FS
1 3 4
FIELD STRENGTH
METER
MANUAL
INSTRUCTION MANUAL
SENCORE FS134 FIELD STRENGTH METER
instrument designed to identify and measure the frequency and signal strength of
FM stations and all VHF and UHF TV stations. Because of the increa se in popu
lari ty of "FM Stereocasting" and the UHF boom, it was realized that a great need
for this type of instrument existed. Sencore engineers did considerable res earch
to develop a Field Strength Meter which is rugged, lightweight, portable and accu
rate and yet has that "P rofessional" appearance.
Strength Meter.
1. Completely solid state construction provides the utmost in portability, light
weight compactness and battery power economy.
2. Printed circu it construction on unbreakable board material gives dependability
and long life.
3. Completely battery operated for field use. Uses standard "C" cells available
anywhere. Provisions have been made for installation of a battery charger accessory.
4. Choice of 75 ohm or 300 ohm input from the front panel.
5. Uses most popular type 75 ohm input jack for direct connection to antenna dis
tribution systems, thereby eliminating messy adapters, which can introduce addi
tional SWR losses.
6. Has built-in matching transformer for 300 ohm input. 300 ohm input terminals
are of the thumb nut type for complete v ersatil ity of any twin lead termination.
7. Built-in 20db (X10) and 40db (X100) attenuators provide control of high level in
put signals, especiall y those signals encountered in distribution systems. The
attenuators can be used with the 75 ohm or 300 ohm input.
TheSen core FS134 Field Strength Meter is a completely solid state portable
Listed below are some of the Special Features of the Sencore FS134 Field
8. Separate VHF and UHF tuners are provided formiximum stability and minimum
losses.
9. Three stage 42 .8 MC high gain IF system controlled by amplified AGC stages
gives stabili ty and good control of both weak and strong input sig nals.
10. Large four inch meter allows operator to read signal strength from several
feet away.
11. Extended logarithmic microvolt range from 30 to 30,000 microvolts permits
antennas to be installed without constantly changing the sensitivity range of the meter .
12. Built-in, 3 1/2 inch speaker, with six transistor audio system to drive it, is
essential when monitoring FM and TV audio signals.
13. Signals as low as 5 microvolts can be heard in the speaker (the meter sta rts
indicating at 30 microvolts) thereby permitting weak fringe area signals under 30
microvolts to be "found" and built up with proper antenna orientation to a level vis-
able on the meter.
14. Extremely good shielding prevents strong signals from being received directly,
they must be received by the antenna, thus making the peaks and valleys of signal
strength more pronounced as the antenna i s rotated. This, of course, makes it
easier to pinpoint signal sources.
15. Detector output jack on the front panel permits external VTVM or oscilloscope
connections when monitoring.
16. Front panel CAL control compensates for decreasing battery voltage and affords
constant accuracy at all times.
SPECIFICATIONS
Tuning Ranges
53 MC to 109 MC - TV Channels 2 to 6 ; FM Channels 201 to 300
173 MC to 218 MC - TV Channels 7 to 13
465 MC to 895 MC - TV Channels 14 to 83
Sensitivity
53 MC to 109 MC - 30 microvolts + 3DB
173 MC to 218 MC - 30 microvolts + 3DB
465 MC to 895 MC - 30 microvolts + 3DB
Selectivity (Bandwidth)
500 KC & 3DB points
Intermediate Frequency
42. 8 MC
Input Impedance
75 ohms - 300 ohms with Built-in Matching Transformer
Image Rejection
53 MC to 109 MC - 40DB
173 MC to 218 MC - 40DB
465 MC to 895 MC - 30DB
IF Rejection
WDB
Audio Power Output
150 milliwatts
Power Consumption and Requirements
24 milliamps (8> 12 volts on VHF (no signal)
35 milliamps @12 volts on UHF ( no signal)
2 milliamps @-1.5 volts
Nine "C" cell batteries are used for power source. An accessory battery charger,
used with a rechargeable battery is available.
Dynamic Meter Range
30-30,000 microvolts (60DB) on logarithmic scale
Physical Specifications
Height - 9 1/2"
Width - 10"
Depth - 5"
Weight - 9 lbs.
Temperture Range
-5 to +105°F Operating Range
-2 0 to +140°F Storage Range
TRANSISTOR AND DIODE COMPLEMENT
Ref. No.
TR1
TR2
TR3
TR5, TR6, TR7 2N1745 IF Amplifiers
TR8
TR9
TRIO
TR11
TR12 2N1304
TR13
TR14 2N1304
TR15
TR16 2N1304
CR3, CR4
of your local TV stations, or from your signal generator. If you do this when the
The following blank spaces are for you to record the signal strength leve ls
FS134 is new, you will always have a handy reference for later use.
Channel
__________
Type
2N2362
2N2361 VHF, Signal Mixer - UHF, IF Amplifier
2N2362
2N2923
2N1304
2N1304
2N404
2N404
2N1304
1N34
Microvolts
__________
VHF, RF Amplifier - UHF, IF Amplifier
VHF, Oscillator
1st Audio
Audio Amplifier
Audio Driver
Audio Driver
Audio Output
Audio Output
AGC Amplifier
AGC Emitter Follower
Meter Balance
AM and Slope Detector
Input Used
Function
__________
Type Antenna
CONTROLS ON THE FS134
as any fine rec eiver. In addition to normal controls found on a recei ver, TUNING,
BANDswitch, OFF-ON switch and VOLUME control, the FS134 has a CAL control
to adjust for changing battery voltage. A front panel met er calibrated in microvolts
and DB and a series of input jacks complete the controls on the panel. Following is
a brief description on how each of these controls are used.
The FS134 is as easy to use as a radio and basically has the same controls
OFF-ON SWITCH. The OFF-ON switch, as the name implies turns the FS134 off
or on, but in addition has a center CAL position which is used in conjunction with
the CAL control and the meter to set the B+ voltage to the FS134 circuits.
CAL CONTROL. The CAL control is adjusted prior to taking a signal strength
measurement by placing the OFF-ON switch in the CAL position and adjusting the
CAL control until the meter indicates at the CAL line. This set s the voltage on the
RF, IF and AGC circuits to 10 volts resulting in constant signal strength accuracy
regardle ss of the battery condition. When it becomes impossible to make this ad
justment the battery voltage has dropped too low and the batteries should be replaced.
BAND SWITCH. The BAND switch selects one of three frequency bands; the low
VHF band, channels 2-6 and FM; the high VHF band, channels 7-13 ; and the UHF
band, channels 14-83. It i s located directly above the frequency dial.
TUNING. The TUNING control at the lower right of the frequency dial turns the
frequency dial and, of course, the internal tuning capa citor at a 6:1 ratio for "fine"
tuning adjustment of the selected signal. It is used for all three bands.
VHF bands each block representing a channel starts at a point representing the
car rier frequency (low frequency end) and stops at a point representing the sound
car rier frequency (high frequency end). This was done to simplify field use of the
FS134.
VOLUME. The VOLUME control adjusts the sound level from the speaker. In nor
mal use the sound level should be kept as low as possible to prevent excessive drain
on the batteries. The VOLUME control has been designed so that it can never be
completely reduced to ze ro to serve as an audible reminder that the unit in ON.
METER. The panel meter has two scales for determining signal strength - one
calibrated in microvolts, the other in decib els (DB). The decibel scale is used pri
marily when checking out an antenna distribution system for the various losses en
countered in pads, feedthroughs, cables et c. The zero DB reference is 1000 micro
volts across 75 ohms.
reducing the possibility of error by reading a wrong s cale.
The tuning dial is calibrated in frequency and by TV channels. On the two
The single microvolt sc ale is used for all VHF and UHF frequencies thus
INPUT JACKS. The basic input on the FS134 is the XI, 75 ohm jack. The signal i s
fed directly thru a pa ss filter to an RF amplifier in either of the VHF bands and in
the UHF band is fed directly to the UHF tuner. When signal levels are high the
signals can be attenuated by connecting into the X10 jack (20DB loss) or the X100
jack (40DB loss). Of course, when using the attenuator jacks the meter indication
microvolts should be multiplied by 10 or 100 respectiv ely, and on the DB indication
20DB or 40DB added respectively. The best meter accuracy is obtained between 30
and 1000 microvolts, therefore when you d esire the most acc urate indication and
the meter reads above 1000, additional attenuation should be used.
trans former. In use, the 300 ohm twin lead from the antenna would be connected
to the thumb screw terminals and the output of the matching transformer would be
coupled through the jumper cable to the appropriate 75 ohm input jack. When using
the 300 ohm input, the meter reading (microvolts) should be multiplied by two and
for best accura cy this product should be multiplied by the conversion f actor (See
page 7 ), which takes into account the losse s in the matching tranformer for the
various frequencies encountered.
