BIRD Thruline 43 User manual

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INSTRUCTION BOOK
THRULINE®
RF Directional Wattmeter
model 43

INSTRUCTION BOOK
THRULINE®
RF Directional
Wattmeter
model 43
mm
30303 Aurora Rd. Cleveland(Solon) Oh. 441 39

SUMMARY SHEET
Circuit
Measures
Insertion VSWR
Accuracy
Dimensions
Weight
Connectors
SO-ohm impedance -THHULINE
RF Power -5W to 5000W FuO Scale Direct Reading
in Watts, Frequency Range 2-1000 MHz in Si^ Std,
Element types, See Table 1, Section 4.
Less than 1.05 VSWR up to 1000 MHz
-5% of FulU Scale Power
Basic Overall 7'lg x 4^*w x3*‘h
4Pounds
Female and Male
Female and Male 'THN’*
Female and Male "C”
Most std. 50-ohm AN types
Not supplied on
regular orders
2Female Connectors standard with equipment,
unless otherwise specified*

TABLE OF CONTENTS
SECTION 1-GENERAL DESCRIPTION
Para^aphs ;Page
Purpose and AppUoation 1-1
2.
Description 1-1
SECTION 2-THEORY OF OPERATION
1* Travelling Wave Viewpoint 2-1
2. Coupling Circuit 2-1
3, Standing Wave Ratio vs* Reflected/Forward Power I^tio 2-1
SECTION 3-INSTALLATION
I* Portability 3-1
2, Connections 3«1
3, Remote Installation 3-2
SECTION 4-OPERATION
1. General 4-1
2, Load Power 4-1
3* Graph -^vs, 0and Its Significance 4-1
4, Measurement &Monitoring of Transmitter Power 4-4
5* Testing of Lines, Connectors, Filters, etc. 4-4
6. Frequency Response 4-5
7. Impedance Mismatch 4-6
SECTION 5-MAINTENANCE
1. Introduction 5-1
2. Trouble Shooting 5-1
3. CaUbratlon Checks -THHUUNF vs. TERMAUNi: Wattmeters 5-2
SECTION 6-PARTS LIST 6-1
LIST OF ILLUSTRATIONS
Figure: Page
1-
1View of Model 43 THHUUNE 1-0
2-
1Schematic Diagram 2-1
3-
1Outline Drawing, Model 43 THRULINE 3-1
3-2 Installation Drawing, RF Line Section 3-2
3-
3Panel Cut for Mounting RF Body 3-2
4
-
la Graph -Percent Reflected Power vs, VSWR (1*0 to 1.3) 4-2
4-lb Graph -Percent Reflected Power vs. VSWR (1,0 to 6,0) 4-3
4-
2Graph -Frequency Response 4-5
5-
1Parts Illustration 5-2
LIST OF TABLES
Table: Page
IRange of Element Types 4-6
n-IV Special Element Types 4-6
APPENDIX
Nomographs of Power Values vs VSWR Conversion

