Reflectors For H.F. use
 

For ham radio it is conventional ( my thoughts) to see reflectors as
element/s placed behind
a feed element where. like other elements in an array receive radio energy
and then reradiate a portion of the received energy.If one wants to emulate
a point
radiation then many elements have to be arranged in parabolic fashion such
that all R.F.
received or transmitted meet at a common point.

Now I really know didly #####about dishes as my world is made up from Yagis
but now
I am starting to think about these things which really raises questions
about what I had previously accepted
For instance,
1
Commercial dishes are not made of reflectors with a fraction of a wave
length ( surface is smooth)
So we have some how shifted from 'resonation' to a 'reflection' mode as in
light even tho a resonance
must still some how occur, but how and with what length reflectors (
multiple long wires?)?
2
If radiation/reception follows a common path then is the dual path radiation
as seen with a Yagi (90 degrees apart)
changed ?
3
What would the result be if multiple electrical connection lines were made
between the horizontal reflectors (vert refl form)?

The emergency operation is now over after a lousy week in hospital but I am
grounded for the rest of the year
( pain and infections and physical inabilities) books and the like is a
hard task but the laptop is at hand if I can find suitable links to study.

Plans are complete and parts available for a 20 metre dipole with eight
reflectors set in quasi parabolic form to deliver
14.5 dbi.BW 63 degrees which I hope then to reduce to 30 degrees for added
gain.
Feed dipole will be of variable length for different band use.
Isn't experimentation great when failure is not considered disasterous to
ones self esteem and resume?

Regards
Art

" wrote in message
news:uEfjd.579123$8_6.52336@attbi_s04...
For ham radio it is conventional ( my thoughts) to see reflectors as
element/s placed behind
a feed element where. like other elements in an array receive radio
energy
and then reradiate a portion of the received energy.If one wants to
emulate
a point
radiation then many elements have to be arranged in parabolic fashion such
that all R.F.
received or transmitted meet at a common point.

Now I really know didly #####about dishes as my world is made up from
Yagis
but now
I am starting to think about these things which really raises questions
about what I had previously accepted
For instance,
1
Commercial dishes are not made of reflectors with a fraction of a wave
length ( surface is smooth)
So we have some how shifted from 'resonation' to a 'reflection' mode as in
light even tho a resonance
must still some how occur, but how and with what length reflectors (
multiple long wires?)?

It is all about keeping things in phase. The parabolic dish just reflects
the signal such that the phase at the feed is the same (or time delay) You
can say they resonate, or have high currents but if an element is 1/4 wave
away. it will pick it up. There some cross bread antennas between dishes and
Yagi too. mostly in 1 to 2 G band.


2
If radiation/reception follows a common path then is the dual path
radiation
as seen with a Yagi (90 degrees apart)
changed ?

Yagi with reflector and director has one fat beam off the end, and some
lobes too.



3
What would the result be if multiple electrical connection lines were made
between the horizontal reflectors (vert refl form)?

On a yagi?


The emergency operation is now over after a lousy week in hospital but I
am
grounded for the rest of the year
( pain and infections and physical inabilities) books and the like is a
hard task but the laptop is at hand if I can find suitable links to study.

Plans are complete and parts available for a 20 metre dipole with eight
reflectors set in quasi parabolic form to deliver
14.5 dbi.BW 63 degrees which I hope then to reduce to 30 degrees for added
gain.
Feed dipole will be of variable length for different band use.
Isn't experimentation great when failure is not considered disasterous to
ones self esteem and resume?

Regards
Art

Good luck with the health. Phase is the name of the game, they use phased
towers at AM band to switch the pattern around from day to night, usually
you will see 6 in a rough circle, all 50 to 150 foot high.

Isn't experimentation great when failure is not considered disasterous to
ones self esteem and resume?

Thomas Edison referred to failed experiments as ways of 'eliminating' the
things that don't work.
So a failed experiment is not a failure at all.
But its a lot more fun when we find things that DO work !!



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On Sun, 7 Nov 2004 01:49:17 -0500, "Hal Rosser"
wrote:

So a failed experiment is not a failure at all.

Hi Hal,

It has been observed that if you haven't failed, you haven't tried
hard enough.

73's
Richard Clark, KB7QHC

calling the longer element 'behind' the driven element of a yagi a
'reflector' is poor terminology. it does not actually 'reflect' it just
resonates at a slightly different point and the combination of phase and
distance from the driven element contribute to the gain in the 'forward'
direction and cancel out signals in the 'backward' direction. actual
reflection requires a conductive surface several wavelengths long in all
directions as is done on parabolic dishes for microwave use. even when you
look at vhf/uhf yagi's that have multiple reflectors they are still only
using the phase shift of the resonance of them to add or cancel energy from
certain directions. the smallest one that might be really called a
reflector is the 'corner reflector' antenna sometimes used at vhf and uhf.

