2 METER RF POWER
AMPLIFIER KIT
Ramsey Electronics Model No.
PA1
Give your handheld a big boost with this economical power
amplifier kit. Thousands have built and enjoyed this kit; one
magazine review even said, “probably the best bargain in Ham
radio!”
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Works with any radio; mobile, fixed or handheld
8 to 10 times the power gain: 10 watts out for every 1 watts in, 20 watts
out for every 2 watts in, 30 watts out for every 3 watts in!
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Easy connection to a radio
Operates on 12 - 14 volts DC, draws a maximum of 5 amps
Just add a T-R relay, case, Pre-amp if desired and connectors
Informative manual answers questions on theory, hookup and uses -
enhances resale value, too!
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Maximum output of 35 - 40 watts, max drive of 8 watts
Mounts in any small aluminum case, which then will act as a heatsink
Yes, this is the amplifier that’s been reviewed in all the Ham magazines!
Clear, concise assembly instructions carefully guide you to a finished
kit that works FIRST time!
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Ramsey Publication No. PA1
Price $5.00
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
2 METER RF POWER
AMPLIFIER KIT
TABLE OF CONTENTS
Kit Building Tips ............................... 5
Parts list ........................................... 5
Assembly.......................................... 6
Parts Layout Diagram ...................... 6
Schematic Diagram.......................... 7
Testing ............................................. 11
Troubleshooting ............................... 11
Transmitting-Receiving .................... 12
Customizing ..................................... 13
Installation........................................ 13
Operating Your PA1......................... 13
Warranty........................................... 15
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
PA-1 • 3
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PA1 AMPLIFIER
All of us at Ramsey say THANKS for your interest in building the world's
most popular 2 Meter amplifier project. Successful construction and
installation of your PA1 amplifier can give your handheld 2 Meter transceiver
an RF power boost beyond the performance of many fixed and mobile units.
BEFORE you begin building your PA1, we ask you to read the warranty
information on page 14 and think about a few details in advance:
The PA1 is a true "Ham Radio" kit project which presumes the expertise that
goes along with your license. You need to know how to "tack solder", wind
simple VHF coils per our directions, and how to finish your PA1 with suitable
enclosure, connectors, T-R switching and I/O wiring.
The Ramsey RFS1 RF-sensing T-R switch kit is available as an easy
companion kit for the PA1.
The Ramsey PR10 Low Noise Pre-amplifier Kit can be worked into your final
T-R installation to boost those hard-to-copy signals.
We ask you to understand that the VHF Power Transistor that is the heart
and soul of this circuit cannot be guaranteed beyond careful tests by BOTH
the manufacturer and our technicians. Because this expensive transistor can
be damaged by either incorrect soldering OR incorrect physical mounting,
there can be NO warranty on this part unless your own additional test
BEFORE ANY soldering and mounting shows a clear defect.
Use of a VHF power output wattmeter is essential to correct adjustment of
the PA1.
If you decide, before beginning any assembly of your PA1 kit, that this
project is not quite what you're ready for, you may return the complete,
unassembled PA1 kit to the Ramsey factory.
OR, if you are ready to join the thousands of hams world-wide who enjoy the
PA1 as the most economical possible HT improvement for the highly-popular
2 Meter band, we will be happy to guide you through every construction step
in the spirit of the "Learn-As-You-Build" philosophy for all Ramsey Kit
manuals for the new millenium.
PA-1 • 4
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KIT BUILDING TIPS
Use a good soldering technique - let your soldering iron tip gently heat the
traces to which you are soldering, heating both wires and pads simultaneously.
Apply the solder on the iron and the pad when the pad is hot enough to melt the
solder. The finished joint should look like a drop of water on paper, somewhat
soaked in.
Electrical part installation - when parts are installed, the part is placed flat to the
board, and the leads are bent on the backside of the board to prevent the part
from falling out before soldering. The part is then soldered securely to the
board, and the remaining lead length is then clipped off.
PA1 PARTS LIST:
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1 PA1 Printed circuit board
1 BLW40 or SD1272 RF Power Transistor
1 Length of pre-tinned #18 wire (for L1,L2)
1 Length of #18 enameled wire (for L3)
1 Length of #24 wire (for winding 6 hole RF choke ferrite bead)
1 6 hole RF Choke ferrite bead (black cylinder) (to be hand-wound)
2 100 pf mica compression trimmers (rectangle shaped) (C1,C3)
2 60 pf variable trimmer capacitors (round shaped) (C2,C4)
2 47 or 56 pf ceramic disc capacitors (C5,C6)
1 .01uf ceramic disc capacitor (marked .01 or 103 or 10 nf) (C7)
PA-1 • 5
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ASSEMBLY DIRECTIONS:
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1. Simply EXAMINE the PA1 circuit board. Notice which way is up or down
in accord with our published drawing. Notice that ALL components are
surface-mounted (tack-soldered) to one side of the PC board. There are
NO component-mounting holes!