Il
Fig. 1-1. Model 43 THRULtNE
1-0

SECTION 1
GENERAL DESCRIPTION
1. PURPOSE AND APPLICATION
The Model 43 THRULINE Wattmeter is an inser-
tion tjrpe RF wattmeter, designed to measure power
flow and load match in 50-ohm coaxial transmission
lines. It is intended for use on CW, AM, FM, and
TV modulation envelopes, but not pulsed modes.
The Model 43, when used in 50-ohm applications,
has an Insertion VSWR of less than 1.05:1 up to a
frequency of 1000 MHz. The meter is direct reading
in watts, expanded down scale for easy reading, and
is graduated 25, 50, and 100 watts full scale. The
power ranges used are determined by the Plug-In
Elements, which fall in ten frequency band groups
covering from 2to 2300 MHz plus additional special
Elements in various power and frequency ranges
(see Section 4). Further characteristics may be
found in the Summary Sheet on page A.
2. DESCRIPTION
The Model 43 THRULINE, Figure 1-1, is aport-
able unit contained in adie cast aluminum housing,
with aformed metal enclosure on the back which is
easily removed. Included with the unit is aleather
earring strap, four rubber shock feet on the base,
and four rubber bumpers on the back, which allow
the Model 43 to stand or lie flat when used. For
additional protection, the microammeter is specially
shock mounted. Aslotted screw is provided on the
lower front face of the meter for zeroing the point-
er. Below the meter, the RF line section face pro-
trudes slightly from the wattmeter housing with the
Plug-In Element socket in the center.
Ashielded cable connects the microammeter to
the dc jack which is atUched to the side of the RF
line section casting. This cable, nearly three feet
long, permits removal of the RF Une section from
the Wattmeter housing. Meter connections may be
maintained with any installations outside of the hous-
ing. This permits permanent additional installations
to be made. See Section 3, INSTALLATION.
Inside the dc jack assembly, there is afilter ca-
pacitor which shunts the meter circuit to prevent
mis-readings caused by stray RF energy existing
in the Plug-In Element. Mounted on the dc jack is
aphosphor bronze spring finger, which protrudes
through alateral hole and into the Plug-In Element
socket of the RF line section. The finger has abut-
ton on its end which mates with the contacts of the
Plug-In Element. The nickel plated brass RF line
section is precision made to provide the best possi-
ble impedance match to the coaxial RF transmission
line in which the Model 43 is inserted. The ends of
the line section are nested in mating slots to provide
additional mechanical support.
At each end of the line section are Bird Quick-
Change type RF connectors, which may be quickly
interchanged with any other Bird ’'QC” connector by
removing the four screws on the mounting flanges.
The Wattmeter housing does not interfere with any
connector changes.
To make measurements, the cylindrical shaped
Plug-In Element is inserted into the line section
socket and rotated against one stop. Asmall catch
in the upper right hand corner of the casting face
presses on the shoulder of the Plug-In Element to
keep it in proper alignment and assure agood con-
tact with the dc jack and between the lower edge of
the Element and line section body. On diametrically
opposite sides of the Plug-In Element body are con-
tacts to provide dc pick-up in either direction.
These contacts make connection with the spring
finger of the dc jack only when the Plug-In Element
is in the precise forward or reverse position, and
with the index pin on the Element on the lower level
of the line section castingface against its respective
stop.
1-1

SECTION 2
THEORY OF OPERATION
1.
TRAVELLING WAVE VIEWPOINT
The best way to visualize the THRULINE idea is
from the TRAVELLING WAVE viewpoint on trans-
mission lines, which illustrates that the voltages,
currents, standing waves, etc., on any uniform line
section are the result of two travelling waves:
FORWARD WAVE travels (and its power flows)
from source to load, and has RF voltage Eand
current Iin phase, with E/I =Zo.
REFLECTED WAVE originates by reflection at
the load, travels (and its power flows) from
the load to source and also has an RF voltage
Cand current Jin phase, with CU »Zq ,
Note that each component wave is mathematically
simple, and is completely described by asingle fig-
ure for power, for instajice:
=Watts Forward «E^/Zq =I^Zq =El
WsWatts Reverse *€VZq =€J
Zo is the characteristic impedance of the uniform
line, and simplifies matters by being apure resis-
tance, usually 50 ohms, for useful lines. The main
RF circuit of the THRULINE is ashort piece of uni-
form air type line section, whose Zo is avery ac-
curate 50 ohms, in which correct measurements
may be made.
2.
COUPLING CIRCUIT
The coupling circuit which samples the travelling
waves is in the Plug-In Element. The circuitry of
the Element and its relationship to the other com-
ponents of the THRULINE are Illustrated in the
schematic diagram, Figure 2-1. Energy will be pro-
duced in the coupling circuit of the Element by both
mutual Inductance and capacitance from the travel-
ling RF waves of the line section. The Inductive
currents will, of course, flow according to the direc-
tion of the travelling waves producing them. The
capacitive portion of these currents is naturally
independent of the direction of the travelling waves.
Therefore, assuming that the Plug-In Element re-
mains stationary, it is apparent that the coupling
currents produced from the waves of one direction
will add in phase, and those produced from waves of
the opposite direction will accordingly subtract in
phase. The additive or ’’ARROW” direction is, of
course, assigned to the forward wave.
The electrical values of the Element circuits are
carefully balanced and so designed that the current
produced from the reverse wave will cancel the other
almost completely. The resultant is adirectivity
always higher than 30 dB, which means that the Ele-
ment is highly insensitive (nulled) to the ’’REVERSE”
direction wave. Being highly directional, the THRU-
LINE Element is sensitive (at one setting) only to
one of the travelling waves which produces standing
waves by Interference. THRULINE measurements
are therefore independent of position along standing
waves. It may be said that the THRULINE doesn't
know, doesn't care, and doesn't need to care where
it is along astanding wave.
3.
STANDING WAVE RATIO vs.
REFLECTED/FORWARD POWER RATIO
As mentioned above, the THRULINE technique
uses the TRAVELLING WAVE viewpoint to measure
most of the outstanding facts about transmission
line operation. Another widely used and related
viewpoint, is the STANDING WAVE, which is quite
elaborately developed both mathematically and In
existing equipment. This technique can be traced to
the early development of slotted lines as tools of
exploration.
The slotted line is astanding wave instrument,
and emphasizes this viewpoint. However, the slotted
line is too long, too expensive if good, not portable,
and slow in operation. These objections increase
rapidly as the frequency drops ^low 1000 MHz.
Whereas the THRULINE is surprisingly quick, con-
venient, and accurate by comparison. With the ex-
ception of phase angle reflection (distance, load to
minimum) it tells everything aslotted line will.
The relationships between TRAVELLING WAVES
and STANDING WAVE viewpoints are given in most
high frequency textbooks.
4
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2-1

