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ASSEMBLY AND OPERATION OF THE
HEATHKIT AMATEUR TRANSMITTER
MODEL DX-35
SPECIFICATIONS
Power Input: 65wattCW, 50 watt peak controlled carrier phone
Output Impedance: 50-1000 Q
Output Coupling: Pi network (coaxial)
Operation: CrystaUVFO, CW, Phone
and Coverage: 80, 40, 20, 15, 11, 10 meters
Tube Complement; 5U4GB Rectifier
12AX7 Speech Amplifier
12AU7 Carrier Control, Modulator
12BY7 Crystal Oscillator
12BY7 Buffer
6146 Final Amplifier
Power Requirements; 115 volts AC, 60 cycles, 175 watts
Cabinet Size: 13" wide x81/2" high x9" deep
Net Weight: 21 lbs.
Shipping Weight: 26 lbs.

4S0
HEATHKIT
TRANSMITTER
MODEL
DX-35

INTRODUCTION
The Heathkit Transmitter rhodel DX-35 was designed to permit maximum versatility at area-
sonable price. It features up to 65 watts input with three switch-selected crystal positions for
the novice operator. It includes controlled carrier phone operation and provision for VFO ex-
citation for the generalclass ham. It has sufficient output to drive larger transmitters when the
station is expanded, yet is small enough for field day .operation.
The DX-35 consists of one power supply, three radio frequency stages and two dual purpose audio
stages. Pi network output coupling is used to facilitate antenna matching. The panel controls
consist of akey jack, operation switch, band switch, drive control, pilot light, final tuning,
meter switch and antenna tuning. The mike connector, crystal switch, output connector, VFO
input and auxiMary socket are located on the rear chassis apron.
The following block diagram and circuit description will give the builder abetter imderstanding
of the transmitter. This knowledge is an invaluable aid to construction and a&;,such it is well
worth reading thoroughly. LETHAL VOLTAGES ARE PRESENT AT MANY POINTS ABOVE
AND BELOW THE CHASSIS. CONSEQUENTLY, GREAT CARE MUST BE EXERCISED WHEN
ANY TEST OR ADJUSTMENTS ARE MADE.
ANTENNA'yl^
XTALS
VFO
INPUT
KEY '
INPUT
Figure I
CIRCUIT DESCRIPTION
OSCILLATOR: A12BY7 tube is operated as amodified Pierce crystal oscillator, with the cry-
stals connected between grid and screen throxigh ablocking condenser. Three crystals may
be switched into the circuit by means of adouble pole switch which breaks both connections to
the crystals to prevent interaction. In the fourth switch position, the 12BY7 grid is connected
to ajack for external VFO control and the screen blocking condenser is grounded for screen
bypass.
The plate circuit is untuned for operation on 80 and 40 meters, tuned to 40 for operation on.20
and 15 meters and tuned to 20 for operation on 10 meters. TheTbscillator is capacity couple'd to
a12BY7 buffer stage.
Plate and screen voltagefor the oscillator st^e are derived from the buffer stage cathode. The
two 12BY7 tubes are operated in series across the 600 volt suplpiy and receive approximately
300 volts apiece. This eliminates the necessity of power-wasting- dropping resistors.
Page 3

BUFFER: The 12BY7 buffer stage has an independent filament supply to prevent heater-to-
cathode breakdown as this cathode is 300 volts above the other tubes. The plate of the buffer
is shunt-fed directly from the 600 volt supply through a1.1 mh RF choke. The plate circuit for
the buffer stage actually appears in the grid circuit of the 6146 amplifier. The buffer plate is
capacity coupled to the amplifier grid coils and is tuned along with the amplifier grid.
FINAL AMPLIFIER: By placing the tuned circuit in the grid of the final amplifier, the normal
grid RFchokeis eliminated. This lessens the possibility of low frequency parasitics due to the
grid choke and also the chance of coupling from the final grid choke to the shunt-feed choke of
the buffer stage. An air trimmer capacitor across the grid coils adjusts the grid drive by tun-
ing the grid for maximum efficiency across the band.
The plate circuit is shunt-fed through a2.5mh RF.choke andcapacity coupled into the pi network
tank circuit. For operation at 80 and 40 meters, a68 ^l|x^ 1000 volt fixed capacitor is automat-
ically paralleled with the plate tuning capacitor by means of the bandswitch. A900 uiif variable’
capacitor is permanently connected across the output of the pi circuit for antenna loading.
s
MODULATOR: A12AX7 tube is used as atwo-stage resistance coupled speech amplifier. The
output of the speech amplifier is split into two channels, one of which feeds one-half of a12AU7
acting as acontrol tube. The control tube averages the audio level in its cathode circuit as a
DC bias which is applied to the other half of the 12AU7 acting as acathode follower. The other
half of the speech amplifier output is applied to the grid of the cathode follower and appears as
asuperimposed audio signal on the DC output of the cathode follower. The combined output of
the cathode follower is applied to the screen of the 6146 RF amplifier and results in avarying
DC screen voltage with an audio component. The net result is achange in both RF output and
modulation as the audio level changes.
