LRL 550B-SS User manual

MICROWAVES FOR EVERYONE
3rd edition
I-95 Industrial Park
651 Winks Lane
Bensalem, PA 19020
800.523.3929 • 215.638.1100
LRL Model 550B-SS
Microwave Training Kit
Microwave Training Kit
5 Experiments

2 Microwaves for Everyone | LRL 550B Microwave Training Kit
INITIAL SET-UP PROCEDURES • INVENTORY & SET-UP
COMPLETE PARTS LISTING
1 #503A with
2K25 Klystron
Tube Mount
1 #504 Frequency
Meter
1 #505 Slotted Line
2 #506 Variable
Flap Attenuator
1 #507 Termination
1 #508 Thermistor
Mount
1 #518 Detector
Mount
4 #523
Waveguide
Stands
2 #531 Horn
Antennas
1 #532
Shorting Plate

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Microwaves for Everyone | LRL 550B Microwave Training Kit
Inventory & Set Up The LRL 550B Microwave Student Lab . . . . . . . . . . . . 4
Introduction A Brief Discussion of Transmission Line Theory . . . . . . . . 9
Experiment 1 Measurement of Power. . . . . . . . . . . . . . . . . . . . 15
Experiment 2 Measurement of Standing Wave Ratio . . . . . . . . . . . . 23
Experiment 3 Measurement of Frequency and Wavelength . . . . . . . . 31
Experiment 4 Propagation of Microwaves . . . . . . . . . . . . . . . . . 37
Experiment 5 Microwave Antennas . . . . . . . . . . . . . . . . . . . . . 43
LRL Model 550B-SS
X-Band Microwave Training Kit Frequency Range
X-Band 8.2-12.4 (GHZ)
The System Klystron is tuned to (9.3 GHZ)
CONTENTS

4 Microwaves for Everyone | LRL 550B Microwave Training Kit
INITIAL SET-UP PROCEDURES • INVENTORY & SET-UP
LRL 510A POWER SUPPLY
(thermistor bridge & amplifier)

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Microwaves for Everyone | LRL 550B Microwave Training Kit
LRL 510A POWER SUPPLY
(thermistor bridge & amplifier) PLEASE READ CAUTIONS CAREFULLY
BEFORE CONTINUING
CAUTION 1:
Klystrons get extremely hot when in use and must not
be handled while hot! Serious burns can result.
CAUTION 2:
Klystron mount, power supplies, and Klystron tube
plate caps have high voltages present when in use.
Exercise extreme CAUTION!
Shock or death can result.
CAUTION 3:
R-F power levels in this kit are not harmful, but a
human eye may be damaged by low levels of
radiation.
Do not look into any waveguide at any time when
units are on.

6 Microwaves for Everyone | LRL 550B Microwave Training Kit
INITIAL SET-UP PROCEDURES • INVENTORY & SET-UP
The following steps will help you test your new 510A Solid State Power Supply to make
sure it is fully operational and ready for use. It also will give you the opportunity to
operate and become familiar with the entire system before attempting the experiments
listed in this manual.
Equipment & Components
• 510A Power Supply
• 503A Klystron Mount - with 2k25 Klystron installed.
• 506 Flap Attenuator
• 518 Crystal Detector
• 508 Thermistor Mount
• 515 24" BNC Cables (2)
• 523 Waveguide Stands (2)
Part 1 • Control Settings
Set switches and controls on 510A as follows:
1. AC Power Switch OFF
2. Speaker Switch ON
3. RF Switch ON
4. Attenuator Switch 0dB
5. Meter Switch POWER
6. VSWR Output Control MAX. COUNTER CLOCKWISE
7. Power Balance Control 12 O’CLOCK
8. Klystron Repeller Control 12 O’CLOCK
Part 2 •Waveguide Component Assembly Procedure
1. Connect 503A Klystron Tube Mount to left side of 506 Variable Flap Attenuator.
2. Connect right side of 506 Variable Flap Attenuator to left side of 518 Detector
Mount with the BNC Connector in the UP position.
3. Connect right side of 518 Detector Mount to the 508 Thermistor Mount with the
BNC Connector in the UP position.
4. Using BNC Cable, connect 518 Detector Mount to VSWR input connector located
on right side of 510A Power Supply.
5. Using second BNC Cable, connect 508 Thermistor Mount to POWER input
connector located at center of 510A Power Supply.
INITIAL SET-UP PROCEDURES

