You can't just hang a diode across a dead short and get anything useful, BUT if locally the wire or connector is compromised and has a significant resistance, then the diode has a chance to significantly conduct. AND the change in resistance that the diode will make starts well below 0.2V.
NEC will not (afaik) do much to calculate the effect of the various tree types and heights in the vicinity of your antenna installation. If you're in the middle of a flat area, and in a large field, I guess it is about perfect.
So unless ur plunkiing down the big$$ to play with the "big boys" and have an antenna farm that's at ~150ft and up, the simulations are certainly useful but only running the antenna is going to tell you ultimately how well it really works. (I know and talk to people with installations like that)
And NEC won't tell you if you happen to have a ton of iron in the ground under you, or really how the particular location happens to work. Some locations just seem to work better than others.
But anyway, it's all good fun...
_-_-
Or the classic "Why can't the built-in potential across a p-n diode be measured externally?" or "Why isn't any current flowing if we short a p-n junction?" Hint: electrostatic potential vs. voltage, not the same. Hope it doesn't sound like a Mr. Simon quiz
.
There are other materials besides gold over copper (or nickel-gold over copper) to prevent copper oxidation ----
IEEE Xplore Abstract - Oxidation study of copper wire bonding
THx-RNMarsh
IEEE Xplore Abstract - Oxidation study of copper wire bonding
THx-RNMarsh
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More diodes and contacts --- Influence of DC bias on nonlinear distortion of contacts - Minowa - 2007 - Electronics and Communications in Japan (Part II: Electronics) - Wiley Online Library
And, a lot of interesting Stuff on copper and alloys in general.http://www.leonardo-energy.org/site...opper_in_electrical_contacts_210815_final.pdf
THx-RNMarsh
And, a lot of interesting Stuff on copper and alloys in general.http://www.leonardo-energy.org/site...opper_in_electrical_contacts_210815_final.pdf
THx-RNMarsh
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Are you confusing antenna performance with propagation modelling here? Just trying to understand these effects?
Welcome to the club.
That what you experienced is exactly the reason why i was hammering at the point of using positive controls and training of listeners, under _the_ _specific_ conditions, which were used for any controlled listening experiment.
Listening under test conditions is different compared to usual/normal/casual listening and the specific test protocol is quite likely influencing any participant as well (provided that he was not used to the specific protocol).
Therefore, listening results from any controlled experiment aren´t more reliable or correct per se, which means in the sense that further conclusions apart from the "null hypothesis could be or could not be rejected" were not warranted, unless the experimenter did incorporated the points mentioned above.
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Bear
Against all rules I found that the best TX (and in the same time RX antenna )is tuned horizontal single long wire lambda half Resonant antenna , with about 75m long wire for 1,6-1,8Mhz AM band,
this unconventional antenna system force pure max. RF voltage output vs conventional max.RF current output , and is for me and for many others people far superior from many positive aspects .
I think you will find that there are still 'no counterpoise needed' verticals being sold. Of course, they need to use the feeder outer as counterpoise - which their buyers will often vehemently deny, and sometimes even the manufacturer will deny. Various 'compact antennas' may still be on sale which use the feeder outer as the actual antenna.bear said:
Yes, -100dB issues don't usually need to be considered in amateur radio. They don't need to be considered in audio either.
Quite a lot in capacitor choice, but (unlike most audio) for good engineering reasons such as: temperature stability (for VFO), dissipation (for PAs and ATUs), voltage rating (ditto).
Modelling nearby trees has nothing to do with propagation as they will be in the near-field zone. Some antennas (e.g. small magnetic loops) may work primarily by inducing currents into nearby large structures which then act as lossy but reasonably effective radiators.billshurv said:
Re Contact issues.
I have spent a lifetime in audio servicing, and so I have gotten to see the faults that emerge long term, and are not predicted in data sheets/catalogues.
In 'old school' gear in the majority of cases the fault root origin is some kind of contact issue.
The majority of these are solder joint issues, with benign or consequential resultants.
Next in line are potentiometer and switch contact issues.
Volume control issues are due to dried/emulsified contact grease/lubricant, and simple carbon track wear which can be accelerated by grit type contaminants, and DC leakage from previous/post stages.
Coke etc spillages are another cause in horizontal oriented gear, ie pro audio.
Switching issues are due to oxidised and/or eroded contact systems, and more commonly in slide type switch mechanisms which are universally
silver plated ime.
Same deal as pots, emulsified lubricants form a 'stiff' waxy layer that allows oxidation but precludes low contact pressure self cleaning/wiping.
Throw into the equation DC leakage and transient currents, and/or environmental contaminants of many kinds.
A very bad contact oxidising/sulphating ? contaminant is outgassing from 'masonite' and asian chipboards.
We have all experienced old school gear with a 'dodgy' pot, and/or dodgy lever action source/mon etc switch.
Operating the switch/pot a 'dozen' times can restore operation for a while, but inevitably the fault condition returns.
The only reliable method to restore reliability in these cases is to dismantle these slide mech switches and polish the contacts with a fine metal polish.
These switching faults are interesting whist returning..ie one channel may go slowly 'off' over a long period until the sound is quite like rectification, and with large peaks/passages temporarily partially restoring correct signal transfer.
And the same happens with RCA's etc...oxidised/sulphated contacts can cause an intermittent/modulated/partially rectified signal throughput.
Dan.
I have spent a lifetime in audio servicing, and so I have gotten to see the faults that emerge long term, and are not predicted in data sheets/catalogues.
In 'old school' gear in the majority of cases the fault root origin is some kind of contact issue.
The majority of these are solder joint issues, with benign or consequential resultants.
Next in line are potentiometer and switch contact issues.
Volume control issues are due to dried/emulsified contact grease/lubricant, and simple carbon track wear which can be accelerated by grit type contaminants, and DC leakage from previous/post stages.
Coke etc spillages are another cause in horizontal oriented gear, ie pro audio.
Switching issues are due to oxidised and/or eroded contact systems, and more commonly in slide type switch mechanisms which are universally
silver plated ime.
Same deal as pots, emulsified lubricants form a 'stiff' waxy layer that allows oxidation but precludes low contact pressure self cleaning/wiping.
Throw into the equation DC leakage and transient currents, and/or environmental contaminants of many kinds.
A very bad contact oxidising/sulphating ? contaminant is outgassing from 'masonite' and asian chipboards.
We have all experienced old school gear with a 'dodgy' pot, and/or dodgy lever action source/mon etc switch.
Operating the switch/pot a 'dozen' times can restore operation for a while, but inevitably the fault condition returns.
The only reliable method to restore reliability in these cases is to dismantle these slide mech switches and polish the contacts with a fine metal polish.
These switching faults are interesting whist returning..ie one channel may go slowly 'off' over a long period until the sound is quite like rectification, and with large peaks/passages temporarily partially restoring correct signal transfer.
And the same happens with RCA's etc...oxidised/sulphated contacts can cause an intermittent/modulated/partially rectified signal throughput.
Dan.
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Exactly.
Some still claim antennas are voodoo, but that's the equivalent of the same tendency in audio.
Even sophisticated test gear for antennas is cheap these days, eg MetroVna - Antenna Analyzer
No, I'm sayin' that the distortions can be very subtle indeed, at least initially.
It is with time that further contact degradation builds to more obvious sonic degradation.
Dan.
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