The 300 ohm balanced input is changed to 75 ohm unbalanced by a matching
THE FS134 OFF-ON INDICATION. There are no pilot lights on theFSl34, but there
are two indicators, one is visual and the other an audible indication that the FS134
is on. The meter on the FS134, when the unit is on and no signal is fed to the input,
will read negative or below the 30 microvolt line on the scale. Just glancing at the
meter will tell if the unit is on. If a signal is present of course, the meter will
read up scale and again you will be able to tell if the FS134 is on. The volume con
trol on the FS134 cannot reduce the volume to ze ro, so there will always be either
the signal sound or low background noise from the speaker. In this way Sencore
has eliminated the power consuming pilot light and has provided more economical
battery life.
OPERATING INSTRUCTIONS
NOTE: THE METER WILL INDICATE BELOW THE 30 MICROVOLT MARK WHEN
NO SIGNAL IS PRESENT.
of signals receiv ed by an antenna or from an antenna distribution system is that the
output impedance of the antenna or system is properly matched to the field strength
mete r. If there is any mismatch, standing waves a re developed, which reduce the
amount of signal actually received by the meter and, of course, the meter indica
tion will not be a ccurate. ALWAYS BE SURE THAT YOU USE THE CORRECT
IMPEDANCE LINE OR CABLE FOR THE ANTENNA OR SYSTEM YOU ARE WORK
ING WITH AND THAT YOU CONNECT TO THE CORRECT INPUT ON THE FS134.
Cables with 75 ohms impedance (from a straight dipole antenna, for example)
should always be connected to the 75ohm input jacks (XI, X10 or X100). Three
hundred ohm twin lead from a folded dipole antenna should always be connected to
the matching transformer input and the short 75 ohm jumper cable used to connect
the output of the transformer to the appropriate 75 ohm input jack .
push the OFF-ON switch to CAL and with the tuning dial set to a point where no
signal is pres ent, adjust the CAL control until the m eter reads at the CAL line.
Push the OFF-ON switch to ON, and you are now ready to measure signal strength.
Measuring Signal Strength With the FS134. Rotate the tuning control to the approx
imate frequency of the signal to be measured and observe the meter indication.
Rotate the tuning control about this point slowly to obtain a maximum meter indica
tion. If the indication is past full scale on the meter, feed the signal into the next
higher attenuator, XI0 or XI00 to obtain a lower meter reading. Then repeat the
tuning procedure until a maximum meter indication is obtained. You can read the
meter directly if 75 ohm coaxial cable is used or multiply by 2 if 300 ohm twin lead
is used. Then this reading must be multiplied by the attenuator used. For exam
ple, 75 ohm coaxial cable plugged into the XI0 jack produces a reading of 245 micro
volts. This will be 245 X 10 or 2450 microvolt s. If 300 ohm twin lead is used giv
ing a signal strength of 350 microvolts in the XI jack, the signal would be 350 X 2
X 1 or 700 microvolts, total signal. When using 300 ohm twin lead connected to
binding posts, the meter reading must be multiplied by 2 to get the cor rect value
of signal strength. For greater accuracy the product must be multiplied by the
conversion factor found in the chart below, which takes into account the losses of
the matching t ransformer. For the average antenna installation, however, it is not
necessary to multiply by the conversion factor. On 75 ohm coaxial cable input,
read the meter direct.
The fir stand most bas ic requirement when attempting to measure the strength
With the input properly connected turn the BAND switch to the desired band,
Low VHF Band (Channels 2-6-FM) Multiply by 1.1
High VHF Band (Channels 7 -13) Multiply by 1.4
UHF Band (Channels 14-8 3) Multiply by 3.0
danger of damaging the meter, because the AGC system will hold the me ter current
at a safe level.
UHF Signal Strength Measurement. UHF signals are measured the same as above
except that all lead-ins, terminations, etc. are much more critical that at VHF
and the finest care must be taken to see that the cables are terminated properly,
cable connectors are tight, cables and lead-ins held well away from metal surfa ces
etc. It is much more difficult to obtain accurate measurements in the UHF band,
so every precaution you take will make the reading that much more accurate.
come by, noise is also down, resulting in good quality pictures at UHF at lower
signal levels than the same quality picture at VHF re quires.
If by chance in the XI jack some signals read beyond full sc ale there i s no
One big advantage at UHF is that although high signal levels are harder to
Tuning the FS134 to Monitor Sound Signals. Most RF signals can be heard through
the speaker on the FS134 although the sound may not be that of voice or music. For
example, the signals from the video portion of a TV signal contain a low frequency
(60 cycle) buzzing sound. However, the speaker is mainly intended for identifying
intelligible sounds such as voice or music. When tuning in an FM station or the
sound of a TV signal, the best sound will occur as the meter indication drops off
slightly and will occur at either side of the peak reading. This is a normal con
dition because slope detection is used in the FS134 sound system. On the video
carrier of a TV signal the maximum 60 cycle buzzing sound will be loudest when
the meter is at its peak indication, because the vide6 carrier is amplitude modu
lated (AM).
Turning the volume control clockwise will increase the sound output. It is
suggested that you keep the sound output as low as useable, or off, when not using
the sound signal to keep the drain on die batteries as low as possible.
Spurious Responses. Although the image rejection ratio for the FS134 is over 100
to 1 on the VHF TV bands it is possible for a "local" signal at the image frequency
to be of sufficient strength to be heard in the speaker and produce a meter reading
when feeding the signal through the XI input. Therefore, if possible, feed the
signal through the X10 or X100 input j ack s and spurious responses, such as this,
will be virtually non-existant. This also applies for UHF signal measurements.
Noise Level in the FS134. The FS134 circuits were designed to keep inherent noise
at a minimum, however extern al noise pickup by the antenna will be amplified and
received the same as an RF signal. Th erefore in extr emely noisy are as the FS134
meter may produce random meter indications caused by noise. The only a lterna
tive is to move the antenna to a les s noisy location. In doing so, this will also im
prove the FM, VHF, or UHF reception.
Determining the Frequency of a Received Signal. The frequency of any signal may
be read directly from the tuning dial. Set the tuning control for maximum meter
indications and read the frequency at the point on the tuning dial where the cross
hair passes through the frequency indication marks on the tuning dial. The FM
band and the VHF TV bands are on the top of the dial, and the UHF TV band is on
the lower half of the dial.
Use of Detector Output Jack. The DET OUT ja ck on the front panel of the FS134 is
provided so that the detected video signal may be monitored with an oscilloscope or
external m eter if desired. It is especially useful when checking boosters or antenna
amplifiers to see if these units are overloading on one or more channels causing a
loss of sync or sync compression or if they are causing cross modulation in the
other weaker channels.
FACTS YOU SHOULD KNOW FOR BEST USAGE OF THE FS134
the tran smission and receiving of VHF and UHF TV signals, and FM signals. The
whole business seems quite confusing when you hear such terms as: microvolt sig
nal strength, field intensity in microvolts per met er, antenna systems with so many
DB gain, DB, DBM, DBJ, 75 ohm coax, 300 ohm twin lead, mismatch, standing wave
ratio (SWR), pads, losses, matching transformers, and many others. Let 's see if
we can straighten some of this out.
to the input of a receiver and talked about SWR losses if this were not done properly.