1SECTION 3
INSTALLATION
Fig. 3-1. Outline Drawing, Model 43 THRULINE
1. PORTABILITY
The Model 43 is aportable instrument, and the
housing is not designed for fixed mounting (see Out-
line Drawing, Figure 3-1). Astrap is provided for
carrying purposes.
While transporting the THRULINE it is best to
»re-insert the original Dust Plug, or aPlug-In Element
with the arrow pointed upward, in the measuring
socket, and secure with the catch. This will shunt
the meter circuit and serve to protect the meter by
dampening needle action during handling or shipping.
•Also, secure spare Plug-In Elements in their recep-
tacles with the pivoting knob clamps; just insert
Element to seat and twist knob one-quarter turn to
hold. Handle the Plug-ln Element with care at all
times. Calibration could be disturbed if they are
dropped.
CAUTION
Do not drop the THRULINE or its Elements or
subject them to hard blows. The microammeter is
shock mounted in the wattmeter housing, but its del-
icate mechanism may be damaged by severe impact.
2. CONNECTIONS
Insert the Model 43 THRULINE In coaxial trans-
mission lines of 50 ohms nominal impedance. It is
indifferent to which respective side the power source
and the load connections are made. If cables other
than 50 ohms are used, amismatch will occur
causing probable serious Inaccuracies in readings.
However, if amismatch cannot be avoided, the re-
sults may be calculated per paragraph 7of Section
4. We strongly urge that you avoid this condition.
The Model 43 is normally supplied with two Fe-
male N-Type connectors which are of the Bird
Quick-Change design. Other "QC" connectors are
available as listed:
3-1

Male N
Female HN
Male HN
Female C
Male C
Female UHF
Male UHF
7/8’* EIA Air Line
Female BNC
Male BNC
Female LC
Male LC
Female LT
Male LT
Female TNC
Male TNC
These may be purchased from Bird Electronic
Corp., as required. See Section 6, Parts List.
The above connectors are quickly changed by re-
moving the four #8-32 round head machine screws
from the corners of the connector flange, and pull
straight out. Reverse this procedure to attach con-
nector, making sure the center contact pin aligns
properly with the socket.
3. REMOTE INSTALLATION
The RF line section can be removed from the
meter housing for remote installation. To remove
the line section from Its housing:
a. Unscrew the six #8-32 flat head machine
screws holding the back cover.
b. Grasp the cover by the side filler tabs and pull
directly backwards. The back cover assembly
will come off with the speed nuts remaining
attached.
c. Remove the, two #10-32 oval head machine
screws on the front of the housing.
d. Slide the line section backwards out of the
housing. Do not loosen the two oval head
screws on the sides of the housing In line with
the meter. These hold the meter supporting
shock ring in place.
e. Substitute the cable which attaches the line
section to the meter with asufficient length of
cable to make the remote installation.
f. To replace the RF line section, reverse the
above procedure.
It may be desirable to have two or more line sec-
tions permanently installed in continuous operating
equipment. In this case, one set of Elements and
one meter may be used to measure several RF
transmission Unes WITHOUT INTERRUPTION OF
RF LINES for insertion of the THRUUNE. Addi-
tional RF line sections (Figure 3-2) are available.
Fig. 3-2. Installation Drawing, RF Line Section
The RF Line Section of the Model 43 blends very
readily to panel type mounting. Alayout for the
panel mount cut is given in Figure 3-3. The thick-
ness of the panel should be about 1/4 inch. On pan-
els less than this, build up the thickness with pads
or washers to achieve aflush-face mounting. Cable
connections are simplified because the RF line sec-
tion may be mounted in any convenient direction.
Attach the line section so that the finger catch is in
the most accessible position.
^RAO OR
45* CHAMFER
^(203)01A. DRILL
AND COUNTERSINK FOR
•10-32 F.H.M.S.-TW0 HOLES
Fig. 3-3. Pan«l Cot for Mounting RF Body
T
4
(
3-2