POWER SUPPLY; The power supply consists of atransformer-operated full wave rectifier cir-
cuit with achoke input filter. Two filter capacitors are operated in series to withstand the
voltage involved. Two Identical resistors across the filter capacitors serve adual purpose of
equalizing the filtervoltage andacting as ableeder resistor to stabilize the output under varyii^
load conditions. A5U4GB tube is used as the full wave rectifier. This tube is aheavy-duty
version of the regular 5U4G. Some of the tube ratings have been exceeded while others are
operated under the maximum permissible. Tests have indicated that by using the heavy duty
tube with choke input and alight current load, no difficulty should be encountered.
NOTES ON ASSEMBLY AND WIRING
Many of these kits will probably be constructed by people just starting in the amateur radio field.
Consequently, the step-by-step instructions in tWs manual have been covered in considerable
detail. Read each step completely through and be Sure it is understood before proceeding with
the operation called for. This will assure that acomplicated step is performed in the proper
sequence in order to complete it with the least possible difficulty.
There is considerable similarity between the screws and nuts of the 3-48 and the 4-40 hardware
supplied. Before using these pieces, examine them closely to determine that you have the part
called for in the instructions. This is particularly true of the small size 4-40 nuts which re-
semble 3-48 nuts in physical size. These nuts may even hold on a3-48 screw, but will, feel
loose. If any doubt exists, try the nut on a4-40 screw to check it. There are only three of these
and they should be used in mounting the crystal sockets.
In the design of the Heathkit DX-35, no effort was spared to obtain the highest quality components
and assemble them in the best possible arrangement. By the same token, the kit builder should
exercise agreat deal of care during assembly and wiring. Only by putting the best possible
workmanship into the kit, can best results be obtained from it. There is also a great deal of
personal satisfaction in aneat, professional-lookingtransmitter, resulting from careful assem-
bly and wiring. Acommon factor of radio frequency instruments is the critical placement of
leads and components. The use of extensive shielding in the DX-35 has eliminated agreat deal
of this. However, the lead dress shown in the pictorials and bottom chassis photograph should
be followed carefully.
Page 4

This manual is supplied to assist you in every way to complete the DX-35 with the least possible
chance forerror. We suggest (hatyou take afew minutes now and read the entire manual, omit-
ting the step-by-step instructions, before any work is started. This will enable you to proceed
witii the work muc'h faster when construction is begun. The large fold-in pictorials are handy
to attach to the wail above your work space. Their use will greatly simplify the construction of
the kit- These diagrams are repeated in smaller form within the manual. We suggest that you
retain the manual in your-files for future reference both in the use of the DX-35 and for its main-
tenance. During the initial testing of the transmitter, it will be out of its cabinet. REMEMBER
THAT VOLTAGES DANGEROUS TO LIFE ARE PRESENT AT PRACTICALLY ALL POINTS
ON THE CHASSIS.
NOTE; Sometimes the builder may find aplace where it is difficult to hold a nut for assembly.
Using long-nosed pliers, press apiece of solder across one side of the nut until the solder is
forced part way into the threads. This will hold the nut and furnish anarrow handle useful for
inserting the nut into tight places.
During the assembly and wiring procedure, arag or some soft material should be placed over
the work bench to prevent marring or scratching the chassis or component finish. Capacitors,
resistors and transformers usually have leads longer than necessary to make the indicated con-
nections. In the interest of both efficiency and appearance, the leads should be cut to an appro-
priate length before the connections are made.
In many cases, the specified wire lengths may seem long. These lengths were chosen so the
wire could be run close to the chassis and formed for the best appearance. Marking the letters
of the tube sockets and terminal strips on the chassis as they are installed will be a great help
during the wiring procedure.
The actual tube markings may differ from the type specified in the parts list by an additional
suffix (A, B, GT, etc. ). This denotes aminor variation which will not affect the operation of
the completed instrument.
In order to expedite delivery to you, we are occasionally forced to make minor substitutions of
parts. Such substitutions are carefully checked before they are approved and the parts supplied
willworksatisfactorily. By checking the parts list for resistors, for example, you may find that
a2KG resistor has been supplied in place of a2.2 KfJ as shown in the parts list. These changes
are self-evident and are mentioned here only to prevent confusion in checking the contents of
your kit. We strongly urge that you follow the wiring and parts layout shown in the manual. The
position of wires and parts is extremely critical in astable transmitter and changes mayser-
iously affect the charjK^teristics of the circuit. Resistors and condensers generally have atoler-
ance rating of *10% unless otherwise stated In the parts list. Therefore, a100 KSl resistor may
test anywhere from 90 Kfl to 110 Kf2. The letter Kis commonly used to designate a multiplier
of 1000. PROPER SOLDERING PROCEDURE
Only asmall percentage ofHeathkil purchasers find itnecessary to return an instrument forfac-
tory service. Of these, by far the largest proportionfunctionimproperly duetd'pooror improper
soldering.
