[Milsurplus] A Ham Radio Math Quiz.. more

[mac]

Dave,

For the target 3 watts out you would be looking at something on the  
order of 11volts P-P across the 5 ohm resistor.

Dennis D. W7QHO
Glendale, CA



On Apr 3, 2010, at 4:24 PM, J. Forster wrote:

> Also, the scope should be hooked ONLY be across the 5 Ohm if you are
> trying to measure the real power. Hooked up across the R and C you are
> measuring the voltage across the vector sum of the R and C impedances.
>
> With your component values and frequency, by FAR the largest voltage  
> will
> be across the 100 pF capacitor and not contribute to the output power.
>
> Zc = about 400 Ohms
> Zr = five ohms.
>
> -John
>
> ==============
>
>
>
>>
>> ----- 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.
>>
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