Bird Technologies 81-37-25 User Manual

YOU'RE HEARD, LOUD AND CLEAR.

Instruction Manual for

VHF & UHF Dual-Section

Isolators

Manual Part Number

7-9095

8625 Industrial Parkway, Angola, NY 14006 Tel: [phone] Fax: [phone] [e-mail] www.bird-technologies.com

Warranty

This warranty applies for one year from shipping date.

TX RX Systems Inc. warrants its products to be free from defect in material and workmanship at the time of shipment.

Our obligation under warranty is limited to replacement or repair, at our option, of any such products that shall have
been defective at the time of manufacture. TX RX Systems Inc. reserves the right to replace with merchandise of
equal performance although not identical in every way to that originally sold. TX RX Systems Inc. is not liable for dam-
age caused by lightning or other natural disasters. No product will be accepted for repair or replacement without our
prior written approval. The purchaser must prepay all shipping charges on returned products. TX RX Systems Inc.
shall in no event be liable for consequential damages, installation costs or expense of any nature resulting from the
purchase or use of products, whether or not they are used in accordance with instructions. This warranty is in lieu of all
other warranties, either expressed or implied, including any implied warranty or merchantability of fitness. No repre­sentative is authorized to assume for TX RX Systems Inc. any other liability or warranty than set forth above in con­nection with our products or services.

TERMS AND CONDITIONS OF SALE

PRICES AND TERMS:

Prices are FOB seller’s plant in Angola, NY domestic packaging only, and are subject to change without notice. Fed­eral, State and local sales or excise taxes are not included in prices. When Net 30 terms are applicable, payment is
due within 30 days of invoice date. All orders are subject to a $100.00 net minimum.

QUOTATIONS:

Only written quotations are valid.

ACCEPTANCE OF ORDERS:

Acceptance of orders is valid only when so acknowledged in writing by the seller.

SHIPPING:

Unless otherwise agreed at the time the order is placed, seller reserves the right to make partial shipments for which
payment shall be made in accordance with seller’s stated terms. Shipments are made with transportation charges col­lect unless otherwise specified by the buyer. Seller’s best judgement will be used in routing, except that buyer’s routing
is used where practicable. The seller is not responsible for selection of most economical or timeliest routing.

CLAIMS:

All claims for damage or loss in transit must be made promptly by the buyer against the carrier. All claims for shortages
must be made within 30 days after date of shipment of material from the seller’s plant.

SPECIFICATION CHANGES OR MODIFICATIONS:

All designs and specifications of seller’s products are subject to change without notice provided the changes or modifi­cations do not affect performance.

RETURN MATERIAL:

Product or material may be returned for credit only after written authorization from the seller, as to which seller shall
have sole discretion. In the event of such authorization, credit given shall not exceed 80 percent of the original pur­chase. In no case will Seller authorize return of material more than 90 days after shipment from Seller’s plant. Credit
for returned material is issued by the Seller only to the original purchaser.

ORDER CANCELLATION OR ALTERATION:

Cancellation or alteration of acknowledged orders by the buyer will be accepted only on terms that protect the seller
against loss.

NON WARRANTY REPAIRS AND RETURN WORK:

Consult seller’s plant for pricing. Buyer must prepay all transportation charges to seller’s plant. Standard shipping pol­icy set forth above shall apply with respect to return shipment from TX RX Systems Inc. to buyer.

DISCLAIMER

Product part numbering in photographs and drawings is accurate at time of printing. Part number labels on TX RX
products supersede part numbers given within this manual. Information is subject to change without notice.

Bird Technologies Group TX RX Systems Inc.

Manual Part Number 7-9095

Copyright © 2006 TX RX Systems, Inc.

First Printing: May 1994

Version Number Version Date

1 05/24/94

2 07/29/99

3 01/17/06

Symbols Commonly Used

WARNING

CAUTION or ATTENTION

High Voltage

Use Safety Glasses

ESD Elecrostatic Discharge

Hot Surface

Electrical Shock Hazard

NOTE

Important Information

Bird Technologies Group TX RX Systems Inc.

Input Connector

Output Connector

Remove screws to

access tuning

capacitors

Remove stickers
to access tuning

capacitors

Remove stickers

to access tuning

capacitors

Input Section

Load

Output Section

Load

Figure 1: VHF or UHF Dual-Section Isolator.

