> On Jun 28, 2023, at 9:48 AM, Tony Duell via cctalk <[email protected]>
> wrote:
>
> On Wed, Jun 28, 2023 at 6:00 AM Grant Taylor via cctalk
> <[email protected]> wrote:
>>
>> Tony's email makes me ask more questions than I have (smart alack)
>> answers to. Maybe ~> hopefully I can ~> will learn something.
>
> I was being a bit of a smart alec too. The point I was making is that
> a bit of normal IDC ribbon cable is not electrically the correct cable
> for an AUI interface but it won't matter over a few inches.
>
> The correct cable is 4 twisted pairs with a overall screen (shield).
> One pair is thicker wires than the other 3 and is used for the power.
> This cable was very hard to get by the metre when I needed some about
> 30 years ago, and a full reel was several hundred pounds. I was lucky
> enough to be given a couple of metres as an 'offcut' by a gentleman
> who worked in network support. You probably need something like that
> if you're makng a 1m cable. But not for what the OP is trying to do.
Not for one meter. For 50 meters, sure, although a piece of Cat 5 Ethernet
cable for the signals along with a separate wire pair for power may well be an
entirely adequate substitute. The rule of thumb I would use is that any
wrong-impedance connection shorter than a 5 percent or so of the wavelength
isn't a problem. For 10 Mb/s Ethernet that translates to 1.5 to 2 meters.
This is also why "UHF" connectors are acceptable at RF frequencies (but not at
UHF frequencies, never mind what they call themselves).
paul
