[TowerTalk] For Sale: PolyPhaser IS-3T1 12 Cond in lineprotector

[jimlux]

WA3GIN wrote:
> Folks can go to TESSCO and purchase gas tube arrestors inexpensively. IT 
> is relatively easy to determine the right unit for your application. I 
> recently purchased  eight gas tubes to homebrew a rotor control 
> protector. The price per gas tube was $1.70. A very low cost way to get 
> reasonably good protection. I love the Polyphaser product line...just 
> can't justify the cost!
> 
> 73,
> dave
> wa3gin
> 

gas tubes are nice, but if you're protecting something that has a low 
damage threshold (like the inputs to most ICs), they're not the right 
technology.

Something like a gas tube (to limit the max voltage to 50-100V, or 
whatever), followed by a resistor (to limit current) and suitable low 
capacitance diode clamps (to limit to the supply voltages) might work 
better. Hopefully, that's what you're getting with a more expensive 
transient protection device.

Fast data is a real challenge, because the C of the diodes limits the 
bandwidth.  Choosing a different driver/receiver chip in the device to 
be protected can help (because an onchip clamp is lower C than an 
external devie)