" wrote in message
news:uEfjd.579123$8_6.52336@attbi_s04...
For ham radio it is conventional ( my thoughts) to see reflectors as
element/s placed behind
a feed element where. like other elements in an array receive radio
energy
and then reradiate a portion of the received energy.If one wants to
emulate
a point
radiation then many elements have to be arranged in parabolic fashion such
that all R.F.
received or transmitted meet at a common point.

Now I really know didly #####about dishes as my world is made up from
Yagis
but now
I am starting to think about these things which really raises questions
about what I had previously accepted
For instance,
1
Commercial dishes are not made of reflectors with a fraction of a wave
length ( surface is smooth)
So we have some how shifted from 'resonation' to a 'reflection' mode as in
light even tho a resonance
must still some how occur, but how and with what length reflectors (
multiple long wires?)?
2
If radiation/reception follows a common path then is the dual path
radiation
as seen with a Yagi (90 degrees apart)
changed ?
3
What would the result be if multiple electrical connection lines were made
between the horizontal reflectors (vert refl form)?

The emergency operation is now over after a lousy week in hospital but I
am
grounded for the rest of the year
( pain and infections and physical inabilities) books and the like is a
hard task but the laptop is at hand if I can find suitable links to study.

Plans are complete and parts available for a 20 metre dipole with eight
reflectors set in quasi parabolic form to deliver
14.5 dbi.BW 63 degrees which I hope then to reduce to 30 degrees for added
gain.
Feed dipole will be of variable length for different band use.
Isn't experimentation great when failure is not considered disasterous to
ones self esteem and resume?

Regards
Art

Hal Rosser wrote:
Isn't experimentation great when failure is not considered disasterous to
ones self esteem and resume?

Thomas Edison referred to failed experiments as ways of 'eliminating' the
things that don't work.

Rumor was that Edison didn't like AC, didn't experiment much with it,
and didn't think it would work. That was good news for Westinghouse.
--
73, Cecil http://www.qsl.net/w5dxp


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"Dave" wrote in message
...
calling the longer element 'behind' the driven element of a yagi a
'reflector' is poor terminology. it does not actually 'reflect' it just
resonates at a slightly different point and the combination of phase and
distance from the driven element contribute to the gain in the 'forward'
direction and cancel out signals in the 'backward' direction. actual
reflection requires a conductive surface several wavelengths long in all
directions as is done on parabolic dishes for microwave use.

Dave
So how does one "create" several conductive surfaces of what ever length
on a continuos electrical surface? My reflectors will consist of individual
elements tho I may well eventually connect them vertically at a later point.
If one should look at it in terms of phase and distance then how is the
length
of the phase changing element determined on a continuos surface?





even when you
look at vhf/uhf yagi's that have multiple reflectors they are still only
using the phase shift of the resonance of them to add or cancel energy
from
certain directions. the smallest one that might be really called a
reflector is the 'corner reflector' antenna sometimes used at vhf and uhf.

Since my wave length is long, does it really matter if the spacings between
reflectors
is :"open" for a small fraction of a wave length?
Can fields exist to deter penatration?

My cruising on the net has not provided one example of a "dish" style
antenna for H.F.
yet it would appear that there are advantages there if backyard space is
small,
especially for multi band use.
..
Surely, somewhere in ham radio history, a demarcation line for dish antennas
has been ascertained based
on advantages versus disadvantages ! If gain and f/b ( prime specs for the
amateur) can be manipulated
into higher extremes using dishes then is it reluctance to change or to lead
that dominates the hobby
based on the notion that all is now known?
There seem to be so many advantages with this aproach now that weight issues
are overcome
with foil coated fishing poles that I wonder what it is I am missing in a
much experimented field where
this portion has been pre dismissed or where coil dissertation is to prove
greater inroads in the hobby..
In this particular case I would welcome negative comments from those with
expertise in the field so
that these aspects can be given more thought,but then expertise is not a
real requirement since
so little is written.


Regards
Art



" wrote in
message
news:uEfjd.579123$8_6.52336@attbi_s04...
For ham radio it is conventional ( my thoughts) to see reflectors as
element/s placed behind
a feed element where. like other elements in an array receive radio
energy
and then reradiate a portion of the received energy.If one wants to
emulate
a point
radiation then many elements have to be arranged in parabolic fashion
such
that all R.F.
received or transmitted meet at a common point.

