Hi Neil,

Have you tried adding a load resistor to the receiving end? If you are
driving the line with a PIC you can use 220 ohms and that will scare
away most noise.

Cheerful regards, Bob

On Tue, Dec 2, 2014, at 07:36 AM, Neil wrote:
> I want to amplify some TTL-level signals for better noise immunity=20
> through about 10'-15' of wire through a vehicle, and trying to figure=20
> out what good options there are.  The data being transmitted is a custom=
=20
> signal (not exactly async serial, and not exactly PWM) of approx=20
> 50-100khz, at 5V.  Only one data-line out and one data-line back in.  It=
=20
> works now, but noise issues we've experienced in other areas has me=20
> worried, and the board is being revised currently, so I want to add this=
=20
> also.  The wiring/harness is pretty much set in stone so I can't really=20
> twist, shield or add wires for differential signaling, etc.  The=20
> electronics at both sides of the line is pretty much all I can change.
>=20
> First thought is 74xx245's etc, but have the impression they're really=20
> for strengthening signals for driving higher loads over short distances=20
> (ie: still chip-to-chip comms).  The last time I used these was  a few=20
> decades ago with a Z80 processor.  Not sure I should use it for long=20
> wires across devices.  Another option is to use discrete transistor=20
> push-pull drivers.  Also, I'm sure I can use a MAX3232 or similar for=20
> this.  But are there any other better options?  Looking at digikey gives=
=20
> me 10k+ options, and filtering by package, supply-voltage, cost, etc=20
> still nets me a couple thousand options.  Favourite devices?
>=20
> Cheers,
> -Neil


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