Correct soldering technique is extremely important. Goodsolder joints are essential if the per-
formance engineered intothe kit is to befully realized. If you are abeginner with no experience
in soldering, ahalf-hour's practice with odd lengths of wire and atube socket will be aworth-
while investment.
High quality solder of the proper grade is most important. There are several different brands
of solder on the market, each clearly marked ’’Rosin Core Radio Solder.” Such solders consist
of an alloy of tin and lead, usually in the proportion of 5050. Minor variations exist in the mix-
ture such.as 40:60, 45:55, etc. with the first figure indicating the tin content. Radio solders are
formed with one or more tubular holes through the center. These holes are filled with arosin
compound which acts as aflux or cleaning agent durir^ the soldering operation.
Page 5

OPERATION SWITCH
X
age 8

iU-move the nuts and washers holding the operation switch and the phone jack. Leave the
''nut on the tuning capacitor in place.
\ivlore actually mounting the panel over the controls, bring it close enough to the chassis
*U) mount the double-pole double-throw slide switch using 6-32 hardware. The side of the
/switch having the yellow and brown wires goes on the side labeled PLATE.
I )
'[ urn the chassis on its back and slip the panel over the control shafts. Replace the flat
^
^washers and 3/8” nuts.
1On the final tuning capacitor, brii^ the nut on the bushing up until it is against the rear of
*
'tiio panel, with the panel perpendicular to the chassis. Add aflat washer and nut on the front
ul' the panel and tighten.
\j Connect a.005 p.fd disc ceramic capacitor from the +meter terminal to the -meter ter-
*\nnal (NS). See Pictorial 3.
)Connect the red wire from the slide switch to the +meter terminal (S).
L\
)
Connect the brown wire from the slide switch to the -meter terminal (S). These wires
should lie flat against the panel to clear the coil.
1Cut both leads of the parasitic choke to 7/8" lei^ths. Connect one lead to aceramic plate
,cap and solder. The other lead will connect to the top terminal of the 2.5 mh RF choke (S).
Press the dial light jewel into the panel space marked POWER, and bend the tabs over on
the rear of the panel.
Install asmall red knob on the shaft marked DRIVE.
Installround skirt knobs on the band and operation switches and orient withthe panel mark-
ings. Tighten the set screws.
('
)
Install around skirt knob on the crystal switch on the rear chassis apron.
()Turn both tuning capacitors to full mesh and install pointer knobs with the indicators at"0"
)insUU ^heVlot light and the tubes as shown in Pictorials 1and 3. Place the tube shield
over the 12 AX7 tube.
This completes the assembly and wiring of the DX-35 Transmitter.
PRF.T.TMINARY OPERATION CHECKS
(
Before applying power to the transmitter, examineyourwiringverycarefullyfor possible shorts,
such as tube pins touching, resistor or capacitor leads contacting the chassis or shield plates
andswttchcontacts shorting to the switch frame. Also be sure no wire clippings or solder drops
are still in the chassis.
If there are any short circmts, serious damage will result to the tubes and components when
power is applied. As an additional check, connect an ohmmeter from tube pin El to ground,
WITH THE POWER OFF. It should read approximately 30 Kf2 in all positions of the operation
switch except the phone position where it will read approximately 22 Kfi. Any abnormal reading
must be completely investigated before applying power.
Again before applying power, check all solder connections. Make sure none have been missed
and that all are good electrical connections. Check the coax connector (center) with an ohmme-
ter for "open”, and the mike connector (center) for 1megohm resistance.
TUNING INSTRUCTIONS
If any of the following tests cannot be performed or show abnormal indications, turn to the section
of the manual entitled IN CASE OF DIFFICULTY. Set the transmitter up as follows: crystal
switch in any position (no crystals or VFO plugged in), key plugged in, operation switch OFF,
Drive control in any position, bandswitch 10-11 meter position, output tumng any position,
GRID-PLATE switch in PLATE position, final tuning any position.
Plug the line cord into a117 volt AC receptacle. Nothing should happen; if anything does, pull
the line cord immediately. There is trouble in the AC power circuits which must be corrected
before proceeding. If operation is normal so far, switch the operation switch quickly past the
CW position to the STANDBY position.
Page 25

Switc^h to PHON^^^^itiSr wm no meter or any other indication yet.
Depress the key momentarily. The meter terminals SO use caution
When the crystal knob index is\olard thrcJLs.^ti Release key.
