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"4-1000A Designed and Built by:
Jay Bennett, AA6GK "
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SPECIFICATIONS
Frequency Coverage:
160 through 10 meter amateur bands; single knob bandswitched.
1800 - 2000 KHz input power:120w output power: 2100w
3500 - 4000 KHz 120w 2200w
7000 - 7300 KHz 120w 2200w
14000 - 14350 KHz 120w 2000w
18000 - 18200 KHz 120w 1800w
21000 - 21450 KHz 120w 1800w
24800 - 30000 KHz 120w 1650w
Modifiable for any frequency between 1.6 and 30 MHz.
Power Requirements:
Plate Supply 240 vac 60 Hz @ 35 amps
3 prong "dryer" type plug provided
optional:
208 vac 60Hz @ 40 amps with 120 vac ct
120 vac 60Hz @ 70 amps
R. F. Cage 120 vac 5% 60Hz @ 5 amps
Demand Power 'ON', 450 watts
Power 'ON', Plate 'ON', 1000 watts
Power 'ON', Plate 'ON', amp keyed: 1600 watts
Power 'ON', Plate 'ON', full output: 4300-6000 watts
Input Characteristics and Drive Requirements:
Input circuits pi-network 50 ohm input adjustable L, Q=2 to 3
Input SWR less than 2:1; SO239 connector
Drive 80 to 180 watts
Output Characteristics:
Output circuits pi-network 50 ohms silver plated coils
vacuum variable tuning and loading capacitors
SO 239 connector
Output power 1500 to 3000 watts rms depending on drive
1500 to 4500 watts peak ssb " " "
Efficiency 50% to 70%
Amplification 11 db. to 13db.
Fusing:
Plate Power supply ac line 25 amp household screw in.
high voltage lead 2 1/2 amp agc
R. F. Cage ac line 5 amp mdl slow blow
note: Plate Power supply and R. F. Cage are safety interlocked
Weight:
Plate Power supply 150 lbs. (72 Kg.)
R. F. Cage 35 lbs. (17 Kg.)
Changeover Relay:
Jennings vacuum relay, 24 volt d.c. coil
Keying line voltage-30 vdc 300 ma max.
FRONT PANEL CONTROLS
Plate Tuning vacuum variable with turns counter
Plate Loading vacuum variable with turns counter
Bandswitch
Wattmeter selector
SWR sensitivity potentiometer
Power on rocker switch and panel indicator
Plate on rocker switch and panel indicator
ALC level potentiometer
Keying control rocker switch and panel 'on air' indicator
REAR APRON
R. F. Cage fuse
Octal socket for plate power supply control leads
Idle bias control switch
Type HN high voltage connector
Keying control jack, RCA audio
ALC output jack, RCA audio
Ground binding post
Input SO 239 connector
Output SO 239 connector
AC power cord- R. F. Cage (polarized)
Note: Low pass filter is screwed to back panel
TOP OF CHASSIS AND INSIDE
Filament voltmeter adjustment
Plate current meter adjustment
Parasitic suppressor adjustment
RIGHT SIDE OF CHASSIS wattmeter scale adjustment pots
INPUT CIRCUIT SUBCHASSIS input circuit inductor adjustments
WATTMETER SENSOR SUBCHASSIS bridge balance trimmers
******************************************************************
* *
* DANGER!! *
* *
* THE PLATE POWER SUPPLY IN THIS AMPLIFIER IS CAPABLE OF *
* *
* 6000 VOLTS AT 30 AMPERES INSTANTANEOUSLY. EXERCISE *
* *
* EXTREME CAUTION! COVER INTERLOCKS ARE PROVIDED FOR *
* *
* YOUR SAFETY. DO NOT DEFEAT THEM. THE VOLTAGES PRESENT *
* *
* INSIDE THE AMPLIFIER COMPONENTS ARE LETHALLY DANGEROUS! *
* *
*****************************************************************
GENERAL DESCRIPTION
Indicator lamps show when power, plate, and drive are applied.
Metering left to right is filament volts(0-10vac), plate volts
(0-10Kvdc), plate current(0-1adc), output power(0-300 and
0-3000
watts forward; 0-300 watts reflected; SWR forward and
reverse).
