[ARC5] BC-AS-230 Transmitter Follies, Part 1

[Dennis Monticelli]

Ben,

Glad to hear that the rig seems to be working.

I would like to comment on that 5 ohm wire-wound resistor.  I would be
suspicious of it because the effective series inductance (ESL) would likely
be a significant percentage of the 5 ohm stamped resistor value.  For
example, it only takes 0.11 uH to equal 5 ohms of inductive reactance at
7MHz.  It's the low value wire-wound resistors that you have to watch out
for.

Dennis AE6C

On Wed, Dec 31, 2014 at 10:49 AM, Ben Hall <kd5byb at gmail.com> wrote:

> Good afternoon all,
>
> This will be quick - a certain 9-year old boy is wanting to go out into
> the garage to fiddle and tinker with stuff.  ;)
>
> Check-out of the BC-230 went swimmingly.  I didn't find any obviously bad
> capacitors, bad resistors, or any hacked wiring.
>
> Last week, I built up a phantom-antenna / dummy load consisting of a 5-ohm
> wire-wound resistor in series with a 100pF door-knob cap.  At some point I
> will replace the wire-wound resistor with something non-inductive, but I
> figured for my testing, this was 'close-nuff.
>
> This morning, I installed four of my tube adapters with 6AQ5's installed
> and built up a temporary harness that would allow the set to transmit in CW
> mode.
>
> After a break for lunch, I turned on the +12VDC supply, let the heaters
> warm up, turned on my variable B+ supply, let it heat up, and slowly ramped
> the voltage up.  I was delighted to see RF output on the scope, antenna
> current indicated on the meter, a frequency output in the 5 MHz region
> (which is appropriate for the coil set installed) on the counter, and a
> nice-looking sine wave on the scope.  :)
>
> I max'ed the antenna coupling control and got the nerve to up the B+ to
> 250 VDC.  At 250 VDC, the antenna current meter was reading 0.6 amps of RF
> and 400 Vp-p on the scope with a nice looking sine wave.  (note that I'm
> not real trusting of that 400 Vp-p measurement - seems wacky to me)
>
> At some point I'll get up to the 300 to 350 VDC suggested in the manual.
> But for now, I'm happy to know it is working as-is w/o any repairs or
> tweaking needed.
>
> thanks much and 73,
> ben, kd5byb
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