SECTION 4
OPERATION
1. GENERAL 2. LOAD POWER
The apparent features of the THRULINE equipment
have been discussed in Section 1, GENERAL DE-
SCRIPTION, and in the Instructions of Section 3,
INSTALLATION. Measurements are made by the
insertion and operation of the Plug-In Elements pre-
viously mentioned.
The Elements determine the power range to be
read on the meter scale, and the major markings
(viz. SOW, lOOW, etc.) are the FULL SCALE POWER
value for that Element. Elements are also marked
for FREQUENCY RANGE. The transmitter fre-
quency must be within the band of the Element used.
Elements are available according to those identified
in the tables on page 4-6.
Power delivered to (and dissipated in) aload is
given by:
=Watts into Load =\^ -\^
i.e., where appreciable power is reflected, as with
an antenna, it is necessary to subtract reflected
from forward power to get load power. This cor-
rection is negligible (less than 1percent) if the load
is such as to have aVSWR of 1.2 or less. Good load
resistors, such as our TERMALINES, will thus show
negligible or unreadable reflected power.
VSWR scales, and their attendant controls, for
setting the reference point, have been intentionally
omitted from the THRULINE for two reasons:
See paragraph 6of this chapter for frequency band
flatness, and performance of the Elements outside
of stated frequencies. Elements for additional ranges
(power or frequency) may be ordered without re-
turning the THRULINE for calibration, since the RF
bodies and meters are standardized, and are de-
signed for awide range of coaxial transmission
power values and frequencies.
ARROW on Plug-In Element indicates Sensitive
DIRECTION, i.e., the direction of power flow which
the meter will read. ARROW and REVERSE are
directional terms used in reference to the THRU-
LINE ELEMENT, and mean respectively the sensi-
tive and null directions of the Element. ROTATE
ELEMENT to reverse the sensitive direction. FOR-
WARD and REFLECTED are directional terms used
in reference to the source -load circuit. Note that
the transmitter may attach to either connector of
the THRULINE. It makes no difference which ex-
ternal RF connection is selected, since the Elements
are reversible and the RF circuit is symmetrical
end for end. Before taking readings be sure that the
meter pointer has been properly zeroed under no-
power conditions.
The THRUUNE used with aTERMAUNE resistor
of proper power rating forms ahighly useful absorp-
tion wattmeter. With ARROW set toward the load,
it is unnecessary to reverse because reflected pow-
er may be neglected.
In cases where readings are being made when the
meter unit is connected to an auxiliary RF line sec-
tion body, always remove any measuring Element
from the unused RF line section. Otherwise, the dc
circuit will be unbalanced or shorted according to
the arrow position of the other Element, causing in-
accurate or no reading on the meter.
(a) Why make something similar to ahypothetical
dc volt ohmmeter with control pots for the voltmeter
multipliers? Even more complications arise when
diodes at RF are Involved.
(b) Experience using the THRULINE on trans-
mitter tune-up, antenna matching etc., i.e., on OP-
ERATING PROBLEMS shows that the power ratio 0
is no mean competitor, in practical usefulness, to
the ratio /? =VSWR.
Atrial is suggested for afew days —forret VSWR
and try thinking in terms of 0=\^ /when the
THRULINE is used. It will be noted that, even with-
out bothering to calculate the ratio exactly, the two
meter readings and give an automatic mental
impression which pictures the situation. Thus, in
an antenna matching problem, the main thing usually
is to minimize ,and anything done experimen-
tally to this end is directly indicated when the THRU-
LINE is in the reflected position. Furthermore, the
ratio of readings, only mentally evaluated, is are-
liable guide to the significance of the remaining re-
flected power.
3. GRAPH-/? VS. <> AND ITS SIGNIFICANCE
Since there are definite simple relationships
p-ri2 where VSWB
and0= W
between standing wave ratio /O and the reflected/
forward power ratio 0indicate by the THRULINE,
the latter may be conveniently used to measure
VSWR. The relationship is given in Fig. 4- la and b.
4-1

