[ARC5] BC-230 first run

[J Mcvey]

Those bc 230s are MOPA like the ARC5s but I have never seen one in one piece, let alone working!
I was wondering if there is a tunable roller inductor in there or do they use the antenna series cap to increase/decrease the inductance presented to the antenna?
Did you try the external variable at half mesh? Better or worse?  

The SCR274 and ARC5 types have a sweet spot antenna reactance range where the roller inductor is effective. Too much or too little reactance and I have difficulty getting it to load.The ARCs will load into a pure 5-10 ohm resistance if the inductor is at zero. Not sure if that would work on the BC230, though.
Loading them into  REAL antennas gets even more interesting! 





 

    On Tuesday, March 29, 2016 10:02 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
 

 I tried the ARC-5 capacitor in parallel with the 5 ohm dummy load as
suggested by a poster, but was unable to get any power output and
not even a glimmer on the RF ammeter. So it was back to series
connection, and an immediate result of 0.7 Amp when the final plate
current was dipped (from about 70 mA to about 40).

Up to now, I've been testing at 6200 KHz, the bottom end of the coil
box. I got to thinking that the ARC-5 cap might not be enough pF at
this frequency, so went up to 7250 KHz, about where a local net is
held. This made no difference to the meter, still the same 0.7 A when
resonated (but see below). The dip is reasonably sharp.

Some observations:
The roller contact appears to be not critical, at least for my dummy
load. Shifting it throws off the VFO frequency and also necessitates a
retune of the final tank so as to get an indication on the ammeter,
which is dramatic as dip approaches max (ammeter rises sharply).
As the final tank is being dipped again, the VFO comes back on tune
and when dipped it is exactly on the former frequency. This behaviour
is not unexpected.

Plate input is about 12 Watts (300 x 40mA) but the ammeter indicates
about 2.5 Watts (0.7 Amp squared x 5 ohms). However, the dummy
load now gets too hot to touch (maybe one watt in each one-watt
resistor?) so perhaps the ammeter is sticking at 0.7 and the true power
is about 5 Watts. Perhaps more output (hotter resistors) is due to the
shift up to 7250 KHz where the ARC-5 capacitor is more effective?

73 de Neil ZL1ANM
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