Now I really know didly #####about dishes as my world is made up from
Yagis
but now
I am starting to think about these things which really raises questions
about what I had previously accepted
For instance,
1
Commercial dishes are not made of reflectors with a fraction of a wave
length ( surface is smooth)
So we have some how shifted from 'resonation' to a 'reflection' mode as
in
light even tho a resonance
must still some how occur, but how and with what length reflectors (
multiple long wires?)?
2
If radiation/reception follows a common path then is the dual path
radiation
as seen with a Yagi (90 degrees apart)
changed ?
3
What would the result be if multiple electrical connection lines were
made
between the horizontal reflectors (vert refl form)?

The emergency operation is now over after a lousy week in hospital but I
am
grounded for the rest of the year
( pain and infections and physical inabilities) books and the like is a
hard task but the laptop is at hand if I can find suitable links to
study.

Plans are complete and parts available for a 20 metre dipole with eight
reflectors set in quasi parabolic form to deliver
14.5 dbi.BW 63 degrees which I hope then to reduce to 30 degrees for
added
gain.
Feed dipole will be of variable length for different band use.
Isn't experimentation great when failure is not considered disasterous
to
ones self esteem and resume?

Regards
Art

" wrote in message
news:%Mwjd.10399$5K2.3472@attbi_s03...

"Dave" wrote in message
...
if the surface is large enough and conductive enough then the incident
waves
are reflected. note, this is a MUCH different effect than having
several
near 1/2 wave resonant 'reflectors' on a yagi.
Exactly, Which is why there is so little information regarding 1/2 wave
resonant VS
smooth surface reflectors. Modeling shows that it is possibly worth while
to
concentrate solely on reflector capture via multi elements as opposed to a
single reflector
and a long boom where as my previous investigation showed that combination
multi element
directors and reflectors showed little advancement. If the drive element
is
multi banded then reflectors
would appear as full wave reflecters which would be an advantage.plus
providing the possible ability
for lesser beam width. I also have the feeling that grounding the highest
element will remove local
static effects. First examination shows that feed position is not as
critical as that required
for smooth dish forms
Regards
Art

of course not, because you aren't reflecting. you are inducing currents in
the elements and those currents add up in the direction you want. if you
really want to investigate this you should get one of the good modelling
programs and try it out in various arrangements.

Note, multiple reflector yagis have been around for ages. there are some
good reasons why they aren't common on hf... first they are hard to build to
withstand weather. and second, the added performance on a relatively short
hf yagi is minimal. when you get into very long vhf and uhf yagis it is
more common to see multiple reflectors, but they are mostly used to
eliminate specific side lobes... and even then the only common designs i
remember have a total of 3 reflectors, one on axis of the boom and one on
each side. a similar effect can be done with the so called 'quagi' where
you have a loop element as the reflector and maybe as a driven element then
plane yagi type directors.

David,
The way all of this came about was that I modelled a 0,1wave length boom
with out restriction
to the number of elements used and without restriction regarding in-line
height.
It was then a surprise to me that where gain was the priority the NEC
program evolved a design with
multi reflectors in quasi parabolic form with parallel elements such as I
mixed up smooth dish
thoughts with standard antenna array thoughts. Thus my search for info and
outside thought.
Now if I placed a constant current COIL in the feed dipole responses would
over whelm me
and place me in a position of immobility (smile)
Regards
Art

ssage ...

" wrote in
message
news:%Mwjd.10399$5K2.3472@attbi_s03...

"Dave" wrote in message
...
if the surface is large enough and conductive enough then the incident
waves
are reflected. note, this is a MUCH different effect than having
several
near 1/2 wave resonant 'reflectors' on a yagi.
Exactly, Which is why there is so little information regarding 1/2 wave
resonant VS
smooth surface reflectors. Modeling shows that it is possibly worth
while
to
concentrate solely on reflector capture via multi elements as opposed to
a
single reflector
and a long boom where as my previous investigation showed that
combination
multi element
directors and reflectors showed little advancement. If the drive element
is
multi banded then reflectors
would appear as full wave reflecters which would be an advantage.plus
providing the possible ability
for lesser beam width. I also have the feeling that grounding the
highest
element will remove local
static effects. First examination shows that feed position is not as
critical as that required
for smooth dish forms
Regards
Art

of course not, because you aren't reflecting. you are inducing currents
in
the elements and those currents add up in the direction you want. if you
really want to investigate this you should get one of the good modelling
programs and try it out in various arrangements.

Note, multiple reflector yagis have been around for ages. there are some
good reasons why they aren't common on hf... first they are hard to build
to
withstand weather. and second, the added performance on a relatively
short
hf yagi is minimal. when you get into very long vhf and uhf yagis it is
more common to see multiple reflectors, but they are mostly used to
eliminate specific side lobes... and even then the only common designs i
remember have a total of 3 reflectors, one on axis of the boom and one on
each side. a similar effect can be done with the so called 'quagi' where
you have a loop element as the reflector and maybe as a driven element
then
plane yagi type directors.