As you know a straight dipole antenna has a characteristic impedance of 75 ohms
and a folded dipole antenna has a characteristic impedance of 300 ohms. Most of
the antenna arrays that have been manufactured over the years were designed for
300 ohm impedance, although recently some new arrays are being designed for 75
ohm impedance.
same impedance as the antenna, and the impedance of the lea d-in must match the
input of the receiv er, or points of mismatch will occur. Connections that are mis
matched will not pass the en tire signal, but rather will r eflect a part of the signal
back up the line. If there are two or more mismatched connections signals can
actually bounce back and forth several times. When some of the signal is ref lected
due to mismatch, standing waves occur. This condition is referred to in terms of
the standing wave ratio (SWR) which can be calculated by dividing the sum of the
two signals (original signal and reflected signal) when they are in phase by the sum
of the two signals when they a re out of phase. The clo ser that the SWR ratio is to
1.0 the bette r the match.
match, by using pads or matching transformers. A matching transformer gener
ally called a Baiun is actually an impedance transforming device that will convert a
300 ohm BALanced input to a 75 ohm UNbalanced output or vice versa. It consists
of two short lengths of 150 ohm twin line that are connected in series on one end
and in p arallel on the other. The 150 ohm lines may be wound around a coil form,
Before putting the FS134 to work let's review briefly some fa cts concerning
We stated earlier the importance of matching the impedance of an antenna
The importance of all this is that the lead-in from the antenna must have the
It is possible to change from one impedance to another with very little mis
or in some cases are wound on a ferrite core.
another, although you may be more familiar with them as attenuation pads with the
same input and output impedances designed for a specific DB attenuation. It is well
to note that any pad, whether it is designed specifically for attenuation or for
matching two impedances, will always introduce some loss. Impedance matching
pads are generally designed for a 6DB loss for ease of calculations in use, since
1/2 of the input voltage will appear at the output.
Pads are resistive networks that can be designed to match one impedance to
FIELD INTENSITY AND SIGNAL STRENGTH
field intensity pattern in terms of microvolts per meter fo r the surrounding country
side. This field intensity figure i s the voltage induced in a conductor one meter
long as the magnetic flux of the transmitted wave passes through the conductor at
the speed of light. Field intensity measurements can be made with the FS134 (see
procedure on page 12).
strength of a received signal is dependent on the antenna array , and how much sig
nal the antenna can pickup from the field intensity pattern. A well designed array
will be able to pick up much more signal than a straight dipole, for example.
had to be devised. The straight dipole was chosen as the reference, and all other
antennas are compared against it. Therefore an antenna arr ay with 20DB gain would
"collect" ten times the amount of signal voltage that a straight dipole would collect.
volts or DB. Microvolts by itself has very little meaning unless you als o consider
the impedance that the voltage is developed acro ss. .In other words, it is the re
ceived power that is important, but since we are always dealing with either 75 ohm
or 300 ohm impedance, we can and do get by with just the voltage term. For ex
ample, consider a 300 ohm antenna array that i-s receiving a 1000 microvolt signal.
The signal power would be E R and would equal .0033 micro-watts. Now let's
assume that you would like to use a 75 ohm coax lead-in. You would place a match
ing transf ormer on the antenna mast to convert 300 ohms to 75 ohms. Assuming
no losses in the matching transformer you would find that the output voltage of the
transf ormer would equal the square root of .0033 m icro-watts times 75 ohms or
500 microvolts. Notice that the microvolts at 75 ohms is just half of the microvolts
at 300 ohms, yet in both cases the power is the same. The FS134 is cali brated for
a 75 ohm input, therefore, when using the built-in matching transformer for 300
ohm input you must multiply the microvolt reading by two.
in cables, pads, etc., the voltage figures resulting become so large and cumber
some that the more convenient DB term is used. A big advantage is that gains and
losses of a system expressed in te rms of DB can be added or subtracted directly
making calculations more simple.
industry has agreed that 1000 microvolts across 75 ohms would be a good zeroDB
reference, since a signal of this strength will produce a good quality picture. Terms
such as DBJ and DBM are expressions of this reference.
output voltages, keeping in mind that the input and output impedances must be the
same.
Transmitted signals fill the air around us. Each station has a plot of their
Do not confuse signal strength in mic rovolts with field intensity above. The
Since some antennas are more effective than others a means of rating them
The strength of received signals is generally refe rre d to in terms of micro
Once a signal is received and is amplified in a booster or experiences losses
To establish a DB scale, however, some reference must be used. The TV
You may recall the formula for calculating DB when you know the input and
DB = 20 log E out
E in
So that you won't have to dig out your old logarithm book you can simplify your ca l
culations with the following DB chart.
Charts and useful fo rmulas:
Coaxial Cable Losses in DB/100 ft.
Type Cable
RG59/U
RG6/U
RG6/U Foam
RG11/U
RG11/U Foam
Ch. 2
2. 8 3.2
2.1
1.7
1.6
1.1
Ch. 4
2.3
1.9
1.8
1.3
Ch. 6
3.6
2.6
2.1
2.0 2.2
1.4
FM
4 .0 5.3
2. 7
2.2
1.5
Ch. 7
4 .0
3.2
2. 7
1. 6
Ch. 10
5.6
4.2
3.3
2.9 3.0
1.9
Ch. 13
5.9
4.3
3.5
2.3
Channel
Bandwidth (MC)
Picture Carr ier (MC)
Sound Carrier (MC)
2
3
4
5
6
7
8
9
10
11
12 204-21 0
13
14-83
Ef (Field Intensity in Microvolts per Meter) = .02 1 X E (Field Strength Meter Read
ing in Microvolts using a matched resonant dipole antenna) X E (frequency in MC)
(470 to 476)+6(ch#-14)
54-60
60-66
66-72
76-8 2 77 .25 81.75
82-88
174-180
180-186 181 .25
186-192
192-198 193.25
198-204 199.25
210-216 211.25
Wave Length in Fee t (Air) =
Wave Length in Met ers (Air) = -------
6 Freq. in MC
55.25 59. 75
61.25
67 .25
83. 25
175.25
187.25
205.25
471.25 + 6 (ch#-14) 475.75 +6 (ch#-14)
-----
Z£Z—_ _
Freq. in MC
65.75
71.75
87 .75
179 .75
185 .75
191 .75
197.75
203 .75
209 .75
215 .75
. In several places above we made refer ence to a straight dipole antenna.
This would be a very handy device to have, because with it you would be able to
make field intensity surveys, actually measure the gain of antenna arrays , (remem
ber the dipole is the reference for all other antennas) et c. The complication is, of
course, that the dipole has to be "cut" to the frequency that you wish to receive.
Sencore has come up with the simple answer! Purchase a "Rabbits Ears" antenna,
remove the 300 ohm line, which isn’t cor rect for the antenna anyway, and attach a
length of 75 ohm coax (RG59B/U) to the arms. The other end of the cable should
have a connector that matches the FS134 input jacks (Jerrold ty peF59Aor equiv
alent). The antenna should then be mounted on the end of a wooden pole.
In use, each arm would be adjusted for 1/4 wavelength of the frequency you
wish to receive times .95 (end loading factor) or in terms of feet would be
235
Fre q. in MC
If you really want to "go all out" you might even calibrate the adjustable a rms by
channels to prevent having to make calculations out in the field.
FIEL D INTENSITY SURVEYS
ability and the fact that it does not require an external source of power. All that is
necessary is a strai ght dipole antenna cut to the frequency being plotted and the
conversion formula, to change microvolts to microvolts/meter, found in the above
section. Seventy five ohm coaxial cable should be used from the dipole to the FS134.
If this cable needs to be quite long, be sure to consider the cable losses in your
calculations. If an antenna other than a dipole is used the conversion fact or (.021)
must be divided by the gain fact or of the antenna for correct results. .
FIELD OR AREA SURVEYS
for the best antenna location, are quite easily performed because of the FS134
portability and internal power source. All that is necessary is an antenna that has
been impedance matched to the FS 134.
cover that the height the antenna is placed above the roof can be just as important
as its orientation. Also don't be alarmed if you discover that a reflec ted signal is
stronger than the one direct from the transmitter, especially in metropolitan ar eas .
Usuallyin an area where there are many reflectio ns, a coaxial lead-in is preferred,
because even though the antenna has a good directional pattern 300 ohm twin line
can pick up unwanted signals, which, of course, results in ghosts.
antenna upwards a few degrees will solve the problem.
signals are "line of sight'transmissions UHF is attenuated easier and can be affected
by anything, including trees, between the transmitting antenna and the receiving
antenna. It can almost be thought of, as a beam of light.
