CATV splitter: how to?

[g579]

My question is: what is the construction of a 5 - 1000 MHz CATV splitter ?
As I saw from some pictures, it consists of two ferrite transformers and some other chips.
Do somebody know some details ? Thanks
g579

 

[AL0117]

Hi,

See the picture below. The 2 transformer could be made on a single binocular ferrite, or on two separate thoruses. The common terminals of the transformers are connected together and from that point you should connect a 2.2-5.6 pF to ground. Between the 2 output terminals is a 2*Z0 resistor ( theoretically for CATV 150 ohm, but it could vary between 150 and 200, to achieve better isolation and output match)).

 

[g579]

Hi AL0117,
Thanks for the fast response.
Could you please clarify some of your text and picture ?
1. Are the common terminals of the transformers (to be connected together) the central points of the transformers ?
2. Is the input GND point the left transformer's bottom point ?
3. The numbers ( 1, 1 at output and 1, 3 at input) are turns ratios ?
Thanks
g579

 

[AL0117]

HI g579,

1,2 and 3 correct. I used some splitters with the following turns data:
from in to central1 1T/ central1 to ground 3T
out1 to central2, and central2 to out2 3T
central1 and central2 tied together and connected to ground through 3.3pF
Between out1 and out2 180 ohm


below is the insertion loss

 

[vfone]

The cheapest splitter is the resistive one. And it is very broadband.

 

[Frosty]

Depends if you wish to have the splitter DC passing on all ports or just make a signal tap.

Usually most CATV systems have 24 V on the centre conductor which powers any inline amplifiers or nodes.

Generally a 'tap' would be DC passing on one leg and DC isolated on the 'tap'

If an insertion loss of 3-8dB is acceptable a balun or transformer is not needed, it would be sufficient for 40-860MHz passband merely to couple the 'trunk' and the 'tap' by means of some microstrip. Depending where yu have tapped the CATV 'trunk' you would also need to adjust for level, so sometimes it is preferred to have a loss of >10dB on the tap, and so avoid the use of in line attenuators on the feeder cable assuming a feeder length from tap to termination of <25m and a desired input level of -35 to -50dBm at the CATV equipment.

 

[g579]

Hi AL0117,
Thnks for your construction details.
After some thinking they seems to be logical.
One question. You have enclosed the transfer characteristics for your splitter.
Have you some data about the reflection and isolation parameters ?
Thanks again.
g579

 

[qiang]

is there any information about this kind of divider?
it is the last year ,the first time i hear of this kind of divider.,and i am intersting about it