2.0
I.OS I.IO U6 1.20 1.25 130
4- la. Graph. —Percent Reflected Power vs. VSWR (1.0 to 1.3).
1
!
I
I
4-2

4-Ib. Groph. —Percenr Reflected Power v». VSWR (1.0 to 8.0).
4-3

Note, that around 0=10%, below which will
appear insignificant and become hard to read, you
are close to the commonly accepted lower limit =
2, below which improved antenna match becomes
less and less worthwhile in many systems. Experi-
mentally, using the THRULINE, it is readily shown
that minimizing 0below 10% produces little gain in
\J^ .TV transmitter antenna lines, and VHP Omni-
range transmitters, are among systems requiring
much lower levels of reflected power for reasons
other than simple power transmission. Note also in
Fig. 4-la, the very small level of reflected power,
0=.06 percent ,corresponding to -1.05. With a
single Element, detection of reflected power is pos-
sible down to about 0=1 percent, >^= 1.2; if
approaches full scale, measurement is possible down
to about 0=5percent, /O =1.5.
LOW-REFLECTION MEASUREMENTS may be ex-
tended below this with two Elements. Say 80 watts
are available, and you have 100 watt and 10 watt
Elements.
Measure with the 100 watt Element. Re-
move 100 WElement and Insert 10 watt Element.
CAUTION:10 watt Element must be ONLY in
the REFLECTED direction. ARROW toward
TRANSMITTER. Insert and remove ONLY this
way.
Now read on the 10 watt Element.
SPECIAL NOTE
DON’T ROTATE 10 watt Element while TRANS-
MITTER is on. Always use great care with
LOW SCALE Elements on HIGH power RF lines.
Inadvertent exposure of these Elements to too
much FORWARD or even too high reflected
power may permanently damage the measuring
Element or the microammeter.
In this case, measurement down to at least .5 watt
reflected is possible which means to
0=percent, or to about =1.16
and detection of reflections is possible down to about
.1 watt,
0=~=.00125, say .1 percent, or to about ~1.06
80
Caution is necessary in the above method, and
preferably it should not be used with Element ranges
differing more than 100 to 10, although 250 to 10 can
be used with extreme caution. With certain Ele-
ments now available down to 1watt full scale this
method is usable with medium and low power
transmitters.
4. MEASUREMENT &MONITORING OF
TRANSMITTER POWER
Little more need be said about this, in view of
LOAD POWER paragraph above. The THRULINE is
useful for continuous monitoring of transmitter out-
put, and may be found useful in continuous monitoring i
of reflected power, for Instance in checking inter-
mittent antenna or line faults.
Like diode devices generally, the THRULINE in-
dicates the carrier component on amplitude modu- ^
latlon, with very little response to sideband compo-
nents added by modulation.
The THRULINE is highly useful for this purpose,
and may be employed in several ways.
(a) VSWR (Insertion) or 0(Insertion) may be mea-
sured with the line terminated in agood load resis-
tor (TERMALINE). The lower limits of sensitivity
in this are given above under LOW REFLECTION
MEASUREMENTS.
(b) ATTENUATION (Power lost by heat in the
line) as well as VSWR (Insertion) and 0(Insertion)
may be measured by inserting the unknown line be-
tween two THRULINES, or between two RF bodies
used with one meter and one set of Elements. (End
of line to be terminated in aload resistor). This
method applies also to insertion between the THRU-
LINE and aTERMALINE absorption wattmeter.
Very small values of attenuation require allow-
ance for normal Instrument errors. The correction
may be determined by direct rigid connection of the
THRUUNES, or of the THRUUNE -TERMALINE
combination, in cascade. Slight juggling of zero
settings is permissible for convenience in elimi-
nating computation, provided readings are being
taken fairly well up on scale.
(c) ATTENUATION BY OPEN OR SHORT CIR-
CUIT METHOD. Neater by far than method (b) is
one depending on the high directivity (null balance)
to which the THRULINE Elements are held. They
should, and do, exhibit good equality between for-
ward and reflected readings when the load connector
is open or short circuited. In this condition 0=100
percent, the forward and reflected waves being equal
in magnitude, and Say that this is checked
on open circuit, and then alength of line of unknown
attenuation, also open circuited, is connected to the
load connector. The ratio 0then shown is the atten-
uation in two passes along the line (down and back).
Expressed in dB, (using the equation NdB =^^g ^),
the dB figure may be compared with published data
for line type and length by remembering to halve
NdB* because twice the line length is actually being
measured.
This measurement should be supplemented by one
of 0(Insertion) as in (a) above, or at least by dc con-
*Or to tiouble the tine tendth.
5. TESTING OF LINES, CONNECTORS,
FILTERS, ETC.
4-4