Drive must be reduced to this amplifier to assure legal
operation
inside the amateur bands. The amplifier can operate class C,
B, AB2, or AB1 depending on Q point (idle bias) setting. In
standby the 4-1000A is biased beyond cutoff and its output
grounded to assure maximum receive noise floor. The unit re-
quires well regulated 208 or 240 volt line capable of 25 to
30 amperes. A separate circuit is recommended, using #10
(#8 for runs in excess of 25 feet). The boost transformer
must be wired in for 208 volt operation; the power trans-
former in the plate power supply must be rewired for 120 volt
operation. 120 volt operation is not recommended. See
page 3 of schematic diagram.
A remote power supply is utilized to save table space and
for safety considerations. R. F. cage and power supply are
fully power interlocked as to prevent the plate power supply
from energizing with certain cover panels removed.
The unit uses an EIMAC 4-1000A (8166) in a grounded grid
configuration. Input pi-networks are used to match 50 ohm
exciter output to the 110 ohm tube input impedance as well as
to assure maximum power transfer with lowest intermodulation
distortion. The input characteristic is low 'Q' providing
less than 2:1 SWR on all parts of all amateur bands.
The plate power supply provides 6000 volts dc at up to 1 amp
with 10% regulation. Vacuum variables and vacuum changeover
relay allow the use of very high voltages while keeping the
R. F. cage physically small-17" wide, 13" deep, 12" high.
The output circuit is a pi-network to transform the 5500 ohm
output impedance to 50 ohms with a design 'Q' of 12. Extra
loading capacitance is switched in on 80 and 160 meters.
The unit has a built in wattmeter that reads RMS watts.
The SWR function allows the wattmeter to function as a SWR
meter by first adjusting the full scale meter deflection,
then reading SWR directly. It is impossible to key the
amplifier with plate voltage off or during plate start up
sequence. Lack of filament voltage precludes operation of
the bias supply. The following is a description of the
automatic plate start up sequence: With Plate switch on
and Control switch on the Power switch is turned on. T1
energizes lighting filament, energizing relay and bias
supplies (through cover microswitch.) Three seconds later
(filament warm up time) plate relay #1 energizes sending
prestart signal to plate power supply prestart relay #2.
The prestart relay energizes the plate transformer T3 through
two 2.5 ohm 40 watt resistors in series with the 240 volt
primary winding of T3. 3 more seconds elapse as the plate
voltage builds to 2/3 nominal thus limiting the current in
the plate supply diode string to a safe value. Finally, plate
relay #3 energizes, closing the main contactor relay, fully
energizing the plate supply by shorting out the prestart
resistors. Extra contacts on the main contactor complete the
keying circuit back to the R. F. cage, allowing the amp to
be keyed. The above sequence take from 5 to 7 seconds.
The relays are arranged so that the slightest power inter-
ruption (20 ms) results in the immediate deenergization of
the plate power supply. The entire prestart sequence must
repeat before plate can be reenergized. The sequence
would start automatically should power come back on later.
The above described sequencing is designed to protect the
silicon diode string in the 6000 volt supply. Try turning
the amp off and on as fast as you can with the Power switch
to see how the protection operates!
Grid current metering is not provided since it is unlikely
that grid dissipation will be exceeded with 6 to 7Kv on
the plate. With 10 years' operation no tubes have been
ruined or suffered from reduced emission.
'Q' point bias is derived by the cathode current drawn
through a selected number of forward biased silicon diodes.
This biasing method provides exceptional linearity since the
bias supply is as 'stiff' in regulation as the plate supply.
Many engineering problems were encountered due to the greater
than one octave frequency range of this amplifier.
The bandswitch is designed to ground the cold end of the
plate tank coil on 40 and 17 meters to move tank self res-
onance away from the operating frequency. The plate RFC #2
is a two section choke. The 160uh lower section is used only
on 80 and 160 meters and is shorted out by a relay on all
other bands to prevent self destructive series resonances
in RFC2. The 80uh top section is sufficient for 40 meters
and up; both sections together provide 240uh at 80 and 160 M.
The 4-1000A is a difficult tube to cure of parasitics in the
95 Mhz range because of its high output capacitance, its
ability to operate at full output to 110 MHz, and its
failure to achieve self neutralization above 20 MHz. The
use of the low 'Q' nichrome series trap in the cathode cir-
cuit is key to stable operation. The use of nichrome wire
in the 40ph plate parasitic trap coil hairpin is key to
reliable high power operation at 28MHz. Substantial tank
circulating current flows through the tube output capacitance
(in addition to C3) on 28 MHz necessitating a minimal value
for
the plate parasitic trap coil, while still maintaining amp-
lifier stability, if reasonable efficiency is to be achieved.
