DRAKE MN2700 User manual

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CHAPTER I
1.1.
1.2.
CHAPTER ll
2.1.
2.2.
2.3.
2.4.
CHAPTER I11
3.1 .
3.2.
3.3.
3.4 .
3.5 .
3.6.
3.7.
TABLE OF CONTENTS
INTRODUCTION .......
PAGE
................... 1.1
Description ....................................
...................................... Specifications
INSTALLATION
........................................... ........ 2.1
........................................................... Unpacking 2-1
Location ............................................................. 2.1
Requirements ........................................................ 2.1
Antenna Connections ................................................ 2.1
OPERATION .......................................... ......
Front Panel Controls ..................................................
Rear Panel Connections .............................................
Use of the Drake B-1000AccessoryBalun ................................
Operating Procedure- .................................................
0ff.the.Air Tuning ....................................................
Reflected Power .....................................................
Use with Transceivers or TIR Combinations ..............................
............
. CHAPTER IV MAINTENANCE

Fig. 1-1 MN2700 Matching Network

CHAPTER I
INTRODUCTION
4. Match an antenna to a transmitter having
The typical modern transmitter or high-power
amplifier has either a pi-network tank circuit or a
broadband transformer output and will work into
resistive loads of 50 to 75 ohms with Voltage
Standing Wave Ratios (VSWR)of 2:l or less. This
resistive load can only he achieved with a resonant
antenna; thus, for multiband operation, multiple
antennas are required. Space and cost considera-
tions render this solution impractical for most
amateurs. In addition, many singleband antennas
will not maintain less than2:l VSWR across the en-
tire band. The MN-2700 impedancematching net-
work can:
1. Measure feedline VSWR, then reduce the
VSWR at the transmitter output to
1:l.
2. Monitor transmitter power output in watts
directly and continuously.
3. Attenuate 2nd harmonic output from a trans-
mitter by 25 to 35
dB; thus it may eliminate
the need for a low-pass
TVI filter.
fixed loading.
5. Give optimum match with multiband
antennas.
6. Precisely match a transmitter to an antenna
across a complete amateur band.
7. Permit off the air transmitter tuning using a
dummy load.
8. Eliminate the necessity of retuning the
transmitter when switching from "barefoot"
to linear amplifier operation since the
transmitter always "sees" 50 ohms resistive.
9. Help localize trouble by comparing trans-
mitter outputinto anantenna and intoa dum-
my load.
10. Allow antenna comparisons with the use of
the internal antenna switch.
11. Permit the use of open-wire feedline antenna
systems, with the use of anaccessory balun.
12. Permit the use of long-wires of various
impedances. The accessory balun can be used
to match the higher impedance ranges.

1-2. SPECIFICATIONS. Power Capability:
Frequency Coverage:
Input Impedance:
Load Impedance:
Balanced Feedlines:
Long-WireAntennas:
1.8 to 30 MHz. Band
Switch marked for 160, Meter:
80, 40, 20, 15, and 10
meter amateur bands;
however, frequency Wattmeter Accuracy:
coverage between
amateur bands is possible Insertion Loss:
by using the nearest band
positions with a small Dimensions:
reduction in matching
capability.
50 ohms (resistive).
50 ohm coaxial with
VSWR of 5:l or less at
anyphase angle (3:l on 10
meters).75 ohm coaxialat Front Panel Controls:
a lower VSWR can be
used.
With the Drake B-1000
accessory balun, tunes
feed point impedances of
40 to 1000 ohms, or 5:l
VSWR referenced to 200
ohms (3:l on 10 meters). Rear Panel
Feed point impedances up Connectors:
to 5:l VSWR referenced
to 50 ohms. Also, 5:l
referenced to 200 ohms
with the Drake B-1000 ac-
cessory balun (3:l on 10
meters).
1000 watts average
continuous duty, 2000
watts PEP
Reads VSWR or forward
power, 0-200 watts or
0-2000watts.
f 5% of reading + 1%of
full scale.
0.5 dB or less on each
band after tuning.
Height: 4-17132 in. (11.5
cm)
Width: 13-3/32 in. 133.26
cm)
Depth: 13 in. (33 cm) in-
cluding connectors.
Weight:
11 lbs. (5kg)
Provide for the adjusb
ment of resistive and
reactive tuning, antenna
switching, band switch-
ing, VSWR calibration,
and selection of watts or
VSWR functions of the
meter.
The rear panel has four
type SO-239 connectors
(one for input and 3 for
outputs), three screw ter-
minal connections (for
long-wire and open-wire
feeder systems), and a
ground post.

