Antena SLOT pentru banda de 23cm

[yo2ya]

A construit cineva din YO o asemenea antena???
Ma intereseaza varianta cu o singura fanta-in special adaptarea, as vrea sa construiesc o asemenea antena pentru un viitor proiect in 23cm.
73 si s-auzim numai de bine!!!
Marius

[yo4cai]

Cred ca merita sa vizitati : Information below is from the old Brian Yee WEB page
Slot Antenna Design
Stephen Bell, KB7TRZ
Introduction
This paper was presented at the 40th Annual West Coast VHF/UHF Conference held on
May 5-7 (1995?) in Cerritos, CA. Some editing was done to make it suitable for this WEB
page.
Abstract
Slot antennas can be used for fixed stations, satellite ground stations and beacons. With
proper mounting, a slot antenna can also be used for ‘microwave mobile’. With a 16-slot
total, the antenna can have 10-12 dBi gain.
Slot antennas can be built from surplus waveguide sections, which will give an omnidirectional
pattern and horizontal polarization. This paper offers a computer aided
method to calculate the proper dimensions for the slots and their locations.
Because the antenna is of one-piece construction, it is rugged and can be built cheaply,
requiring only access to a reasonably precise drill press or milling machine. (Note: A
precise milling machine is almost a necessity…de W3RJW)
Getting Ready
The first step in construction of the antenna is to select a section of waveguide which
covers the desired frequency. Waveguide dimensions for several microwave bands are
listed in table 1. If your waveguide doesn’t match the dimensions exactly, go ahead and
run the program. The program will tell you if the waveguide is too small (if you attempt
to operate a waveguide below its cutoff frequency, it will have unacceptable SWR and
losses)
Usable Frequency
(GHz)
Typical
Waveguide
Long Dimension
“a” Inches
Short Dimension
“b” Inches
1.12-1.7 WR650 6.500 3.250
1.7-2.6 WR430 4.300 2.150
2.2-2.3 WR340 3.400 1.700
2.6-3.95 WR284 2.840 1.340
3.3-4.9 WR229 2.290 1.145
3.95-5.85 WR187 1.872 .0872
4.9-7.05 WR159 1.590 .0759
7-11 WR102 1.020 0.510
8.2-12.4 WR90 0.900 0.400
10-15 WR75 0.750 0.375
18-26.5 WR42 0.420 0.170
TABLE 1 – Waveguide Dimensions
Running the Computer Aided Design File
Once the waveguide has been selected, just enter its cross-sectional dimensions and the
desired operating frequency into MathCad program file *slot_ant.mcd or slot_a2.mcd. In
order to edit the file and make the calculations, you must have a copy of MathCad
running under MS Windows.
The program file references the slot antenna dimensions shown in Figure 1. Note that
all calculated dimensions (from the MathCad program) are given in both inches and
millimeters. For the best pattern, a pair of ground planes (wings) can be added to either
side of the antenna. The ‘wings’ should be flush with the top of the waveguide and
extend at least a half wavelength below the bottom slot. The wings need to protrude out
from the sides by several wavelengths, if possible.
Machining the Slots
Drill Press - “Just” drill many overlapping holes, then file out the slots to the desired
dimensions.
Milling Machine – The ideal method: fast and accurate, less prone to mistakes.
Feeding the Antenna
The simplest feed for the slot antenna is to use a coaxial to waveguide transition. These
transitions are often available on the surplus market. (Note: Another method is build
the antenna long on the bottom and use a N chassis mount jack and probe antenna to
replicate a transition as part of the antenna …de W3RJW)
Figure 1. Front View of Waveguide Slot Antenna
MathCad Software
There are two versions of the MathCad slot antenna program. It was discovered that the
original program running on MathCad 3.1 had some problems when users tried to run it
on later versions, namely Version 6.0, etc. For users of the older MathCad, use
*slot_ant.mcd, otherwise use slot_a2.mcd. Many thanks to Steve Muther, WF6R, for
getting the program running in MathCad 6.0.
Ham Band Slot Antennas
Here are some worked examples of waveguide slot antennas using the MathCad
program by Stephen Bell. These examples are based on a 16-slot design
(8 slots per face). All dimensions are in inches.
Band
(MHz)
Waveguide
“a”
Dim.
“b”
Dim.
Offset
from
Center
Slot
Length
Slot
Vert.
Spacing
Slot
Width
Head-
Space
1296 WR650 6.50 3.25 0.49 4.46 6.39 0.64 6.39
2304 WR340 3.40 1.70 0.21 2.56 3.90 0.39 3.90
3456 WR284 2.84 1.34 0.31 1.71 2.57 0.26 2.57
3456 WR229 2.29 1.15 0.15 1.71 2.57 0.26 2.57
5760 WR187 1.87 0.87 0.25 1.02 1.23 0.12 1.23
5760 WR159 1.59 0.76 0.15 1.03 1.34 0.13 1.34
10368 WR102 1.02 0.51 0.14 0.57 0.69 0.07 0.69
10368 WR90 0.90 0.40 0.08 0.57 0.74 0.07 0.74
10368 WR75 0.75 0.38 0.05 0.57 0.88 0.09 0.88
24192 WR42 0.42 0.17 0.05 0.24 0.30 0.03 0.30
Below are several more antennas using the MathCad program. These are 32 Slot
antennas (16 slots per face)… de W3RJW
Band
(MHz)
Waveguide
“a”
Dim.
“b”
Dim.
Offset
from
Center
Slot
Length
Slot
Vert.
Spacing
Slot
Width
Head-
Space
5760 WR159 1.59 0.76 .103 1.025 1.341 0.134 1.341
10368 WR90 0.90 0.40 0.059 0.570 0.736 0.074 0.736
Below is an 8 Slot design for 2304 MHz (4 slots per face)… de W3RJW
Band
(MHz)
Waveguide
“a”
Dim.
“b”
Dim.
Offset
from
Center
Slot
Length
Slot
Vert.
Spacing
Slot
Width
Head-
Space
2304 WR340 3.40 1.70 0.296 2.563 3.901 0.390 3.901
*Brian Yee’s home page no longer exists as far as I can tell. Likewise the links to
the programs are also gone. Here is a link to a basic program that purports to
perform the same calculations as the MathCad programs.
http://www.ham-radio.com/sbms/sd/slotant.htm
de W3RJW Succes !