[Milsurplus] A Ham Radio Math Quiz

[Richard Brunner]

More:
Upon further reflection, 100 pf is correct because the phantom antenna
is simulating a short antenna, and 100 pf is the antenna capacitive
reactance.   The 100 pf reactance is tuned out, or neutralized, in the
transmitter tuning/loading adjustments.  With C .001 mfd it would be a
helluva big antenna.

Richard, AA1P



It works when C is 0.001 microfarad.  Xc is 42.12 Ohms, Xt is 42.42
Ohms, I is 0.832 Amps, and P is 3.46 Watts.

With C = 100 pf you only have .1362 Watts.  It's just a typo...
100 volts p-p is indeed only 35.3 volts rms...

Richard, AA1P


On Sat, 2010-04-03 at 18:05 -0500, David Stinson wrote:
> ----- Original Message ----- 
> From: "Peter Gottlieb" <nerd at verizon.net>
> 
> > What's the intent and application of this?
> 
> I'm working with a 1930s MOPA transmitter, 
> which is speced to deliver about 3 watts out.
> 100 pFd in series with 5 Ohms is the "phantom antenna"
> designed for it.   Scope says 100 Volts PtP or about 
> 70 Volts RMS across the load at 3870 KC.
> Z of the load should be about 411 Ohms.
> I know the output is low and I'm not finished looking
> for the cause, but I don't believe the solutions I'm 
> getting, so I'd like to see how the many people 
> smarter than me solve this problem, so I can 
> find my errors.
> 
> Thanks,
> Dave S.