Ameco PT User manual

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AMECO PREAMPLIFIER
MODEL PT
The AMEC0 Model PT Preamplifier is a unit that may be added to most existing trans-
ceivers in the frequency range ot l.B to 54 MHzf improving the gain, noise ftgure,
spurious signal and image rejection of the receiver section. This All-New pf ImgCO
Preamplifier has been designed -oecifically for use with a transceiver. The sophis-
ticated control circuitry incorpoi '-t permits the PT to be added to virtually any
transceiver without modiflcation. Ttre fundamental requirement is that the transceiver
have control circuitry built in for use with a !'1near ampl if ier. This I inear ampl if ier
control circuitry is used to bypass the preamplifier during transmit mode or to control
the I inear ampl ifier dlrect!y. When the transceiver I inear ampl ifier control
ci rcuitry actuates the relay in the PT, additional contacts in ifr.-pf -"ontiol the
linear so that loss of linear amplifier facility does not result.
The PT consists of a tuned RF amplifier, covering all the amateur bands from 150
throuqh 5 meterc sndi in oiiili,-::,, lll ..i:. l;.ig,: ,Ioadcasts, as wel i as otlrgr services
within this frequency range. The Mo"del PT employs a low noise frame grid tdbei pro-
viding a noise figure of 1.5 to'3.5 db, over the frequency range of i.B to S4'nnz.
The PT Preampl if ier wi ll be found especial ly ef fective wiir, tr,or" transceivers em-
ploying the Pl output network of the transmitter section as the receiver RF stage
input. Most transceivers of this type begin to suffer a noticeable decrease in sensi-
tivity on l5 meters and especiatly on 10. The PT will be most beneficial on these
bands and the inclusion of 6 meters makes it r.rsable with those second receivers having
a 6-meter range or with the newer 6-meter single-sideblna tnansceivers.
ln addition, the output of the frame grid RF amplifier seition feeds an isolation net-
work with two outputs. One output is used to feed the transceiver input when re-
ceiving, while a second output is used to feed a second receiver, which may be of the
general coverage or amateur-band-only type. The built.-in relay of the pT also includes
a set of contacts with three terminals brought out to tfie reai of the cabinet so that
either normally-open or normally-closed receiver mutinglmay ne employea in the sec-
ond receiver, whenever the transceiver transmits.
The PT is designed specifical ly for I I7-vol t 60-cycle operation.
The input and output impedances are nominally 50 ohms to match most popular types of
amateur installations. The input and output impedances of the pT are not critical and'
therefore no adjustments or modifications are necessary with other impedances.
The AMECO PT is truly a great step forward in increasing the flexibility of a trans-
ggiver equipped amateur station. The use ofra second reieiver with its extremely
Ax-rble operating characteristics will be greatly appreciated by the contest, DX,
?y-Brffiious.operator,.both with cw and single sideband. once the operator has
A DIVISION OF
AEFTOTRON, INC RALEIGH, N.C
INSTRUCTIONS
ustomed to a typical setup using a transceiver, together with a pr and a
$v"r, he will wonder how he ever got along wiihout it.