.0 the VKO lack or any other ot three
f’DM to 7150 should be used.
bandswitch to 10 meters and connect adummvJri^H *crystal switch for this socket. Set the
bolt to the center of the coax connector ^^gi'ound
"onTroUo'?;" :cTor“llJ retedf^XValrtr“1
“> ‘-ding
=fehir.et^;rii^- -d ^"^LrreT.: rafpirc^n^i^
providing iLmsj.0L^^,,,eSS£:
tor coil screwdriver, tune the 20 meter oscilla-
12BY7 tubes. screwdriver adjustment on top of the chassis between the two
key and tune fir mltL^swftcT^^^ PLATE. Depress the
maximum, not exceeding 3ma. Tune thl 40 mSei^nr nf" adjust the DRIVE control for
and power transformer) for maximum. No fuX; Sf/arV
this socket. Set the bTndswitcrfor^^^ the crystal switch for
key. Adjust the plate for minimum current depress
set the operation switch to CW position. Depress the ifev^anJ^'"^ ^key and
100 at the same time zaaintalnina the din in n)atja Vand advance the antenna tuning toward
bulb should reach full brilliance with fplate curren^^^^^
and set the operation switch to STANDBY Connect aRelease the key
phone to the mike connector and remove the ZT\: .^
the microphone. The light should vary in brilliLce ^Normon^^?^^ position and speak Into
Its antenna removed; the speech should be clear.
*^the signal on areceiver with
l" «on rS.ratoSrttor‘Se.‘"wi?k^ ^j""'
-n'c“/ iS “ofo?rh?c^rr
Crystals may be changed through the door in the back of^tlS’cabinet.'^^^'^^
meter bands, 40 meter
be used for operation in the 10 -11 Lter b^ meter bands. 20 meter crystals can
operation
Pin 2and gr^^d^^pL”? o?\r250
operating aVFO. The VF 1nnwpr rTiL ,?^control on pin 8for
£BftJ»ite&43fi-Phone/tiie plgigLc^rent ^o PHONE- 'When
100 mills on modulatiom to 5gjnills) and kick' iipfrafeout
IN CASE OF DIFFICULTY
consequently, the first step is to
the wiring will locate an error consist^tly oveHooked Slaving a friend check
Page 26

Also, with miniature sockets there is apossibiUty of shorts between adjacent socket terminals
due to the close spacing. This should be checked and if any doubt exists, the terminals should be
pried apart until obvious spacing can be seen between them.
Sometimes apparently good solder connections will have an insulating coating of rosin between
the wire, the terminal and the solder. This is often the case when insufficient heat was applied
in soldering. An ohmmeter check of any questionable connections will test for this condition.
Naturally, all voltages should be "off” f6r such tests.
Be sure to reread the circuit description on Page 3so that "cause and effect” reasoning maybe
employed as the search for trouble progresses. Usome difficulty still persists after the steps
outlined have been completed, attempt to localize the trouble to aparticular stage in the trans-
mitter circuit. Use the tuning procedure as abasis for localization and refer to the block dia-
gram and schematic to visualize circuit relationships. The panel meter and station receiver are
extremely valuable tools to use in locating trouble.
NOTE: For the tracing procedures outlined below, use the schematic diagram for reference.
If any activity is noted when the line cord is plugged in and the operation switch is in OFF posi-
tion the AC circuit should be traced. One side of the line cord is connected directly to one side
of the primary of the power transformer. The other side of the line cord is connected to one
black cable wire which should connect to either 11 or 12 of the operation switch; the other black
cable wire returns from switch terminal 12, if 11 were used before, to the other primary side
of the transformer. Contacts 11 and 12 of the switch thus control line power to the transformer.
Also check the two .005 disc ceramic capacitors connected across the line for shorts.
If the tubes and pilot light do not light up when the operation switch is set to STANDBY position,
again check the AC circuit with power off to determine why the transformer is not receiving
power. If the tubes light up and the meter also reads in PLATE position, or some other indica-
tion of high voltage being applied is apparent, check the following. Unplug the line cord then with
an ohmmeter, check from lug FF5 toground. It should read an open circuit. This is the power
transformer center tap. The white cable wire at FF5 should connect to terminal 7 of the opera-
tion switch and through terminal 6to ground but not be grounded in the STANDBY condition.
Check this wiring to be sure it is correct. CAUTION: The following tests are made with power
on; use extreme care. With the operation switch in PHONE position, the KEY depressed, and
the meterin PLATE position, it should read about 1/2 to 2/3 scale, when not tuned to resonance.
