1. RF Hybrids Jeffrey E Brown Georgia Transmission Corporation

2. 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

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

4. 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.

5. Ametek 1RU Hybrid

6. Radio Tx
Radio Rx
Tuner
Skewed Hybrid

7. DCUB Scheme with Skewed HybridTx Rx Tx Rx
Tx/Rx
Tx/Rx

8. Single Freq Tuner
235.5 kHz
One Coax
232.5 kHz

9. HYBRIDS

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

11. Dual Channel Uni Directional Transfer Trip

12. 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

13. Radio Tx #1
Radio Tx #2
Tuner
X Hybrid

14. X Hybrid - Reactive

15. 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.

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

17. HYBRIDS

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

19. 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

20. Balancing Transformer (ph-ph coupling)

21. HYBRIDS

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

23. 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

24. 1. 50 Ohms from Hybrid (fixed)

25. 2. External

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

28. 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.

29. UPLC Impedance

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

31. UPLC Impedance

32. 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.

33. 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?

34. HYBRIDS

35. 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)

36. 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.

37. 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.

38. 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.

39. Real Example #1

40. Real Example #2

41. Real Example #3

42. Real Example #4

43. Real Example #5: Extra Credit

44. This is how crazy it gets….

45. Thanks…
Questions????