CHAPTER ll
INSTALLATION
Carefully remove the MN-2700 from the shipping
carton andexamineitfor evidenceof damage.Ifany
damage is discovered, immediately notify the
transportation company that delivered the unit. Be
sure to keep the shipping carton and packing
material for the transportation companytoexamine
if there is a damage claim. Keeping these items is
recommended in any case, since having them
available makes shipment of the unit much easier
shoulditeverbe necessary toreturnittothefactory
3. REQUIREMENTS.
Connect the RF output of your transmitter or
amplifier to the XMTR connector of the MN-2700,
using 50 ohm coaxial cable such as RGdlU. Cable
length is not critical. In installations using a
transceiver or transmitter-receiver combinations,
the matching network should be the last item the
out-goingRF signalpasses through before entering
the feedline to the antenna. The effects of this on
receiver operation will be discussed
in Chapter 111,
Operation, of this manual.
for service. Connect the EXT GND post of the matching net-
work to the station ground with a short piece of
NOTE heavy braid.
Fill out theenclosedregistration card and
return it to the factory within 10 days of
2.4. ANTENNA CONNECTIONS.
purchase to insure registration and
validation of the warranty. Antennas such as beam antennas, single band
dipoles, trap dipoles, and verticals fed with coaxial
cable should be connected to the rear oanel connec-
-9-2 LOCATION.
tors marked ANT 1 or ANT 2.
-
Connectend-fedlong-wireantennastotherear panel
TheMN-2700will work properlyin almost any loca- screw terminals labeled
LW3 or LW4. A good RF
tion. Select a location on the operating table that ground shouldbe connected to the
EXT GND post.
will allow yoq to reach the control knobs easily. Antennas fed with balanced feedline should be con-
Figure
2-1 illustrates recommendedviewingoptions nected as explained in Chapter 111, Section
3-3 of
using the hardware furnished with the unit. this manual.
--- STANDARD
I
-
1, \ -4-
- OPIIONAL ftfl
~H,E,,,AL
rruo lox 14x 5/8 LONG
IUPPLI€O WITH UNlI
Fig. 2-1 Viewing Angle Options

