Ptek FM50E, FM25E, FM250E Operating Manual And User Manual

Operating Manual and User Guide

FM SERIES

BROADCAST FM EXCITERS

FM25E

FM50E

FM250E

PTEK

Limited Warranty

p

PTEK (SELLER) warrants that products are free from defects in material and workmanship and meet

erformance specifications provided, however, that:

(A) SELLER’ liability under this Warranty is limited to repairing or replacing, at its option, any

product delivered here under not conforming to this Warranty;

(B) This Warranty is limited to a period of two years;

(C) Minor deviations from specifications which do not affect performance are excluded from this

Warranty; and

(D) SELLER shall be liable under this Warranty only if:

(1) It is promptly notified in writing by the Buyer upon discovery of the failure of any product to

conform to this Warranty,

(2) The product is returned to SELLER, transportation charges prepaid by the Buyer,

(3) The product is received by SELLER not later than ten days after the last day of the two-year

period of this Warranty, and

(4) SELLER’ examination of the Product discloses to SELLER’S reasonable satisfaction that

such defects or failures as may exist have not been caused by misuse, neglect, improper
installation, repair, alteration, accident or shipping.

The Buyer will prepay freight to and from SELLER on products serviced here under at SELLER’ plant; but
SELLER may, at its option, elect to perform any repairs here under at the Buyer’s place of business.

The foregoing constitutes SELLER’S entire Warranty expressed, implied and/or statutory, except as to
title, and states the full extent of SELLER’S liability to the Buyer or to any other party for any breach of
such Warranty and for damages, whether direct, special, incidental or consequential; and, other than as
expressly provided in this document. No Warranties, expressed or implied, including any Warranty or
merchant ability or of fitness for a particular purpose, are made. No employee, representative or agent of
SELLER has any authority, expressed or implied, to alter or to supplement the terms of this Warranty.

Warranty Service

The Limited Warranty covers parts and labor to the original purchaser for two year. Damage
caused by misuse or shipping is excluded from the warranty. Before returning units or material,
contact the factory for a Returned Material Authorization (RMA) number. Ship all material
prepaid. Defective material should be addressed to:

PTEK

PTEK

111 N. Vista Rd. Ste 3E

Spokane Valley, WA 99212

[phone]

[e-mail]

Safety

BEFORE APPLYING POWER

Verify that the line voltage is 115V

GROUND THE EXCITOR.

To minimize shock hazard, the excitor chassis must be connected to an electrical ground. the excitor must be
connected to the ac power mains through a three-conductor power cable, with the third wire firmly connected to an
electrical ground (safety ground) at the power outlet. Any interruption of the protective (grounding) conductor or
disconnection of the protective earth terminal will cause a potential shock hazard that could result in personal injury.
If the excitor is to be energized by any other source be certain the that chassis is connected to a separate safety
ground.

Fuses

Only fuses with the same required current, voltage rating, and specified type (normal blow, time delay, etc.) should be
used. Do not use repaired fuses or short-circuited fuseholders. To do so could cause a shock or fire hazard

DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE

Do not operate the power amplifier in the presence of flammable gases or fumes.

.

DO NOT REMOVE THE EXCITOR COVER

Operating personnel must not remove the exciter cover. Component replacement and internal adjustments must be
made only by qualified service personnel.

Output connector

The type N output connector carries dangerously high RF voltages which present a shock and burn hazard.
operate this excitor with out the out put connector properly terminated in either an adequately rated load or antenna.

NEVER

Page 4

Specifications

MONAURAL
OPERATION

Audio Input Impedance:

600 ohms, balanced

GENERAL

Rated Power Output:

25W, 50W, 150W, 300W

Power Consumption:

150 W (for 50W model)

Frequency Range:

87.7 to 108 MHz, in 200 kHz steps (other step size to

order)

Frequency Control:

Phase locked loop frequency synthesis from high

stability master oscillator

Audio Input Level:

+10 dBm (6.93 volts peak-to-peak) at 600 ohms for

75 kHz deviation

Audio Frequency Response:

+/-0.5 dB; flat or 75 microsecond pre-emphasis, 20

Hz to 15kHz (other time const. available)

Total Harmonic Distortion:

0.15% max.; 20 Hz to 15 kHz

FM S/N Ratio (FM Noise):

70 dB min. below 75 kHz deviation at 400 Hz,
measured within a 20 Hz to 15 kHz bandwidth with
75 microsecond de-emphasis

Asynchronous AM S/N Ratio (AM Noise):

60 dB RMS. below carrier; reference: 100% AM
modulation, at 400 Hz with 75 microsecond de­emphasis, no FM modulation

Synchronous AM SIN Ratio (Incidental AM Noise):

57 dB below carrier; reference: 100% AM
modulation, full power at 400 Hz with 75uS de­emphasis, FM +/- 75 kHz, 400Hz

Frequency Stability:

+/- 1.2 kHz

Output Impedance:

50 ohms

Output Connector:

Type -"N" female

VSWR:

1.5:1 for full power, derate to 0 at inf.

Modulation Type:

Direct carrier frequency modulation

Modulation Capability:

To 100 kHz deviation

Multi-Meter Indication:

Deviation, Forward Power, Reverse Power, Final I & V

Harmonic Attenuation:

-70 dB, min.

ENVIRONMENT

WIDEBAND
OPERATION

Inputs:

Composite Unbalanced 10k Ohms
SCA 1 Unbalanced 10k Ohms

Altitude: Ambient Temperature

0-10,000 ft -10 to +50oC

Input Level:

1.25 V RMS. (3.54 volts peak-to-peak) for 75 kHz
deviation

Wideband Amplitude Response:

+/-0.5 dB, 20 Hz to 100 kHz

Front panel layout

12

3

4

OUTPUT POWER W (REV X0.1)

DEVIATION kHz

10

15

5

25

1.0

0

10

0

PTEK

50

2.0

20

AMPS

VOLTS

20

25

75

30

3.0

100

4.0

30

40

OPERATE

OFF

8

Rear panel layout

1

7

FM Series

REVERSE POWER

ADJ
POWER

FM25E

6

FINAL VOLTAGEFORWARD POWER

FINAL CURRENT

DEVIATION

. DEVIATION

REMOTE OFF

DRIVE LOW

FAULT

PTEK

5

23

AC IN

FUSE

RF OUTPUT

FINAL

LOWER

RAISE

CURRENT

VOLTAGE

COMPOSITE

8

REMOTE

FWD REV

ON

OFF

PWR PWR

GAIN

GAIN

GAIN

SCA

MONO IN

600 OHMS

4

10MHz 1MHz 100kHz

FREQUENCY

5

Page 6

Key Element Description

METER

1

OPERATE

2

Indicator

REMOTE OFF

3

DRIVE LOW

3

FAULT

5

6 Meter Select Switch This switch selects one of the following to be presented on the meter (1):-

ADJ POWER

7

8 Ventilation Filter This provides for filtering the environmental air as it is drawn into the cabinet

Switch and

Indicator This red LED indicator is lit when the FM Broadcast Amplifier remote off

Indicator This red LED indicator is lit when the FM Broadcast Amplifier can not make

Indicator This red LED indicator is lit when the FM Broadcast Amplifier is in a fault

control This control adjust the output power from rated full power to less than 50%.

Indicates Forward Power, Reverse Power, Final Voltage, Final Current and
Deviation

This switch sets the FM Broadcast Amplifier to the Operate Mode; 110 VAC is
applied to the line transformers and this amber indicator is lit.

terminals (rear panel) are open circuit.

the power requested, because for example low drive power.

condition. This can be for one or combination of the following:­Over drive, High supply Voltage, High load VSWR, Over temperature.

Forward Power, Reverse Power, Final Voltage, Final Current and Deviation.

by the internal fan (not used on FM10E).

Key Element Description

AC IN

1

2

3

4

5

6

8

& FUSE 110 VAC input and Fuse 10A

COMPOSITE

SCA

RF OUT

FREQUENCY SELECTION

Accessory connector

SERIAL NUMBER

Unbalanced wide band composite input

Unbalanced wide band input

TYPE N RF Output

Set switches for frequency selection (only takes effect when unit is switched
from off to on)

Connections for; Remote off and DC indications of Forward Power, Reverse
Power, Final Voltage, Final Current and Deviation.

