[ARC5] ARC-5 dummy load
J Mcvey
ac2eu at yahoo.com
Sat Aug 20 19:38:33 EDT 2016
Found a bag 100 ohm 5 watt wire wound resistors the other day. I didn't what to do with them, so I tried making a lo-z dummy load for theARC-5 /SCR274 equipment.
10 of these in parallel is 10 ohms, 50 watts. You say "hey those are inductive WW resistors!" . Yes but the inductance is greatly reduced inparallel. In fact at 3.5 mhz it was 5+j17 which is more than swamped by the series 100 pf transmit cap (-j454).
The TX units are supposed load into 5 to 12 ohms with high capacitance, so it's in the sweet spot.The resistors got warmer than I thought they would, although the meter said it was pushing 2 amps. That's only 40 watts.There is some serious reactive voltage at the cap. I had the cap barrel laying too close to metal and I saw some blue corona discharge.
I'm a bit suspicious of this BC442 meter which never seems to budge above 2 amps. I get the same max current with a 5 ohm load!!Are they known to be inaccurate?
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