INSTALLAT ION
To install the Model PT, it is necessary that
observed. the following steps be carefully
DO NOT PLUG THE PT INTO THE AC OUTLET UNTIL INSTRUCTED TO DO SO IN STEP 4.
1. Remove the power plug of the transceiver power supply from the wall socket.
and plug it into the AC outlet (marked TRANSCEIVER) on the rear of the PT. FAILURE
TO USE THIS OUTLET AS DIRECTED CAN CAUSE DAMAGE TO THE AUXILIARY RECEIVER. SEE
PARAGRAPH 4. lf an electric clock is used in the station, it may be plugged into
the clock outlet. (rHe cuocr oUTLET ls tilRED BEFoRE THE swlTcH, s0 THAT lT 1s
ALWAYS ENERGIZED.) An additional outlet also is provided for the second receiver.
An outlet marked SPARE may be used for a rotator; however, under no circumstances
should a linear amplifier be powered through the PT. THE LINEAR AMPLIFIER SHOULD
BE PLUGGED DIRECTLY INTO THE WALL OUTLET BECAUSE OF THE HIGH CURRENT DRAIN.
2. Remove the coaxial antenna line from the transceiver and connect it to the jack
marked ANTENNA on the rear of the PT. The coaxial cable comlng out of the rear
of the PT, terminating in a coaxial connector, should then be connected to the
transceiver antenna jack.
ln those installations employing a Iinear amplifier and the transceiver, the PT
is inserted between the linear amplifier and the transceiver (llOf AETWEEN THE
AI+TENNA AND THE LINEAR AMPLIFTER)
Another cable coming out of the rear of the PT is terminated in an RCA-type phono
connector. This should be plugged into the linear amplifier control circuItry of
the transceiver and, in turn, the cable normally coming from the linear to the
transceiver should then be plugged into the jack marked LINEAR KEY on the rear of
the PT (in those.installations employing a linear). ln some transceivers (such as
Swan), a set of terminals on the rear of the chassis is connected to relay con-
tacts. (Refer to the transceiver lnstruction Manual.) Remove the RCA-type phono
connector from the control cable (2-conductor zip cord) coming out of the rear
of the PT, connect the leads to the normally-open (during standby) contacts, as
referenced in the transceiver lnstruction Manual. Some transceivers may require
modification for external Iinear amplifier control. The PT is designed to work
with the control circuitry employed by most popular linear amplifiers, that is,
the linear is controlled by contacts normally open, when the transceiver is in
a standby position. Some of the more popular amplifiers, employing this control
circuitry, are the Henry 2K series, Collins 30L1, Hammarlund HXL-I, and so forth.
At this point, the PT unit may now be plugged into the AC outlet. The switch on
the front panel will control not only the power to the PT, but also all items
plugged into the rear outlets. This provides for simplification of station opera-
tion and insures that the relay control circultry will be energized whenever the
transceiver is in use. FAILURE T0 D0 THIS WILL CAUSE THE TRANSMITTEB, P0WER T0 BE
FED T0 THE SEC0ND RECEIVER, WHICH MIGHT CAUSE EqUIPMENT DAMAGE. A resistor/fuse,
located on the underside of the chassis of the PT, is also incorporated to pro-
tect the second receiver against such failureg however, the proper use of the
PT will minimize risk of damage.
3.
4.

5.
6.
7.
8.
INSTALLATION OF A SECOND RECETVER
To connect a second receiver, it is necessary to run a coaxial line from the AUX
RCVR auto radio-type jack, on the rear of the PT, to the receiver. An auto audio-
type plug is supplied with the PT, and a coaxial cable of the RG58/U type should
be i nstal led as fol lows:
l. Remove outer vinyl covering for 1-7/8 inches.
2, Strip braid and inner insulation off center conductor
7 /8 i nch.
3. Push braid back to form a bead all around.
4. lnsert center conductor through pin ufitil braid is
aga i nst end of pl ug.
Bend center conductor to hold plug in place.
Roll braid between fingers to roll it over the end
of the plug for about l/15 inch.
Solder the braid to the four tabs of the plug.
Solder the center conductor to the pin and cut off
excess wi re.
After installation of the above, the PT will feed the second receiver as well as the
transceiver. This will make it possible to receive and transmit on separate frequen-
cies when using the PT or to scout the band without disturbing the setting of the
tuning dial of the transceiver. lt also will be possible to use general coverage
receivers without having to disconnect the antenna from the transceiver installation
and by means of the proper frequency selection of the PT, all band reception may be
had.
The rear of the PT contains three terminals (designated AUX CONTACTS) for muting the
second receiver. This is highly desirable when transmitting so that noise and slgnals
do not ride through on the transmitter audio. Under certain conditions, feedback
also might develop, particularly with certain relative frequency settings between the
transceiver and the second receiver. Before connecting the muting terminals, it will
be necessary to determine from the receiver lnstruction Manual if normally-open or
normally-closed contacts are required for muting. ln those receivers, muting against
ground, the terminal marked COM should be connected to ground or chassis of the re-
ceiver. ln those receivers requiring normally-closed contacts for reception, the
terminal marked NC should be connected to the muting Iead. Those receivers requiring
normally-open contacts for reception, will require that the leads be connected to
COM and N0 terminals. Most receivers, however, use normally-closed contacts for re-
ceiving, which open during transmit. After wiring in the muting contacts to the
second receiver, each time the transceiver transmitter section is actuated, the
second receiver should si lence.
lf it is desirable to use VOX operation with the second receiver, it is necessary to
observe certain precautions so that the output of this second receiver will not trip
the VOX circuitry. Although it is possible to modify the transceiver, so as to feed
audio from the second receiver in for anti-trip purposes, this is not normally rec-
ommended unless the person performing the task has a very thorough knowledge of the
circuitry and can perform these operations. For split frequency operation, it usually
is best to use a footswitch or other such control circuitry with the transceiver in
the V6X, PTT or manual modes of operation. lf, however, VOX is desired, it is best to
experiment with the placement of the microphone with respect to the speaker of the
second receiver, so as to attenuate the audio path between the two as much as possi-
ble. Keeping the second receiver volume at a modest-to-low level also will be very
helpful and the use of a cardioid-type microphone will further improve the situation.