If the meter shows little or no indication, check the screen voltage at pin 3of the 6146 tube
with aVolt-Ohm-Millameter (VOM), using aDC range of at least 150 volts. The screen should
read about 40 volts. If less than this, trace back through contact 3of the operation switch,
through contact 1to pin 8 of the 12AU7 tube; all should read 40 volts. Switch the meter to ahigher
range, 500 volts, and check pin 6of the 12AU7. This should read about 400 volts. If the volt-
ages are missing or very far from normal, using the voltmeter on a750-1000 volt scale and the
schematic diagcam, trace the voltage back to its source at the rectifier pin 1.No voltage at El
indicates an open power transformer primary, open power transformer center tap outlined in
the steps above, deifictive rectifier tube 5U4GB orashort circuit. The latter would probably
have made itself known by now.
If the oscillator slug tuned coils cannot be adjusted as described, make sure the 40 and 20 meter
coils have not been interchanged, that the windings are connected in series (outside lead of 40
meter coilshould connect to inside lead of 20 meter coil) and that the coils are connected prop-
erly to the switch.
If too little or no grid drive is available, there is the possibility that the final grid coils have
been interchanged. Arough check can be made by noting the size of wire and apparent number
of turns. Fine wire and more turns are used on the low frequency coils, with progressively
larger wire and lesser turns as 10 meters is approached.
Page 27

No grid drive may be traced back to the oscillator. Turn the power off and remove final tube.
Then turn to CW and listen with areceiver for the oscillator. Try different crystals. If no
signal is heard, check plate voltage of oscillator at pin 7and screenvoltage at pin 8. Alsomake
sure KEY is closed. There should be about 300 volts on the plate and about 200 on the screen.
As the two 12BY7 tubes are in series, no volt^eon the oscillator may be due to an open circuit
or defective 12BY7 in the buffer stage. Consequently, both stages must be operating properly
to obtain grid drive. The plate voltage of the buffer stage will be about 600 volts to ground and
its cathode should be about 300 volts to ground. Kthe voltages differ greatly remove power and
completely check the circuit.
Failure to obtain adip when tuning the final amplifier may be due to lack of grid drive, incor-
rectly wired tank coil, loading capacitor advanced too far (insufficient capacity, shorted coax
line or, on 80 and 40 meters, ashort in the padding capacitor (68 mmf 1000 volts).
NOTE: When using the DX-35 onCW with theVF-1, the VF-1 operation switchshould be placed
in the standby position and the key plugged into the DX-35, For best results with either crystal
or VFO, the grid should be adjusted to between 2and 3milliamperes.
INSTALLATION AND OPERATION
NOTE: It should be noted that an Amateur Radio Operator and Station License is required to
place this transmitter on the air. Information regarding licensing and amateur frequency al-
locations may be had from publications of the Federal Communications Commission or the Am-
erican Radio Relay League. This transmitter can be used for novice operation only if the fol-
lowing two requirements are met: (a) CW operation only, (b) Crystal control only, on assigned
novice frequencies.
CffiOUNDING: The importance of agood ground that presents low impedance at all frequencies
cannot be emphasized too strongly. What may be a perfectly satisfactory ground at 80 meters
could place the transmitter considerably above ground at the higher RF frequencies. As an ex-
ample, the length of the ground wire is sometimes critical. An 8foot wire from the transmitter'
to groundwould be a direct short at 80 meters but becomes one-quarter wave length at 10 met-
ers and therefore places the chassis at ahigh RFpotential. Some hints that will be of assistance
in obtaining agood ground are;
1. Connection for the ground should be made to cold water or well pipes and/or multiple pipes
or rods driven approximately eight or more feet into moist earth. Asalt solution poured
around the ground rods will further increase the conductivity to ground. Amore elaborate
installation might include asystem of wires approximately one-quarter wave length long
laid afew inches under the surface of the earth in agrid or radial pattern. The use of one
or all of these grounding systems may be combined to form agood groxmd reference.
2. The electrical connection to the ground pointshould consisbof ashort heavy conductor (#12
wire or heavier, or copper braid). If ashort ground wire is difficult to obtain because of
transmitter location, several leads of random lei^h may be used. The use of random leads
lessens the possibility that all leads should become one-quarterwavelengthat the frequency
of operation. If the transmitter becomes hot at one particular frequency, the addition of a
ground wire cut to one-half wave length at this frequency may clear up the difficulty.
Some of the symptoms of inadequate grounding are manifested in the form of:
1. Inability to load the antenna properly,
2. High RF potentials on the chassis or case of the transmitter.
3. Undue voltage strain on output circuit components.
4. Final plate current reading affected by touching the panel or case.
Page 28

LOCATION: The transmitter should be located where free circulation of air is possible and
objects should not be placed on the case as this might restrict the circulation of air. Good ven-
tilation is essential to insure maximum component life. The considerations mentioned with re-
gard to grounding will also affect the selection of agood location, as will the point of entry of
the antenna feeder.
OPERATION: The tuning procedure outlined previously will also apply when loading an actual
antenna. Some special cases involving particular antenna types will require special considera-
tion and will be covered under antennas.
