Page 1
YOU'RE HEARD, LOUD AND CLEAR.
Instruction Manual
Vari-Notch
4” Diameter
Manual Part Number
®
Cavity Filter
7-9150
8625 Industrial Parkway, Angola, NY 14006 Tel: 716-549-4700 Fax: 716-549-4772 sales@birdrf.com www.bird-technologies.com
Page 2
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.
Page 3
Manual Part Number 7-9150
Copyright © 2007 TX RX Systems, Inc.
First Printing: October 1996
Version Number Version Date
1 10/18/96
2 07/19/07
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.
Page 4
Page 5
+10
-10
-20
-30
-40
-50
-60
-70
0
Passband
Rejection Notch
Analyzer
Input
Figure 1: Spectrum Analyzer/Tracking Generator display of the lowpass 4” Vari-Notch filter.
Response curve shown for model number 15-52-01 (215-250 MHz)
GENERAL DESCRIPTION
The 4" Vari-Notch® cavity filter is designed to pass
a relatively narrow band of frequencies (pass-
band) while simultaneously rejecting a wide band
of frequencies (rejection notch). A variety of models are available that cover the range of frequencies from 132 to 960 MHz. The portion of the
frequency range that each model will tune across is
determined by the cavity's physical length.
Two types of 4" Vari-Notch filters are available, lowpass and highpass. Lowpass filters have the passband below the notch frequency while highpass
filters have the passband above the notch. The
cavity itself remains identical for both types. Figure
1 shows the response curve of a lowpass filter.
There are two adjustable parameters in a 4" VariNotch filter including the passband frequency and
the rejection notch frequency. Both of these
parameters are labeled on the response curve
shown in figure 1. All of the physical components
of the filter are labeled in Figure 2, with the adjustable parts shown in emboldened italics. The tuning
rod is used to adjust the passband while a variable
capacitor is used to adjust the rejection notch.
Generate
Output
TUNING
Required Equipment
The following equipment or it's equivalent is recommended in order to properly perform the tuning
adjustments for the 4" Vari-Notch filter.
1. IFR A-7550 Spectrum Analyzer with optional
Tracking Generator installed.
2. Eagle Return Loss Bridge (model
RLB150N3A).
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).
5. Insulated tuning tool (TX RX Systems Inc. part#
95-00-01).
6. 1/4" open-ended wrench.
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 1
Page 6
Tuning Rod
1/4" Shaft Locking Nut
Cavity Resonator
Variable Capacitor
Schematic Symbol
Loop Assembly
Input/Output Ports
Figure 2: The 4” Vari-Notch filter.
Tuning Procedure
Tuning of the filter requires adjustment of the passband and the rejection notch. The passband is
adjusted while observing the return loss response
and the rejection notch is adjusted by monitoring
the output of a tracking generator after it passes
through the filter. To insure proper tuning of the 4"
Vari-notch filter all adjustments should be performed in the following order:
1. Rough tune the passband.
2. Rough tune the notch.
3. Final tune the passband.
4. Final tune the notch, always the last adjustment
made.
PASSBAND
The peak of the passband will correspond very
closely to the point of minimum reflected energy
from the filter and maximum forward power through
it. A transmitter connected to the filter will operate
best when the reflected energy is lowest, therefore
the return loss response will be used to set the
passband. The passband can be checked and
adjusted using the following procedure.
Checking the passband
1. A zero reference for return loss must be established at the IFR A-7550 prior to checking the
passband frequency, this is done by connecting
the return loss bridge to the analyzer / generator as shown in Figure 3.
2. Set-up the analyzer / generator for the desired
frequency (center of display) and for a vertical
scale of 10 dB/div.
3. Do not connect the return loss bridge to the
cavity, leave the "load" port on the bridge open.
This will supply the maximum amount of
reflected energy to the analyzer input.
4. Insure that the IFR A-7550 menu's are set as
follows: DISPLAY - line
MODE - live
FILTER - none
SETUP - 50 ohm/dBm/gen1.
