On Oct 24, 2006, at 9:05 PM, craxd wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
On Oct 22, 2006, at 5:20 PM, craxd wrote:
Jim,
It's a wonder Tom didn't add a "by the way" saying, scopes and dip
meters are very inaccurate and should never be used. : ) At least
he
answered you by e-mail, he never would me.
He did not tell me this via e-mail. He said dipmeters were
worthless
during a discussion of various means of grounding grids after a
dipmeter measurement showed a result that contradicted his dicta
about grounding grids.
No, I meant I wouldn't doubt that he would have said
this to Jim.
If a scope is calibrated properly, or a dip meter the same, they
can't lie. They can only show you the truth.
That IS the problem here.
If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known
accurate
freq counter, it will show the truth if you want precision. A
calibrated scope can only show a waveform that it produces from
what
it sees at the input jack.
Correct. He didn't like the fact that an oscilloscope indicated a
worst-case potential in a SB-220 that was only about 1/3 of what
he
predicted it would be. This potential is on the verge of arcing
the
Tune-C, so even if the voltage tried to rise much higher, the cap
would zap and limit the voltage like a zener diode. The reason he
wanted the potential to be higher was to explain away what I said
was
parasitic arcing by the SB-220's occasional 110MHz oscillation.
The peak or peak to peak voltage one reads is exact,...
Porcine shampoo. I'm a guy who used to calibrate oscilloscopes.
A calibrated oscilloscope is one way power meters can be calibrated
and it's much faster than using a bomb-calorimeter. However, an
oscilloscope is as useless as tits on a boar hog for measuring
cleanliness of a SSB signal.
Well it's according to what you term clean. Harmonics no, unless you
build or use a front end for this like the poor mans spectrum
analyzer, or one of the commercial add-on units. Over modulation,
hum, noise, regeneration, and parasitics can all be seen using a
standard scope.
But not SSB IMD.
...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org
