Again there is a lot of false theories flying around
Agree AirNav, but how about your own (theories) ?:
Thought I might know quite a bit of RF amplifier properties, I NEVER heard about this one:
attach a mast amp which should bleed any excess static away
A (mast) amp might survive static discharge if its input is well protected against. Otherwise it will of course be destroyed too.
You might even find what is called "sacrifice amplifiers", to protect sensitive (and high value) equipment. They are "victimized" in order to anticipate harm from the equipment "behind" them. Static may "BLEED to a GROUND" if supplied, I agree, but the amplifier itself cannot "bleed" it. Where should it bleed it to ?
No need for a mastamp of course, if the equipment itself is protected against "ESD"sufficiently. Maybe you've
lost in translation
as I did according to your opinion a couple of postings before, AirNav ?
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dc block (bleed away excess static)
NO, it wont do, no matter how often you are going to repeat:
A „DC Block“ (finally a “capacitor”, sometimes mounted in a coaxial [discrete] housing, sometimes directly found on an electronic component board as its integral part) by definition is supposed to serve as a “DC barrier” between electronic circuits, -instruments, -amplifiers etc etc. that carry a DC (a bias- / supplyvoltage in most cases) beside of an AC (signal) component on an output, that is supposed to be connected to another electronic circuit, -instrument -amplifier etc.etc. input, that happens to be sensitive to DC., which, depending on its magnitude, might destroy components of the follow up devices’s input circuitry.
A typical example would be a RF “spectrum analyzer”, whose input attenuator circuitry is situated almost directly behind its front- / input- connector. Care must be taken to not only prevent the attenuator from “seeing” higher RF power levels than it is spec’ed for, (+30 dbm appearing a typical value) but also to keep away any DC component, (that the RF possibly might be “riding” on) as long, as the analyzers input itself is not set “AC coupled”. The latter then assuring, that a DC Block, (!) e.e. capacitor as mentioned before, already is taking care of the “barrier function”, that has been described previously.
While a “DC Block”, among other applications, is well known in the one described above, it is NOT supposed to be a measure against ESD hits, if introduced between an external antenna, and a receivers input behind such an antenna.
I honestly agree with AirNav, that “ESD” (to their words) has been discussed “in a lenght”. Nevertheless, AirNav keeps on claiming a “DC Block” to be a solution to the phenomenon it is about, which it is NOT at all.
There have been other “voices” in this discussion, trying to correct AirNavs “opinion”. No
success so far. AirNav saying, no ESD problems until now occuring to those RBs, making use of a DC Block. Are there really any users who do? I doubt! Would be interested to hear from about, show up, please !
Maybe to try the “other way round” for those who are concerned: just “google” for “DC Block”. No need to check all of those thousands of answers to find out that a lot of “well known manufactorers” (and distributors) not only specify their DC Blocks, but are also describing typical applications. NOT ONE OF THEM mentioning ESD countermeasures as such an application. Why even should they?
One more aspect: Electrostatic Discharge must be “given its way”. Remember your “wrist grounding” via “earth lead” to a heater plumbing (f.i.) before mounting a “static sensitive device” to your PC, or the aircraft, whose static charge (if there still is once ground) is “depleted to ground” by the fuel truck driver, providing a connection between the aircrafts body and a “static point” prior to refueling.
In case of the DC Block sitting in front of a receiver, static charge, if no further measure provided to “find its way to ground”, might cause a capacitor / DC Block to “break through” above a “threshhold”, depending on its specifications, then hitting the receivers sensitive input by its intension finding a way to bleed off via the component board – powersupply – mains.
There are better and usefull measures too that have been discussed “in a lenght before”, and might be looked for if there is interest.
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purchase an antenna with an anti static design
Fully agreed. Waiting for your answers on alternatives as Glyn has been asking for. The only one that I know has been mentioned before.
Regards
Karl
