Extending CAT5 cable

Given that CAT3 is spec'd only to 16MHz, * and CAT5 is spec'd to 100Mhz, you might run into problems with wideband signals.

As this cabling isn't horribly expensive, why not use CAT5?

• I'm obliged to anticipate the obvious objection -- "But that doesn't mean it won't work at 100MHz." True. But it isn't spec'd at that frequency, so you have no guarantee how it will perform.

I see it working best if your only using one pair.

Greg

why would you use cat3? Also where do you even get cat3 unless you're a copper thief these days?

I'd use silver satin, or some 1980s 50 foot coiled kitche telephone cords, with a handset swivel thingy on it, with nothing but the finest and most reasonably priced rj11 to rj45 adapters from Black Box.

Well the obvious reason to use CAT 3 is because as a former telephone systems contractor I happen to have a s*it load of it and I didn't want to have to buy any additional CAT 5 at this time. Was that so difficult to figure out? Most people that visit this group are not thieves, nor are they idiots. So don't act like one. You have no audience. We ask questions because we're looking for some advice from someone more knowledgeable than ourselves. And personally I really appreciate it when I get assistance with a problem. So if you really need to be a smart ass, please don't bother responding to my posts. Lenny

ds,

I just thought of something else. If CAT3 is spec'd out to 16MHZ and a typical NTSC TV channel was 6MHZ wide with 250KHZ guard bands on either end why would CAT3 cause any problems in a video application? It seems to exceed the requirements for TV video. Lenny

Regardless of the cable, it will have high frequency loss. It should work fine, unless you start to see two of everything. Shadows ?

Greg

The main problem is driving and terminating the CAT cable at the correct impedance. Improperly terminated cable for video make for some poor video but it depends on your needs/demands. What I think is bad may be more than sufficient for you - or not.

G²

It's not flat to 16 MHz. NTSC channels start at 54 MHz so the video has to be baseband. Even with BalUns the response isn't flat for baseband video. Switching to a different cable with different twist rates can cause problems, as well. This is from a retired TV broadcast engineer. :)

ideo

I do understand what you're saying about impedance mismatches and I can also see where marrying this cable with some (probably) Chinese baluns which are "supposed" to be constructed correctly could upset impedances, but Base band video was what I was referring to. So in that sense the response demands of the cable and the baluns would be limited to 4 or at best 5MHZ right, and then in theory wouldn't even CAT 3 be overkill? Lenny

I do understand what you're saying about impedance mismatches and I can also see where marrying this cable with some (probably) Chinese baluns which are "supposed" to be constructed correctly could upset impedances, but baseband video was what I was referring to. So in that sense the response demands of the cable and the baluns would be limited to 4 or at best 5MHz (right?), and then in theory wouldn't even CAT3 be overkill?

Probably. But CAT5 or CAT5e aren't horribly expensive, nor do you need a lot. I understand you don't want to waste materials you already have, but why not just buy the matching type, and that will be one less thing to worry about?

It has a lot more tilt than you think. What brand & type number is the CAT3 you have on hand?

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This Belden CAT3 has: MHz Loss @ 100 meters 0.772 2.2 1.000 2.6 4.000 5.6 8.000 8.5

Which is a 3.4 dB rolloff between .772 MHz and 4 MHz at 328.08 feet.

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This Belden CAT5 has: MHz Loss @ 100 meters 1.000 2.000 4.000 4.100 8.000 5.800

The loss at 4 MHz is 1.5 dB less at 328.08 feet.

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well hell, use some double cotton covered wire then.

It was foolish for me to to assume most people have bought cable in the past 20 years.

ed

rds,

st

The cable I have comes from various sources. No big name brands so figuring exact losses would be difficult however the Belden specs are eye openers. Thanks Michael for posting those. Lenny

I can't blame anyone for not wanting to spend money if they don't have to. (I'm no different.) But isn't it time to "knuckle down, buckle down, do it, do it, do it"?

Sometimes there are so many variables that the only thing to do is TRY IT!!! There is no obvious reason it won't work, but there is also no way to guarantee it WILL work.

Understanding theory is all well and good. Applying it properly is another thing. In the final test, the emperical results are what counts.

One story goes that Thomas Edison assigned a simple task to a newly hired engineer - calculate the volume of a light bulb. The newbie measured the bulb at the points he felt were critical and spent the afternoon calculating the volume. Edison looked at the numbers and said "You're off by at least 10%". Edison then took the light bulb, drilled a little hole in it, filled it with water, then drained the water into a graduated cylinder. And showed the engineer his numbers were off by 10%.

PlainBill

But Edison measured the inside volume. The engineer calculated the outside volume. To proof this, the engineer submerges the light bulb and measured the water rise. To prove his measurement he measured the force to keep it submerged.

So he proved that Edison was wrong. The glass of the bulbs in those times was very thick.

But Edison measured the inside volume. The engineer calculated the outside volume. To proof this, the engineer submerges the light bulb and measured the water rise. To prove his measurement he measured the force to keep it submerged.

So he proved that Edison was wrong. The glass of the bulbs in those times was very thick.

You're missing the point of the story. There are ways to measure things that are quick and elegant -- rather than applying a brute-force approach.

hat

The hole in the bulb was pretty slick. So was the water for that matter. I picked up a couple of baluns today and I am TRYING it tomorrow, CAT3, CAT 5, Coax, etc. and I'll let you guys know. Thanks for everyone's input. I really do appreciate it. Lenny

No. Edison asked the engineer: "calculate the volume of a light bulb". He did not ask to measure it.

Edition should have asked: "what is the inside volume of this light bulb". Then the engineer could decide to use other physical means to get the right answer.

Don't mess with engineers.