5. The flat line across the screen is the return loss
curve. Select the "Mode" main menu item and
then choose the "Store " command.
6 Next select the "Display" main menu item and
choose the "Reference" command. This will
cause the stored value
to be displayed at the
center of the screen as the 0 dB reference
value.
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 2
Page 7
+40
+30
+20
+10
-10
-20
-30
-40
0
Analyzer
Input
Generate
Output
+40
+30
+20
+10
-10
-20
-30
-40
0
Analyzer
Input
Generate
Output
RLB - 150 Bridge
REFLECTED
LOAD
SOURCE
Figure 3: Setting the return loss reference.
7. Connect the "load" port on the RLB to one of
the input /output ports and make sure the
remaining port is connected to a 50 ohm load;
refer to Figure 4. The display will now present
the return loss curve for the 4" Vari-Notch filter
being measured. The passband is that fre-
quency range over which the return loss is
15 dB or greater.
The resonant frequency is adjusted by using the
tuning rod, which is a sliding adjustment (invar rod)
that rapidly tunes the response curve across the
frequency range of the filter. Resonant frequency is
increased by pulling the rod out of the cavity and is
decreased by pushing the rod into the cavity. For
ease in making adjustments, rotate and slide the
rod while gently tapping on it with a screwdriver or
other small tool. This will break the surface tension
on the probe contact fingers and allow smoother
movement of the tuning rod.
Once the desired response is obtained using the
tuning rod, it is "locked" into place by tightening the
1/4" shaft lock nut. Failure to lock the tuning rod
will cause a loss of temperature compensation and
detuning of the cavity.
REJECTION NOTCH
The rejection notch will track with the tuning of the
passband and therefore should be the last adjust-
RLB - 150 Bridge
REFLECTED
4" Diameter
Vari-Notch
Filter
LOAD
SOURCE
50 Ohm Load
Figure 4: Checking the passband.
ment made to the 4" Vari-Notch filter. The rejection
notch is adjusted by changing the amount of
capacitance in the loop assembly. The capacitor is
a variable tubular-piston type.
Checking the rejection notch
1. The rejection notch is checked by connecting
the tracking generator to the input of the cavity
filter while the spectrum analyzer is connected
to the output, as illustrated in Figure 5.
2. Insure that the IFR A-7550 menu's are set as
follows: DISPLAY - line
MODE - live
FILTER - none
SETUP - 50 ohm/dBm/gen1.
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 3
Page 8
+10
-10
-20
-30
-40
-50
-60
-70
4" Diameter
Vari-Notch
Filter
0
Analyzer
Input
Generate
Output
Also, the interconnecting cable between the two filters, when cut to the correct length (odd multiple of
a 1/4 λ), will provide up to 6 dB of additional attenuation due to a mismatch of impedance between the
cable and the filters. The 6 dB of mismatch attenuation does not occur at the filters passband but,
only at frequencies where moderate to high attenuation occurs, such as at the rejection notch frequency. Because each of the filters in the multicavity arrangement are identical, the passband for
the entire arrangement is generally the same as
the passband for the individual filters. However,
each filters individual insertion loss is also additive.
When tuning a multi-cavity arrangement, each filter
is tuned individually prior to interconnecting them.
Then each is fine tuned to peak the overall
response of the multi-cavity arrangement.
Figure 5: Checking the
Adjusting the rejection notch
The notch is adjusted by turning the variable
capacitor. Because of the filters sensitivity to tool
contact, an insulated tuning tool must be used to
make the adjustment. Access to the capacitor is
obtained by removing the silver dot, small screw or
rubber button on the side of the loop assembly.
MULTIPLE CAVITY VARI-NOTCH FILTERS
Vari-Notch filters can be ordered in multiple cavity
arrangements of either two or three combined cavities. In these arrangements, identical filters are
connected in a cascaded fashion with the output of
each filter fed to the input port of the succeeding filter. The advantage to this arrangement is that the
amount of attenuation provided by each of the filters is additive. In the case of the rejection notch
frequency, the dual cavity can provide attenuation
of over 60 dB (30 dB for each filter).