^tinuity and leakage checks, since the attenuation
measurement alone can be in error from faults such
as open or short circuits part way down the line.
Open circuit testing is somewhat to be preferred
<to short circuit, since the reference short (used to
check equality initially) must be good, and because
the initial equality is somewhat better on open than
on short circuit.
Again, for quite low values of measured attenua-
tion, it is advisable to note exact readings (or dif-
ference) on the initial equality check, and to allow
for this difference.
6. FREQUENCY RESPONSE
The Plug-ln Elements have avery flat frequency
response over afrequency ratio of more than 2-1/2
to one. This characteric^c provides apractically
flat response within the assigned frequency ranges
for all the Elements, see Table Iin this Section.
An illustrative set of curves for three Elements of
one of these frequency bands is shown in Fig. 4-2.
Notice that on the LOW POWER Element, the fall-
off above and below the assigned frequency band is
more pronounced than it is for the HIGH POWER
Element. The degree of drop in response varies
progressively less for each power level from low to
high, with the average difference at approximately
the mean power level. These curves. Fig. 4-2, may
be assumed to be about typical for all of the listed
band types (H, A, B, C, D&E) at their respective
stated frequencies.
Harmonics, or sub-harmonics, may be known to
exist in the measured circuit (outside of the Element
frequency band). If so, arough approximation of the
response of the Element to these harmonics may be
made by the use of these curves. The frequency
ordinate to be read on the g^aph will be obtained by
proportioning the frequency of the Element used with
that of the one illustrated. Interpolation of the curve
values will give an approximation of the extent that
these harmonic signals are being measured by your
Element.
The use of the Elements for direct power mea-
surements outside of their stated frequency range
is not recommended.
FREQUENCY RESPONSE
THRUUNE ELEMENTS
100^250 MHx (C*8«rtes)
Fig. 4-2. Graph —Representative Frequency Response
4-5

7. IMPEDANCE MISMATCH
There may be cases where it is necessary to use
the THRUUNE on other than the 50-ohm circuit for
which it is designed.
Using the THRUUNE, you will be inserting a4-
inch length of 50-ohm air line and the load on the
transmitter will be changed from its original condi-
tion without the THRUUNE. For apower reflection
factor under 10% and frequency below 200 MHz, the
4-lnch length mismatch is not too serious. But go-
ing any higher than these values, even if the trans-
mitter is tuned up with the THRUUNE in place, the
load impedance will be very different when it is re-
moved.
The THRUUNE, of course, indicates zero reflec-
tion when the load, at its load connector, is 50 ohms,
pure resistive. An ideal condition on a70-ohm line
on the load side of the THRUUNE will show 3% re-
flected power, i.e., THRUUNE load is 70 ohms re-
sistive, VSWR in the 50-ohm THRUUNE is 70/50 »
1.4. The THRUUNE can also show this same re-
flected percentage with 50/1.4 =35.7 ohms pure re-
sistive load which could exist with 10% reflected
power on the 70-ohm line (VSWR =2on the 70-ohm
line). From this you can see that the 70-ohm line
could have as much as 10% reflected power and
VSWR =2when the THRUUNE indicates 3%reflected
power of VSWR *1.4.
It should be especially remembered that with 70-
ohm lines it is most important to get the reflected
power indication and subtract it from the forward,
because of this factor being so much more critical
here than with intended 50-ohm line.
TABLE I-STANDARD ELEMENTS (CAT. NOS.)
TYPE Freq.
Band
MHz
WATTS FULL SCALE
510 25 50 100 250 500 1000 2500 5000
H2-30 ---50H lOOH 250H 500H lOOOH 2500H 5000H
A25-60 5A lOA 25A 50A lOOA 250A 500A lOOOA --
B50-125 5B lOB 25B 50B lOOB 250B 500B lOOOB --
C100-250 5C IOC 25C 50C lOOC 250C 500C lOOOC --
D200-500 5D lOD 25D 50D lOOD 250D 500D lOOOD --
E400-1000 5E lOE 25E 50E lOOE 250E 500E lOOOE --
In addition to the Standard Types listed above,
other special Elements are provided as follows:
(See Bird Gen. Catalog)
Table n—Low Power Elements 1and 2.5 watts
in nine narrow band units from 60 to 950 MHz.
Table m—High Frequency Elements 1, 2.5, 5,
10, and 25 watts in four frequency bands; 950-1260
MHz, 1100-1800 MHz, 1700-2200 MHz and 2200-2300
MHz, respectively.
Table IV —Low Frequency Elements IK, 2.5K,
5K, and lOK watts in one frequency band; .45 to 2.5
MHz.
SPECIAL NOTE
For the convenience of users, aset of VSWR conversion nomo-
graphs is appended to this hancbook. With these charts, VSWR's
may be directly ascertained from forward and reverse power
values read from the THRUUNE Wattmeter.
4-6
I

