WiMo GS-31 Operating Manual

6m DISCOVERY

LINEAR AMPLIFIER

(GS – 31)

Operating Manual

WiMo Antennen und Elektronik GmbH

Am Gäxwald 14, D-76863 Herxheim Tel. [phone] FAX 6978

http://www.wimo.com e-mail: [e-mail]

INDEX

1. Specifications

2. Introduction

3. Installation

4. Operating Controls

5. Operation

CAUTION
There are dangerously high voltages inside the amplifier when the power is
switched on. DO NOT remove the covers unless the power has been disconnected
and sufficient time has elapsed for the capacitors to discharge.

NOTE

The 6m Discovery is capable of a greater power than the CW rating shown in the
specifications. In order to achieve the stated PEP output, the amplifier must be
capable of operating CW at the same level for short periods. Do not try to operate the
amplifier at greater than the recommended level.

If the amplifier is operated for long periods at levels greater than the recommended
ones, then damage may occur. This applies particularly to the GS 31 valve, so great
care should be taken not to exceed 1Amp plate current or to drive with more than
100W continuous wave drive. Also, care should be taken not to exceed 1.5 : 1 SWR.

WiMo Antennen und Elektronik GmbH

Am Gäxwald 14, D-76863 Herxheim Tel. [phone] FAX 6978

http://www.wimo.com e-mail: [e-mail]

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1. SPECIFICATIONS

Function………………….The 6m Discovery is a desk top linear RF amplifier with a

nominal output of 1000W covering the range 50 – 54MHz for
amateur radio use.

Type of emission…………………………………………………SSB/FM/CW/RTTY

Dimensions………………………………….……14in wide x 9.75in high x 17in deep

360mm x 250mm x 430mm

Weight……………………………………………………………………………..25kg

Output power…………………………………...…………………….1000W CW/SSB

Gain……………………………………………...………………………12dB nominal

Power requirements………………………………..………230V AC at 15A, 50/60Hz

Duty cycle………………………………………Full O/P with normal amateur service

Cooling………………………………..……………………….……Forced air cooling

Frequency coverage………………………..……………………………..50 – 54 MHz

Input impedance……………………………..…………50 Ohms with tuned I/P circuit

Valve……………………………………….………………………single GS 31 triode

Harmonics………………………………….…………3rd harmonic: better than –45dB

Plate voltage……………………………………..……………………SSB: 2800V DC

Cabinet……………………….……………chassis – Zintec steel, covers – aluminium

RF compartment – aluchromed aluminium

Antenna relay…………24VDC antenna relays automatically transfer the driver to the

antenna when in STBY or OFF. Standard in-built are coaxial
O/P relay and short throw I/P relay.
The amplifier requires a relay contact in the driver to key the
amplifier.

Metering………………………… ……………Plate current, Grid current and RF O/P

Protection………………………… …………..All power circuits protected by fuses

Grid protection circuit

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2. INTRODUCTION

The 6m Discovery is a high quality linear amplifier which is designed around a GS 31
medium mu triode in grounded grid configuration. The amplifier uses a Pi – L
network in the output circuit and a tuned input circuit. The amplifier is forced air
cooled to give you the ability to operate at full output power for as long as you wish.
The recommended maximum drive is 100Watts.
The GS 31 must be allowed to warm up properly hence a 2 min. start up timer is
fitted. When the amplifier is switched on, the WAIT light will come on. After the time
has elapsed the WAIT light will go out allowing you to operate the PTT.
It is recommended that you use a Bird (or equivalent) power meter capable of
measuring 1500W at the correct frequency.
Please read the instructions carefully before operating the equipment. RF amplifiers at
this power level and frequency can be easily damaged by improper use. Please follow
the precautions on page 1 of this manual.

The Discovery is fully self-contained and has three separate voltages:-

1. HIGH VOLTAGE which is 2800V, the main voltage applied to the valve

anode.

2. HEATER SUPPLY which is 13V at 3A.

3. CONTROL VOLTAGE which is 12V used for the LED control condition

of the amplifier, 24V for pulling in the Tx/Rx relays.

