Vishay makes Transient Voltage Suppressors (TVS) in clamp voltages from
10 volts to several hundred volts. A common size can handle a 1500 watt
surge. They are very fast, I think faster than MOVs and have a sharper
knee so the clamp voltage doesn't rise as much as MOVs with increased
current. Both unidirectional (diode in reverse) and bidirectional (for
ac circuits) are available around $1 each qty 1. For low power
circuits, they are a good choice. I think the construction is basically
back to back heavy duty zeners for the bidirectional version, at a price
far below stud mount zeners.
for one TVS source - see Mouser
http://www.mouser.com/Circuit-Protection/TVS-Diodes-Transient-Voltage-Suppressors/_/N-5g3g?P=1z0z819Z1yzv44xZ1z0x7vi&Keyword=tvs&FS=True
OTOH, MOVs are available for 10,000's of joules in the screw mount
sizes, for motor, power contactor, or mains transient suppression.
Grant KZ1W
On 6/23/2011 11:52 PM, K8RI on TT wrote:
> On 6/24/2011 1:15 AM, Kostas Stamatis wrote:
>> Hello to all...
>> I want to protect from lightning and static charges my rotator cable as a
>> controller cable for a switch. I have seen some solutions in DXengineering
>> but i would prefer a reliable homebrew solution. Anyone with some ideas?
> Diacs were mentioned, but those are more of a control device. Neon
> lamps (NE-51s) work well with tube input and control but are a bit high
> in voltage for rotator control.
>
> For low voltage protection, I'd (1) keep the cables inside the tower and
> bypassed to the tower at the rotator and base of the tower. The problem
> with solid state circuits is the need for a low clamping voltage. They
> make some huge Zeners with a 3/4" threaded base which will handle huge
> current. Used are normally very cheap, but new are very expensive. the
> nice thing about the big zeners is you can get one just a few volts
> above the maximum working voltage of the circuit. These are one place
> where I do favor MOVs. As the rotator lines are low voltage and
> relatively protected by their very nature *IF* they are protected at the
> rotator and base of the tower the voltage is unlikely to rise very high
> and MOVs may last a very long time...but no guarantee. The same with
> the massive Zeners.
>
> There's the possibility of using 0.1 uf disk ceramics (You need a low Z
> at 1 MHz) on each of the leads at the rotator, and those or zeners or
> MOVs at the base of the tower and bulkhead connector at the station
> entrance.
>
> I think most rotator damage comes from cable pick up, or from wiring
> pick up in the house with the current going back to the rotator.
>
> 73 and good luck,
>
> Roger (K8RI)
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