GENERAL DESCRIPTION

Isolators perform two important functions. Their pri­mary function is to keep other RF frequencies out
of the transmitter so that intermodulation products
cannot be generated. isolators have a substantial
amount of reverse isolation. They also insure that
the transmitter never sees any significant reflected

struction and theories of operation of ferrite isola­tors refer to the TX RX Systems Inc. publication
“SEMINAR SUBJECTS” titled “An Elementary
Introduction to Ferrite Isolators, Circulators and RF
Loads” (literature number C2003H92). Contact
your TX RX Systems sales representative if you

wish to order a copy.
power so it will always operate with maximum sta­bility at full-power output. Isolators prevent energy
from getting to the transmitters output by dumping
RF energy entering the output of the isolator into a
dummy load.

Dual-Section Isolators

Dual section units have two load ports, one for

each section of the isolator, refer to Figure 1.

Although loads of equal power rating may be used

for both ports, it is customary to use an output load
This manual deals primarily with the procedures
necessary for field tuning ferrite isolators to new
frequencies. It is assumed that procedures in this
manual will be carried out by a skilled electronics
technician who is familiar with the communications

capable of dissipating the maximum expected

reflected power that might be encountered. A small

load (5 watts) is usually installed on the first section

where the high reflected power is not a factor. The

model number on the isolator label indicates the
system. For a more detailed discussion of the con-

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 1

3.313"

84 mm

0.188"
5 mm

3.125"

79 mm

0.313"
8 mm

1.438"

37 mm

4.688"

120 mm

5.813"

148 mm

3.250"

83 mm

5.500"

140 mm

0.219" (6 mm) Dia
Mounting Holes
4 places

Figure 2: Mounting hole layout.

value of the loads installed. See the specification
charts at the end of this manual.

VHF models maintain their specifications over a

2.5% bandwidth which equals 3.8 MHz at 150
MHz. UHF models have a minimum bandwidth of

1.25% which equals 5.75 MHz at 460 MHz. When
the frequency of operation needs to be changed
by more than about half of the above mentioned
bandwidth figures, tuning of the isolator will ensure
optimum performance.

INSTALLATION

All isolator models may be mounted on most sur­faces but should not be located where they will be
exposed to moisture or very high humidity. TX RX
Systems' isolators are well shielded magnetically

and may be mounted on steel cabinets or panels.
A mounting hole layout is shown in Figure 2.

The isolator loads can get quite
hot during operation. This can
occur when an antenna system
component fails causing high
reflected power which is then dis­sipated by the isolator load.
These loads can get hot enough
to burn skin so use caution when
servicing these devices.

Recommended Test Equipment for Tuning

The following equipment or its equivalent is rec­ommended:

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 2

+30

+20

+10

-10

-20

-30

0

Analyzer
Input

Generate

Output

+30

+20

+10

-10

-20

-30

0

Analyzer
Input

Generate

Output

RLB - 150 Bridge

Reflected

To device to be tested.

This connector left open

for setting 0 dB reference.

Load

Source

Figure 3: Proper hookup of RLB-150 Bridge.

1) IFR Model A-7550 Spectrum Analyzer/Track­ing generator combination or equivalent.

2) Eagle RLB-150 Return Loss Bridge (35 dB
directivity).

3) Double shielded coaxial cable test leads
(RG142 B/U or RG223/U).

4) 50 Ohm load with at least -35 dB return loss
(1.10:1 VSWR).

Bridge

Dual
VHF

Isolator

Loads that will

be used during

actual operation

1

TUNE

5

3

2

6

4

Any good

quality

50 ohm

load

Figure 4: Tuning for maximum return loss.

5) Metal blade tuning tool for adjusting ceramic
and/or piston variable capacitors (TX RX Model

makes this stored trace the zero reference. The
procedure for doing so is outlined below.

# 95-00-01).

Tuning Procedure

It is necessary to be able to set zero references for
both insertion loss and return loss measurements
in order to determine if specifications are being
met. This procedure is not outlined in the A-7550
manual but consists of using the “STORE” trace
function to save the reference trace level and then
putting the A-7550 into the reference mode which

SETTING 0 DB INSERTION LOSS REFERENCE
Set the A-7550 for the desired frequency and
bandwidth. Connect the output and input leads
together through a female barrel connector (UG 29

-N or UG 914 -BNC) and proceed as follows:

1) Make sure that the unit is in “LIVE” mode.