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3. INSTALLATION

SETTING UP

a) Unpack the amplifier and check that it is undamaged. The carton should also

contain a power cable, operating manual, phono plug (for relay switching
lead) and spare fuse. Please retain the packing and box should it be necessary
to ship it or move it to another location.

b) Ensure you have a reasonable airflow around the site you have chosen to

install your amplifier. Do not enclose the cabinet or restrict the airflow in any
way. Try to avoid extremes of heat, humidity or dust in order to give many
hours of trouble-free operation.

c) Ensure ALL connectors to be used by yourself are of a sufficient electrical

standard to carry the higher RF output generated by the amplifier. To properly
tune the amplifier a high quality Wattmeter (e.g. Bird thruline) should be used
to measure the output and, if possible, a similar meter between the driver and
the amplifier to correctly measure the input.

d) NEVER attempt to operate the amplifier without first connecting an antenna

or 50Ohm dummy load. Check the SWR of the antenna with the amplifier in
the OFF or STBY position and do not operate the amplifier if the SWR is
greater than 2 : 1.

e) Check that the front panel switches are in the STBY and OFF positions.

CONNECTIONS

a) POWER CABLE. The amplifier is supplied with a 3-wire Mains cable

terminated in an IEC connector to go into the socket on the rear panel. The
other end is left free for you to connect whichever plug is suitable for your
electricity supply. The supply must be 230VAC, single phase, 50/60Hz.

b) OUTPUT COAX. Any good quality 50 Ohm coax capable of carrying up to

1500W at 50MHz is suitable. This needs an N-type connector to go on to the
amplifier and whatever connector is required for your wattmeter.

c) INPUT COAX. Good quality 50 Ohm coax with an N-type connector to the

amplifier and a connector of your choice for your driver.

d) RELAY SWITCHING LEAD. A phono plug is supplied for you to make a

lead to go into the PTT socket on the rear of the amplifier and connect to the
antenna relay on your driver. This cable sends the keying signal from your
driver to switch the amplifier to transmit. Do not apply any voltage to the
amplifiers relay control as it has its own in-built power supply.

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4. OPERATING CONTROLS

FRONT PANEL CONTROLS

ON/OFF SWITCH…………………………………………....Mains power on and off

STBY/TX……………………………………….…………Amplifier standby / operate

PLATE METER……………………..0 – 1.5A, monitors the plate current of the valve

GRID METER…………………………...0 – 400mA, monitors the grid current which

should not rise above 300mA

GRID / RF OUT…………………..switches the grid meter to monitor relative RF O/P

LOAD CONTROL…………………………………..Adjusts the loading of the output

TUNE CONTROL…………………………………….Adjusts the tuning of the output

POWER LED………………………………....Shows that the amplifier is switched on

WAIT LED………………………………..Lit until the valve has warmed up and then

goes out when the amplifier is ready to use

GRID TRIP LED………………….……Indicates grid current has exceeded safe level

TX LED…………………………………………Shows when the amplifier is ON AIR

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REAR PANEL

FUSE HOLDER…………………………………………………1.25” (30mm) 10A

MAINS……………………………………..IEC connector for mains cable, 230VAC

TX………………………N – type connector, coaxial INPUT to amplifier from driver

ANT…………………….N – type connector, coaxial OUTPUT to antenna through a

suitable power meter

PTT…………………………………….……Phono connector for relay switching lead

WiMo Antennen und Elektronik GmbH

Am Gäxwald 14, D-76863 Herxheim Tel. [phone] FAX 6978

http://www.wimo.com e-mail: [e-mail]

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5. OPERATION

SET-UP

Connect all the cables as previously described in the manual, then double-check.
When you are satisfied that everything is correct and the STBY/TX switch is on
STBY, switch the amplifier on. There is a slight delay while the soft-start operates,
then the POWER and WAIT lights should be on. After approximately 2 minutes the
WAIT light should go out, indicating that the valve has warmed up and is ready for
operation. Now put the STBY switch to TX, which puts it into the operate mode. With
no RF drive applied, key the amplifier and check that the Plate meter shows a
standing current of about 80 – 100 mA. The green TX LED will be on when the
amplifier is keyed.