Nearly 50 watts is dissipated in the parasitic suppressor
globar
on 10 meters in c.w. operation. Plate efficiency suffers on
10, 12, and 15 meters (a low of 50% on 10) because of the
above
design limitations; however the amplifier still provides
nearly
12 db gain. Prolonged c.w., RTTY, and key down tuning at
over 1500 watts rms output above 25MHz should be avoided.
CONNECTION TO EXCITER/TRANSCEIVER
Using 50 ohm coax connect driver/transceiver to amplifier
input connector.
Plug in octal power supply control cable.
Connect Amphenol HN high voltage connector to amp; make
sure it's tight.
Run at least #8 ground wire to ground binding post. An
adequate earth ground is essential.
Connect Amphenol 7 pin connector to power supply.
Plug power supply into 240 volt outlet.
Connect amplifier to load through at least RG8 coax.
Connect driver/transceiver keying circuit to amplifier;
requires a 'make' contact to ground for keying.
Connect driver/transceiver ALC line to amp if desired.
Plug amplifier into 120 vac.
Make sure amplifier is level.
TUNING PROCEDURE
Turn on amplifier power and plates; verify plate voltage is
on.
Turn control switch off.
Load driver/transceiver into desired load. Verify that the
load is less than 2:1 SWR, using the wattmeter/SWR meter.
2:1 SWR is 11% reflected power. If greater than 2:1 SWR
exists correct it before proceeding.
Set bandswitch to desired band.
Preadjust turns counters as follows:
BAND PLATE LOAD Note:
160M 0720 to 0870 0460 "LOAD" presets
80M 0970 to 1080 0330 are for a 50 ohm
40M 1170 to 1190 0210 resistive load at
20M 1290 to 1300 0640 center of band.
17M 1325 0680
15M 1335 to 1350 0790
12M 1300 0750
10M 1360 to 1500 0900
Set Wattmeter to 3000 fwd; turn on control switch.
Set exciter/transceiver for low power c.w. operation.
Key exciter/transceiver into amplifier; note changeover relay
operating. Quickly resonate PLATE control for maximum output
on wattmeter. Retouch driver tuning and loading if necessary.
Increase power and retouch amplifier "PLATE" and "LOAD" for
maximum output. DO NOT run amplifier key down off resonance
at maximum power as damage to the 4-1000A may result. 4-1000A
should be medium orange at full power output.
Avoid full power tune ups on 10M of over 15 seconds duration.
Reduce exciter/transceiver mike gain and/or carrier level
to legal limit.
Switch exciter to desired mode and your on the air!
WATTMETER ADJUSTMENT
Adjustment of the null circuit and the meter multipliers
should
only be attempted with the proper equipment. This consists of
either a directional wattmeter of known accuracy or an
accurate
ohmmeter, SWR bridge, RF ammeter, and dummy load. The null
adjustment rarely needs adjustment; if adjustment is required,
remove R. F. cage top cover. Dismount the R. F. head from the
rear panel. Using exciter power on c.w., load up into dummy
load on 20M. Set the wattmeter switch on 'SWR, ref." With
exciter power on, advance the SWR sens. control until meter
deflection is observed. Using an insulated screwdriver or
diddle stick, adjust the trimmer in the R. F. head for minimum
meter reading. Reverse the coax cables to the R. F. head.
Set the wattmeter switch to "SWR fwd." Null the other trimmer
as outlined above. This completes the adjustment. Reconnect
coax cables and remount R. F. head.
Jumper the cover micro switch and tune up the linear to 300
watts as outlined in tune up procedure. 300 watts should
be as measured on external wattmeter or R. F. ammeter in
series with dummy load of known resistance. Set the linear
wattmeter switch to "300 fwd". Adjust the 300 fwd pot on the
right side of the chassis for full scale deflection on the
linear wattmeter. Set the wattmeter switch to "3000 fwd."
Tune up to maximum power, but not more than 3000 watts as
shown on the external metering. Adjust the 3000 fwd pot to
read whatever power is indicated by the external metering.