ACCESSORY SOCKET
The octal accessory socket on the rear of the
chassis was provided to furnish power for an
external VFO such as the Heathkit V-F-1. Fila-
ment power is provided between pins 2and 7
with 7being ground for operation of an external
unit having one side of the filament at ground
potential. Pin 4supplies B+ voltage through a
20 Kn 10 watt resistor. This provides approxi-
mately 250 volts at 20 milliamperes. Pin 8is
connected to the cathode keying circuit and allows
an external VFO to be keyed along with the DX-35.
Pin 1is grounded for the shield cable between
the transmitter and VFO. See Figure 8.
ANTENNAS: The pi network output circuit of the model DX-35 will match pure resistive loads
from approximately 50 to 1000 U. The loadingadjustment will matchall impedances within these
limits. Therefore the transmitter will match antennas and unbalanced lines within these limits,
also, provided such antennas or lines are nonreactive. Reactive antennas or lines present a
somewhat different problem, however, since the reactance takes the form of impedance which
may raise or lower the antennas impedance beyond the matching range of the transmitter output
circuit.
Balanced antenna systems should be fed through an antenna coupler so that neither leg of the line
nor the antenna will beat ground potential. Normally the output of the transmitter is unbalanced
since one side of the output circuit is grounded.
When loading to either abalanced or an unbalanced system, the maximum loading point of 125
milliamperes in the final stage should not be exceeded. In many instances, the transmitter will
load to ahigher level, but the harmonic suppression of the pi network is better if the output
coupling capacitor is not reduced to absolute minimum value. Then too, the extra 10 or ISwatts
which would be gained by maximim loading would not make any appreciable difference at the
receiving end of the transmissi<^
END-FED HERTZ AND MARCONI ANTENNAS
This type of antenna consists merely of asingle wire from one-fourth wave length long to any
even multiple thereof. One end of the wire is coupled to the transmitter and the other end sup-
ported in space. If this antenna is operated against ground, it is known as aMarconi antenna,
while if the length is one-half wave length or more, it is known as aHertz antenna. The great-
est disadvantage of feeding a single wire is the necessity of bringing part of the radiating element
into the radio room where its proximity to nearby objects increases losses. The greatest ad-
vantage of such an antenna is the simplicity with which it may be constructed and its compact
size where space is at apremium. Providing the reactance of such antennas is not excessive,
they may be loaded satisfactorily with the pi network output circuit of the DX-35.
Page 29

The length of such antennas should be calculated from the information given in the Radio Hand-
book or the ARRL Antenna Manual. Random lengths mayalso be used effectively except for some
critical antenna lengths where the antenna impedance becomes too high or too low to be matched
satisfactorily at the output of the transmitter. When such asituation is encountered it can usu-
ally be recognized by the action of the loading controls on the transmitter. Should it be found
that increasing the loading (reducii^ the output coupling capacitor value) does not raise the final
amphfier plate current reading on the meter and yet the final amplifier has not become fully
loaded, it is very likely that the antenna being used has ahigher than normal reactance at the
frequency of operation, resultii^ in the transmitter looking into ahigher overall impedance.
Kit is found that achange in coupling capacitor value has little effecton the final amplifier load-
ing and does not affect the final amplifier tuning in the normal fashion, the antenna in use is
probably presenting lower than normal impedance to the transmitter.'
When the antenna impedance is too high or too low for satisfactory loading, the situation can
usually be remedied by changing the length of the feedUne to the antenna, the length of the an-
tenna itself or the point at which the feedline is connected to the antenna. Small changes not to
exceed one-quarter wave lengfth should be effective in correcting the impedance mismatch.
Another cure for such difficulty would be to introduce inductance or capacitance in series with
the antenna and feeder to cancel out the undesirable reactance in the antenna. Of course amore
elaborate method would be the use of an antenna tuner if some element in the situation made it
impractical to employ the methods outlined above.
BALANCED ANTENNA FEEDERS AND SYSTEMS
In the average station it will be found expedient to have the radiating portion of the antenna some
distance from the transmitter. This statement assumes that the amateur will have hie antenna
up high and clear of nearby objects, whereas the actual transmitter may be in the basement or
any other room in the home. In such a case, some form of transmission line must be used to
efficiently connect the transmitter to the antenna. In many instances, the transmission line is
of the "balanced” type in which neither leg of the line is grounded. Such transmission lines may
be either tuned or untuned, but in either case, abalanced line must be fed through an antenna
coupler or "balun” colls. The coupler also provides the means for matching the impedance of
the antenna, which will vary depending upon the type of antenna employed. Atypical antenna
coupler circuit is shown in Figure 9on Page 30.
Basically the antenna coupler is an Impedance transformer, transforming the impedance of the
transmitter to the impedance of the transmission line and antenna system.
