[hpsdr] ALEX - Call for comments - Protection devices.

[Lyle Johnson]

>>> Quick search, subject: "Front End Protection"
>>>
>>> 1. Good old NE2(A1A) Neon Bulb
>>> 2. Two diodes antiparalel
>> The JRC NRD-525 receiver used two anti-paralleled diodes as a mean of input protection, but the common advice on its
>> Yahoo discussion group was to remove them as soon as possible, as they can generate IMD products in presence of strong
>> BC stations. I suppose the same holds for two LEDs in anti-parallel.

A high value resistance to ground to prevent static buildup (100K to 1 
Meg) in parallel with a spark gap offers no distortion and clamps 
induced surges (not direct hits by lightning, of course).  Caps in the 
front end filters should be rated somewhat higher than the spark gap - 
you don't want to use 25V caps in a 70V-protected system!

Try searching Digikey for "surge arrestor gastube" for EPCOS' offerings. 
  The lowest voltage ones ought to be suitable.

73,

Lyle KK7P



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