Reverse the leads on the R. F. head. Set the wattmeter
switch to "300 ref." Adjust the output power to 300 watts
as indicated on the external metering. Adjust the 300 ref. pot
for full scale reading. Correct the R. F. head wiring and
remove micro switch jumper. Replace top cover. This
completes the adjustment.
Page 7
BIAS OR 'Q' POINT ADJUSTMENT
Adjusting the 'Q' point of the tube varies the class of op-
eration. Turn on the amplifier power and plate voltage. Key
the amplifier without drive. Adjust switch on the rear apron
for a plate current of: 120 - 140 ma class AB1
100 - 120 ma class AB2
80 - 100 ma class B
40 ma class C
This completes the adjustment.
INPUT CIRCUIT ADJUSTMENT
Load up amplifier into dummy load on 1900 KHz c.w. Reduce
power
to 1000 watts output. Using small long screwdriver, adjust
160M
slug through top cover for minimum driver SWR. Slugs are
inside
top cover behind the wattmeter instrument. DO NOT touch the
tank
coil or the 4-1000A plate circuit! Reload amplifier near band
edges and recheck driver SWR. It should be possible to center
the 2:1 passband over the entire band. Top cover MUST be left
in place on 160M, 15M, and 12-10M bands since plate tank
tuning
is affected by top cover placement. Repeat adjustment
procedure
in the center of each band. Adjust 12-10M slug at 28.00 MHz.
This completes the adjustment.
FILAMENT VOLTMETER ADJUSTMENT
Unplug the plate power supply. Remove the top cover of the R.
F.
cage. Remove parasitic suppressor, chimney, and 4-1000A from
its
socket. Connect and accurate ac VOM or DVM to the 2 tube
socket
pins closest to the front of the amplifier. Replace tube in
socket being careful to maintain VOM probe contact; neither
probe
can touch ground. Turn on power switch and adjust the filament
voltmeter pot (located under the input circuit sub chassis)
until
both instruments read the same voltage, about 7.6 vac nominal
with tube lit. This completes the adjustment. Remove probes,
replace tube, chimney, parasitic suppressor, top cover, and
finally plug in the plate power supply.
CURRENT METER ADJUSTMENT
Unplug the plate power supply and remove the right side cover.
Remove the R. F. cage top cover. Connect a 1.5 volt battery
in series with an accurate milliameter OR a metered current
source capable of 500madc across the 3 ohm 125 watt green re-
sistor that sits vertically near the diode string in the plate
power supply. Adjust the current meter adjustment pot (located
under the input circuit sub chassis) until identical currents
are read on both instruments. Use proper polarity. This
completes the adjustment. Reinstall all covers and plug in
the plate power supply.
Page 8
PARASITIC TRAP ADJUSTMENT
Completely disconnect R. F. cage. Remove top cover. Unhook
parasitic suppressor, remove chimney, and remove 4-1000A.
Remove small Phillips screw on top of blower flange between
blower and back panel. Remove small Phillips screw between
rear
of tube base and chimney (if they were installed). Remove flat
head machine screw in copper strap on top of chassis directly
forward of screw #2 above. Turn amplifier upside down. Remove
bottom cover. Remove pressurized sub chassis. Unsolder
nichrome
trap coil from tube pin and solder to #14 bus wire immediately
adjacent. This bus wire is grounded. Turn unit right side up.
replace tube in socket. Preset amplifier bandswitch, plate,
and load controls for 12-10M operation. Unsolder plate lead
from top of plate RFC2. Reconnect parasitic suppressor to
tube.
Using a grid dip meter, determine the parasitic resonant
frequency near 95 MHz by finding the dip on the parasitic
suppressor near the 4-1000 plate cap connection.
Turn the unit upside down. Using the same dip meter and same
frequency found above, adjust the parasitic trap capacitor for
resonance. This completes the adjustment. Carefully resolder
trap coil onto tube pin. Replace pressurized sub chassis and
bottom cover plate. Turn unit right side up. Resolder
plate wire to RFC2. Avoid sharp pointed solder joints.
Replace tube, chimney, plate cap connection, and top cover.
MISCELLANEOUS NOTES
The relay and plate supplies are full wave bridges.
The relay supply is unfiltered d.c. to improve regulation.
