8 dB Directional Coupler 4 Port Drop Tap for Cable TV Antenna Distribution
Skywalker
The SKY2342-8 with 8 dB Loss from Input to Tap is one in the Series of Directional Couplers with an Integral (4) Port Drop Tap, is made for MATV (Master Antenna TV), CATV (Cable TV) and TV Antenna Distribution with a bandwidth of 5-1000 MHz in Homes, Offices, Apartments and Hotel/Motel Systems. It Features a Main Feed Input and Output (DC Power Passing) with (4) Drop Ports (NOT DC Power Passing) for Feeding Television Wallplates with the Output levels being reduced from the from the input feed by the tap value (in this case -8 dB), and can be installed In-wall or on Exterior with a Grounding Connection.
SPECIFICATIONS
Tap Loss: -8dB
Bandpass: 5-1000 MHz
Insertion Loss (IN-OUT):
005-400 MHz / 1.6 dB
400-500 MHz / 1.7 dB
500-600 MHz / 1.8 dB
600-1.00 GHz / 1.6 dB
Isolation (TAP-TAP): 25 dB
Return Loss (All Ports):18 dB
Here we have accumulated some Design and Usage Tips when using this Particular Series of Direction Multi-taps.
In Example: the 8dB value has No Signal present on the Main Output as the Input signal goes to directly feed the 4-way Splitter within for the (4) Tap Outputs. However, the DC Voltage will still be present on the Main Output if it was present on the Main Input. We would call this a "Self-terminating" Tap in RF theory and yet some installers like placing 75 Ohm Terminators on any unused Outputs to maintain Impedance Match, which is also a good practice. If Your system has No DC Voltage present because you have not installed any in-line Drop Amplifiers, then you can place a regular 75 Ohm Terminator anywhere in the system as needed.
If You have Introduced DC Voltage into the system via a Power Inserter to feed In-line Amplifiers in the middle of a run of these taps (or any like them), it is best to Block the DC Voltage after feeding the Amplifier in use if it is not needed past this point farther along the run as most have not method of blocking DC Voltage passing thru Input or Output. You can do so with an In-line Voltage Blocking Adapter such as the Holland Electronics VBC (Voltage Blocking Coupler). This will allow you to place other passives in your drop system without worry of burning them up, incurring shorts in RG Cables, and place Terminators as necessary for any unused ports or cables.
Commensurately, if you need to use inline Attenuators, the (4) output ports have no DC Voltage present in either circumstance and it would be safe to install regular attenuators like the Holland Electronics FAM-* Series there however, if you wish to Attenuate The Main Input/Output Distribution line with DC Voltage being present to feed an inline Amplifier; use either the Holland Electronics FAMP-* Series Power-passing inline Attenuators made for this purpose.
Coaxial Drop Cable Directional Couplers
RF Directional Couplers are like splitters in that they can feed two lines from one, or combine two signals into one cable or feed. The insertion and coupling loss is different however, when compared to a simple two way with an equal split of one half, or 3 dB. The Directional Coupler will "Tap Off" Some signal to feed a local TV or similar component and send the Majority "Thru" to continue on down the Line to Continue or Repeat this exercise over and over again.
This type of Distribution occurs in "Loop Run" systems that essentially run one cable past each user in a "Loop", Tapping signal to feed each as it passes. This example is used in most Hotels and Motels as the cable runs up or down from floor to floor passing the next room above or below, using a Tap to "tap-off" signal to each room as it passes. In a more Domestic Situation, a coupler is handy to feed a device close to the origin of the signal (like where the Cable TV company attaches to the house outside) and send the majority through a relatively long run to feed other devices at the end. Cable TV Companies do this quite often in "Tapping-Off" signal to feed the Cable Modem. Another Situation would be that one device simply requires more than the other and both would be Accommodated using this Device. They are typically rated in dB as to the Loss incurred from "Input" to "Tap" leg, with the "Thru" Leg suffering comparatively less loss. The Higher the dB Tap value, the lower the "Thru" leg loss.
If you are adding several Directional Coupler Drop Taps to an existing Cable TV or Antenna feed, you may need to compensate for the loss that you are about to introduce. The gain of a Line Amplifier should be selected to zero out the loss that follows it. In other words, if you have fifty feet of cable and a two-way splitter, then a 10 db amplifier will be fine. Conversely, if you have an eight-way splitter and hundreds of feet of cable, you will need an amplifier with a higher gain. Just as in the case of a Pre-Amplifier, however, bigger is not always better.