2. Taking care that your soldering tip is clean, pre-tin all mounting pads on
the board. You are using enough heat if the solder flows VERY easily and
remains shiny. That is the only acceptable result. A smooth build-up of
solder thickness is fine and will make parts installation even easier.
3. The power transistor will be installed as a later step. Right now, simply
position it in place and observe how far its flat leads extend toward the
input and output pads. Scribe a line into the tinned pads at each end of
these two leads as a guide to the amount of pad space required by the
transistor. NOTICE THE ORIENTATION OF THE TRANSISTOR'S
COLLECTOR LEAD! Set the transistor aside for now, safely.
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4. In installing the coils leading in and out of the transistor's pads, the idea
is to stay on the other side of your marks, so that the transistor can be
installed flat and neatly on the board.
5a. Examine C1, one of the mica compression trimmers. Neatly re-form the
two outer tabs at right angles so they form "feet" which permit the trimmer
to sit level in its correct position. Make sure the inner pins do not touch the
PC board.
PA1 PARTS LAYOUT DIAGRAM
PA-1 • 6
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PA-1 • 7
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❒ 5b. Tack-solder C1, one of the Mica compression trimmer capacitors,
using enough heat for a solid, good connection.
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6. Install C3, the other compression trimmer, just like C1.
7a. Bend the leads of C2, the round trimmer capacitor, at right angles so
that it can also sit in a level and flat position. The two leads at one end go
to the ground plane, and the single lead goes to the pad with C1.
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7b. Install C2.
8. Install C4, just like C2. Now that you are accustomed to how easy good
tack-soldering can be, and you can see some finished work on your PC
board, this is a good time to begin making and installing the three coils and
RF Choke.
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9a. Cut a 1" length of #18 tinned bare wire and form it as shown, making a
gentle loop around a tool handle.
9b. Install L1 using a pair of needle-nose
pliers to hold it as you solder it in place. Let L1 from 1"inch of bare wire
one end cool before soldering the other.
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10a. Use another length of #18 tinned bare
wire to make a 1-turn 1/4"-diameter coil. Spread the turn itself to 1/4" and
trim the leads to approximately 1/4". Bend the ends as needed so that the
coil sits in position as shown on the board.
10b. Install L2 the same way as you did with L1 in step 9b.
PA-1 • 8
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11a. Using the #18 enameled wire, wind a 5-turn coil for L3. The inside
diameter is also 1/4", the turns should be close-wound, and the ends
should be 1/4-inch long. Using a small knife or sandpaper, scrape the
insulation from each end, tin the bare ends with solder, and gently bend the
ends as needed so the coil sits in its position correctly and neatly.
11b. Install L3.
L3 side view
L 3 top view
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12a. The RF choke consists of a ferrite bead with 6 holes. It is easily
made by passing or "lacing" 5 turns of the #24 bare wire through its holes.
This will fill 5 holes with a lead coming out at each end. (Note that trying to
fill the 6th hole would cause both wire ends to come out of the same end of
the ferrite bead.) Trim the ends to 1/4" and bend as needed for neat
installation.
RFC1
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12b. Install the RF choke.
13. Install bypass capacitor C7, .01 uf (marked .01 or 103 or 10 nf) from
the DC voltage pad to the ground plane.
VERY IMPORTANT: PLEASE READ!
The RF Power Transistor MUST be mounted to its heatsink (usually the metal
case enclosure) B-E-F-O-R-E it is soldered to the circuit board. This is
necessary for the sake of your investment as well as the health of the
transistor. It is VERY easy to crack the transistor's case and break off the leads
if you attempt to tighten the nut AFTER soldering. As has been explained,
Ramsey Electronics' warranty on this transistor covers ONLY fresh, non-
soldered units which prove to be electrically defective before any installation
attempt.
So...NOW is the time to decide how you are going to enclose your PA1. If that
decision is still to come and you wish to experiment with the performance of the
PA1 before designing a finished accessory such a "docking booster", then
PA-1 • 9
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make a suitable HEATSINK for Q1 and install it before proceeding. A piece of
heavy aluminum or copper the same size as the PA1 circuit board will work fine.
Even when securing Q1 to such a heatsink, do not use too much force. Observe
the correct orientation of Q1 on the actual circuit board when mounting it to the
heatsink. The collector lead (output side) has a 45-degree cut that is plainly
visible.
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14. Pre-tin both the upper and lower surfaces of all four leads of power
transistor Q1.
15. After reviewing the mounting information, mount Q1 to its heatsink or
section of metal enclosure.
16. After double-checking the orientation of the collector lead, solder all
four Q1 connections.