Serial number for reference purposes

Page 7

Installation-Electrical

Refer to the Table below for the following description. The installer should assure the ac line voltage is turned OFF
before performing this procedure. The electrical connections are installed at the Exciter rear panel.

OR (NOT BOTH)

FUSE

AC IN

RF OUTPUT

RG8 TO ANTENNA/PA

PART OF USER SUPPLIED REMOTE CONTROL

FINAL

REMOTE

ON

LOWER

CURRENT

VOLTAGE

OFF

FROM STEREO ENCODER OR STL

RAISE

FWD REV
PWR PWR

COMPOSITE

GAIN

GAIN

GAIN

SCA

MONO IN

600 OHMS

BALANCED MONO IN

10MHz 1MHz 100kHz

FREQUENCY

Page 8

Turn-On Checkout

Refer to the Table below for thefollowing procedure.

Stereo pilot level adjustment

With Stereo encoder (optional)connected
to composite input, adjust composite gain
control to give deviation meter reading
shown (aprox 7.5kHz)

Page 9

Frequency Selection

PLEASE NOTE, FREQUENCY CHANGES

SHOULD BE MADE WITH THE UNIT TURNED

OFF

10s MHz Switch

“0” is 10 (100MHz)

Page 10

100kHz Switch1MHz Switch

Example Shown 104.5MHz

Reading the front panel meter

FINAL VOLTAGE

FORWARD POWER

REVERSE POWER

POWER Watts

50

0

0

0

25

2.5

DEVIATION kHz

AMPS VOLTS(X10)

PTEK

POWER Watts

50

0

0

0

25

2.5

DEVIATION kHz

AMPS VOLTS(X10)

PTEK

POWER Watts

50

0

0

0

25

2.5

DEVIATION kHz

AMPS VOLTS(X10)

PTEK

50

50

50

FINAL CURRENT

DEVIATION

Use the range selection switch
(shown Left) to select the meter
range

Forward Power

100

150

200

250

300

100

10

7.5

75

5

The forward power reading is amount of power going to the
antenna. The example shown is a reading of 250 Watts. This
setting can be changed with the front panel raise lower
switch and should be set to the licenced power output (see
“calculation transmitter power setting”).

Reverse Power

100

150

200

250

100

10

250

100

10

300

300

100

7.5

7.5

75

150

75

200

5

5

The Reverse power reading is amount of power returning
from the antenna. The example shown is a reading of 2.5
Watts. A correctly matched antenna should not return any
power back to the transmitter. The ration of Reverse Power
to Forward Power in this example 2.5/250 would give a
return loss of 1% or -20dB this would classified as a good
antenna. Reverse Powers approaching 10% will cause the
transmitter to reduce the output power (See antenna VSWR
Effects)

Final Voltage (V)

This is the voltage applied to the output amplifier stage. The
example shown is a reading of 48 Volts. Used in conjunction
with the final current reading will give an alternate method
of measuring output power. (Output power = V*I*0.7). 0.7
is the efficiency of the output power amplifier.

POWER Watts

50

0

0

0

25

2.5

DEVIATION kHz

AMPS VOLTS(X10)

50

100

150

200

250

5

75

7.5

300

100

10

Final Current (I)

This is the current consumed by the output amplifier Final
stage. The example shown is a reading of 8 Amps. Used in
conjunction with the final Voltage reading will give an
alternate method of measuring output power as described
above. This reading will change with output power setting,

PTEK

also antenna match will give different results.

Continued over

POWER Watts

50

0

0

0

25

2.5

DEVIATION kHz

AMPS VOLTS(X10)

50

100

150

200

250

5

75

7.5

300

100

10

Deviation

This is the deviation in kHz caused by the program audio to
the carrier. The meter is peak reading and will vary in
accordance with the program (music speech etc.) The peaks
should not be more than 75kHz as indicated in this example.

PTEK

350

VSWR Effects

300

Exciter Power Output Vs VSWR

250

200

Power Watts

150

100

50

0

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2

Antenna VSWR

Power Output FM250E
Power Output FM150E
Power Output FM50E
Power Output FM25E

Frequency Adjustment

The transmitter frequency should be checked at lease once every 5 years. If the frequency offset is greater than +/- 1.5kHz,
adjustments can be made by tuning C52; see diagram for location.