The FS134 is ideally suited for field intensity surveys, because of its port
Surveys to determine where signal le vels are the highest and/or the searc h
In searching for the best location to install an antenna, you will often dis
Sometimes when it i s extremely difficult to eliminate reflection s, tilting the
Installing UHF antennas is more cri tical than VHF antennas. Although both
When installing UHF antennas, here are several things to keep in mind.
1. Try to pick a spot where there is aline of sight path to the transmitting antenna.
An antenna mounted in late fall behind a tree may work good all winter, then in
spring when the leaves come out, the signal level is dr astically attenuated.
2. The height of a UHF antenna is critical. Especially if the antenna is mounted
on a metal roof. Even if the roof does not appear to be metal, keep in mind that
some insulations use aluminum foil and this gives the same effect. Generally the
antenna should be mounted 5 to 10 wavelengths above the roof.
3. The lead-in should have low loss, and if twin lead i s used, should be kept away
from the mast, roof, and building with good quality stand-offs.
4. Quite often the best signal area is not the best location to physically mount the
antenna, in which case a compromise will have to be made.
UHF, VHF, AND FM ANTENNAS ALL ON THE SAME MAST
space requirements to mount the FM, VHF and UHF antennas on the same mast.
Some of the newer antenna arrays are designed to receive all of these signals with
a single antenna.
installation becomes more c rit ical, because in addition to the problems with UHF
discussed above, the antennas will interact somewhat, and usually the final place
ment of each ‘antenna will be a compromise for the b est signal level on all three
mediums, FM, UHF and VHF.
rechecking all three signals each time an antenna is moved. With the FS134, you
can switch back and forth between these frequencies with ea se and adjust for the
best performance on all three bands.
SETTING UP A TV DISTRIBUTION SYSTEM
plex systems used in Motels, Hotels, Hospitals, etc. to simple systems used in
dwellings where two to four TV sets are operated off a single antenna.
operated from an antenna. When the signals from an antenna are strong enough
and the number of se ts to be operated is not too g reat (2, 3 or 4), couplers are gen
era lly employed which maintains the correct impedance match to all TV sets con
nected to it, and also provides some isolation between TV sets.
checked across the band at each set of output terminals from the coupler and also
at each TV set to determine if the signals a re being distributed properly.
the distance between the sets is quite great, the signals received by the antenna
will have to be amplified, and then distributed to each TV via a network of cables,
pads and matching transformers. It is important that each TV outlet is properly
matched and also that the signal strength is of the proper level. Those outlets
close st to the amplifier must have internal attenuation to prevent the signal from
being too strong, whereas the outlets on the end of the line have very little atten
uation, because the signal has already been attenuated by cable los ses , feed thru
pads, etc.
an existing system. The main purpose of a system is to provide good signal levels
at all outlets. With the FS134 each outlet can be checked across the band for pro
per le vels making it easy to pinpoint trouble spots.
tions. By using a scope in the DET OUT jack it is easy to see if one or more chan
nels are overloading the amplifier. It can also be checked without a scope, by
measuring signal levels from the antenna and checking them against the amplifier
input specifications. An overloaded amplifier is easily recognized by cross modu
lation or windshield wiper" effect in some channels or by excessive sync buzz and
unstable sync in the receiver. The channel (s) with cross modulation a re the vic
tims and not the culprit of an overloaded amplifier - the culprit is the channel that
does not display cross modulation effect s, but may appear rather strong. It over
drives the am plifier and spills" over into the other channels. The amplifier gain
must be reduced or the antenna reoriented to reduce the strong signal. Of course,
the FS134 would be used to determine the best gain setting and antenna orientation.
Sometimes it will be necessary due to customer's requ estor because of
When three different antennas have to be mounted on the same mast, the
Generally it is best to place the UHF antenna first, then VHF, then FM,
TV Distribution systems are coming more in the public domain from com
Some form of distribution must be used whenever two or more TV sets are
The FS134 is very useful with these system s because signal levels can be
When a large number of sets are to be operated from a single antenna and
The FS134can be used in the installation of anew system or in checking out
The FS134 can also be used to check out the am plifier for overload condi
to establish the better unit for the area. By using the same antenna or signal
source, different boosters can be evaluated and compared. Signal overload can be
detected as well as poor gain on a channel by using the built-in speaker or by use
of the detector output jack and a scope.
CHECKING RANDOM NOISE LEVE LS AND INTERFERENCE
TV signal boosters can be checked and their gain and bandwidth compared
a simple dipole antenna connected to the unit. By tuning the FS134 across its range,
and rotating the dipole antenna, you can approximate the direction and the frequency
of the inte rference or noise. By taking readings at two points, the source of the in
terference can be plotted by trigonometry.
CALIBRATION OF SIGNAL GENERATORS
the signal to the FS134 and using the microvolt scale on the unit. The frequency
can be checked and compared to the dial of the FS134 and the signal generator re
calibrated if it is too far off. It i s important that the output impedance of the gen
erator is matched to the FS134 input or the microvolt check will not be accurate.
checks. CAUTION: Do not overload FS134 with exce ss signal generator output.
required. The pad is merely 3 resistors connected as shown in sketch below.
The FS134 can be used to check out noise levels and interference by using
The output of signal generators can be calibrated in microvolts by applying
Loss factor introduced in matching must be considered when making microvolt
INTERNAL ADJUSTMENTS
Alignment of the FS134 will not usually be required unless an elect ric al
component in the IF section or tuner assembly was changed. If frequency indications
are far off at all points on the frequency dial, alignment is nec essary. Also if the
sensitivity measured is greatly different at both ends of the frequency dial, align
ment may be necessary .
Most signal generators have an output impedance of 52 ohms. In order to
match the 52 ohms generator output to the FS134 75 ohms input, a matching pad is
RF
SIGNAL
GENERATOR
82Λ
KEEP ALL RESISTOR LEADS
AS SHORT AS POSSIBLE
keep signal level from generator below 40 microvolts.
Alignment accuracy will depend on accu racy of signal gener ator. Always
75/1 COAXIAL CABLE
Λ
-------
360Λ
(RG 59B/U)
-ΞΞΞΞ-C FS134
/L_
75Λ. CONNECTOR
(JERROLD NO. 5 9A )
INTERMEDIATE FREQUENCY ALIGNMENT
1. Connect signal generator output to input j ack (XI) on FS134.
2. Set FS134 Bandswitch to "CHAN 2-6- FM", and turn A6 (see drawing below) out
three turns.
• MAX M A X M IN
100MC 42.8MC 4 2.8 M C
3. Set Signal Generator to 42. 8 MC and set signal generator output so that meter
on FS134 reads less than 40 microvolts.
4. Adjust A1 (IF transformer closes t to speaker) and then A2, A3 and finally A4 on
tuner. Repeat adjustments to obtain a peak and reduce generator output each time.
5. Adjust A6 to get a minimum indication on meter while increasing generator out
put to the point where indication will fall below 40 microvolts.
6. Set Bandswitch to UHF and adjust A5 for maximum.
RF ALIGNMENT, CHANNEL 2 THROUGH 6 AND FM BAND
1. Set FS134 Bandswitch to "CHAN 2-6-FM".
2. Rotate tuning control so that cross h air passes through 70 MC on frequency in
dicating dial and set signal generator to exactly 70 MC.
3. Adjust A7 and A8for maximum meter indication. Repeat adjustments A7 and A8.
4. Set signal generator and FS134 to 108 MCand adjust A9for maximum indication.
5. Set signal generator to 100 MC and rot ate tuning control on FS134 for maximum
meter indication.
6. Adjust A10 while rocking signal generator frequency control back and forth for
the highest maximum (below 40 microvolts) on FS134 meter.
7. Repeat steps 2 and 3 and then steps 5 and 6.
RF ALIGNMENT, CHANNELS 7 THROUGH 13
1. Set FS134 Bandswitch to "CHAN 7 -13".
2. Rotate tuning control so that cross-hair passes through 180 MC on frequency
indicating dial and set signal generator to exactly 180 MC.