, .
Fig. 3-2 Rear Panel Connections

CHAPTER Ill
OPERATION
3-1. FRONT PANEL CONTROLS. (Figure 1-1)
VSWR SETControl:
Varies the sensitivity of the VSWR sensing
circuitry.
Meter:
Displays either forward power in watts or
VSWR as selcted by meter switches.
VSWR SET Switch:
Used tocalibrate themeter for VSWR measure
ments.
VSWR READ Switch:
Causes meter to indicate VSWR.
200 and 2000 Watt Switches:
Causes meter to indicate forward power, either
200 or 2000 watts full scale.
ANTENNA Switch:
Selects the desired antenna and grounds all
unused antenna terminals. Positions areprovid-
ed for Dummy Load (whichcan alsobe used for
an additional antenna or as a grounding posi-
tion for antennas
1 through 4), 2 coaxial-fed
antennas (1,2)and two long-wireantennas (3,4
without accessory balun). With accessory
B-1000 balun, balanced feedline capability or
1:l and 41 match to long-wire antennas are
available.
BAND Switch:
Selects the fixed capacitors and inductors for
each band. In the DIRECT position, bypasses
the matching network and connects the RF
through the meter circuitry directly to the
antenna selected.
REACTIVE Tuning:
Tunes out the series reactive componentof the
antenna impedance.
Reactive Range Switch:
Switchesin additional fixed capacity toprovide
additional reactive tuning range.
RESISTIVE Tuning:
Varies the resistive component of the MN-2700
output impedance to match the series resistive
component of the load.
Resistive Range Switch:
Switchesin additional fixed capacity to provide
additional resistive tuning range.
3.2 REAR PANEL CONNECTIONS. (Figure 3-2)
XMTR Jack:
50-239 socket for input from the transmitter
DL Jack:
50-239 socket for the connection of a dummy
load (oranother coaxial fed antenna).
ANT 1-andANT
2:
50-239 sockets for 2 separate coaxial fed
antennas.
LW3 and LW4:
Screw terminals for two longwire antennas,
when used without the accessorybalun (1:l im-
pedance ratio to matching range of network).
Numbers correspond to ANTENNA selector
switch position.
3.3. USE OF THE DRAKE B.1000 ACCESSORY
BALUN
Installation:
Remove the three screws at terminals marked
LW3, LW4, NC and then reinstallthese screws
through the holes in the balun board to the
matching terminals on the MN-2700. Also, in-
stall the two mounting screws
in the other two
corners of the balun board
to the MN-2700.
BalancedFeedlines:
The two wires of the balanced feeders are con-
nected on the top of the balun board, under the
heads of terminal screws marked BAL and
BALlLW(1:l or 4:l). The ANTENNA selector
switchisplaced inposition 3 when this antenna
system is used.
Long-WireAntenna Using Balun:
(Cannot be used when balanced feeders are at-
tached.) Connect the longwire to the terminal
marked BALILW
(1:1 or 41). In ANTENNA
switch position 3, the antenna will be matched
with a
1:l impedance ratio. In position 4, the
antenna will be matched with a 4:l impedance
ratio, providing for a higher impedance range
matching capability.
It is absolutely necessary
to have a good RF ground.

Multiband Antenna:
A doublet antenna
135 feet long, center fed with
open-wirefeeders 67 feet long, can be matched
using the accessory balun on 80 through 10
meters. The feeders make a good 160meter ver-
tical when connected together and to the
BALILW
(1:l or 4:l) terminal of the balun
TO MATcmm I "lw~-r+I 1
NETWORK
BALILW (1:l or 4:l)
*
8010 METER CONFIGURATION
(POS31BAL ON MN2700) ~ , -
TO MATCHING
160 METER INVERTED 'L'
(POS 4/UNBAL ON MN2700)
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Fig. 3-3 Multiband Antenna
--.. -.
CAUTION
An antenna or a dummy load MUST
be
connected totheMN-2700 beforeenergiz-
ing the transmitter to avoid damage to
the matching network and the transmib
ter. Initial tuning must be done with low
transmitter power. Final small ad-
justments may be made atfull power. Do
not change any switch positions under
high power.
Preset the operating controls as follows:
BAND Switch: To desired band
Resistive Tuning: To
5
Reactive Tuning: To 5
Resistive Range: To
o - 10
Reactive Range: To
o - 10
VSWR Set Control: Fully Counterclockwise
Meter Switches: To VSWR READ
Energize the transmitter, apply low power to the
matching network, adjust the transmitter plate
tuning to resonance, and adjust loading to
minimum (max. capacity).TheVSWR meter should
read upscale.
Vary theRESISTIVE tuninguntil the
VSWR dips. If there is not enough tuning range to
dip the VSWR, switch
in or out theresistive range
capacitorasneeded todip theVSWR. Thenturnthe

