RF Hybrids Jeffrey E Brown Georgia Transmission Corporation

RF Hybrids Hybrids are used to: Separate transmitters from receivers Skewed Hybrid Separate transmitters from transmitters Balanced Resistive (R) Hybrid Balanced Reactive (X) Hybrid Combine and Split signals Balancing Transformers Signal Rejection and Acceptance High Pass Filter Low Pass Filter

Terms and Definitions Terms: Insertion Loss Trans-Hybrid Loss Return Loss

Skewed Hybrid: DCUB Scheme 30 dB 6.5 dB 30 dB – 20 dB = 10 dB Trans-hybrid loss Should be >20 dB 20.0 dB 29.5 dB Purpose: The Transmitter is 1 W = 30 dB. A lot of times the Receiver will be getting less than 1 W. You can see the losses above. The Purpose of the Skewed Hybrid is to keep the Transmitter off the Receiver.

Ametek 1RU Hybrid

Radio Tx Radio Rx Tuner Skewed Hybrid

DCUB Scheme with Skewed Hybrid Tx Rx Tx Rx Tx/Rx Tx/Rx

Single Freq Tuner 235.5 kHz One Coax 232.5 kHz

HYBRIDS

Radio Tx #1 Radio Tx #2 Tuner Balanced R Hybrid

Dual Channel Uni Directional Transfer Trip

Dual Channel Bi-Directional TT 235.5 kHz Single Freq Tuner Tx 1 Tx 2 232.5 kHz 233.0 kHz Rx 1 One Coax Rx 2 233.5 kHz

Radio Tx #1 Radio Tx #2 Tuner X Hybrid

X Hybrid - Reactive

R vs X So what is the difference between the R and X? The last unit that goes into the yard should be an X and not an R.

Dual Channel Uni Directional Transfer Trip should X Hybrid or R Hybrid could

HYBRIDS

Hybrid Layouts can get complicated quick. Single Phase Coupling Two Phase Coupling Three Phase Coupling

Ametek Balancing Transformer 3 dB Rule 3 dB gain is twice power 3 dB loss is half power 38.5 dB 40.0 dB 37.0 dB 37.0 dB 35.5 dB 35.5 dB Ametek Balancing Transformer

Balancing Transformer (ph-ph coupling)

HYBRIDS

Hybrid Losses For the most part are fixed. Require 50 Ohm Termination on each port.

appropriately terminated In 50 ohms. Fact: To have the typical losses talked about in this presentation each terminal on the Hybrid must be appropriately terminated In 50 ohms. Trans-Hybrid Loss = 20 to 40 dB Loss Trans-Hybrid Loss = 20 to 40 dB Loss 50 Ohm locations: Radio Hybrid External Transmitter 50 Ohm Characteristic: Radio Transmitter Coax and Triax Cables Device Device

1. 50 Ohms from Hybrid (fixed)

2. External

Coaxial Type 50Ω Load with Adapter UHF female to BNC female adapter

3. Radio can have 50 Ohm Load Ametek has 50 Ohm jumper on the back plane, but it does not add 50 Ohms to the receiver. It is for the transmitter. Some competitor radios have a 50 Ohm termination for the receiver. Research your radio… Which should be Ametek.

UPLC Impedance

DCB Scheme No Hybrids No hybrids, but the receiver needs a 50 ohm load for reference. How does it get it?

UPLC Impedance

2W vs 4W 50 Ohm >4k Ohm Fact: Receiver is high impedance but needs to be 50 ohms. In 2 Wire the 50 ohm (Tx) is in parallel with 4k ohm (Rx) which equals 50 ohms. In 4 Wire the Tx is 50 ohm and the Rx is >4k ohm so we need to add a 50 ohm to the Receiver. This 50 ohm can be in the radio, in the skewed hybrid, or external.

Hybrids Which Scheme does not need a Hybrid? What are the three places you can find your 50 ohm impedance for your receiver? What is the purpose of a Skewed Hybrid? What is the purpose of an R Hybrid? If you only have two Transfer Trip Transmitters on the local end what Hybrid do you need? What hybrid do you need at the other end of the line? Where is the 50 ohm load to be located on the remote end?

HYBRIDS

Single Frequency Tuner Tuners Single Frequency Tuner Dual Frequency Tuner Wide Band Tuner One Coax One Freq Grouping Two Coaxes Two Freq Grouping (low F and hi F) One Coax Freq Band (FLO to FHI)

DCUB Standard Example Draw Hybrids and their connections here. Scheme types for your example. Frequencies that will clue you in on what hybrids will be needed. Add appropriate tuner here.

DCB Standard Example Draw Hybrids and their connections here. Scheme types for your example. Frequencies that will clue you in on what hybrids will be needed. Add appropriate tuner here.

Bi Directional Dual Channel TT Standard Example Draw Hybrids and their connections here. Scheme types for your example. Frequencies that will clue you in on what hybrids will be needed. Add appropriate tuner here.

Real Example #1

Real Example #2

Real Example #3

Real Example #4

Real Example #5: Extra Credit

This is how crazy it gets….

Thanks… Questions????