3. Adjust All and A12 for maximum. Repeat adjustments All and A12.
4. Set signal generator and FS134 to 216 MC and adjust A13 for maximum.
5. Set signal generator to 210 MC and rotate tuning control on FS 134for maximum
meter indication.
6. Adjust A14 while rocking signal generator frequency control back and forth for
the highest maximum (below 40 microv olts) on FS134 meter.
7. Repeat steps 2 and 3 and then 5 and 6. .
FS134 VHF CALIBRATION PROCEDURE, CHANNEL 7-13
Calibration accuracy will be only as good as that of signal generator used.
1. Set Bandswitch to "CHAN 7-13" and set tuning control for 195 MC.
2. Set slide switch on FS134 to "CAL" and carefully adjust "CAL" control to CAL
line. Then set switch to "ON".
3. Set signal generator to 195 MC and set generator output control to just get an
indication on FS134 meter.
4. Rock signal generator frequency control to obtain a peak meter indication on
FS134 and then reduce generator output to keep meter reading near 30 microvo lts.
5. Set signal generator output control to exactly 30 microvolts and while rocking
frequency control on generator slightly, adjust 30 microvolt adjust on FS134 until
meter indication just comes up to 30.
-----
.
6. Set generator output control to 1000 microvolts and while rocking frequency
control on generator slightly, adjust "1000 microvolt adjust" on FS134 until meter
reads 1000 microvolts at the peak.
7. Repeat steps 5 and 6.
FS134 VHF CALIBRATION PROCEDURE, CHANNEL 2-6-FM
1. Set Band switch to CHAN 2-6- FM and set tuning for 70 MC.
2. Set slide switch on FS134 to "CAL" and car efully adjust "CAL" control to CAL
line. Then push switch to "ON".
3. Set signal generator to 70 MC and set generator output control to exactly 30
microvolts.
4. While rocking frequency ol on generator slightly, adjust control in tuner
until meter indication comes 30.
UHF CALIBRATION PROCEDURE
1. Set FS134 Band switch to "UHF".
2. Rotate tuning control so that cross -hair passes through 500 MC on bottom sec
tion of frequency indicating dial and set signal generator in the vicinity of 500 MC
where FS134 meter will indicate.
3. Set signal generator output to 1000 microvolts and while rocking signal gener
ator frequency control back and forth for highest maximum m eter reading on the
FS134 adjust A15 so that FS134 meter reads 1000 mic rovolts.
ADJUSTING THE FREQUENCY DIAL
The frequency dial is adjusted by loosening the two screws under the cen ter
trim cap, positioning the dial and retightening the screws. Hie trim cap is removed
by unscrewing i t CCW from the condenser shaft.
■„ * dial will normally be adjusted so that the ends of the bands
will fall under the frequency indicator line when the tuning is set to each extreme.
However, if there is a channel in your area, on which you would like to have a very
accurate frequency indication, merely tune this channel on the FS134 and adjust the
dial until the mark for this channel falls under the indicating line.
(latest production models only)
DISASSEMBLY INSTRUCTIONS
Removing the FS134 from the case.
1. Remove the two 6-32 phillips screws at the top of the panel.
2. Place the unit face down on a cloth and remove the two 8- 32 RH screws on the
bottom of the case.
3. Lift the case off the unit.
The attenuator shield must be removed before aligning the IF transformers.
1. Remove the screw on the side of the panel.
2. Remove the nut and washer that holds the shield and speaker grill to the panel.
3. Lift the shield off the panel.
Replacing the Batte ries.
become too weak and they must be replaced.
When the CAL control adjustment can no longer be made, the batteries have
1. Remove the single 8-32 RH screw that holds the two battery brackets at the out
side edge of the chas sis.
2. The battery brackets will now slide to the side disengaging from the chassis
clamp that holds the inside end of the brackets.
3. Separate the two battery b rackets and fold open to completely expose the b atteri es.
Save the three pieces of insulating paper for reuse with the new ba tteries.
The 12 volt supply consist s of the six batteries mounted on the bottom bracket
and the two b atterie s in series on the upper bracket. The single battery on the upper
bracket is the minus 1.5 volt supply. Generally the 1.5 volt supply batt ery will not
require replacement as frequently as the others, because of the lower current drain.
4. Remove the old batteries from the brackets and replace with new "C" cells,
being sure to observe the correct polarity during the replacement. The brackets
are marked with plus (+) signs to indicate the direction the positive end of the bat
tery (sm all button) should be placed. CAUTION: If battery polarity is not correct,
the cir cuit may be damaged.
5. Reassemble the batt ery bracke ts, placing the large piece of insulating paper
between the batteries, and a lso being c areful not to pinch any wires with the battery
clip s. Install the battery brackets on the main chas sis. Be sure that both brackets
are under the chass is clamp before inserting the screw. Insert a piec e of insulat
ing paper at each side of the brackets between the ba ttery clips and the inside of
the upper bracke t to prevent the termin als from shorting.
6. Test the battery replacement by sliding the OFF-ON switch to CAL and seeing
if the unit can be calibrated properly. When the batterie s are new and the CAL
control is turned all the way up the meter will read almost to full sca le.
dent, the batteri es are left too long in the set or leak, only the bracket will become
damaged. This is much easier to replace and is les s expensive than the main chassis.
The second purpose is the optional charger for rechargeable batteries. The charger
comes mounted on a similar bracket and is put in, in place of the regular battery
bracket.
The two pie ce battery bracket se rves two very useful purposes. If by acci
for trouble shooting.
1. Remove the tuner cover by taking out the six RH sheet metal screws.
2. Remove the single RH sheet metal screw located above the IF transformer (A4).
3. Disconnect the five small wires that come through the IF chassis and connect to
the tuner PC board. The red wire is +10 volts, the bare wire and the black wire are
ground, the green wire is signal out, and the orange wire i s AGC.
4. Disconnect the long red wire attached to the feed thru capacit or at the top of
the tuner cha ssis.
5. Place the unit face up and unscrew the trim cap in the center of the frequency dial.
6. Remove the p lastic indicator by removing the four screw s in the corne rs.
7. Remove the dial held by two screws and washers near the center.
8. Remove the band switch lever knob held with one screw and washer, and remove
the tuning knob by lifting straight up.
9. Remove the four fla t head screws that were exposed when the frequency dial was
removed, and the tuner assembly will now be free from the rest of the unit, except
for the input cable from the attenuator. This can be left on for restringing the dial,
but may be disconnected at the attenuator end for further disassembly and/or trouble
shooting.
10. Grasp the tuner and pull st raight back away from the panel until the tuning
shaft is free of the clearance hole in the panel, then lift straight up and the tuner
will separate from the unit.
The tuner assembly must be removed if the dial cord has to be replaced or
Disassembling the Tuner PC Board from the Tuner Chassis
1. Remove the 75 ohm antenna cable and the IF output cable from the UHF tuner.
The UHF tuner is the silver colored can mounted on the battery side of the tuner
chassi s. Pull the two cables through the holes in the tuner chassis.
2. Disconnect the red and orange wires that connect from the band switch to the
feed thru cap acitors in the tuner chass is.
3. Turn the tuning condenser shaft fully CCW to prevent damage to the condenser.
4. Remove the nut and washer holding the band switch and the three 6-32 sc rews
holding the tuning condenser. The PC board assembly can now be removed from
the chassis.
Stringing the Dial Cord
Stringing the dial cord is not difficult if the procedure below is followed.
1. Prepare a .025D non-stretchable dial cord by looping each end and tying a knot.
The distance between the two loops should be 31 5/8 inches. Hint: When tying the
second loop make the distance to the loop (before tying knot) 32 1/8 inches. The
extra half-inch will be taken up with the knot. Make the knots as close to the ends
of the cord as possible and still leave a sm all loop.
2. String the cord by following the diagram below. Turn both pulleys (UHF and
VHF) fully CCW. St art the string on the UHF pulley, hooking it on the tab and then
bring it to the outside. Go around the pulley 3/4 turn CCW and then over to the
VHF pulley. Go around the VHF pulley 2/3 turn CCW, then bring the cord inside
go around the hub once, then back to the outside of the pulley and continue CCW
over to the tuning shaft. Wrap the cord around the tuning shaft CCW for Four com
plete turns. Watch that the turns lay side by side and do not overlap. Bring the
cord back to the VHF pulley and make one complete turn around it CCW and then
bring it to the UHF pulley making a 3/4 CCW turn around it. The cord should now
be a ll used up with the loop and knot jus t inside of the pulley. It is important that
the knot does not end up on the outside of the pulley, because tuning may be "jerky"
at mid range.
