Matt,

Slot antennas began life as slots in curved surfaces, eg., aircraft
fuselages and wings. Most structural alloys will do fine. Rectangular
tubes are unusual. They are often unsightly protusions.

The maths is more complicated with curved surfaces.

But if you just copy somebody else's slot, and scale dimensions according to
frequency, the maths reduces to simple A*B/C schoolboy arithmetic.

I doubt if you are interested in an exceptionally well-defined beam. So the
differences between a rectangular and a circular tube of roughly the same
perimeter will probably be of no great consequence.

( Hi Richard - so we meet again!
----
Acqured nom-de-plume, Punchinello.)

Slot antennas began life as slots in curved surfaces, eg., aircraft
fuselages and wings. Most structural alloys will do fine. Rectangular
tubes are unusual. They are often unsightly protusions.

The maths is more complicated with curved surfaces.

But if you just copy somebody else's slot, and scale dimensions according
to
frequency, the maths reduces to simple A*B/C schoolboy arithmetic.

I have not found any round rather then square designs on the net. Do you
know of any? If I found one I could scale it down to 33cm. I have not
found any 33cm slotted designs period. I have found a calculator for
rectangular waveguide though which I ran for 33cm. Not sure how I would
adapt its results to round though.

Matt


I doubt if you are interested in an exceptionally well-defined beam. So
the
differences between a rectangular and a circular tube of roughly the same
perimeter will probably be of no great consequence.

( Hi Richard - so we meet again!
----
Acqured nom-de-plume, Punchinello.)

"Matt" wrote in message
...
Slot antennas began life as slots in curved surfaces, eg., aircraft
fuselages and wings. Most structural alloys will do fine. Rectangular
tubes are unusual. They are often unsightly protusions.

The maths is more complicated with curved surfaces.

But if you just copy somebody else's slot, and scale dimensions
according
to
frequency, the maths reduces to simple A*B/C schoolboy arithmetic.

I have not found any round rather then square designs on the net. Do you
know of any? If I found one I could scale it down to 33cm. I have not
found any 33cm slotted designs period. I have found a calculator for
rectangular waveguide though which I ran for 33cm. Not sure how I would
adapt its results to round though.

Matt

It should be close, yoy may have to move the slots closer of further apart
by the velocity factor inside the waveguide (going from rectangular to
round, round could be faster so slots may be further apart, but not by much)
How many slots, how many wavelengths long?

Slot antennas began life as slots in curved surfaces, eg., aircraft
fuselages and wings. Most structural alloys will do fine. Rectangular
tubes are unusual. They are often unsightly protusions.

The maths is more complicated with curved surfaces.

But if you just copy somebody else's slot, and scale dimensions
according
to
frequency, the maths reduces to simple A*B/C schoolboy arithmetic.

I have not found any round rather then square designs on the net. Do you
know of any? If I found one I could scale it down to 33cm. I have not
found any 33cm slotted designs period. I have found a calculator for
rectangular waveguide though which I ran for 33cm. Not sure how I would
adapt its results to round though.

Matt

It should be close, yoy may have to move the slots closer of further apart
by the velocity factor inside the waveguide (going from rectangular to
round, round could be faster so slots may be further apart, but not by
much)
How many slots, how many wavelengths long?

I am wanting 10 slots, 5 per side. I think 7" inch aluminun pipe for
waveguide in 33cm band.

Another question. I have heard for injection into the waveguide you should
use a 1/4 wave stub. I also heard its not supposed to farther then half way
into the waveguide. If I were to use 2" x "8 waveguide how would I do that
since the 1/4 wave stub is 3.2 inches and the waveguide is only 2 inches
wide?

Matt

On Fri, 17 Dec 2004 09:26:51 -0600, "Matt"
wrote:

Another question. I have heard for injection into the waveguide you should
use a 1/4 wave stub. I also heard its not supposed to farther then half way
into the waveguide.

Hi Matt,

What you've "heard" is vague at best. You really need another source
of information, or at least more sources. Try searching the
googlegroups archive of this news group.

In your particular situation (you will eventually have to convert all
this to coax or wire) you either probe excite a waveguide or you loop
excite it.

73's
Richard Clark, KB7QHC

"Matt" wrote in message
...
Slot antennas began life as slots in curved surfaces, eg., aircraft
fuselages and wings. Most structural alloys will do fine.
Rectangular
tubes are unusual. They are often unsightly protusions.

The maths is more complicated with curved surfaces.

But if you just copy somebody else's slot, and scale dimensions
according
to
frequency, the maths reduces to simple A*B/C schoolboy arithmetic.

I have not found any round rather then square designs on the net. Do
you
know of any? If I found one I could scale it down to 33cm. I have not
found any 33cm slotted designs period. I have found a calculator for
rectangular waveguide though which I ran for 33cm. Not sure how I
would
adapt its results to round though.

Matt

It should be close, yoy may have to move the slots closer of further
apart
by the velocity factor inside the waveguide (going from rectangular to
round, round could be faster so slots may be further apart, but not by
much)
How many slots, how many wavelengths long?

I am wanting 10 slots, 5 per side. I think 7" inch aluminun pipe for
waveguide in 33cm band.

Another question. I have heard for injection into the waveguide you
should
use a 1/4 wave stub. I also heard its not supposed to farther then half
way
into the waveguide. If I were to use 2" x "8 waveguide how would I do
that
since the 1/4 wave stub is 3.2 inches and the waveguide is only 2 inches
wide?

Matt

The 2" by 8" sounds wrong for gernic waveguide. it is usally in about a 1:2
ratio
It may be more like 4" by 8" for 900 Mhz.
The field max is in the middle of the waveguide, and the probe end needs to
be there.
ARRL had an article on the rectangular waveguide antenna.
The beam on this antenna if mounted horozontally is very narrow in the
horozontal but wide in the vertical. Fan shaped beam.