C52

A qualified service technician should make adjustments. Alternatively the unit can be returned to the factory for service.

Circuit Description

General

The FM250E is housed in a 3U (5.25”), 19” rack-mounting case. Internally there are 4 PCB assemblies and 2 cased
power supplies.

Functional

Two 24V power supplies are connected in series to provide 48V for the power amplifier and 24V of the exciter and
fan.

Audio inputs (SCA Composite and Mono) are connected directly to the exciter board, premphasis is applied to the
mono channel only. These input are then summed together and feed to a veractor diode used to tune the VCO
(voltage controlled oscillator). A sample of the VCO’s output frequency is used by a synthesizer to compare again a
reference oscillator. This generates an error voltage which is used to tune additional veractor diodes in the VCO to
maintain a constant frequency. The main output from the VCO is amplified up to 25W.

The output from the exciter board is used to drive the power amplifier to 300W. Integral to the power amplifier is a
harmonic filter used to reduce harmonics generated in the power amplifier to acceptable levels. This output is then
feed back to the exciter board and on to the output connecter via a forward and reverse power detector.

The exciter board also contains control circuitry, which levels the output power to a level set by a reference voltage.
The detected forward power and reverse power are summed and compared to the reference voltage. The gain of the
reverse power path is 10 times that of the forward power. This ensures that should the load be remove the forward
power will be reduced to a safe level.

The reference voltage used by the control circuit is generated by a microprocessor. This value can be changed by
using the up/down control on the front panel or by remote contact closure from the rear panel accessory connectors.
The microprocessor also feeds the frequency information to the synthesizer.

Metering on the from panel is a multimeter, each function is selected by a rotary switch. The voltages for Current
and voltage are provided by the PSU metering boa r d, fo r ward and revere voltages by the synthesizer board. Al l
these voltages are also connected to the rear panel for remote metering.

Mounted on the exciter board is a magnetically latched relay used for remote on/off functions. This requires only a
momentary contact closure for either on or off. Cycling the AC power will not change the state of this relay.

FCC Compliance statement

THIS DEVICE HAS BEEN VERIFIED TO COMPLY WITH PART 73 OF THE FCC RULES.

Accessory connector

Pos Function

1 Remote on; Momentary ground to turn the unit on.
2 Remote off; Momentary ground to turn the unit off.
3 Forward Power DC indication 2.4V=12W
4 Reverse Power DC indication 2.4V=1.2W
5 Final Voltage DC indication V=Vsupply/10
6 Final Current 1A=0.1V
7 Raise Ground to Raise Output Power
8 Lower Ground to Lower Output Power
9 600 ohms balanced mono input

10 600 ohms balanced mono input

Efficiency V Output Power

FM25E FM50E FM150E

Power

Output

(Watts)

25.0 52% 50.0 48% 150.0 57%

22.5 49% 40.0 42% 120.0 51%

20.0 47% 32.0 38% 96.0 45%

17.5 46% 25.6 33% 76.8 40%

15.0 44% 20.5 30% 61.4 35%

12.5 42% 16.4 26% 49.2 32%

10.0 33% 13.1 23% 39.3 28%

Efficie n cy

(%)

Power

Output

(Watts)

Efficie n cy

(%)

Power

Output

(Watts)

Efficie n cy

(%)