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 4
Page 9
Isolation Curves for Transmitter/Receiver
The curves shown below for use with filters, duplexers, and multicouplers, indicate the
amount of isolation or attenuation required between a typical 100 watt transmitter and its
associated receiver at the TX (carrier suppression) and RX (noise suppression) frequency
which will result in no more than a 1 dB degradation of the 12 dB SINAD sensitivity.
100
90
80
70
Attenuation
60
50
40
100
132 - 174 MHz Band
For TX Power of:
25 watts -
50 watts 100 watts 250 watts 350 watts -
.2 .3 .4 .5 .6 .7 .8 .9 1 2 3 4 5 6 7 8 9 10
400 - 512 MHz Band
subtract 6 dB
subtract 3 dB
no correction
add 4 dB
add 5.5 dB
Frequency Separation (MHz)
90
80
70
Attenuation
60
50
40
NOTE
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 5
For TX Power of:
25 watts -
50 watts 100 watts 250 watts 350 watts -
.2 .3 .4 .5 .6 .7 .8 .9 1 2 3 4 5 6 7 8 9 10
These are only "typical" curves. When accuracy is required, consult the radio manufacturer.
subtract 6 dB
subtract 3 dB
no correction
add 4 dB
add 5.5 dB
Frequency Separation (MHz)
Page 10
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 7-9150-2 07/19/07 Page 6
Page 11
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 7-9150-2 07/19/07 Page 7
Page 12
Power Ratio and Voltage Ratio to Decibel
Conversion Chart
Loss or Gain Power Ratio Voltage Ratio
+9.1 dB 8.128 2.851
-9.1 dB 0.123 0.351
- dB +- dB +
Voltage
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
Voltage
Ratio
Power
Ratio
Voltage
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
Voltage
Ratio
Power
Ratio
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 8
Page 13
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 50
Ω
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
Volt s 50
Ω
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 9
Page 14
Free Space Path Loss Estimator
Frequency in MHz
50 150 170 450 500 800 900
0.1 50.58 60.12 61.21 69.66 70.58 74.66 75.68
0.25 58.54 68.08 69.17 77.62 78.54 82.62 83.64
0.5 64.56 74.10 75.19 83.64 84.56 88.64 89.66
1 70.58 80.12 81.21 89.66 90.58 94.66 95.68
2 76.60 86.14 87.23 95.68 96.60 100.68 101.71
3 80.12 89.66 90.75 99.21 100.12 104.20 105.23
4 82.62 92.16 93.25 101.71 102.62 106.70 107.73
5 84.56 94.10 95.19 103.64 104.56 108.64 109.66
6 86.14 95.68 96.77 105.23 106.14 110.22 111.25
7 87.48 97.02 98.11 106.57 107.48 111.56 112.59
8 88.64 98.18 99.27 107.73 108.64 112.72 113.75
9 89.66 99.21 100.29 108.75 109.66 113.75 114.77
10 90.58 100.12 101.21 109.66 110.58 114.66 115.68
Path Length (miles)
12 92.16 101.71 102.79 111.25 112.16 116.25 117.27
14 93.50 103.04 104.13 112.59 113.50 117.58 118.61
16 94.66 104.20 105.29 113.75 114.66 118.74 119.77
18 95.68 105.23 106.31 114.77 115.68 119.77 120.79
20 96.60 106.14 107.23 115.68 116.60 120.68 121.71
30 100.12 109.66 110.75 119.21 120.12 124.20 125.23
40 102.62 112.16 113.25 121.71 122.62 126.70 127.73
50 104.56 114.10 115.19 123.64 124.56 128.64 129.66
Formula: Path Loss (dB) = 36.6 + 20 log (MHz) + 20 log (miles)
TX RX Systems Inc. Manual 7-9150-2 07/19/07 Page 10
Page 15
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.
Page 16
8625 Industrial Parkway, Angola, NY 14006 Tel: 716-549-4700 Fax: 716-549-4772 sales@birdrf.com www.bird-technologies.com
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