2) From the Mode Menu, “STORE” the trace.

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 3

+30

+20

+10

-10

-20

-30

+6

+4

+2

0

0

-2

-4

-6

Analyzer
Input

1

Generate

Output

Bridge

2

TUNE

5

3

6

4

Analyzer
Input

1

Generate

Output

RF

2

TUNE

5

3

6

4

Figure 5: Tuning for maximum return loss.

3) Switch to the Display Menu and select
“REF”. The trace should appear at the 0 dB
level.

Figure 6: Tuning for passband symmetry.

4) Set the A-7550 for 10 dB per division and set a
zero dB return loss reference as outlined in
paragraph 2.

5) With the equipment connected as in Figure 4,
adjust tuning capacitor #1 for maximum return

SETTING 0 DB RETURN LOSS REFERENCE

loss at the desired center frequency.

Set the A-7550 (see Figure 3) for the desired fre­quency and bandwidth. Connect the Return Loss
Bridge to the A-7550 but leave the LOAD port
open. Repeat steps 1, 2, and 3 above.

6) Reversing the bridge and load connections as
shown on Figure 5, adjust capacitor 2 for maxi­mum return loss at the desired center fre­quency.

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 4

+30

+20

+10

-10

-20

-30

+30

+20

+10

0

0

-10

-20

-30

Analyzer
Input

1

5

3

TUNE

4

Generate

Output

RF

Load

Removed

2

6

Figure 7: Tuning for reverse isolation.

7) Set the A-7550 for 2 dB per division vertical
scale and set a zero dB insertion loss reference
as outlined in paragraph 1.

Load

Removed

Analyzer
Input

1

Generate

Output

RF

2

TUNE

5

3

6

4

8) Connect the A-7550 to the isolator as shown in

Figure 6, Adjust capacitors 3 and 4 for a cen-

Figure 8: Tuning for reverse isolation.

tered and symmetrical response.

9) Set the A-7550 for 10 dB per division and reset
the zero dB insertion loss reference per para­graph 1.

10) Connect the equipment as shown in Figure 7

and adjust capacitor 5 for maximum attenua­tion (reverse isolation). Be sure to remove the
output load as this allows the observation of
the isolation produced by a single section.

11) Reconnect the output load and disconnect the
input load as shown in Figure 8. Adjust capac­itor 6 for maximum attenuation (reverse isola­tion). Then reconnect the input load.

12) Repeat steps 4 through 12. The isolator is now
ready to be put back in service.

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 5

VHF Dual Junction Circulators and Isolators

Frequency
Range (MHz)

118-136 81-35A-25-00 81-35A-25-20 81-35A-25-50 81-35A-25-60 81-35A-25-100

132-150 81-36-25-00 81-36-25-20 81-36-25-50 81-36-25-60 81-36-25-100

144-174 81-37-25-00 81-37-25-20 81-37-25-50 81-37-25-60 81-37-25-100

220-250 81-52-25-00 81-52-25-20 81-52-25-50 81-52-25-60 81-52-25-100

Number of Junctions 2

Junction Type Lumped constant

Max Continuous Input Power 81-35A-15-xx: 100 W; all others: 150 W

RF Load Model Number None 82-01-05 82-01-05 82-01-05 82-01-05

82-01-05 82-01-16 82-01-17 82-01-15

Continuous RF Load Power None 5/5 W 5/25 W 5/60 W 5/100 W

Isolation Bandwidth 2.5% of center frequency

Typical Insertion Loss 0.9 dB

Max Insertion Loss 1.1 dB

Peak Reverse Isolation >60 dB

Min Reverse Isolation >50 dB

Nominal Impedance 50 ohm

Min Return Loss (VSWR) 20 dB (1:22: 1)

Temperature Range -30 to +60 Celsius

Connectors, Input/Output/Load N

Dimensions, HxWxD, inches 3.94x6.25x1.78 5.0x6.25x1.78 8.81x6.25x1.78 9.91x6.39x1.78 9.91x6.39x2.9