All dial lamps and indicators are NE51s.
A whisper fan is located in the plate power supply to cool
the bleeder resistors.
The 10 and 12 meter bandswitch setting is optimized for 10M
however satisfactory output and input SWR results can be
obtained on the '10-12' bandswitch setting down through
24.0MHz.
The selected nichrome dropping resistors in the filament
circuit are chosen to provide 7.60 vac at the tube pins with
120 vac applied to the primary of T1. Since the filament
voltage can be from 7.125 to 7.875 vac (+5%), the chosen value
allows the ac line voltage to fluctuate between 113 and 124
vac
without detrimental effect on the 4-1000A.
The r. f. cage blower is rated at 160 cfm; tube requires 35
cfm.
The blower motor dropping resistor is designed to reduce
blower
speed and noise while maintaining adequate air flow.
The ALC output becomes more negative with increased drive.
THE HIGH VOLTAGE IS LETHALLY DANGEROUS! ! THE TUBE EMITS SOFT
X-RAYS WHEN OPERATING AT FULL POWER! ! KEEP COVERS IN PLACE
AND
USE EXTREME CARE WHEN TESTING WITH COVERS REMOVED! !
Page 9
INPUT COIL TABLE
50 ohms to 110 ohms 'Q'?2
BAND C1 L1 C2
160M 1820pf 32t #25 close wound 1360pf
80M 910pf 16t #25 close wound 750pf
40M 780pf 9t #20 close wound 470pf
20M 670pf 6t #16 close wound 470pf
17M 430pf 5t #18 close wound 3/8" form 350pf
15M 305pf 4t #16 close wound 267pf
12-10M 200pf 3 1/2t #16 spaced to 1/2" long 250pf
all coil forms are 1/2" dia (ex. 17M) Miller 4400 series
ceramic
with tunable slugs
OUTPUT COIL DETAIL AND PI-NETWORK DESCRIPTION
The output tank is made up of three sections. The 12-10M coil
is 5 turns of flattened 3/8" copper tubing 2 1/2" in dia. and
5" long. The center section is a PI-DUX 195-2 with the 10M
coil
removed. The 160M end section is 21t of #12 3" in dia. and
31/2"
long (a piece of B&W 3033 coil stock). On 40M and 17M the
coil cold end must be grounded to move output tank coil self
resonant points away from the operating frequency. Plate
design
impedance is 5500 ohms. 'Q' = 12. All tank components are
silver plated.
BAND C3 L2 C4
160M 215pf 38.0uh 1800pf
80M 112pf 18.0uh 875pf
40M 56pf 10.5uh 435pf
20M 24pf 6.0uh 220pf
17M 22pf 4.5uh 200pf
15M 19pf 3.4uh 150pf
12-10M 21-14pf 2.0uh 130-115pf
Taps are moved for maximum efficiency at 2000 rms watts output
12M-10M 15M 17M 20M 40M 80M 160M
BIBLIOGRAPHY
The 4-1000A in Grounded Grid
Larry Kleber K9KLA
July, 1963, QST pp 29-34
A Power Supply for That Big Linear Amplifier
Carl Smith and Doug Demaw W1CER (W1FB)
December, 1969, QST pp 41-43
Some Notes on the Design and Construction of Grounded
Grid Linear Amplifiers
Doug Blakslee W1KLK
December, 1970, QST pp 22-32
Care and Feeding of Power Grid Tubes
Laboratory Staff, copyright 1982
Varian-Eimac
301 Industrial Way
San Carlos, CA 94070
Putting the SB200 on 160 Meters
Stafford and North KG2M
November, 1987, QST pp 32-35
Technical Correspondence, RFC Design
Jay Bennett AA6GK
June, 1988, QST p 50
Technical Correspondence, Stable High Voltage Metering
December, 1988, QST p 43
Improved Anode Parasitic Suppression for Modern Amplifier
Tubes
Rich Measures AG6K
October, 1988, QST pp 36-39
Calculating Power Dissapation in Pasasitic Suppressor
Resistors
Rich Measures AG6K
March, 1989, QST pp 25-28
Adding 160-Meter Coverage to HF Amplifiers
Rich L. Measures AG6K
January, 1989, QST pp 23-28
QST is published by:
The American Radio Relay League
225 Main Street
Newington, Ct 06111
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