17a. The final circuit-wiring steps consist of the CORRECT installation of
two small 47 or 56 pf disc capacitors. This step is more critical than many
builders may realize, because excess lead-length of C5 and C6 will reduce
power output and induce feedback! The bodies of C5 and C6 should fit
snug against Q1 and you should see little or no capacitor wire lead at all!
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17b. Install C5 in accord with 17a.
17c. Install C6, just like C5.
FINAL PC BOARD WIRING BEFORE TESTING:
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18. Solder the 12-volt DC power line connections.
19a. Use good-quality coax terminated to fittings for your own application.
19b. Install coaxial input and output lines.
Take a moment now to review your work. Touch up any solder joints that need
to look smoother and shinier. This effort can actually improve performance as
well as make you proud of your work and enhance the resale value of your
amplifier. There should be NO evidence of excessive wire length or rough-
looking solder joints.
PA-1 • 10
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INITIAL TESTING
Required for testing:
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1 to 5 watt 2 Meter transmitter or transceiver.
12 volt DC power source, 5 amp minimum.
RF wattmeter suitable for VHF use.
Correct cables and connectors.
50-ohm 30-50 watt dummy load (use antenna for testing only in accordance
with appropriate frequency selection, transmission ID procedures).
DC voltage may be applied to the PA1 at all times. As a Class C amplifier, it
draws current only with RF drive. For the first test, use just 2 or 3 watts of RF
drive. NEVER exceed 8 watts!
Adjustment is accomplished by turning all 4 trimmers for maximum RF power
output. However, to keep this procedure from becoming like trying to crack a
combination lock, do it in this order:
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1. Turn both compression trimmers (C1,C3) fully clockwise.
2. While turning C2 (RF input side), watch for a sudden peaking of RF
output. C2 has the most direct and critical control over the driving of Q1.
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3. After some power output is noted from peaking C2, then adjust both C3
and C4 for maximum output. Then readjust C1 and C2 as needed.
That's all there is to it! If you cannot get the proper amount of power output or
gain, there is something wrong with the amplifier or test set-up that needs to be
corrected before further tests are conducted.
TROUBLESHOOTING HINTS:
The amplifier should produce at least 8 to 10 times power gain, for example: 2
watts in for 20 watts out. If the amplifier does not give you this gain, make sure:
C5 and C6 are tight, snug against Q1 with virtually no lead length.
Good RF wiring technique was used in hooking up the coax input and output
leads - short lead length on the coax shields and center conductor wires.
Proper adjustment of all trimmers.
At least 12 volts actually measured at the PC board power connection point.
Maybe an SWR problem? Change input and output coax lengths.
PA-1 • 11
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TRANSMIT-RECEIVE ["T-R"] SWITCHING CONSIDERATIONS:
T-R switching of a single antenna with a 2 Meter transceiver and the PA1 RF
amplifier may be accomplished in any of these ways:
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1. Internal connections to your transceiver, making use of its built-in T-R
switching circuit or relay.
2. External T-R relay controlled by transceiver microphone switch or relay
line.
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3. RF-activated T-R switch such as the Ramsey RFS-1 kit.
4. PIN-diode T-R switching.
You have to make your own decision about whether to tie into any of the
internal circuitry of your transceiver. It depends on how comfortable you are in
doing so, how dependent you are on factory or professional service, and the
policy of the service center on modified equipment.
We developed the RFS-1, T-R relay kit exactly for those situations where PA1
operation is needed but there is reluctance to make additional connections in
and out of a costly hand-held transceiver. The RFS-1 kit is very economically
priced and includes a heavy-duty 12-volt relay. Sorry, but we cannot make the
PC board or individual parts available separately from the entire RFS-1 kit.
The use of PIN diodes for T-R switching is discussed amply in recent editions of
the ARRL Handbook and in ham radio magazine articles. A practical circuit
requires two suitable PIN-diodes, RF chokes, bias supply and either a quarter-
wave line or tuned circuit for receiver isolation.
PA-1 • 12
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CUSTOMIZING YOUR PA1 INSTALLATION:
Since it's up to you to supply the enclosure, connectors and any desired
operating conveniences, it's likely that each one of those thousands of PA1s in
use today has its own personality. For some good ideas, take a look at "Turn
Your HT into a 40W 2M Mobile Rig" by N8KDD in 73 Magazine, December
1989. The author's ideas are great, and we would only point out that his
mention of the PA1 assembly instructions pertain to the simple sheets supplied
prior to the publication of this manual. Also, we do find the relays supplied with
the RFS-1 kit to be quite suitable for the application.
The economy of the PA1, or even the factory-wired PA10, makes it possible for
you to set up permanent 40-watt rigs in various vehicles, at home, at the office,
all with their own permanent antennas, all of them ready to make your 2 Meter
HT or shirt-pocket wonder ever more versatile!
