Hello Chris,
About RCDs tripped by RF : That's an interesting subject, even though I
never experienced such a problem myself (no surprise since I mostly run
QRP on any band).
After discovering that the name RCD is also officially used here in DL
(we formerly just called them Fehlerstrom-Schutzschalter, but that's
another story), I read a bit on the subject and learned that there are
indeed types designed to trip on 'higher frequency' components, and on
very short pulses ! These types of RCDs shall react on frequency
components up to 1 kHz. With typical tripping currents of 50 mA (or even
less), they may even get 'critical' at a few hundred kHz (with an 'error
current' of a few Amperes). The german Wikipedia article contains a bit
more info about those 'Type A' and 'Type B' RCDs than the english
article, so I quote ...
From
https://de.wikipedia.org/wiki/Fehlerstrom-Schutzschalter#Typen_nach_Art_des_Fehlerstroms
:
>>
Die zusätzliche Empfindlichkeit wird durch spezielle Magnetwerkstoffe
für die eingesetzten Ringbandkerne und Resonanzschaltungen zur
Beeinflussung des Frequenzgangs erreicht.
<<
Shortened, in english:
The additional sensitivity is achieved by special magnetic materials for
the toroid core, and resonant circuits (!!) to trim the frequency response.
Maybe you are already "close to resonance" of the frequency-trimming
circuit, or even though the RF flows as a common-mode signal through the
core, it causes strange (non-linear) effects in the RCD's current
transformer.
If you have a couple of 'monster' clamp-on ferrites (such as used for
thick coaxial cables), you can attach them close to the RCD to reduce
the problem, and (even more important) improve the counterpoise (RF
ground) near the antenna to prevent those RF currents entering the house
(or at least stay away from the RCD).
All the best,
Wolf DL4YHF .
Am 20.10.2015 um 11:25 schrieb Chris Wilson:
Hello John,
Monday, October 19, 2015
Thanks John, yes it does help, much appreciated, but what I am still
unsure of is if my Scopematch, that shows voltage and current
waveforms, is also, on the current waveform, displaying antenna
current? Does it not "do the same job" as a current meter?
With apologies to Kev, who has never heard of anyone with so many LF
issues ;) I have had to run half power recently, as full power is
tripping the house RCD after a minute or so of transmitting. I am
ordering some FT-240-77 material toroids, and building an isolation
matching transformer, instead of the auto transforming coil, in the
hope it cures this domestically disharmonious issue! I also have a two
piece E core to try. The fact it also triggers the workshop alrm is
not so big a deal as I can at least turn it off when transmitting. Has
anyone else had issues with RCD's and LF?
Thanks again.
Chris,
The arrangement I have here comprises a 5A FSD RF ammeter between
the transmitter and the antenna isolating transformer, and another
such ammeter (switchable between 5A and 500mA FSD) between the
isolating transformer and the earthy end of the antenna matching
network.. The intended impedance at this point is 50 ohms.
Hope this helps, John
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