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Microwaves for Everyone | LRL 550B Microwave Training Kit
6. Insert 8-Prong Plug from 503A Klystron Mount into socket located on left side of
510A Power Supply.
7. Place a 523 Waveguide Stand under each side of Test Assembly, and adjust each
stand until the assembly is elevated in a stable position.
Part 3 • Operation and Checkout
1. Turn AC POWER switch ON.
2. Turn 506 Flap Attenuator to 24dB.
3. Observe meter and adjust POWER BALANCE knob to obtain a zero meter
reading. Turning knob clockwise increases meter reading; counter-clockwise
deceases reading.
4. Allow 3-5 minutes warm-up at this time.
5. Readjust POWER BALANCE knob to compensate for drift if necessary.
NOTE: The meter reading must be at zero to progress further.
6. Set Variable Flap Attenuator to 0dB.
7. Slowly turn KLYSTRON REPELLER knob clockwise and stop when you get a peak
reading on the meter. (Normally about 2 o’clock). NOTE: Adjust Variable Flap
Attenuator as needed to keep meter level between 70% and 100%.
8. Turn METER knob to VSWR position.
9. Fine tune KLYSTRON REPELLER knob as needed to obtain a stable, peak meter
reading. NOTE: This reading should be between 50% and 100% and must be stable. If not,
adjust VSWR OUTPUT knob on right side of 510A Power Supply.
10. Turn METER knob to KLYSTRON position.
11. Remove BNC Cable from VSWR Input Connector at right side of 510A Power
Supply and reconnect cable to KLYSTRON connector on left side of 510A Power
Supply.
12. Adjust Variable Flap Attenuator as needed to attain a peak meter reading. DO NOT
exceed a 100% reading on the meter.
13. Record meter reading and Variable Flap Attenuator level as your Klystron life
reading. NOTE: You can compare this reading to current readings anytime in the future to
determine the condition of the Klystron tube.
14. You have now successfully operated and checked out your Microwave Trainer. It is
important that you turn off the Trainer properly as described below.
Part 4 • Shut Down Procedure
1. Turn off AC POWER switch located on right side of 510A Power Supply.
2. Unplug 510A Power Supply from 115AC Power Source.
3. Wait for Klystron Tube to cool down (minimum of 10 minutes).
4. Disconnect all cables and disassemble waveguide components.

8 Microwaves for Everyone | LRL 550B Microwave Training Kit
introdUCtion – Let’S tALK ABoUt trAnSMiSSion LineS
Transmission lines come in a variety of physical types – coaxial, parallel conductors, and
waveguide are the most common. No matter which type we use, there are four elements
that inuence any physical transmission line:
A. Series inductance: L
B. Series resistance: R
C. Shunt or parallel capacitance: C
D. Shunt or parallel conductance: G
First, let us consider how a unit length of line is represented by Figure 1.1.
Figure 1.1 Unit Length of Transmission Line
The four different elements are represented by the fractional distribution along the entire
length of the line. If the line is to be satisfactory for practical use, it must remain
fractional proportional for any length – long or short. Once this principle is understood,
we can now use the simplied circuit diagram in Figure 1.2.
Figure 1.2 Simplied Unit Length of Transmission Line
INTRODUCTION