Dimensions, HxWxD, mm 100x159x45 127x159x45 223x159x45 252x162x45 252x162x74

Weight, lb (Kg) 2.60 (1.18) 2.78 (1.26) 3.24 (1.47) 3.88 (1.76) 4.60 (2.09)

UHF Dual Junction Circulators and Isolators

Frequency
Range (MHz)

Number of Junctions 2

Junction Type Distributed Parameter

Max Continuous Input Power 250 W

RF Load Model Number None 82-01-05 82-01-05 82-01-05 82-01-05

Continuous RF Load Power None 5/5 W 5/25 W 5/60 W 5/100 W

Isolation Bandwidth 1% of center frequency

Typical Insertion Loss 0.7 dB

Max Insertion Loss 0.8 dB

Peak Reverse Isolation >60 dB

Min Reverse Isolation >50 dB

Nominal Impedance 50 ohm

Min Return Loss (VSWR) 20 dB (1:22: 1)

Temperature Range -30 to +60 Celsius

Connectors, Input/Output/Load N

Dimensions, HxWxD, inches 4.19x8.75x1.78 5.22x8.75x1.78 8.97x8.75x1.78 10.09x8.75x1.78 10.09x8.75x2.9

Dimensions, HxWxD, mm 106x220x45 133x220x45 228x220x45 256x220x45 256x220x48

Weight, lb (Kg) 2.95 (1.34) 3.13 (1.42) 3.59 (1.63) 4.22 (1.92) 4.95 (2.25)