Hook the spring to the loop in the end of the cord and then to one of the holes
in the pulley making sure that there is sufficient spring tension to prevent the cord
from slipping on the tuning shaft, while tuning.
3. "Tune" the condensers from one end to the other with the tuning shaft, while
observing the "stop" on the UHF tuner shaft. If the "stop" does not completely
make contact at each end of the range, turn the condensers to mid range and while
holding the UHF pulley rotate the VHF pulley a small amount and recheck. When
the stop on the UHF tuner shaft makes contact at each end, put a drop of cement on
the string where it passes around the hub of the VHF pulley. This will secure the
alignment of the two pulleys.
CIRCUIT DESCRIPTION
printed circuit board construction, operating from nine internal 1.5 volt "C" cell
batteries. It will receive frequencies in three bands; 53-109MC (VHF low band and
FM), 173-218 MC (VHF high band) and 470-89 0 MC (UHF band). It reads the
strength of signals fed to the input on a panel met er in terms of microvolts or in
decibels, with a maximum sensitivity of 30 microvolts for each band.
be fed directly into the tuner on the XI jack or will be attenuated to one tenth or one
one hundredth if connected to the X10 or X100 ja cks. Signals fed to the FS134 via
a 300 ohm twin line are connected to the 300 ohm input on the matching transformer
and the output of the matching transformer coupled to one of the 75 ohm jacks via a
short jumper cabl e.
VHF bands or are coupled to the UHF tuner for UHF operation. The low band VHF
filter is a low p ass f ilter consisting of C17, C18, L7, C21 and C22. It will pass
all frequencies up to 110 MC; frequencies above 110 MC a re attenuated. Signals at
42. 8 MC (the FS134 IF frequency), are attenuated with an IF trap consisting of Cl5
and L5. The amount of low band signal reaching the RF amplifier is controlled
with R8. (Early production units have a fixed res istor divider in place of R8.)
L8 and C22. It will pass all frequenc ies above 173 MC and attenuate all frequencies
below 173 MC. Two additional coils are used in both high and low band filters.
These coils have no reference number because they are part of the printed circuit.
They are across C17 and C22.
(TR1) for low VHF band operation and through R7 and C14 to the base of the R F
amplifier for high VHF band operation. For UHF operation, the UHF signals have
been converted in the UHF tuner, to signals at the 42. 8 MC IF frequency. These
signals appear across L4, are coupled through Cl3, which serves a s a UHF sen
sitivity adjustment, and then through Cl4 to the base of TR1. Fo r UHF operation
TR1 (R F Amplifier) and TR 2 (Mixer) serve as 1st and 2nd IF amplifiers respec
tively, making a total of five IF amplifiers for the UHF band.
circuit. It operates at fixed gain. The tuned circuit for the low VHF band consists
of L2 (RF coil), C3 (trimmer) and C7A (tuning condenser). The tuned ci rcuit for
the high VHF band consi sts of LI (RF coil), C2 (tri mmer) , C4 and C5 (padder) and
C7A (tuning condenser). For UHF operation the tuned IF tank of L3 and C6, serve
as the collector load.
TR2. For both VHF bands, TR2 serves as a mixer, mixing RF signals from TR1,
with local oscillato r signals from TR3, which are coupled through R9 and Cll. IF
signals are developed a cross T1 in the co llector circ uit of TR2. The gain of the
mixer is controlled with AGC voltage.
for the low VHF band, and through a range of 130. 2 MC to 175. 2 MC for the high
VHF band. The oscillator i s temperature compensated with a 2. 2PF N1500 capa
citor (C20) from the collector to ground. Supply voltage to the oscill ator is inter
rupted for UHF operation, to prevent spurious operation, and likewise supply volt
age to the UHF tuner is interrupted for VHF operation.
TR5, TR6 and TR7. These stag es ar e all quite s imilar, except the gain of the first
two stages, TR5 and TR6, is controlled with AGC voltage whereas the last stage,
TR7, operates from fixed 10 volts. The 1st stage is neutralized with a 4PF capa
The Sencore FS134 Field Strength Meter is completely solid sta te with
Signals fed to the attenuator (see schema tic), via 75 ohm coaxial cable, will
As the signals enter the VHF tuner they couple through pass filters for the
The high band VHF filter is a high pass filter consisting of C17, L6, C19,
The output of the filter is coupled through C14to the base of the RF amplifier
For VHF operation TR1 ser ves as an RF amplifier with a tuned collector
Signals from TR1 couple through a 3. 3 PF capacitor, C9, to the base of
The local oscillato r, TR3, osci llates through a range of 95. 8 MC to 151. 8 MC
Signals from the tuner ar e fed to the IF amplif ier, consisting of three stages
citor, C35, and the 2nd and 3rd stages are neutralized with 3. 3PF capacitors, C37
and C39 respectively.
The output of the IF amplifier i s coupled to the detector through C41. The
detector consisting of two IN24 diodes CR2 and CR3 is a doubler that will develop
the demodulated signal across C42 with a positive DC voltage reference that is
equivalent to approximately two times the average RF level. R35, 1.8 meg resistor
to +10 volts is used to balance out threshold voltage so that CR2 and CR3 will con
duct on weak signals.
prevent loading, and i s also fed to the 1st audio stage, TR8. The first audio stage
amplifies the audio signal, which is then controlled with the volume control R20,
and coupled through C46 and R40 to the base of the audio amplifier, TR9. The 47
ohm resis tor R21, prevents the volume from being tuned all the way down, which
and is further amplified in the push-pull audio driver (TRIO and TR11) and the audio
output stages (TR12 and TR13). The output impedance of TR12 and TR13 was de
output transformer.
tive DC level proportional to RF carrier level. This DC leve l appearing in the
emitter of TR8 is divided down in the resistor network of R50 and R52, from where
it is fed to the AGC amplif ier, TR14. The AGC amplifier i s a DC amplifier that
amplifies the DC voltage present on the base. Any AC signal on the base of TR14
receives full negative feedback from the c ollector through C51 and C52 eliminating
all traces of AC signal in the collector. The DC level at the collector of TR14,
which is proportional to R F carrier level, is DC coupled to the AGC output, TR15,
an emitter follower. TR15 supplies AGC voltage to the mixer and the 1st and 2nd
IF stages and also feeds the meter circuit. As RF carrier level increases the AGC
voltage becomes le ss positive, thus reducing the overall gain of the system.
nected to the AGC voltage through int ernal control, R57 (1000 microvolt adjust).
The positive terminal of the meter is connected to the meter balance stage, TR16,
which sets the point that the meter will start to indicate. R62, the 30 microvolt
adjust, an internal control, is set so that with a 30 microvolt signal fed into the
FS134, the meter will read at the le ft edge of the scale (30 microvolt mark). With
a 1000 microvolt signal fed into the FS134, R57 i s adjusted so that the meter will
read at the 1000 microvolt mark. These adjustments are made at 195 MC at the
factory, however, for extreme accuracy at any particu lar frequency, they could be
made at that frequency.
sure the voltage on the +10 volt line, so that when R23, the CAL control is set for
the "CAL" indication on the meter there will be approximately 10 volts supplied to
the tuner, IF and AGC c ircuits. This adjustment is provided to take into account
changes in battery voltage, as the b atteri es become weak.
The detected signal is fed to the DET OUT jack, through a 47K resistor to
serves as an "ON" indicator for the FS134. The audio signal is amplified in TR9
signed for 45 ohms, permitting a 45 ohm speaker to be driven d irectly without an
The detected signal at the base of the 1st audio am plifier, TR8, has a posi
When the OFF-ON switch is ON the negative terminal of the met er i s con
In the CAL position of the OFF-ON switch the met er is connected to mea
FS134 TROUBLE CHART
SYMPTOM PROBABLE CAUSE CORRECTIVE MEASURE
Weak Sound Batteries weak, bad elec- Replace batt eries, check for l eak-
trolytic C46, C47, C49or age or lo ss of capacity and repla ce
C50. if defective.