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Microwaves for Everyone | LRL 550B Microwave Training Kit
The most widely used unit of measurement for transmission lines is the meter. This
should come as no surprise to you because wavelength and frequency have been
expressed through this unit of measure since the very start of microwave technology.
The expressions of L, R, C, and Gare representative of one unit length of transmission
line dx. When unit lengths appear as two or more lengths, they can be seen as depicted
in Figure 1.3.
Figure 1.3 Several Unit Lengths of Transmission Line
However, the importance of fractional proportionality along any length of line may be
described simply as shown in Figure 1.2. If we apply a voltage ebetween the input
conductors shown in Figure 1.2 and the voltage varies at the rate de/dt, the shunt
current, di per unit length of dx equals the sum of the capacitive current and the
conductive current:
Consequently, the shunt current represents the way in which the input current i is able to
change in a unit length dx Therefore:
When the input voltage eis changing with time, the current will follow. This current
change can be shown as di/dt. The current change causes the series voltage to change
along dx and can be expressed as:
These equations are usually most helpful when a general approach (Fig. 1.1) to trans-
mission lines is desired. However, with most applications, a general approach is not
necessary. In practical use, a short transmission line is utilized, and the line is said to be
“lossless” there by simplifying our analysis even further. The application circuit is shown
in Figure 1.4:
dis
dx
de
dt
=EG+C
and
di
dx
dis
dx
+= 0 ( )
di
dx
de
dt
= - eG+ C
de
dx
di
dt
= - iR+ L
( )

10 Microwaves for Everyone | LRL 550B Microwave Training Kit
introdUCtion – Let’S tALK ABoUt trAnSMiSSion LineS
Figure 1.4 Lossless Transmission Line
In Figure 1.5, we will examine this line as a number of T sections connected together to
represent the line.
Figure 1.5 Sectioned Lossless Line
When we close “s1”, a signal travels through the line. The energy Qtaken from the signal
source is: Q = it where t is the time of current ow. As the signal ows down the line, its
energy will be stored in the capacitors. So any single section is Q = Ce. If capacity Cand
voltage eare shown, it follows that it = Ce. Once C1has fully charged, C2is still at zero
charge and the inductance Lbetween them has a voltage equal to e. Therefore:
Simplifying this relationship produces:
If we divide:
di
dt
e = L
et = Li
et
it =Li
Ce

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Microwaves for Everyone | LRL 550B Microwave Training Kit
We end up with:
This last equation is most often referred to as “impedance” or ZO. Accordingly:
Figure 1.6 Terminated Line
Figure 1.6 shows a line terminated with an impedance load ZL. When a signal is applied
to this line, <100% of the total signal reaches ZLbecause oa small amount of it is
reected back toward the input. For this reason, the incident current iI ows in the
opposite direction of the reected current iR. So the total current iTfelt by the load ZLwill
be: iT=iI- iR, but because the direction of the signal does not affect its potential, the total
voltage et felt across load ZLwill be: eT= eI+eR. The impedance must equal the total
voltage and the total current. It does not matter if we look at the end load or any other
point along the line.
So:
We can then restate the equation for ZOas:
e
i= √L/C
e
i=Z0= √L/C
eT
iT
ZL= = eI+ eR
iI+ iR
eI
iI
= - = Z0
eR
iR

12 Microwaves for Everyone | LRL 550B Microwave Training Kit
introdUCtion – Let’S tALK ABoUt trAnSMiSSion LineS
Now we can see a ratio between incident and reected voltages:
This ratio is called the voltage reection coefcient. We can also look at the current
reection coefcient as:
Let’s look back at the equation: eT= eI+ eR. Combining this equation with the
relationships described by the previous equation, we can conclude: eR= GVeIso that
eT= eI+ GVeI. When a transmission line experiences a time when the incident and
reected voltages are in phase, this yields a maximum voltage and can be expressed as:
emax = eI(1+ GV ). Equally important is the circumstance when the incident and reected
voltages are completely out of phase, which may be expressed as : emin = eI(1- GV ).
The relationship that these two points in time share is known as VSWR, or voltage
standing wave ratio, expressed as:
VSWR is very useful in determining how well a load is matched to the signal source.
This fact is very important because most signal sources suffer damage when not
properly “loaded”. Since the maximums and minimums take place alternately, every
half wavelength VSWR is helpful in matching loads to frequency. Shown by:
We can also use this ratio to give us the amount of reected power.
Consequently, the relationship of the power standing wave ratio and the voltage
standing wave ratio is: PSWR = ( VSWR )2. Now we can consider how much power is really
used by the load. More commonly referred to as the loads’ transmission
coefcient voltage, current and power coefcients tare expressed as follows:
ZL- Z0
ZL+ Z0
eR
eI
= = Gv
Z0- ZL
Z0+ ZL
iR
iI
Gi= =
or simply:
VSWR = =
emax
emin
1+ GV
1- GV
VSWR - 1
VSWR + 1
GV=
ƒ = u
l
rR
rI
GP= = | GV | 2= | Gt| 2
tv+ Gv= 1
ti+ Gi= 1
tp+ Gp= 1
tp= | tv| 2 = | ti| 2

