YOU'RE HEARD, LOUD AND CLEAR. Instruction Manual Vari-Notch® Duplexers (4” Cavities) Manual Part Number 7-9176 8625 Industrial Parkway, Angola, NY 14006 Tel: 716-549-4700 Fax: 716-549-4772 sales@birdrf.com www.bird-technologies.
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.
Manual Part Number 7-9176 Copyright © 2004 TX RX Systems, Inc. First Printing: September 1997 Version Number Version Date 1 09/19/97 2 04/09/98 3 04/26/99 4 06/23/04 Symbols Commonly Used WARNING ESD Elecrostatic Discharge CAUTION or ATTENTION Hot Surface High Voltage Electrical Shock Hazard Use Safety Glasses Bird Technologies Group NOTE Important Information TX RX Systems Inc.
GENERAL DESCRIPTION Vari-Notch® duplexers are used to provide simultaneous operation of a transmitter and receiver (or two transmitters) which are at different frequencies while connected to a common antenna. These duplexers are frequently used in radio repeater systems. This instruction manual (part# 7-9176-1) covers the installation, tuning, and maintenance of Vari-Notch duplexers constructed from 4” diameter cavities.
Resonant cavity filters are the basic building blocks of the system. Also important, are the interconnect cables between each filter which have cut length's equivalent to either 1/4 λ or 3/4 λ of that channels pass frequency. The exception is the antenna cable that couples each channels final filter to the antenna port, which is cut to 1/2 λ of the other (or remaining) channels pass frequency.
INSTALLATION Vari-Notch duplexers should be securely installed in a dry, vibration-free environment. Attachment of the cavity shells to a ground bus is recommended in order to maximize lightning protection. A lightning protection device placed in the antenna feedline, preceding the duplexer, is recommended.
require no further adjustment or maintenance. These devices will stay properly tuned unless they have been physically damaged or are tampered with. Check for loose or corroded connectors on the interconnect cables whenever an inspection is performed on other station equipment. Because duplexers are passive devices, field repairs are rarely required. Field repair of duplexers is limited to the replacement or repair of damaged cables.
WARNING Tuning while under transmit power can result in damage to the duplexer. 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.
handle or other small tool. This will break the surface tension on the probe contact fingers and allow smoother movement of the tuning rod. Cavity Tuning Tip When tuning a cavity that has been in service for some time it is not unusual to find the tuning rod hard to more in or out. This occurs because TX RX Systems Inc. uses construction techniques borrowed from microwave technology that provide 300 500 dBm 40 KHz/DIV MHz KHz RES large area contact surfaces on our tuning probes.
1. Reassemble the duplexer by reinstalling the cavities and interconnect cables in their original locations. 4. Set-up the analyzer / generator to the desired frequency (center of display) and for a vertical scale of 10 dB/div. 2. The passband for the channels are fine tuned first, in a manner very similar to tuning a single cavity. 5. Do not connect the RLB to the duplexer at this time, leave the "load" port on the bridge open.
300 500 dBm 40 KHz/DIV MHz KHz RES 30 VariNotch Filter 20 10 0 VariNotch Filter 50 Ω Load -10 -20 High Frequency Pass Channel Reject the Low Frequency Channel -40 -40 40 dB ATT GEN 0 dBM 10 MSEC GENERATE OUTPUT ANALYZER INPUT Load Source Reflected VariNotch Filter VariNotch Filter Low Frequency Pass Channel Reject the High Frequency Channel RLB - 150 BRIDGE (RLB) Figure 6: Equipment setup for fine tuning the passband of each channel. 13.
20. Repeat step 17 and 18 for the remaining channel (cables and equipment stay connected where they are). Remember to replace the small screws or rubber buttons on the side of the loop assemblies. 300 50 dBm -30 KHz/DIV 21. With the tuning completed, reconnect the equipment cables and antenna feedline. Test the system for proper operation.
DUPLEXER PROBLEMS AND REMEDIES Duplexers are passive devices requiring little or no service once installed in a system. The proper design and application of a given Duplexer will give years of trouble free service. When problems do occur in a duplex system it is necessary to identify as many abnormal conditions as possible to zero in on the specific cause of the problem.
2. Check the unit label. If needed, the duplexer may be field tuned. Consult the instructions and/or the factory if the duplexer is still under warranty or beyond field tuning capability. 3. Check cable, by substitution, using a termaline wattmeter, or a thruline wattmeter into a known good load. Check the antenna line input for reflected power. 4. To eliminate high input VSWR reduce the number of between series adapters by making up proper interconnect cables.
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.
POWER FWD./REV. VS. VSWR 500 400 V S W R 300 200 100 FORWARD POWER (WATTS) 1.1:1 50 40 1.15:1 30 1.2:1 20 1.25:1 1.3:1 10 1.4:1 5.0 4.0 1.5:1 3.0 1.6:1 1.8:1 2.0 2.0:1 1.0 2.5:1 3.0:1 0.5 40 20 10 8.0 6.0 4.0 2.0 1.0 0.8 0.6 0.4 0.2 REFLECTED POWER (WATTS) FOR OTHER POWER LEVELS, MULTIPLY BOTH SCALES BY THE SAME MULTIPLIER TXRX Systems Inc.
Power Ratio and Voltage Ratio to Decibel Conversion Chart Loss or Gain +9.1 dB -9.1 dB Power Ratio 8.128 0.123 Voltage Ratio 2.851 0.351 - dB + Voltage Ratio 1 0.989 0.977 0.966 0.955 0.944 0.933 0.923 0.912 0.902 0.891 0.881 0.871 0.861 0.851 0.841 0.832 0.822 0.813 0.804 0.794 0.785 0.776 0.767 0.759 0.75 0.741 0.733 0.724 0.716 0.708 0.7 0.692 0.684 0.676 0.668 0.661 0.653 0.646 0.638 0.631 0.624 0.617 0.61 0.603 0.596 0.589 0.582 0.575 0.569 Power Ratio 1 0.977 0.955 0.933 0.912 0.891 0.871 0.851 0.
Return Loss vs. VSWR Watts to dBm Return Loss VSWR Watts dBm 30 1.06 300 54.8 25 1.11 250 54.0 20 1.20 200 53.0 19 1.25 150 51.8 18 1.28 100 50.0 17 1.33 75 48.8 16 1.37 50 47.0 15 1.43 25 44.0 14 1.50 20 43.0 13 1.57 15 41.8 12 1.67 10 40.0 11 1.78 5 37.0 10 1.92 4 36.0 9 2.10 3 34.8 2 33.0 1 30.
8625 Industrial Parkway, Angola, NY 14006 Tel: 716-549-4700 Fax: 716-549-4772 sales@birdrf.com www.bird-technologies.