TRANSCE IVER
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LINEAR KEY I
ACCESSORY ]
EXTERNAL CONTROL]
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ANTE NNA
AUX RCVF LiNEAR AMPLIF!ER
KEY
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ANTENNA
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(SEE PAGE 3)
T0 MODEL Pr r
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MARKED .,AUX F:VR.. I
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INSTALLATION DIAGRAM
TRAilSCEIVER
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TRANSMIT
TRANSM IT
RECEIVE
PF:EAIIP
P'TEATP
swrTcH
PT'S ITION
':UNCTION DIAGRAM
4
CONTROL
RF INPUT RELAY
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TRANSCEIVER
AUXILIARY RECEIVER
AIITENNA
RECE t VE
SWITC H ING

OPE RATION
With the P0WER switch in the on (up) position and
sition, the transceiver should work in the normal
the PREAMP position, the pre-ampl ifier section of
of the receiving system and, therefore, since it
as fol lows:
the PREAMP swi tch i n the OUT po-
fashlon. With the PREAMP switch in
the PT then will increase the gain
is in operation, it should be used
l. Turn the MHz switch to a position that includes the desired frequency. For ex-
ample, the 2O-meter amateur band is'14 to 14.35 MHz. This is between the l0 and
23, therefore the switch must be at the line between l0 and 23.
2. When a signal is received, peak it by "alrrting the TUNING control for maximum
swing on the receiver S meter or maximum volume if no meter is used. ln tuning
over a band, the tuning knob of the PT should be adjusted fairly frequently. For
example, at AMHz, it may have to be adjusted every 50 kHz. At 50 MHz, it may
have to be adjusted every 200 kHz.
l. When the PREAMP switch is left in the OUT position, the unit is in standby con-
dition with power applied and its frame grid tube warmed up. lnstantaneous
pre-amplification is available when the switch is placed in the PREAMP position.
4. Because the PT adds considerable amplification (approximately 20 db) to the re-
ceiver section of the transceiver, which may often have sufficient gain, partic-
ularly on the lower frequency bands, overloading resulting in cross modulation or
desensitization, or both, may occur. For this reason, a manual GAIN control is in-
cluded on the front panel. Normally, this control should be turned fully clock-
wise; however, under strong Iocal signal conditions; it may often be found de-
sirable to reduce this control to a point where the local signals tune considera-
bly sharper and, therefore, occupy less space on the band. Although this will re-
duce the sensitivity, it will be very often found, particularly when desired
signals are strong, that reduction will provide an over-all and more usable sig-
nal than when the pre-amplifier was not in the circuit. This is particularly true
in those transceivers having considerable front-end gain without provisions for
separate RF gain and lF gain controls.
When switching the
tuning control , or
under certa i n cond i
ticularly with the
PT in and out of the circuit
both, at i ncorrect sett i ngs ,
t ions, an appreciable s i gnal
GA I N control at max imum. Th i s
with the band switch or the
i t wi I I be not iced that,
will still come through, par-
is normal .
Some'transceivers, having especially good AVC action, will tend to make tuning the
PT difficult, particularly on strong signals. This can be overcome by watching the
S meter very carefully while peaking the PT, peaking up on a weak signal, or peaking
up on the background noise in the absence of a signal. The true worth of the PT will
be more fully realized under extremely poor band conditions whenever signals are
very weak.
NOTE. lf the receiver sensitivity appears to be very Iow, regardless of
the setting of the band switch and the tuning control, the fuse/resistor
in the antenna circuitry should be checked. (ffre fuse/resistor in the
antenna circuitry is located on the underside of the chassis, at the
right front.)