Page 11

4 3 2 1

C

C

B

B

A

PTEK

1814 SCHOOLDALE DRIVE

SAN JOSE

CA 95124

A

BLOCK DIAGRAM

REVDWG NOFSCM NOSIZE

10/27/2003

C

SHEETSCALE

234

1

A

1OF1

5

4

3

2

1

44V

R1
100

R2
100

R3
100

R4
100

R13
100k

AGC2

C2

0.01u

C47
1000p

L1

C48
47u

FWD PWR

C5

0.01u

D1

1N4148

D D

44V IN

44V

Q1 MRF150

C6
47p

R5
120

IPARF

C27
120p

T2

1 5

4 8

PCB TRFMR

R6
22

C7

1000p

Q2
MRF150

L2

T1

48

6

C8
62p

15

C9
47p

L3

C10
47p

L4

C11
47p

L5

C12
24p

NOT USED ON EXCITERS

R7

120

RF OUT

C14
47p

D2

1N4148

REV PWR

C15

0.01u

C C

R11
100

R12
100

C16

0.01u

R9
100

R10
100

AGC1
AGC2

1
2
3
4
5
6
7
8
9

J12

10
11
12
13
14
15

R20

PRINTED

C42

0.01u

C43

0.01u

C39
47u

C30 0.01u

16

B B

470

PRINTED

PRINTED

C31 0.01u

IPARF

C44

REV PWR

FWD PWR

0.01u

C45

RF IN

PRINTED

Q3
MRF171

C36
39p

C37
39p

C38
39p

C33
15p

C34
15p

C32 0.01u

C35
15p

17
18
19
20

CON20

0.01u
R21 10k

AGC1

C46
33p

R22

NOT USED ON EXCITERS

100k

A A

Title

Schematic PA 300W 88 to 108MHz

Size Document Number Rev

B

Date: Sheet

5

4

3

2

110853 <RevCode>

1

12Monday, March 08, 2004

of

5

4

3

2

1

J1

2

2

1

1

D D

R1

2.4k

R2

2.4k

24V

R3

2

10k

R4

R5

2.4k

2.7k

R6

2.4k

1 3

R7

3.3k

J2

R8

4.7k

1
2
3
4
5

C C

6
7
8

9
10
11
12
13

C2
1000p

24V

C1

411

3

+

2

-

1

0.01u

FWD PWR
REV PWR

U1A LM324

14

To Front Pan Metering

CON14
J3

1

2

3

4

5

6

R9 100

J4

B B

2

2

1

1

0V IN

R10 0.01

C3 1000p

7

8

9
10
11
12
13
14

R11 10k

CON14

MTG1

13

1

2

MTG2

A A

1

Title

Current & Voltage Metering

Size Document Number Rev

B

5

4

3

2

1

Date: Sheet

11Monday, January 09, 2006

of

5

4

3

2

1

M1

D D

A

METER A

J1

1
2
3
4
5
6
7
8

10

9
8

7
9
10

C C

11
12

12

11

SW1

1
2
3
4
56

13
14

1

3

DOWNUP

SW2

2

B B

D1

OUT OF RANGE LO

D2

OUT OF RANGE HI

D3

REMOTE OFF

A A

Title

PCB ASSY FRONT PAN METERING

Size Document Number Rev

110849 A

A

5

4

3

Date: Sheet

2

11Monday, March 08, 2004

of

1

5

D D

J2
BNC

2

J3
BNC

2

J4

TYPE N

2

1

EXCITER 88 to 108MHz

1

1

COMPOSITE IN

SCA IN

RF OUT

4

J1

1
2
3
4
5
6
7
8
9
10
11
12
13
14

3

J1

1
2
3
4
5
6
7
8

9
10
11
12
13
14

PSU METERING

2

1

JP1

48V IN +

1

1

JP1

48V IN -

1

1

JP1

REAR TERMINAL BLOCK

REMOTE ON

REMOTE OFF

FWR PWR

C C

FINAL VOLTAGE
FINAL CURRENT

MONO IN BALANCED
MONO IN BALANCED

REV PWR

RAISE
LOWER

J5

1
2
3
4
5
6
7
8
9
10

24V +

1

1

1 2

FAN 24V

1

JP1

1

1

1

48V OUT
+

48V OUT

-

J1

1
2
3
4
5
6
7
8
9
10
11
12
13
14

1

1

24V
PSU

AC IN
Neutral

1

1

D2

1

1

24V+24V+ 24V-24V-

AC IN
LIVE

1

1

FRONT PANNEL
METERING

14
13
12
11
10
9
8
7
6
5
4
3
2
1

J1

D1

1

1

1

48V +

1

1

1

24V
PSU

B B

48V -

1

1

AC IN
Neutral

1

AC IN
LIVE

1

1

1

J6
PLUG AC MALE

1 2

3

1 2

AC ON

A A

Title

Size Document Number Rev

5

4

3

2

Date: Sheet

<Title>

<Doc> <RevCode>

D

of

1

11Monday, March 08, 2004