Referring to Figure 9, coil LI should match the
impedance of the coaxial cable as closely as pos-
sible at the frequency of operation. The circuit
consisting of L2, Cl and C2 must tune to the
transmitter frequency. If it is desired to series
tune the antenna, the shorting bar between 3and
4is opened and the transmission line connected
at these points. For parallel tuning, 3is shorted
to 4and the transmission line connected to 1and
2. Taps are provided on the coil L2 to facilitate
matching the transmission line.
Such aunit can be built up from this or other su^ested circuits or may be purchased commer-
cially as acompleted iinit. In any case, feeding folded dipoles, end-fed "Zepps"and similar an-
tenna types will require an antenna coupler or balim coils since the normal output of the DX-35
is designed for single-ended, unbalanced operation.
o2
Figure 9
Page 30

LOW PASS FILTERS: The harmonic rejection of the pi network output circuit of the DX-35 is
excellent and will attenuate harmonics considerably when the transmitter is properly grounded
and carefully tuned. However, additional harmonic attenuation may be hadwith the use of alow-
pass filter between the output of the transmitter and the feed line or antenna. Such afilter should
be designed to handle the maximum power output of the transmitter and must be operated into its
nominal impedance.
Needless to say, no attempt has been made here to cover the theory of antennas, as such, since
much has been written on this subject. The possibilities in different antenna types and different
feed systems are many and the factors mentioned herein only scratch the surface of the subject.
Each operator will need to do his own investigation into the advantages and disadvantages of the
various systems to determine just which one will best suit his needs. Basic data is available
through the Radio Amateur Handbooks and other technical publications.
Some formulas that should prove helpful are listed as follows;
,,,300,000 meters
1wave length in space =
^kc
468
Center fed dipole one-half wave long (length in feet) =
Folded dipole one-half wave long (length in feet) *
Zerp antenna one-half wave long (length in feet) =492
f’mc
REPLACEMENTS
Material supplied with Heathkits has been carefully selected to meet design requirements and
ordinarily will fulfill Its function without difficulty. Occasionally improper instrument opera-
tion can be traced to afaulty tube or component. Should inspection reveal the necessity for re-
placement, write to the *h Company and supply all of the following information:
A. Thoroughly identify the part in question by using the part number and description found in
the manual parts list.
B. Identify the type and model number of kit In which it is used.
C. Mention the order number and date of purchase.
D. Describe the nature of defect or reason for requestii^ replacement.
The Heath Company will promptly supply the necessary replacement. Please do not return the
original component until specifically requested to do so. Do not dismantle the component in
question as this will void the fJteantee. If tubes are to be returned, pack them carefully to
prevent breakage in shipment a«) broken tubes are not eligible for replacement. This replace-
ment policy does not cover the free replacement of parts that may have been broken or damaged
through carelessness on the part of the kit builder.
SERVICE
In event continued operational difficulties of the completed instrument are experienced, the fa-
cilities of the Heath Company Service Department are at your disposal. Your instrument may
be returned for inspection and repair for aservice charge of $5.00 plus the cost of any additional
material that may be required. THIS SERVICE POLICY APPLIES ONLY TO COMPLETED
INSTRUMENTS CONSTRUCTED IN ACCORDANCE WITH THE INSTRUCTIONS AS STATED
IN THE MANUAL. Instruments that are not entirely completed or instruments that are modified
in design will not be accepted for repair. Instruments showing evidence of acid core solder or
paste fluxes will be returned not repaired.
Page 31

The Heath Company is willing to offer its full cooperation to assist you in obtaining the specified
performance level in your instrument. Factory repair service is available for aperiod of one
year from the date of purchase or you may contact the Engineering Consultation Department by
mail. For information regarding possible modification of existing kits, it is suggested that you
refer to any one or more of the many publications that are available on all phases of electronics.
They can be obtained at or throi^h your local library, as well as at any electronic outlet store.
Although the Heath Company sincerely welcomes all comments and suggestions, it would be im-
possible to design, test, evaluate and assume responsibility for proposed circuit changes for
specific purposes. Therefore, such modifications must be made at the discretion of the kit buil-
der according to information which will be much more readily available from some local source.
SHIPPING INSTRUCTIONS
Before returning aunit for service, be sure that all parts are securely mounted. Attach atag
to the instrument giving name, address and trouble experienced. Pack in arugged container,
preferably wood, using at least three inches of shredded newspaper or excelsior on all sides.'
DO NOT SHIP IN THE ORIGINAL KIT CARTON AS THIS CARTON IS NOT CONSIDERED
ADEQUATE FOR SAFE SHIPMENT OF THE COMPLETED INSTRUMENT. Ship by prepaid
express if possible. Return shipment will be made by express collect. Note that acarrier can-
not be held liable for damage in transit if packing, In HIS OPINION, is insufficient.