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Microwaves for Everyone | LRL 550B Microwave Training Kit
Up to now, everything we have talked about applies to all types of transmission lines.
In the experiments that follow, we will be using only waveguide lines. In wave guide
velocity, surfaces and physical dimensions enter the picture; so lets talk about this by
looking at Figure 1.7.
Figure 1.7 Wave Travel along a Surface
Looking only at the RF wave that is traveling near the surface, the velocity Vgis expressed:
But when a wave front enters the waveguide at angle Qwe see the wavelength of the
RF wave and the physical dimension “a” of the waveguide are expressed:
Because the frequency in free air is the same as the frequency inside the waveguide,
frequency can be expressed:
when V0 is free air and Vg is waveguide velocity. The wavelengths are l0 and lg .
Because: sin2 Q = 1 - cos 2 Q
taking the square root of each side gives:
sin Q= V0
Vg
cos Q=
l0
2a
and
ƒ = =
V0
l0
Vg
lg
V0
Vg
= = sin Q
l0
lg
l0
2
lg
= 1 - 2
l0
2a
√
l0
lg
= 1- 2
( )
l0
2a√
l0
lg
1- 2
( )
l0
2a
=
or

14 Microwaves for Everyone | LRL 550B Microwave Training Kit
MeASUreMent oF MiCroWAVe PoWer – eXPeriMent 1
Introduction
Microwave power is made up of the same things that make up power at any frequency.
Voltage and current owing through a load E x I =P. The problem in measuring
microwaves results from the fact that most high frequencies cannot be measured with
standard voltmeters or standard current meters. So in the experiment, we will explain the
most popular form of measuring microwaves.
Discussion
When microwaves are absorbed by most materials, they tend to heat up; if they have a
negative or positive temperature coefcient, their base resistance decreases or
increases. This fact becomes very useful because these materials can be utilized to
make a device called a bolometer.
We can use a bolometer as one leg of a bridge network (Figure 1.1) to monitor changes
in resistance.
Bolometer
Figure 1.1 Simple Power Bridge
We see that the total current iTcan be adjusted with the potentiometer labeled Rs. When
we use Rs to adjust the current to balance the brige half of the TOTAL current will ow
through Rb, our bolometer.
So we see:
Power will be expressed:
iB= ½ i T
PT= iB
2Rb= ¼ i T 2 Rb
EXPERIMENT 1

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Microwaves for Everyone | LRL 550B Microwave Training Kit
Now let’s apply RF power to Rb. It gets hot, and its resistance changes; now the bridge
is no longer balanced. When we adjust Rsto balance the bridge again, the total current
changes. This DC power change is equal to the RF power already applied. DC power is
seen as:
so RF power is the difference between ptand pDC. shown:
This is equal to:
Another way of expressing this relationship is:
Now we want to express:
Therefore:
The power bridge in Figure 1.1 is acceptable for measurements when RF power is
1mw or above, but when it goes below 1mw, Di becomes difcult to deal with. A bet-
ter method of measurement is shown in Figure 1.2 where the voltages e1& e2are read
across the meter as:
Figure 1.2 Directly Calibrated Bridge
PDC = ½ iDC
2 Rb
PRF = PT – PDC
PRF = ¼ Rb( iT
2– iDC 2)
PRF = ¼ Rb( iT– iDC ) ( iT+ iDC )
( iT– iDC ) by Di
PRF = ¼ Rb( iT+ iDC ) Di
em= e2– e1

