RF & UHF stuff. Although specify the centre frequency
and bandwidth you want to obtain if you don't want to be flamed.

They are more than a little intolerant of ill specified problems.

--
Regards,
Martin Brown

In article , Capitol
scribeth thus
tony sayer wrote:
In articleNb2dnagS9oT1crnInZ2dnUVZ8tOdnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit8 TV receiver locations& 6 recording
locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..

So, you are limited to 4 channels at a time?

No. All the multiswitch does is to distribute the Four outputs of an
ASTRA sat system to any receiver so receiver 1 may be tuned to the
Hi-band and Vertical polarisation, RX 2 to the Low band Horiz
polarisation and the rest to any off them or combination.

Its just like TV distribution of course every TV or satellite receiver
has to have a suitable tuner.

Incidentally, loft aerials
don't work very well in this location, the additional problems of a low
pitched concrete roof and rain/snow etc rather rules one out.

We if the existing one works at like gutter height then perhaps a hi
gain amplified one might well do the trick in the loft. Modern Digital
reception is very tolerant of ghosting which may have plagued analogue
so if its above a sufficient threshold?.

I somehow doubt a more esoteric aerial will improve matters is in the
end is all down to how much metal is up there to develop the required
volts in the right place!.

Nowhere else it could go then?.?.
--
Tony Sayer

In article , Martin Brown |||newspam|||
@nezumi.demon.co.uk scribeth thus
On 08/04/2015 14:42, Capitol wrote:
tony sayer wrote:
In articleNb2dnagS9oT1crnInZ2dnUVZ8tOdnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric
coating".

Doesn't really suit8 TV receiver locations& 6 recording
locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..

It does require a satellite tuner on the end of each though.

So, you are limited to 4 channels at a time? Incidentally, loft
aerials don't work very well in this location, the additional problems
of a low pitched concrete roof and rain/snow etc rather rules one out.

It is hard to get a dish these days with less than two LNB outputs. Mine
has four of which only one is actually used. Splitters do exist. No idea
if they are any good since I only have one satellite tuner.



Splitters don't work as such Martin as unlike TV reception you have to
direct the LNB to one of two combinations of frequency band and either
plane of polarisation. So a sat receiver sends a request as it were to
the LNB to tell it to pass a certain frequency band and polarised
signal..

Hence the Multiswitch alluded to earlier..
--
Tony Sayer

tony sayer wrote:
In articlesO2dnY5JzL6crbjInZ2dnUVZ7qidnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In articleNb2dnagS9oT1crnInZ2dnUVZ8tOdnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit8 TV receiver locations& 6 recording
locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..

So, you are limited to 4 channels at a time?

No. All the multiswitch does is to distribute the Four outputs of an
ASTRA sat system to any receiver so receiver 1 may be tuned to the
Hi-band and Vertical polarisation, RX 2 to the Low band Horiz
polarisation and the rest to any off them or combination.

Its just like TV distribution of course every TV or satellite receiver
has to have a suitable tuner.

Incidentally, loft aerials
don't work very well in this location, the additional problems of a low
pitched concrete roof and rain/snow etc rather rules one out.

We if the existing one works at like gutter height then perhaps a hi
gain amplified one might well do the trick in the loft. Modern Digital
reception is very tolerant of ghosting which may have plagued analogue
so if its above a sufficient threshold?.

I somehow doubt a more esoteric aerial will improve matters is in the
end is all down to how much metal is up there to develop the required
volts in the right place!.

Nowhere else it could go then?.?.

So each TV point requires a satellite receiver?

In article , Capitol
scribeth thus
tony sayer wrote:
In articlesO2dnY5JzL6crbjInZ2dnUVZ7qidnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In articleNb2dnagS9oT1crnInZ2dnUVZ8tOdnZ2d@brightvie w.co.uk, Capitol
scribeth thus
tony sayer wrote:
In article6MydnfbUCciHQb7InZ2dnUVZ8tadnZ2d@brightvie w.co.uk, Capitol
scribeth thus
Martin Brown wrote:

Unless you are a big fan of Dave why not install FreeSat? I doubt if
pigeons can do much harm to a dish beyond adding "dielectric coating".

Doesn't really suit8 TV receiver locations& 6 recording
locations.

Well using a "multiswitch" does that...

Can't see how that helps.

Right U use a certain type of LNB which has four outputs. IIRC its
called a Quad or Quattro. Each one of the outputs which receives signals
is on either the upper or lower part of the band and vertical or
horizontal polarisation.

Each outlet then can take whichever one of the four inputs it needs and
by such means a lot of receivers etc can get a feed..

So, you are limited to 4 channels at a time?

No. All the multiswitch does is to distribute the Four outputs of an
ASTRA sat system to any receiver so receiver 1 may be tuned to the
Hi-band and Vertical polarisation, RX 2 to the Low band Horiz
polarisation and the rest to any off them or combination.

Its just like TV distribution of course every TV or satellite receiver
has to have a suitable tuner.

Incidentally, loft aerials
don't work very well in this location, the additional problems of a low
pitched concrete roof and rain/snow etc rather rules one out.

We if the existing one works at like gutter height then perhaps a hi
gain amplified one might well do the trick in the loft. Modern Digital
reception is very tolerant of ghosting which may have plagued analogue
so if its above a sufficient threshold?.

I somehow doubt a more esoteric aerial will improve matters is in the
end is all down to how much metal is up there to develop the required
volts in the right place!.

Nowhere else it could go then?.?.

So each TV point requires a satellite receiver?

Yes ..

Like a TV receiver, or the same as a set top box. Some sets have
satellite built in least our Sony does...
--
Tony Sayer