REACTIVE tuning control clockwise. Readjust the
RESISTIVE tuning for a dip. If this dip is
downscale from the first dip, you are tuning in the
right direction, and should continue to alternately
move theREACTIVE tuning control clockwise and
tune the RESISTIVE tuning for a dip, until a
minimum VSWR indication is obtained.
If the sec-
ond dip found reads higher on the meter than the
first dip, the REACTIVE tuning control must be
turned counterclockwise a short distance, and the
RESISTIVE tuning adjusted for a dip. Continue
alternating these actions until a minimum VSWR
reading is reached. Again, if additional tuning
range is needed, switch
in or out the range
capacitors to obtain minimum VSWR reading.
If thedips found during the tuning procedure areso
far downscale that it becomes difficult to tell
whether a particular dip is lower or higher than the
preceding one, you can increase the meter sensitivi-
ty and get readings that arefartherupscaleby turn-
ing the VSWR SETknob clockwise. With this add-
ed sensitivity it may not be possible to dip to the
meter zero, but anyresidual reading will represent a
very small power level, probablyless than 0.1 watt.
b5. OFF-THE-AIRTUNING.
If a 50 ohm dummy load that iscapable of handling
full transmitter power output isavailable, itand the
MN-2700 can be used to tune upwith minimdm in-
terference. Connect the 50 ohm dummy load to
DL connector on theMN-2700, switch theANTEN-
NA switch toGNDIDL,switchtheBAND switch to
DIRECT, and turn on the transmitt@r. The
transmitter (and high-power amplifier, if used) can
now be tuned to match the 50 ohm dummy load.
Then turn off theamplifier and reduce thetransmit-
ter power output, without changing the transmitter
I
tuning. Aslittleas10wattsinput totheMN-2700is
enough. Set the BAND switch to the desired band,
the ANTENNA switch to the desired antenna, tune
the matching network for minimum VSWR, and
then increase the transmitter power to normal
operating level.
3-6. REFLECED POWER.
It is possible to read reflected power with the
When the matching network has been adjusted MN-2700,although the instrument was not primari-
the lowest possible dip, it is properly tuned to pre- ly designed
to dothis, T~ read reflected power, first
sent a 50 ohm resistive load to the transmitter. Ad-
rotate the VSWR SET knob fully counterclockwise,
just the transmitter plate tuning and loading con- and
press either the 200 WATTS or 2000 WATTS
trols as directed by the transmitter instruction
meter switch, Increase transmitter Dower to the
manual. desired level (donot exceed full scale on the meter).
then press the VSWR SET button. Rotate the
Make a note of the settings of the RESISTIVE and
VSWR SET knob clockwise until the meter in-
tuning and range
and the
dicates the same forward power. Press the VSWR
BAND switch. The next time you operate on this READ button, The
meter now indicates reflected
band, you can tune up quickly by returning the
power,
MN-2700controls Co the same settings.
With the range switch in 0-10 position, the tuning
control would be recorded as the number on the
knob dial between
0 and 10.With the range switch
in the 10-20 position, 10 should be added to the
number on the dial
- record a number between 10
and 20. In the 20-30 switch position, add 20 and
record a number between 20 and 30.
Push the VSWR SETbutton and rotate theVSWR
SETknob clockwise until the meter needle lines up
with the SET mark (full-scale)on the meter face.
Push the VSWR READ button. The meter will now
indicate VSWR.
3.7. USE WI rRANSCElVERS OR TIR COM-
BINATIONS.
Adjustment of the MN-2700 with a transceiver is
done exactly as described in Sections 3-4and
3-5
Since thereceived signal will be passed through the
matching network, it is necessary to change the
BAND switchtoeither DIRECT, or tothe band the
receiver is tuned to. If this isnot done, thereceived
signal will be attenuated by the matching network
whenever theBAND switch setting is not the same
as the band being tuned.

NOTES

CHAPTER IV
MAINTENANCE
The MN-2700 should be practically maintenance
free, sinceitis a passive device. If either, orboth, of
the AA-119 diode rectifiers for the wattmeter are
damaged, they must be replaced with the sametype
diodes. Substitution of other type diodes may
seriously degrade the accuracy of the wattmeter. If
any problems arise that cannot be corrected, either
return theunit toyour dealer,or write
to our Service
Department. Please describeyour problem in detail,
including external connections, control settings,
type of antenna, transmitter, ete. Do not return
your MN-2700 to the factory without proper
authorization. Sendyour requests for authorization
to the following address:
R.L. DRAKE COMPANY
540 Richard Street
Miamisburg, OH 45342
ATTN: Customer Service Dept.
Telephone: (AreaCode 513)866-3211
Telex No. 288-017

NOTES