[TowerTalk] homebrew low voltage surge suppressors?

[K4SAV]

Thanks for the post Red.  It is good information.  I don't have any 
argument with anything you said.

In suppressors intended for VHF these inductors can be made to work 
because the inductor can be much smaller. However when applied to 
operation at 160 meters there is a problem getting the inductor into 
saturation before the suppressor fires.

The delay in these suppressors is in nanoseconds when the rate of change 
(dv/dt) is around 20,000 to 30,000 v/us. Driving a lightning pulse into 
50 ohms will have a dv/dt in this range. (They will be slower for slower 
ramp rates.) To keep the suppressor from firing (like ICE says it 
operates), the inductor has to saturate before it has about 1000 volts 
on it (or whatever the suppressor rating is, which could be less). With 
a lightning pulse waveform, that happens at an inductor current of about 
1 amp. For a 44 uH inductor, the current produced by 1500 watts of RF on 
160 meters and an SWR of 1.5 to 1, is about 1 amp RMS (1.4 amps peak). 
So if you made it saturate at 1 amp, it wouldn't work for high power. If 
the inductor saturates at a higher current, the suppressor takes the 
full load.

My original post calculating inductor current was in error. Inductor 
current should be insignificantly small for lightning waveforms.

Jerry, K4SAV

Red wrote:

>The inductor core in the ICE suppressor saturates due to the low 
>frequency components of a surge and becomes a short circuit, thus 
>relieving the gas tube of much of the current.  That can happen before 
>the gas tube begins to conduct, as gas tubes exhibit a delay.  In 
>addition, the suppressor appears as a mismatched load when a surge is 
>applied (combined operation of the inductor and gas tube) and much of 
>the surge energy is reflected back to the antenna.  Of course, the 
>antenna  is also a mismatched load to much of the surge energy, so some 
>of that energy is reflected back to the surge reflector, and goes back 
>and forth.  In the process, energy is dissipated in the feedline.  
>Spreading of the energy among several components of the system helps 
>these small suppressors to survive fairly large surges. 
>
>The gas tubes used are typically rated for up to 20,000 Amperes. Their 
>life is limited at that current level, though.  The voltage across them 
>while they are conducting is typically 15 to 20 Volts.   Gas tubes 
>operate just like spark gaps.  The advantage over a simple spark gap 
>(spark plug, for example) is that the characteristics are regulated by 
>the composition of the gas and the electrodes and by the gas pressure in 
>the tube.  Thus they can achieve high operating voltage when not 
>conducting, low operating voltage while conducting, and stable 
>characteristics that is independent of atmospheric conditions of 
>pressure and temperature.  The working parts are protected from 
>contaminants and oxidation, which affect simple spark gaps.
>
>A major component of the PolyPhaser and ICE suppressors is the blocking 
>capacitor, which limits the energy that is passed to the rig while 
>energy is being dissipated in the suppressor, feedline, and antenna.
>
>These devices work quite well.  Similar technology and components, 
>including gas tubes, have been widely used for years to protect 
>electronic components from surges.  Read _Protection of Electronic 
>Circuits from Overvoltages_, by Ronald B. Standler, 1989; John Wiley & 
>Sons, Inc., particularly Part 2, Chapters 7 through 15, for information 
>about gas tubes, varistors, avalanche and Zener Diodes, semiconducor 
>diodes and rectifiers, thyristors, impedances and current limiters, 
>filters, isolation devices, and parasitic inductance and how these 
>devices may be used to protect electronic equipment from overvoltage 
>stresses such as those associated with lightning.  This book may not be 
>available in many public libraries but is available on inter-library 
>loan from college and university libraries.
>
>73 de WOØW
>
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