The hams at Ramsey Electronics thank you and hope you'll have as much fun
using your amplifier as you had building it!
INSTALLATION NOTES:
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1. The best location for the relay is as close to the PA1 amplifier PC board
as possible with a short solid connection from the relay contact to
the amplifier input. If more than 1 inch, use coax.
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2. All coax shields must be grounded with the shortest possible lead length
to your metal chassis ground point!
3. One short, solid ground path to power amp PC board (or metal chassis
or enclosure) is required.
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4. Expect the relay to pull about 100 ma.
5. Miniature coax type RG-174 is ideal for all connections.
OPERATING NOTES:
❒ 1. If the relay chatters, it is a sign of high SWR, which you will wish to
resolve anyway by antenna system or amplifier output adjustments.
❒ 2. If the relay action is "sloppy", there may be insufficient RF to drive the
RFS-1 circuit. This can occur when using a "low power" HT setting
(È watt ) to conserve the HT battery, while still transmitting a good
5 watts from the PA1. The RFS-1 may be made more sensitive by
reducing the value of R2 to 1 or 2K ohms.
❒ 3. As designed, the RFS-1 will handle all input power levels safe for the
PA1 RF amplifier itself, up to 8 watts drive.
PA-1 • 13
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A NOTE FOR EXPERIENCED BUILDERS ON LINEAR OPERATION FOR
SSB, AND OTHER EMISSION TYPES:
Please undertake this conversion ONLY if you understand the theory and
practice involved. Otherwise, please get help from another ham experienced in
amplifier design. This conversion changes the power transistor form Class C to
"biased on" Class B operation. The transistor is not under warranty as we've
already explained, and improper configuration can easily damage it.
Linear operation configuration consists of applying 12 volts DC through a
simple 4-part adjustable circuit, through the original RF choke to the base of RF
power transistor Q1, carefully checking Q1's collector current right from the
start.
CONVERSION STEPS:
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1. Lift the ground side of the RF choke.
2. Solder a 1 amp diode's cathode lead (banded end) directly to the
emitter-ground connection of the RF power transistor. Keep this cathode
very short so that the diode can temperature-track the transistor.
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3. Connect the following to the lifted end of the RF choke, keeping all wires
as short and neat as possible:
- anode lead of diode
- one end of a 270-ohm resistor
- one end and center of a 500-ohm trimmer pot
❒ 4. Solder the other end of the 270 ohm resistor to the PA1 groundplane foil.
❒ 5. Connect the remaining end of the 500 ohm pot through a 51 ohm resistor
to a neatly routed wire to the +12 volts DC input to the PA1.
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6. Set up a 0-100 milli-ammeter or VOM to monitor Q1's collector current.
7. Keeping your tests short, adjust the 500 ohm pot for about 50 mA of
collector current. Do not exceed 100 mA!
PA-1 • 14
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PA1 WARRANTY NOTICE:
The PA1 kit is the only item in the entire Ramsey product line that is not
covered under any warranty. Because of the variety of ways in which this kit can
be constructed and mounted mechanically, we cannot offer any kit repair
service. So, if this kit appears too complex for your abilities, please return it for a
complete refund. The PA1 kit is designed for the advanced builder who
appreciates the convenience of having all the hard-to-get parts available from
one reliable source. Thousands upon thousands have successfully tackled this
project and many have even written magazine articles detailing their efforts,
thus earning enough to pay for their kit! The PA1 kit does not require
superhuman skills to build, just proper care and techniques in assembly that RF
circuitry demands.
PA-1 • 15
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PA1 2 METER RF POWER AMPLIFIER
Quick Reference Page Guide
Kit Building Tips................................ 5
Parts list............................................ 5
Assembly.......................................... 6
Parts Layout Diagram....................... 6
Schematic Diagram .......................... 7
Testing.............................................. 11
Troubleshooting................................ 11
Transmitting-Receiving..................... 12
Customizing...................................... 13
Installation......................................... 13
Operating Your PA1.......................... 13
Warranty........................................... 15
REQUIRED TOOLS
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Soldering Iron Ramsey WLC100
Thin Rosin Core Solder Ramsey RTS12
Needle Nose Pliers Ramsey MPP4 or RTS05
Small Diagonal Cutters Ramsey RTS04
<OR> Technician’s Tool Kit TK405
ADDITIONAL SUGGESTED ITEMS
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Holder for PC Board/Parts Ramsey HH3
Desoldering Braid Ramsey RTS08
Digital Multimeter Ramsey M133
Price: $5.00
Ramsey Publication No. PA1
Assembly and Instruction manual for:
RAMSEY MODEL NO. PA1
2 METER RF POWER AMPLIFIER KIT
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
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