406-430 81-65-25-00 81-65-25-20 81-65-25-50 81-65-25-60 81-65-25-100

450-470 81-70-25-00 81-70-25-20 81-70-25-50 81-70-25-60 81-70-25-100

470-490 81-71-25-00 81-71-25-20 81-71-25-50 81-71-25-60 81-71-25-100

490-512 81-72-25-00 81-72-25-20 81-72-25-50 81-72-25-60 81-72-25-100

510-530 81-75-25-00 81-75-25-20 81-75-25-50 81-75-25-60 81-75-25-100

82-01-05 82-01-16 82-01-17 82-01-15

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 6

Power Ratio and Voltage Ratio to Decibel

Conversion Chart

Example: Given a gain of +9.1 dB or a loss of -9.1 dB

Loss or Gain Power Ratio Voltag e R a t i o

+9.1 dB 8.128 2.851

-9.1 dB 0.123 0.351

- dB +- dB +

Vol ta ge

Ratio

1 1 0 1 1

0.989 0.977 0.1 1.012 1.023

0.977 0.955 0.2 1.023 1.047

0.966 0.933 0.3 1.035 1.072

0.955 0.912 0.4 1.047 1.096

0.944 0.891 0.5 1.059 1.122

0.933 0.871 0.6 1.072 1.148

0.923 0.851 0.7 1.084 1.175

0.912 0.832 0.8 1.096 1.202

0.902 0.813 0.9 1.109 1.23

0.891 0.794 1 1.122 1.259

0.881 0.776 1.1 1.135 1.288

0.871 0.759 1.2 1.148 1.318

0.861 0.741 1.3 1.161 1.349

0.851 0.724 1.4 1.175 1.38

0.841 0.708 1.5 1.189 1.413

0.832 0.692 1.6 1.202 1.445

0.822 0.676 1.7 1.216 1.479

0.813 0.661 1.8 1.23 1.514

0.804 0.646 1.9 1.245 1.549

0.794 0.631 2 1.259 1.585

0.785 0.617 2.1 1.274 1.622

0.776 0.603 2.2 1.288 1.66

0.767 0.589 2.3 1.303 1.698

0.759 0.575 2.4 1.318 1.738

0.75 0.562 2.5 1.334 1.778

0.741 0.55 2.6 1.349 1.82

0.733 0.537 2.7 1.365 1.862

0.724 0.525 2.8 1.38 1.905

0.716 0.513 2.9 1.396 1.95

0.708 0.501 3 1.413 1.995

0.7 0.49 3.1 1.429 2.042

0.692 0.479 3.2 1.445 2.089

0.684 0.468 3.3 1.462 2.138

0.676 0.457 3.4 1.479 2.188

0.668 0.447 3.5 1.496 2.239

0.661 0.437 3.6 1.514 2.291

0.653 0.427 3.7 1.531 2.344

0.646 0.417 3.8 1.549 2.399

0.638 0.407 3.9 1.567 2.455

0.631 0.398 4 1.585 2.512

0.624 0.389 4.1 1.603 2.57

0.617 0.38 4.2 1.622 2.63

0.61 0.372 4.3 1.641 2.692

0.603 0.363 4.4 1.66 2.754

0.596 0.355 4.5 1.679 2.818

0.589 0.347 4.6 1.698 2.884

0.582 0.339 4.7 1.718 2.951

0.575 0.331 4.8 1.738 3.02

0.569 0.324 4.9 1.758 3.09

Power

Ratio

dB

Vol ta ge

Ratio

Power

Ratio

Vol ta ge

Ratio

0.562 0.316 5 1.778 3.162

0.556 0.309 5.1 1.799 3.236

0.55 0.302 5.2 1.82 3.311

0.543 0.295 5.3 1.841 3.388

0.537 0.288 5.4 1.862 3.467

0.531 0.282 5.5 1.884 3.548

0.525 0.275 5.6 1.905 3.631

0.519 0.269 5.7 1.928 3.715

0.513 0.263 5.8 1.95 3.802

0.507 0.257 5.9 1.972 3.89

0.501 0.251 6 1.995 3.981

0.496 0.246 6.1 2.018 4.074

0.49 0.24 6.2 2.042 4.169

0.484 0.234 6.3 2.065 4.266

0.479 0.229 6.4 2.089 4.365

0.473 0.224 6.5 2.113 4.467

0.468 0.219 6.6 2.138 4.571

0.462 0.214 6.7 2.163 4.677

0.457 0.209 6.8 2.188 4.786

0.452 0.204 6.9 2.213 4.898

0.447 0.2 7 2.239 5.012

0.442 0.195 7.1 2.265 5.129

0.437 0.191 7.2 2.291 5.248

0.432 0.186 7.3 2.317 5.37

0.427 0.182 7.4 2.344 5.495

0.422 0.178 7.5 2.371 5.623

0.417 0.174 7.6 2.399 5.754

0.412 0.17 7.7 2.427 5.888

0.407 0.166 7.8 2.455 6.026

0.403 0.162 7.9 2.483 6.166

0.398 0.159 8 2.512 6.31

0.394 0.155 8.1 2.541 6.457

0.389 0.151 8.2 2.57 6.607

0.385 0.148 8.3 2.6 6.761

0.38 0.145 8.4 2.63 6.918

0.376 0.141 8.5 2.661 7.079

0.372 0.138 8.6 2.692 7.244

0.367 0.135 8.7 2.723 7.413

0.363 0.132 8.8 2.754 7.586

0.359 0.129 8.9 2.786 7.762

0.355 0.126 9 2.818 7.943

0.351 0.123 9.1 2.851 8.128

0.347 0.12 9.2 2.884 8.318

0.343 0.118 9.3 2.917 8.511

0.339 0.115 9.4 2.951 8.71

0.335 0.112 9.5 2.985 8.913

0.331 0.11 9.6 3.02 9.12

0.327 0.107 9.7 3.055 9.333

0.324 0.105 9.8 3.09 9.55

0.32 0.102 9.9 3.126 9.772

Power

Ratio

dB

Vol ta ge

Ratio

Power

Ratio

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 7

POWER IN/OUT

VS

INSERTION LOSS

The graph below offers a convenient means of determining the insertion loss of filters, duplexers,
multicouplers and related products. The graph on the back page will allow you to quickly determine
VSWR. It should be remembered that the field accuracy of wattmeter readings is subject to
considerable variance due to RF connector VSWR and basic wattmeter accuracy, particularly at low
end scale readings. However, allowing for these variances, these graphs should prove to be a useful
reference.

INSERTION LOSS (dB)

500

400

300

250

200

150

125

INPUT POWER (Watts)

100

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

.50

.25

75

50

50

75 100

125 150 200

250

300

400

500

OUTPUT POWER (Watts)

FOR LOWER POWER LEVELS

DIVIDE BOTH SCALES

BY 10 (5 TO 50 WATTS)

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 8

500

400

300

200

100

50

40

30

20

POWER FWD./REV.

