[TowerTalk] STEPPIR QUESTION

[W5LT]

You might check out the new SD-100 SteppIR controller. It is standard
equipment on the DB-series antennas, and supposedly has a much more robust
output circuit arrangement. 
The driver board can even be located 100s of feet from the controller
itself, as in up/on the tower. 
Bob, W5LT 

-----Original Message-----
From: jimlux [mailto:jimlux at earthlink.net] 
Sent: Monday, July 13, 2009 10:16 PM
To: Dan Zimmerman N3OX
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] STEPPIR QUESTION

Dan Zimmerman N3OX wrote:
>> Is there a way to build an external box with something like
opto-isolators
>>
> to better isolate the driver chips from getting nailed so easily?
> 
> 
> Well, you need to build something that can source as much current as the
> driver chips.
> 
> Wonder what happens if you replace each output with a thousand-volt MOSFET
?
> 

Circuits made to take big transients would do something very much like 
that.. They use a fairly decent FET or IGBT with 100V or more. Then a 
fast clamp on the output (like a back to back thyristor/DIAC) to limit 
the voltage (zeners might work, but because their voltage stays high, 
they dissipate more power).. Finally, a series transient suppressor (a 
LC circuit of some sort) to limit the di/dt, and then a vacuum gap 
across the whole thing where it goes to the outside world.