SECTION 5
MAINTENANCE
1. INTRODUCTION
With the simple construction and generally self-
contained nature of the THRULINE equipment, there
is only amoderate amount of maintenance required.
One of the major precautions is in handling; use
reasonable care and do not drop the THRULINE
equipment or the Plug-In Elements.
The main factor in maintenance is care and clean-
liness. The Element socket should be kept plugged
as much as possible to prevent the intrusion of dust.
When aPlug-In Element is used for this purpose
(use highest power Element available), it should be
positioned with the ARROW pointing upwards. This
protects the meter and will not expose the Element
crystal to dangerous potentials if the RF line section
should be energized. If any of the contacts or line
connectors become dirty, they should be cleaned with
alittle dry cleaning solvent,
Inhibisol**or its equiva-
lent, or trichlorethylene, on acotton swab stick.
Avoid excessive skin contact or inhalation of fumes
when using. Observe special care if carbon tetra-
chloride is used. Clean all contact areas and es-
pecially the exposed faces of the Teflon* insulators.
It is particularly important to keep the mating
surfaces of the socket and Plug-In Element clean.
This applies to the bore of the socket and the cir-
cumference of the THRULINE Element body, but
most important to the bottom rim of the Element
body and the seat at the base of the socket in the line
section. Also, check the ends of the insulated dc con-
tacts on the THRULINE Element to see that they are
clean and smooth. These parts should be carefully
cleaned with acotton swab stick and dry cleaning
solvent, as above. There must be agood contact be-
tween the base of the Plug-In Element and its socket
to assure stable operation of the THRULINE.
In cleaning the socket bore, the operator should be
careful not to disturb the spring finger of the dc con-
tact. It is important that the operating position of
this part be properly maintained. If the spring finger
of thedc contact requires adjustment, it may be done
manually if carried out with care. The button must
be positioned far enough out to maintain good con-
tact with the Element, but not so as to interfere with
easy entry of the Element body. The dc jack (with
spring finger) may be removed for access by un-
screwing the two #4 -40 fillister head machine screws
which fasten it to the side of the RF line section.
Then retract its assembly, watching carefully not to
lose the small teflon positioning bead that straddles
the base of the phosphor bronze spring and nests in
acounterbore on the side of the RF body. When re-
placing the assembly, be sure that the bead is again
properly inserted.
If there is any evidence of the contamination inside
the RFline section, the reachable portions should be
likewise wiped and the interior carefully blown out.
Under no circumstances attempt to remove the RF
center conductor. It is tightly frozen in place and
any attempt to remove it will ruin the assembly.
Keep all connections tight, and keep the nut of the
meter cord plug turned tight on the line section dc
jack. This connection may often be serviced by sim-
ply loosening the nut of the dc plug, swinging the
body several times through afraction of aturn, a.nd
retightening the knurled nut securely.
There are no replacement parts furnished with
this equipment. As previously mentioned, compo-
nents of these matched units cannot be interchanged
or individually replaced. The replaceable portions
to the Line Section are standard parts of the coaxial
line fastenings.
2. TROUBLE SHOOTING
As abrief guide to the operator in Isolating occa-
sional difficulties that may occur in the use of the
THRULINE, the following summary is Included. The
remedies for same are referenced to the text in this
section or are self-evident;
POSSIBLE CAUSES
No radio frequency power.
Arrow on Plug-ln Element
pointing wrong direction.
No pick-up from dc contact
finger in the RF line section
•adjust per Paragraph 1.
Open or short circuit in dc
meter cable ~replace de-
fective cable (RG-58/U)
Meter burned out or damaged.
Faulty load.
Faulty transmission line.
Dirty dc contacts on Elements
—Clean as in Paragraph 1.
Sticky or defective meter.
Bad load, or poor connectors
—see Paragraph 1.
Shorted or open transmission
line.
Foreign material in line sec-
tion or in RF connector
bodies —See Paragraph 1.
DIFFICULTY
No Meter Indication
Intermittent or in-
consistent meter
readings.
High VSWR or high
percent reflected
power.
5-1

3. CALIBRATION CHECKS-THRULINE VS.
TERMALINE WATTMETERS
It is recognized that calibration of absorption
wattmeters is difficult and likely to be inaccurate
unless comparison is made with atransmission
(through) type of standard. The THRULINE being of
such type, anatural question is: can aTHRULINE
be used to check or recalibrate absorption watt-
meters, such as the Bird Electronic TERMALINE,
both being rated at iS percent accuracy? The main
question is one of exact power calibration.
The answer is aqualified yes, although with both
instruments being ak^ut equally old and known to be
undamaged, there is not too much reason to prefer
either on probable accuracy. The edge is somewhat
in favor of the THRULINE, because each Element
covers only 2-1/2 to 1in frequency and will be flatter
originally over this range than the TERMALINE can
be held initially over its very much wider (16.7 to 1)
frequency range. Also the THRULINE will probably
exhibit smaller change^ with time, because of the
narrower frequency range, because it is simpler in
general design and easier in function (does not have
to serve as apower load), and because it does not
become heated in operation.
Certainly if the absorption wattmeter has gone
years since calibration, or is reasonably suspected
of inaccuracy, it may well be calibrated against the
THRULINE as standard. (Rather than use correction
factors, one can, with the TERMALINE Wattmeter,
make use of the calibration adjustment screws used
in factory calibration. These are concealed and not
mentioned in instruction book to discourage tam-
pering. Correspondence is necessary.)
If such calibration is undertaken, care and thor-
oughness are advised.
Fig. 5-1. Ports Illustration.
5-2
I