SPECIFICATIONS
AH prices are subject to change without notice. The Heath Company reserves the right to dis-
continue instruments and to change specifications at any time without incurring any obligation
to Incorporate new features in instruments previously sold.
WARRANTY
The Heath Company limits its warranty of parts supplied with any kit to aperiod of three (3)
months from the date of purchase. Replacement will be made only when said part is returned
postpaid, with prior permission and in the judgment of the Heath Company was defective at the
time of sale. This warranty does not extend to any Heathkits which (ittKe been subjected to mis-
use, neglect, accident and improper installation or applications. Material supplied with akit
shall not be considered as defective, even though not in exact acco»*^?jice with specifications, if
it substantially fulfills performance requirements. This warrant«.ii not transferable and ap-
plies only to the original purchaser. This warranty is in lieu of*^i other warranties and the
Heath Company neither assumes nor authorizes any other personWassume for them any other
liability in connection with the sale of Heathkits.
The assembler is urged to follow the instructions exactly as provided. The Heath Company as-
sumes no responsibility or liability for any damages or injuries sustained in the assembly of
the device or in the operation of the complete instrument.
HEATH COMPANY
Benton Harbor, Michigan
Page 32

papt parts
No. per Kit DESCRIPTION PART
No. PARTS Per Kit DESCRIPTION
Resistors Switches-Meters- Tubes
1-18 15600 U1/2 watt 60-2 1DPDT slide switch
1-25 147 Kn 1/2 watt 63-113 1Bandswitch
1-26 1100 Kfi 1/2 watt 63-114 1Operation switch
1-29 1220 Kn 1/2 watt 63-115 1Crystal switch
1-33 2470 1/2 watt 407-33 1 3 ma meter
1-35 31meg 1/2 watt 411-2 15U4GB tube
1-37 22.2 meg n1/2 watt 411-25 112AU7 tube
1-40 110 meg Q1/2 watt 411-26 112AX7 tube
1-49 122 0, 1/2 watt 411-69 212BY7 tube
1-lA 1470 n1watt 411-75 16146 tube
1-5A 222 Kn 1watt 412-1 1#47 pilot light
1-7A 147 Kf2 1watt 413-2 1Pilot light jewel
1-20A 1330 SI 1watt Sockets-•Terminal Strips-Knobs
1-24A 14700 n1watt 431-15 4l-lug terminal strip
1-28A 1100 Kfl 1watt 431-10 23-lug terminal strip
1-30A 2220 KU 1watt 431-11 15-lug terminal strip
1-46A 227 Kn 1watt 431-12 34-lug terminal strip
1-47A 13900 n1watt 431-16 42-lug terminal strip
1-lOB 247 Kn 2watt 432-3 1Microphone connector
1-18B 233 KO 2watt 434-21 1Pilot light socket
2-100 112 SI 1% precision 434-38 3Crystal socket
2-101 1500 1% precision 434-39 3Octal socket
3-8J 215 KJ7 10 watt 434-42 1Phono socket
3-9J 120 10 watt 434-43 19-pin miniature shielded socket
434-56 39-pin miniature socket
Capacitors 436-4 1Phone jack
20-31 368 1kv silver mica 436-5 1Coaxial jack
21-7 133 upMisc ceramic 100-M54 2Pointer knob, large
21-9 1loop '00 V. disc ceramic 462-19 3Pointer knob, small
21-13 1500 p00 V. disc ceramic 462-36 1Red knob, small
21-14 3,001 p00 V. disc ceramic
21-27 9.005 uf )0v. disc ceramic
21-31 4.02 4fd 600 V. disc ceramic Colls-Chokes-Transformers
21-42 1.01 pfd 1600 volt 40-79 140 meter oscillator coil
21-43 11 .001 pfd 1kv disc ceramic 40-8O 120 meter oscillator coil
23-10 1.05 pfd 600 volt paper 40-81 180 meter buffer coil
25-33 320 pfd 450 V. electrolytic 40-82 140 meter buffer coil
25-35 12pfd 50 volt electrol^ic 40-83 120 meter buffer coil
26-9 1450 (xpf yble, dual 40-84 115 meter buffer coil
26-31 1140 ppf vr ble 40-85 110 meter buffer coil
26-32 111 Mpf van -jle 40-86 1Amplifier plate coil
45-4 11.1 mh RF choke
Mptal Parts 45-21 12.5 mh RF choke, 250 ma.
90-4? 1Cabinet 45-19 1Parasitic choke
5nn_ivTafi 1Chassis 46-12 17henry 150 ma filter choke
203-88F119-120 1Panel 54-38 1Power transformer
204-9 1Angle bracket
204-M100 1Tube mounting bracket
204-M101 1Switch mounting bracket
206-3 1Tube shield
206-M40 1Amplifier shield
206-M42 1Oscillator shield
206-43 1Coaxial shield
page 33