Meter can be cal
ibrated, but no
other indications.
Broken cable at switch in Remove tuner cover and locate
tuner, poor switch contact, broken cable or poor switch contact.
UHF inoperative
Chan 2-6 FM
inoperative
Chan 7-13
inoperative
No sound or meter
indications
Unit will not CAL
Unit seems in
sensitive
Meter calibration
falls off rapidly
after calibrating .
Frequency dial
appears to stick
when tuning.
Broken wire to side of UHF Reconnect broken wire if loose,
tuner, poor switch contact, locate and repair bad contact on
Poor switch contact, pos
sibly on rear wafer of
switch.
Poor switch contact, pos
sibly on rear wafer of
switch.
Open connection, loose
battery, open CAL control.
Weak batte ries.
Poor switch contact in
tuner.
Weak batteri es, internal
short.
Insufficient spring ten
sion in dial stringing
system.
- tuner switch.
Locate and repair.
Locate and rep air.
Locate open connection, possibly
in battery compartment, tighten
loose battery. Check CAL control
and replace if defective.
Replace batteries .
Locate poor contact by pressing
each contact with an insulated tool,
while unit is receiving a signal.
Replace batt eries, if short ex ists
locate' short before replacing bat
teries.
Remove tuner and incr ease spring
tension on dial string system.
Cannot pick up
signals at low end
of both VHF bands.
Motor boating or
erra tic operation.
Distorted or
scratching sound
from speaker.
Tuning condenser plates
touching when plates sta rt
to mesh.
Corroded or poor bat
tery contacts.
FS134 incorrectly tuned Retune FS134 for better quality
defective or warped speaker sound. Replace speaker if defective,
cone.
Closely examine and gently move
plates with an on-metalic alignment
tool while tuned to point where sig
nal pickup disappears.
Clean battery contact, and see that
proper press ure exi sts between
contact and battery terminal.
WARRANTY AND SERVICE INSTRUCTIONS
market. Although the FS134 is completely solid state and there are no tubes to re
place there is always the possibility of something going wrong. The FS134 is cov
ered by a standard 90 day warranty as explained on the warranty policy enclosed
with your instrument.
factory service department. Be sure to state the nature of the trouble to insure
faster ser vice. To save money on shipping costs and also to prevent further dam
age to the FS134, REMOVE THE BATTERIES, before shipping the unit. If you wish
to repair your own FS134, we have included a schematic and par ts list and a ch art
for location of the troubles you may encounter. Special replacement parts are
available and may be ordered direct from the fa ctory servi ce department.
replacement part is issued.
RECHARGEABLE BATTERY SYSTEM FOR THE FS134
fit in the' FS134 in the p resent battery bracket. This system will enable you to use ,
a rechargeable battery such as Burgess # CD28, to eliminate battery rep lace ment."
Simply hook up the AC leads from the system as describe d in the instructions with
the rechargeable system. The battery is not furnished by Sencore, only the re
charger. The recha rger is over-charge proof, and can be left on over night or all
day without damaging the battery. To order the rechargeable system, simply write
the factory ser vice department, enclosing a check or money order for $ 9 . 9 5 The >
part number is 39G15.
You have just purchased one of the finest piec es of test equipment on the
For best service out of warranty work, the FS134 should be returned to the
We reserve the right to examine defective components before an in-warranty
ACCESSORIES
You may purchase as an a ccessory, a recharg eable battery system that will
SENCORE. INC
FORM NO. 2 68 ! j; 4
3200 SENCORE DRIVE, SIOUX FALLS. S. DAKOTA 57107
SENCORE
SCHEM A TIC AND PARTS LIST
for
FS1 34 FIELD STRENGTH METER
320 0 Sen core Drive
Sioux Falls, South Dakota 571 07
Phone (605) 339-0100
FS13 4 PARTS LIST
REFERENCE
C2,C3 ,C4,C6
C25,C26
C 7
CR2, CR3
LI
L2
L5
L3
L6, L8
L7
L9, L10
Ml
R20
R23
R57, R62
R73
SI
S2
T1,T2,T3,T4,
T5
TR2
TR3
TR5, TR6,TR7
TR4,TR8,TR9,
TR14,TR15,TR16
TR10,TR12
TR11,TR13,
DESCRIPTION
Capacitor, trimmer, 1.5-10pf
Capacitor, two ga ng tuning
Diode, 1N695
Coil, RF tuning, VHR high band
Coil, RF tuning, VHF low band
Coil,luh
Coil, 3uh
Coil, .043uh, VHF high band filter
Coil, .21uh, VHF low band filter
Coil, Os c. tuning, VHF bands
Meter, 0-500 microamp
Potentiometer, 5K, 10 %
Potentiometer, IK, 30%
Potentiometer, 10K, 30%, PCmtg.
Control-100K, PC mtg.
Switch, 9P3P bandswitch
Switch, 4P3P on-off
Transformer 1F44M C
Transformer, balun 75-300 ohm
Transistor, 2N3284
Transistor, 2N3285
Transistor, 2N3286
Transistor, 2N5172
Transistor, 2N1304
Transistor, 2N404
Frequency Dial
Frequency Indicator
Battery Clip
75 ohm coax plug
75 ohm Coax jack
UHF Turner Assembly
Speaker
Knob, bandswitch
Knob, cal, volume, tuning
Case
Cov er
Panel
Battery Mounting plate
Battery Mounting bracket
Frequency dial trim cap/screw
Jumper cable assembly
PART NO.
24G99
24B137-2
19G28A
46A22
46A23
46A19
46G33
46A27 .50
46A41
46A24
23B18 20.00
15A51 1.00
15G50 1.00
15A53
15C 7-13
25B81 8.00
25G82
28C28 2.00
28A 29-1 .75
19G24
19G25 3.00
19G22 2.25
19G29 .50
19G5 1.25
19G4
33B137
33A138
33G143
35G11
36G15
60B1 -2
48A1
21G4
21G16 .25
10C212
10C193
10C141C 10.00
10A145
10A146A
30A35/33A151 .75
13G26/35G11
PRK
.25
6.50
.50
1.50
1.00
.25
.25
.50
1.25
.75
.50
1.50
3.75
1.25
1.25
.50
.25
.50
1.00
25.50
4.00
.25
10.00
5.00
.75
1.00
2.75
(PRICES SUBJEC T TO CHA NGE WITHOUT NOTICE)
$2.00 minimum billing
NOTE: The following alignment procedure replaces that found on pages 15, 16, and
17 of theFSl34 manual #268. Disregard the UHF calibration procedure on page 17.
ALIGNMENT OF THE FS134 IF AND RF CIRCUITS
The IF ci rcuits must be in alignment before the RF circuits are aligned or the unit
is calibrated.
1. Unplug the lead from the VHF tuner to the UHF tuner and inject the output of the
signal generator into the VHF tuner through this ca ble. Set the BANDSWITCH
to the UHF position.
2. Set the signal generator to 43. 4 MHz and the output so that the FS134 meter reads
less than 40 microvolts.
3. AdjustAl, A2, A3, A4, and A5 for maximum reading on the FSI34 meter. Re-
peateach adjustment toobtain a peakand reduce the signal generator output each
time to keep the FS134 meter reading below 40 microvolts.
4. Plug the lead back into the UHF tuner and inject the signal into the XI jack on the
frontpanel. Set the BANDSWITCH to the CHAN 2-6 FM position. Adjust A6 for
a minimum reading at 43. 4 MHz while increasing the generator output to keep the
FS134 meter reading around 40 microvolts.
100 MC
MAX
RF ALIGNMENT, CHANNEL 2 THROUGH 6 and FM BAND
1. Set the FS134 BANDSWITCH to CHAN 2-6-FM position, and set the TUNING con
trol until the cro sshair passes through 60 MHz on the frequency indicating dial.
2. Inject a 60 MHz signal from the generator into the XI jack. Adjust A7 and A8
for maximum meter indication.