VS

VSWR

V
S

W

R

1.1:1

1.15:1

1.2:1

10

FORWARD POWER (Watts)

5.0

4.0

3.0

2.0

1.0

0.5

40

20

10

8.0 6.0

4.0

2.0

REFLECTED POWER (Watts)

FOR OTHER POWER LEVELS

MULTIPLY BOTH SCALES

BY THE SAME MULTIPLIER

1.0 0.8

0.6

0.4

1.25:1

1.3:1

1.4:1

1.5:1

1.6:1

1.8:1

2.0:1

2.5:1

3.0:1

0.2

TX RX Systems Inc. Manual 7-9095-3 01/17/06 Page 9

Power Conversion Chart

dBm to dBw to Watts to Volts

dBm dBw Watts

80 50 100kW 2236

75 45 31.6 kW 1257

70 40 10.0 kW 707

65 35 3.16 kW 398

60 30 1000 224

55 25 316 126

50 20 100 70.7

45 15 31.6 39.8

40 10 10.0 22.4

38 8 6.31 17.8

36 6 3.98 14.1

34 4 2.51 11.2

32 2 1.58 8.90

30 0 1.00 7.07

29 -1 0.79 6.30

28 -2 0.63 5.62

27 -3 0.50 5.01

26 -4 0.40 4.46

25 -5 0.32 3.98

24 -6 0.25 3.54

23 -7 0.20 3.16

22 -8 0.16 2.82

21 -9 0.13 2.51

20 -10 0.10 2.24

19 -11 79 mW 1.99

Volts 5 0Ω

dBm dBw Watts

18 -12 63 mW 1.78

17 -13 50 mW 1.58

16 -14 40 mW 1.41

15 -15 32 mW 1.26

14 -16 25 mW 1.12

13 -17 20 mW 1.00

12 -18 16 mW 0.890

11 -19 13 mW 0.793

10 -20 10 mW 0.707

9 -21 7.9 mW 0.630

8 -22 6.3 mW 0.562

7 -23 5.0 mW 0.501

6 -24 4.0 mW 0.446

5 -25 3.2 mW 0.398

4 -26 2.5 mW 0.354

3 -27 2.0 mW 0.316

2 -28 1.6 mW 0.282

1 -29 1.3 mW 0.251

0 -30 1.0 mW 0.224

-5 -35 316 uW 0.126

-10 -40 100 uW 0.071

-15 -45 31.6 uW 0.040

-20 -50 10 uW 0.022

-25 -55 3.16 uW 0.013

-30 -60 1 uW 0.007

Volts 50Ω

Bird Technologies Group TX RX Systems Inc.

Return Loss vs. VSWR

Watts to dBm

Return Loss VSWR

30 1.06

25 1.11

20 1.20

19 1.25

18 1.28

17 1.33

16 1.37

15 1.43

14 1.50

13 1.57

12 1.67

11 1.78

10 1.92

9 2.10

Watts dBm

300 54.8

250 54.0

200 53.0

150 51.8

100 50.0

75 48.8

50 47.0

25 44.0

20 43.0

15 41.8

10 40.0

5 37.0

4 36.0

3 34.8

2 33.0

1 30.0

dBm = 10log P/1mW

Where P = power (Watt)

Insertion Loss

Input Power (Watts)

50 75 100 125 150 200 250 300

3 25 38 50 63 75 100 125 150

2.5 28 42 56 70 84 112 141 169

2 32 47 63 79 95 126 158 189

1.5 35 53 71 88 106 142 177 212

1 40 60 79 99 119 159 199 238

Insertion Loss

.5 45 67 89 111 134 178 223 267

Output Power (Watts)

Free Space Loss

Distance (miles)

.25 .50 .75 1 2 5 10 15

150 68 74 78 80 86 94 100 104

220 71 77 81 83 89 97 103 107

460 78 84 87 90 96 104 110 113

860 83 89 93 95 101 109 115 119

940 84 90 94 96 102 110 116 120

Frequency (MHz)

1920 90 96 100 102 108 116 122 126

Free Space Loss (dB)

Free space loss = 36.6 + 20log D + 20log F

Where D = distance in miles and F = frequency in MHz

Bird Technologies Group TX RX Systems Inc.

8625 Industrial Parkway, Angola, NY 14006 Tel: [phone] Fax: [phone] [e-mail] www.bird-technologies.com