16 Microwaves for Everyone | LRL 550B Microwave Training Kit
MeASUreMent oF MiCroWAVe PoWer – eXPeriMent 1
Now that current is small enough to ignore, we see:
Or: use the common denominator
and: If is very small
using ohm’s law on the meter:
So:
Now the meter reading is directly proportional to the bolometer resistance.
Equipment and Components
• 1 Microwave RF source (supplied- 510A).
• 1 Thermistor mount (supplied- 508).
• 2 RF attenuators (supplied- 506).
• 3 1000 ohm 1% metal lm; 1/2 watt resistors
• 1 10K ohm potentiometer
• 1 0-30 volt DC power supply
• 2 Volt-ohm meters
em= eDC ( )
Rb+ DRb
2Rb+ DRb
–Rb
2Rb
e1= eDC
Rb
2Rb
e2= eDC ( )
Rb+ DRb
2Rb+ DRb
em= eDC ( )
DRb
4Rb+ 2DRb
DRb
4 Rb+ 2 DRb ≈ 4 Rb
im= em/ Rm
im≈ ( DR )
eDC
4RbRm
and
em ≈ eDC ( )
DRb
4Rb
and

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Microwaves for Everyone | LRL 550B Microwave Training Kit
PLEASE READ CAUTIONS CAREFULLY
BEFORE CONTINUING
CAUTION 1:
Klystrons get extremely hot when in use and must not
be handled while hot! Serious burns can result.
CAUTION 2:
Klystron mount, power supplies, and Klystron tube
plate caps have high voltages present when in use.
Exercise extreme CAUTION!
Shock or death can result.
CAUTION 3:
RF power levels in this kit are not harmful, but a
human eye may be damaged by low levels of
radiation.
Do not look into any waveguide at any time when
units are on.

18 Microwaves for Everyone | LRL 550B Microwave Training Kit
MeASUreMent oF MiCroWAVe PoWer – eXPeriMent 1
SEE CAUTION ON PREVIOUS PAGE
Objective
To show the relationship between a thermistor’s resistance cold and when RF power is
applied.
Part 1
1. Hook up circuit in Figure 1.3.
2. Fill in Table 1-1 starting at zero volts and not exceeding 1 volt.
Record the currents rst.
Figure 1.3 Set-up for Determining a Thermistor Volt-Ampere Characteristic
Table 1.1 Data for Procedure, Part 1
Thermistor
Voltage
Thermistor
Current
Thermistor
Power
Thermistor
Resistance
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0

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Microwaves for Everyone | LRL 550B Microwave Training Kit
The thermistor element as such cannot be removed from the waveguide mount.
However, its two terminals are readily accessible through the (BNC) connector mounted
on top of the guide.
Under no condition should the student try to remove the thermistor element. Note: Show
Thermistor Voltage from 0.0 up to 1.0 volt. DO NOT GO BEYOND 1.0 VOLT.
3. Then calculate the power readings.
4. Then calculate the resistance readings.
5. Using information from Table 1-1 plot a volt ampere curve.
6. Then plot a power verses resistance curve.
Part 2
1. Hook up circuit in Fig. 1.4.
Figure 1.4 Simple RF Power Bridge
503A
506
508

20 Microwaves for Everyone | LRL 550B Microwave Training Kit
MeASUreMent oF MiCroWAVe PoWer – eXPeriMent 1
iTimiDC RF
Power
The thermistor element as such cannot be removed from the waveguide mount.
However, its two terminals are really accessible through the (BNC) connector mounted
on top of the guide.
Under no condition should the student try to remove the thermistor element.
4. Apply RF power to bridge as in Figure 1.5 keeping attenuators with full ap
insertion (maximum attenuation). Enter reading from imin Table 1.2.
2. Balance the bridge with 10 K ohm potentiometer (This is zero current through
meter im).
3. Enter reading from meter iTas total current iTon Table 1.2.
Table 1.2 Data for Procedure, Part 2