3. Set signal generator to 100 MHz and adjust A9 for maximum meter indication.
Adjust A10 while rocking signal generator frequency control back and forth for
the highest maximum (below 40 microvolts) on the FS134 meter.
4. Repeat steps 2 and 3.
RF ALIGNMENT, CHANNELS 7 THROUGH 13
1. Set FS134 BANDSWITCH to CHAN 7-13 and rotate the TUNING control until the
crossha ir passes through 180 MHz on the frequency indicating dial.
2. Set the signal generator to 180 MHz and adjust All and A12 for maximum in
dication on the FS134 meter. Repeat both adjustments for best peak.
3. Set the signal generator to 210 MHz and adjust A13 for maximum meter indication.
Adjust A14 while rocking the signal generator frequency control back and forth
for the highest maximum, keeping the generator output below 40 microvolts on
the FS134 meter.
4. Repeat steps 2 and 3.
30 and 1000 MICROVOLT CALIBRATION PROCEDURE
The accuracy of the calibration of theFS134 will only be as goodas that of the signal
generator used.
1. Set the BANDSWITCH to CHAN 7-13 and the TUNING control to 195 MHz.
2. Set the slide switch on the FS134 to CAL and carefu lly adjust the CAL control
until the meter reads on the CAL line of the met er. Then set the switch to the
ON position.
3. Set the signal generator to 195 MHz and adjust the output until you just get an
indication on the meter jus t above 30 microvolts.
4. Rock the signal generator frequency control back and forth to obtain a peak in
dication on the FS134 meter and then reduce the generator output to 30 micro
volts and adjust the 30 microvolt adjust on the IF board in the FS134 until the
meter reads 30 microvolts.
5. Set the generator output to 1000 microvolts and while rocking the frequency control
on the generator slightly, adjust the 1000 microvolt adjust until theFS134 meter
reads 1000 microvolts at the peak.
6. Repeat steps 4 and 5.
UHF ADJ. PROCEDURE:
1. Set the BANDSWITCH to UHF, the TUNING control to 550MHz, adjust the CAL
control, and note the meter reading for a zero db lOOOuv signal.
2. Set the TUNING control to 800MHz, adjust the CAL control, and note the meter
reading for a zero db lOOOuv signal.
3. Adjust R73 the UHF ADJ. for the best compromise of accuracy at 550MHz and
800MHz.
FORM #732
L _ r _ _ 3 0 0 λ I N P U T ^
____
CO NOITION S
BANDSWITCH 7-1 3
NO S4GINAL INPU T
VO L UME-MINIM UM
SLOE SW ITCH IN
N POSITION AND
?
S I3 4 CALIB RAT ED
* VARIES BETWEEN
UNITS.
FE T VM USED FOR
MEASUREMENTS
|
FSI34 SCH EM AT IC
ISSUE DATE 11 -22 -7 2
RUN 10 R 7 3 ADDED
SEN CO R
INSTALL ATI ON INST R UC T IO N S
FOR THE FS134
BATTERY CHARGER ACCESSORY N O . 39G15
Installation Instructions for the FS134 Battery Charger A ccessory. No. 39G15
operate from a rec hargeable battery, or it can be operated directly from the AC
line. The battery used with this accessory is a nickle-cadmium battery, Burgess
type CD28, Eveready type Y5383 or equivalent. The battery is not supplied with
the a ccess ory; it is available from most pa rts d istributors.
FS134, which compri se the + 12 volt supply. The minus 1.5 volt supply, consis ts
of a single "C" cell, which is not rech argeable because the low c urrent drain on
this supply, only 2 MA, makes this unnecessary.
from the AC line without the rechargea ble battery installed, however the voltage
developed is higher than 12 volts and also there may be exces sive 60 cycle hum at
high volume levels. It is best to always have a battery installed.
cannot be damaged due to overcharging. As the battery comes up to charge the
1N816 stabistor diode reduces the c urrent to the batt ery to a safe level.
The 39G15 Battery Charger Accessory for the FS134 permits the FS134 to
The rechargeable battery rep laces eight of the nine "C " cell batteries in the
The FS134 equipped with a 39G15 battery charger acces sory can be operated
The 39G15 battery charger has been designed so that the rechargeable battery
Installing the 39G15 in the FS134
1. Remove the FS134 from the case by first removing the two phillips screws at
the top of the panel. Place the unit fa ce down on a cloth and remove the two
round head scre ws on the rear of the case. Lift the case off the unit.
2. Remove the single screw holding the battery bracket assembly to the chas sis.
Slide the batterybracketassembly towards the side of the unituntil the assembly
disengages from the chassis hold down clamp. The battery b racket and battery
plate assembly may now be folded open exposing the batteries. Save the three
pie ces of fish paper fo r use when the unit is reassembled .
3. Remove the six " C" cel l batter ies from the battery plate and remove the two
"C" cells that are in series on the battery bracket; the b attery bracke t is the
U shaped bracket. Do not remove the single "C" cell on the battery bracket,
because this will still be used for the minus 1. 5 volt supply.
4. The two battery clips on the battery bracket will be used to mount the recharge
able battery. However, since the rec hargeable battery is a li ttle shorter than
two "C " cells in seri es, it is necessary to extend the contac ts on the clips.
Two 2-56 x 3/8 screws, spacers and nuts are supplied with the 39G15 kit.
Place a spacer over the screw and place this through the center hole in one of
the contacts from the inside. Secure this with a nut from the other side of the
contact. Do the same with the other contact. The rech argeab le b attery will now
make proper contact.
5. Disconnect the black and red wir es that go to the ba ttery clips on opposite cor
ners of that battery plate. One wire comes from the + clip on the bat tery brack
et, the other comes from the c enter terminal of the CAL control. The battery
plate can be discarded.
6. Place the 39G15 battery charger plate in the vicinity of the unit and connect the
two red leads disconnected in step 5 above, to terminal"A"on the 39G15 battery
charger ( see wiring diagram). Solder this connection.
PRIMARY 8 “ BLACK-CONNECT
RE D LEAD FROM
CAL CONTROL
TO AC INTERLOCK
ON PANEL
330H M S
BLK LEAD
FROM PLUS(+)
BATTERY
TERMINAL
IN8I6
8“BU£z
CONNECT TO
HBATTERY
TERMINAL
10" BLUE-—
CONNECT TO
GROUND ON
CHASSIS
SPEAKER TERMINAL
MOUNTING
PLATE
7. Pass the long blue wire from terminal E of the cha rger through the hole in the
chassis and connect to the speaker terminal with the yellow and black wire.
Solder the blue wire to this terminal.
8. Remove the spaghetti from the terminal on the negative battery clip on the batt ery
bracket, but leave the black wire from the OFF-ON switch connected. Connect
and solder the black lead from terminal "D"on the 39G15 charger to the negative
battery terminal. Be sure that the terminal does not short to the battery clip
frame. Wrap a piece of electrical tape around the terminal to prevent shorting.
9. Pass the twisted pair of black wires from the transformer on the charge r through
the hole in the chassis and connect to the AC interlock on the panel. Solder
both connections.
10. Install the rechargeable b attery in the b attery bracket being sure to observe
polarity.
11. Fasten the battery bracket and charger plate to the chassis. Use the fish paper
as before. The large piece goes between the charger plate and the ba ttery
bracket, and the two smaller p ieces are used at each end of the bracket.
12. Install the unit in the case.
13. To recharge the battery, merely insert the cheater cord into the AC inter lock
on the FS134 sub panel and plug the other end into 117VAC line. The FS134
should not be turned on.
To operate the unit from the AC line merely turn the unit on and operate as
you would from batteries.
To operate the FS134, as a portable instrument, remove the cheater cord.
You can operate the FS134 for approximately 10 hours before the battery needs
to be recharged.
TO CIRCUIT
TO CIRCUIT
BROWN
RECHARGEABLE
RED 33-tl IN8I6
15 V ±_ BATTERY
117 VAC
YELLOW
BURGESS CD28
EVEREADY Y 53 8 3
BLACK
OF F-ON
SWITCH
£
^ BLACK
X
I-
I I— ' 3200 SENCORE DRIVE, SIOUX FALL S , SOUT H DAKOTA 5710 7
FORM 888 Printed in U.S.A.
SENCOR
Loading...