A baseball / softball field backstop does FB for 6 and 10meter mobile, just
trying to explain to the cops why you parked on the infield is rough! Do expect
to be asked to walk the baseline heel/
toe Hi
73
WG8Z
Greg Z
to thine own sound be true
WG8Z

Art:

Here is a URL with a couple of photos of HF antennas with real reflectors. For more, do a search for FRD-10, FLR-9, and
Wullenweber. Just look at the photos; most of the text is, unfortunately, not very accurate. While I never knew the
German originators of the design during WW2, I did work with the engineer who developed the US version back in the 50s.
http://www.mindspring.com/~cummings7/wullen.html
--
Crazy George
Remove N O and S P A M imbedded in return address

i dont' know if i would really call them 'reflectors'. from the shape and
spacing i would think they were more of a vertical ground screen behind the
monopoles. kind of like having a dipole mounted above a ground screen, it
would provide some directionality outward and shield them from noise from
the building inside.

"Crazy George" wrote in message
...
Art:

Here is a URL with a couple of photos of HF antennas with real reflectors.
For more, do a search for FRD-10, FLR-9, and
Wullenweber. Just look at the photos; most of the text is, unfortunately,
not very accurate. While I never knew the
German originators of the design during WW2, I did work with the engineer
who developed the US version back in the 50s.
http://www.mindspring.com/~cummings7/wullen.html
--
Crazy George
Remove N O and S P A M imbedded in return address

Art Unwin wrote:
"So how does one "create" several conductive surfaces of what ever
length on a continuous electrical surface?"

First examine the ways it has already been done and ask why? A
non-resonant reflector provides a much wider bandwidth than a resonant
reflector as used in an array like a yagi, for one thing.

Plenty of grid-dish, corner-reflector and similar non-resonant reflector
antennas are in use to reduce wind-loading. You have no need at lower
frequencies to use solid reflectors. Surface irregularities are not much
problem. The solid dishes at 2-GHz are built that way for convenience,
not because they need to be. The same is true at lower frequencies. At
higher frequencies, the conductors are so close together, there isn`t
enough reduction in wind-loading to be worth the construction effort
required with grid-reflectors.

Grid reflectors only need a collection of conductors parallel with the
radiating element(s) illuminating (driving) the antenna, and placed for
best results. Reflecting elemants in a grid reflector placed
perpendicular to the driven element don`t work. Curvature is used tn
dish reflector bars for focus. An angle is used in the corner-reflector
for more gain than a flat reflector. None of the reflectors needs
cross-connections between the reflector bars anymore than ground radials
need their far-ends interconnected. Such connections allow eddy currents
which only cause loss. The only current of value is that in the
direction of the ground radials or in the direction of the reflector`s
parallel conductors, as the case may be. So the eddy currents are bad.

Spacing between reflector bars is related to wavelength and capture
area.. Measure it in a good grid antenna and scale to your frequency.
Or, see Kraus for capture area etc.

Best regards, Richard Harrison, KB5WZI

Crazy George`s information on the Wullenweber is great. I have no
information on this monster but a pair of loops or Adcock directional
antennas can be mounted perpendicularly and their outputs can be
connected with a goniometer to provide the effect of rotating the
directional antenna while the array remains unmoved in place. Terman
shows how on page 1051 of his 1955 edition. Could our military be
extravagant with taxpayer money?

Best regards, Richard Harrison, KB5WZI

Terman
shows how on page 1051 of his 1955 edition.

Not in 1947 edition:-(

73,
Chip N1IR

Chip, N1IR wrote:
"Not in 1947 edition (sad face)."

Too bad. Authors neeed new additions to new editions so owners will
upgrade.

Terman`s topic "Goniometer" starts on page 1050 of his 1955 edition.
His illustration is Fig. 26-29: "Crossed loop antennas connected to
goniometer."

Each loop`s feedline is connected to a fixed goniometer coil and these
are crossed at right angles. A rotating pickup coil is mounted inside
the fixed coils and shares their axis. The output to the radio is taken
from the goniometer`s rotating coil. Terman writes:
"Thus the rotation of the goniometer secondary is equivalent
electrically to rotating the loop (or Adcock) antenna."

In 1960, the chief of our Argentine oil exploration and production
called me into his office on Tierra del Fuego to ask me if Dr.
Maldonado, our physician, and not Alec Eussler, our atomic physicist
(aka radio technician) should be ordering the goniometer.
Our chief, George Blackwell thought the goniometer was diagnostic
equipment for a social disease.

Best regards, Richard Harrison, KB5WZI