SECTION 6-PARTS LIST
Refer-
ence Des-
ignation Part Name and Description Function Drawing
No.
A-401 Housing Assembly: Aluminum die casting, 7Ig x4w
X3h, w/latch and thumbscrew each side for spare
Elements, four rubber bumpers on base, leather
carrying strap at top. Gray Enamel.
Houses and protects
meter, holds RF
line section and
spare Element.
4210-018
A-402 Cover Assembly: Aluminum alloy sheet, .040 thk.
,
6-1/2 Ig X4w Xl-l/2h overall, has four rubber
bumpers and slot closing ears. Gray Enamel.
Closes back of
housing. 4210-005
E-401 Elements, Plug-In: Brass, w/teflon bottom cover,
1-7/16 Ig X1-1/4 cap dla. x1body dia. Gold Plate.
Furnished in power and frequency types per Table I,
Section 4.
Measuring Element
for THRUUNE. 4250-020
£-402 Line Section Assembly: Brass Casting, normally
suppUed w/two female connectors, 5-1/8 Ig
X1-1/4W Xl-15/16h, 50-ohm line section and
socket for Plug-ln Element. Has dc jack at side.
Nickel PUte.
RF Line insertion
section and
measuring base.
4230-018
H-401 Carry Strap: Black Leather, 9Ig between centers,
5/32 X7/8 section. Carries meter
housing. 8580-003
J-400 Connectors, RF: All types have 1-1/4 sq. mtg. RF connection for See individual
flange, and 1/8 dia. x5/16 Ig. slotted connector standard type part numbers
pin at rear. Brass, with Teflon insulator. Nickel
plate. Fifteen types, vlx: connectors. listed below.
J-401 Female •’N” -1-5/32 Ig. 4240-062
J-402 Male **N“ -1-1/4 Ig. 4240-063
J-403 Female "HN” -1-5/32 Ig, 4240-268
J-404 Male "HN” -1-3/8 Ig. 4240-278
J-405 Female "C” -1-1/16 Ig. 4240-100
J-406 Male "C" -1-7/16 Ig. 4240-110
J-407 Female UHF (SO-239) 1-1/4 Ig. 4240-050
J-408 Male UHF (PL-259) 1-5/8 Ig. 4240-179
J-409 Female "BNC" -1-5/32 Ig. 4240-125
J-410 Male "BNC" -1-9/32 Ig. 4240-132
J-41S Female "LC” -2-1/32 Ig. 4240-031
J-414 Male "LC" -2-1/2 Ig. 4240-025
J-415 Female *’LT* -2-3/32 Ig. 4240-018
J-416 Male "LT* -2-1/2 Ig. 4240-012
J-417 7/8" EIA Air Une 2-3/4 Ig. 4240-002
J-411 DC Connector Assembly: Brass fitting,
w/phosphor bronze spring at rear, Tdia. flange
X1-1/4 overall, 5/8 -24 thd, on connector body,
center contact on front, teflon insulators. Nickel Plate.
DC Jack for line
section assembly. 4230-010
M-401 Microammeter: 30ua full scale. Flush 3-1/2" bake-
lite case, solder terminals, special scale.
Replacement Meter Kit Consisting of:
1-2080-002 Meter
1-4220-097-1 Cable Assembly
3-4220-098 Bumper Feet
Meter for power read-
ing. (For replacement
usually furnished as
8-000 Kit.
2080-002
8-000
P-401 Connector, Plug: Part of cable W-403, Brass
fitting 1-1/4 Ig X5/8h x3/4d, water proof.
Nickel Plate. Navy type D6-491859.
DC Plug for
RG-58/U meter
cord.
7500-076
W-403 Meter Cable Assembly: RG-58/U cable, 2-3/4
feet long, w/dc plug P-401 at one end. Meter Cord. 4220-097-1
6-1

AppCNdix
cumdd‘d3/\od aaic^idad
d
4:0
sTd
id
IS
20
25
3d
40
5d
FORWARD
POWER'RF
WATT3

Following the vertical and horizontal grid, determine
intersection of forward and reverse power values. Slanted
lines passing closest to this point indicate VSWR.
FORWARD
POWER*
RF
WATTS