COAX splitter

[Marks256]

I need one of these https://www.firefold.com/ProductInfo.aspx?productid=COAXSPLIT-2

I was wondering if any special circuitry was needed for it, or if i could just connect them all together and call it good.

In case someone doesnt know what it is, it is a "Y" adapter for the coax cables that are used with TVs and what not (not sure what the proper term is...)


Anyways, i do plan on buying one when i get a chance (they are cheap), but it might be a while before i get anywhere, so maybe something temporary?

Thanks

 

[dknguyen]

Special circuitry for what? It's just a thing of copper that splits into two isn't it?

 

[Nigel Goodwin]

You shouldn't just join the leads together, it ruins the impedance matching (RF is imedance matched for maximum power transfer, but mainly to prevent reflections). The Y splitters can be either resistive (three resistors in a star) or the lower loss inductive (transformer) type.

 

[dknguyen]

Ohhh, I see. He wants to know if he can get by without one of those Y-adapters. I thought he was asking if he had to do anything extra to use that Y-adapter in the photo

 

[mramos1]

You will want to match the impedance (like said) as well make sure you do not need more than 900Mhz. Is this for a cable box or sat? Video? I forgot the impedance.. But you want to look at both maybe.

EDIT: Marks, it is $1.99, come on man..

 

[Sceadwian]

So Nigel, what resistors would you use to match the 75ohms?

 

[Marks256]

EDIT: Marks, it is $1.99, come on man..

Yeah, i am cheap...

You shouldn't just join the leads together, it ruins the impedance matching (RF is imedance matched for maximum power transfer, but mainly to prevent reflections). The Y splitters can be either resistive (three resistors in a star) or the lower loss inductive (transformer) type.

That is why i asked. How would i match the impedance? I tried to look for a circuit, but i couldn't find anything.

 

[Marks256]

Oh, sorry. It will just be from my antenna to a VCR and a usb capture card.

 

[mramos1]

Marks, so that is 75 ohms?

Sceadwian, too funny. Wonder if mouser.com has them. I need some 37.5 ohm resistors.

Marks, shipping will be more than $1.99.

 

[Sceadwian]

I found a picture of the innards of a cheap splitter, it's just a few turns of wire wrapped around a common ferrite bead, problem is the picture is so small I can't tell how it's wound. Looks like the in and one of the outs are just a straight piece of wire (with maybe turns around the ferrite) and the out is a seperate piece of wire wrapped around the ferrite bead seperatly. I can't see the number of turns though. Some more research on ferrite splitter and coax might yield some results. Not sure what kind of bead would be appropriate, but it shouldn't be large.

 

[Roff]

The resistive splitter shown here is simplest, if you have plenty of signal strength. Personally, I would never make anything that is this inexpensive.

 

[Marks256]

Guys, i just need this to hold up until i can get to a store and buy one...

 

[Sceadwian]

Just do the resistors Marks. Keep in mind this is going to be absolutely crappy as far as signal quality goes. At the very least wrap the whole thing in electrical tape to issolate it and then wrap that entire thing in foil wrap connected to all three grounds.

 

[mneary]

If you keep the wires short, especially the cable shield interconnection, the signal will be reduced quite a bit (6 db) with a resistive "T" but quality shouldn't suffer (except as related to receiver sensitivity). If you can keep everything less than an inch long you probably don't need to shield the resistors.

If your VCR and capture card are less than 5 feet apart, I would try first just connecting all of the wires together. You might be able to tolerate the quality loss until you get to the store. You'll have some ghosting, and a few channels might get really weak.

 

[Marks256]

Ok, thanks guys (maybe gals, too).