The antenna end of mine, looks very similar to PG0A/PA3FYM implementation,
drawn at
http://remco.org/wordpress/wp-content/uploads/2008/01/pg0a-k9ay-small.jpg
I guess he uses the LED as a rectifier? Not even remotely the best idea I
have seen. LED's are horrible for anything with high peak currents (like
charging capacitors).
Also, it is generally a bad idea to have high peak currents (like charging
electrolytics) in iron or ferrite cores. You can pass some current through
the secondary, but you better be sure the current level is a long way from
altering the core's magnetic properties, and this flux level would include
any flux from external signals. This has nothing to do with your diodes
blowing, just to say the circuit you linked does not look the least bit good
for multiple reasons.
Uses an isolation transformer (not an autotransformer) and provides
galvanic isolation between antenna, antenna ground rod, and the coax.
I do not use LED's in mine, I just use regular diodes, and these are the
diodes that are blowing. I'm starting to believe that it's during RTTY
contest weekends when I'm on 10 a lot, that the diodes are blowing, and I
think Tom's suggestion about bypassing effective for 10M (not just 160M)
may be most relevant.
Is this a + , - , and AC logic system?
That circuit has a terrible bypassing and isolation scheme. It has no diode
bypassing for the common mode path from the cable through the diodes to the
relay coils and to the loops, except for what the electrolytics might
marginally provide at radio frequencies. That circuit can also induce
significant common mode into the loops, exactly what the isolated secondary
is attempting to cure! The wiring undoes the goal of the isolated secondary.
I would give that circuit a completely failing grade. 0 out of 100. Bad
design.
Of course this is getting more and more common these days, as we look at
systems with tunnel vision to focus on and cure one thing.
73 Tom
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Topband Reflector
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