t.
ALIGNMENT PROCEDURE
The preamplifjer in the PT has no adjustments. All tuning is done by the variable con-
denser.
Cl 'is a reactance cancelling capacitor which'is used to reduce the SWR to less than l.l:l
The adjustment procedure is as follows:
l. Connect a transmitter to a standing wave bridge.
2. Connect the PT Pl to the bridge.
3. Connect a good 50 ohm dummy load (such as. Bird, Sierra, etc.) to the PT Jl.
4. Short PT PZ during this whole test, the power MUST be on the PT.
5. Tune up the transmitter on 52 MHz if ava'ilable, otherwise on the h'ighest frequency on
the transmitter. Use 35 watts minimum.
6. Switch to read reflected power.
7. Adjust C1 for a mjnimum reading.
Do not disturb Cl except in the complete procedure above.
REPLACEMENT OF THE FUSE/RES|STOR
To replace fuse/resistor R10, use only Allen Bradley or 0hmite carbon composit'ion,
l/1O-watt size. Do not use l/4-watt or deposited carbon resistors as they will not
break quickly enough.
Unsolder the remains of the broken res'istor from the lug and the spring wire.
Solder one end of the rep'lacement resistor to the terminal lug. Hook the other end
oVei ttre spring wire and pu11 the lead until the spring is -dEiieeted about 1/16 inch.
hlh'ile holding this position, solder the resistop lead to the spring wire.
Before unsoldering diodes CR2 and CR3, check with an ohmmeter. Diodes are good if
the reading is .l00 ohms or less jn e'ither polarity. If the reading is high in one
pol ari ty, repl ace the two d'iodes wi th type 'l N281 on1y.
PARTS LIST
Most components used in th'is unit are available as over the counter items at any radio
parts supply store. Listed below, are specia'l items that are obtainable from AEROTR0N
on1y.
ITEM DESCRIPTION PART NO.
R10
CR2
CR3
K1
LI
L2
L3
L4
S2
TI
T2
100 ohm, t70%, 7/10 watt, comp.
Diode, I N28l
D'iode , I N28l
Re"lay, 4PDT, I l0 VDC coi I
Cojl, l.B-4 MHz
Coil, 4-.l0 MHz
Co'il, l0-23 MHz
Coi1, 23-54 lt1z
Swjtch, rotary, 2 po1e, 4 posjtjon
Transformgr, Toroid
Transformer, Power
47a5 loo3 oor
4804 0000 006
4804 0000 006
4507 0000 002
lB20 l615 021
I 820 1 615 022
tB20 t6t5 023
1805 I 615 024
5ll0 0000 017
5649 I 601 A25
56.1 0 0000 0t 9
2.
3.
4.

AUX CONTACTS
TRANSCEIVE R
ANTENNA
Pl r
AUX RCVR
J2
LINEAR KEY
J3 I
>-t-
'_L=
TRANSCEIVER LINEAR KEY
P?
N0TESI
I. UNLESS OTHERIIISE SPECIFIED CAPACITOR VALUES ARE IN MICROFARADS . RES1STOR
RESISToR VALUES ARE IN oHi{S, 1/2 WATT, !201.
2, 47K IIHEN DSI INCTUDES 33K RESISTOR,
IOOK !]HEI'I NO RESISTOR IS IN DSI.
SCHEMATIC DIAGRAM - MODEL PT . PREAMPLIFIER
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A DIVISION OF AEROTRON, INC.
P. O. BOX 6s27
BALEIGH. NORTH CAFIOLINA 27608
4201 r6t5 701 - 9/69 PRINTED IN U.S.A.