TUNE-UP

Now set your driver to about 30W output, in either CW or FM mode, and using the
two dials tune for maximum output on your power meter. This should indicate about
400W output. The amplifier will give about 1000W RMS when 80W of drive is now
applied with very slight adjustments being necessary.
In the tune mode with 600W O/P, the plate meter should rise to about half scale.

CAUTION. Maximum grid current should NEVER exceed 300mA.

The amplifier is now ready for operation.

OPERATION

The mode of operation, SSB or CW, can now be selected and operate as normal.
When the amplifier is in the STBY position the RF goes straight through from the
transceiver to the antenna, and when it is in the TX position the amplifier comes into
operation.

To key the amplifier, an earth on transmit is required from the transceiver (relay) to
the PTT socket on the back of the amplifier. When the transceiver and amplifier are
keyed, the green TX LED indicator on the front panel is lit.

During operation, keep a careful eye on the Grid meter making sure it does not exceed
300mA.

GRID PROTECTION

There is grid protection fitted to this model of 6m Discovery. If the Load control is
increased, the grid current increases. As the grid current reaches approximately
300mA the yellow LED on the front panel will flicker on and an audible ‘clicking’
will be heard, also it will not be possible to key the amplifier. To rectify this, reduce
the Load until normal grid current is achieved.

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If excessive grid current is reached, then the relay will lock and the yellow LED will
remain on. To re-set the amplifier, turn the Load control anti-clockwise then put the
STBY/TX switch to STBY then back to TX. The LED should now have gone out and
the amplifier is able to be keyed once more. Tune the amplifier correctly to achieve
maximum output with minimum grid current.

WiMo Antennen und Elektronik GmbH

Am Gäxwald 14, D-76863 Herxheim Tel. [phone] FAX 6978

http://www.wimo.com e-mail: [e-mail]

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OPERATING PRECAUTIONS

To ensure safe and reliable operation please regard the following precautions:-

HIGH VOLTAGES CAN BE LETHAL. Never try to operate your amplifer with the
covers removed. If it is necessary to work inside the cabinet, always disconnect the
Mains supply and allow the capacitors to discharge fully.

Never operate the amplifier into a load or antenna with an SWR greater than 2 : 1.

Always tune the amplifer for resonance using low drive at the operating frequency.

The components in the amplifier are designed to be used within the parameters of the
specifications on page 2 of this manual. Excessive drive giving output in excess of
these specifications will shorten valve life and could affect the reliability of other
components.

WiMo Antennen und Elektronik GmbH

Am Gäxwald 14, D-76863 Herxheim Tel. [phone] FAX 6978

http://www.wimo.com e-mail: [e-mail]

(9)

WARRANTY

Linear Amp UK Ltd warrants to the original purchaser that this product
shall be free from defects in material or workmanship for 12 months from
the date of the original purchase. Valves are excluded from this warranty.

Notification should be given as soon as possible after discovering a
possible defect. Carriage charges for any parts or units submitted for
replacement or repair under this warranty must be paid by the purchaser.

Correct maintenance, repair and use are important to insure proper
performance from this product. Carefully read the operating manual. This
warranty does not apply to any defect Linear Amp UK Ltd determines is
caused by (1) improper maintenance or repair, including the installation
of parts or accessories that do not conform to the quality and specification
of the original parts; (2) misuse, abuse, neglect or improper installation;
(3) accidental or intentional damage; (4) acts of God.

Linear Amp UK Ltd is not responsible for damage to other equipment or
property or any other consequential or incidental damage of any kind.

This warranty is not transferable from the original owner on sale of the
unit to another.

WiMo Antennen und Elektronik GmbH

Am Gäxwald 14, D-76863 Herxheim Tel. [phone] FAX 6978

http://www.wimo.com e-mail: [e-mail]