Hi Dan,
That may be why the ammeter burned out... :)
I didn't have a scope and wideband CT when I had the 6" coil. In fact, I
didn't even know that wideband CT's even existed until years later... :)
I did measure peak secondary base current with a Pearson wideband CT and
Tek scope on a 10" coil a few years later. Base current pretty much
matched theoretically-predicted current. This was long before the
excellent simulation models and tools we have today. Then, all we had
was basic TC theory, Conservation of Energy, and Excel spreadsheets.
Comparing primary bang size versus secondary peak current, and then
back-figuring peak secondary energy, I found that about 85% of the
primary bang energy made it to the secondary during by the peak of the
first ring-up when P:S coupling (k) was about 0.2. So in that sense,
agreement was pretty good.
Bert
Daniel Kunkel wrote:
Thanks for the info Bert. Did you find that your actual base current was
close to the predicted current (5a seems kinda low based on the numbers
from JavaTC on some medium sized spark gap coils).
On Tue, Jun 25, 2019 at 1:37 PM Bert Hickman <bert@xxxxxxxxxxxxxxxxxxxxx
wrote:
Hi Dan,
Many years ago, I tried using an older thermocouple type RF ammeter
(that I got at a hamfest) in series with the secondary base ground
circuit in a 6" coil. As I recall, it was a 0-5A unit. It worked quite
well at lower power levels, but I accidentally burned it out when trying
to run it at slightly higher power levels. The resistance/heating
element in the meter apparently was a bit fragile, particularly when
trying to handle the high-current peaks from a spark-gap TC. YMMV...
I had much better success using a wideband current transformer and
oscilloscope.
Bert
Daniel Kunkel wrote:
Hello list,
I have been thinking about using a current meter to monitor the base
current of the secondary coil, mainly as a tuning aid. It appears there
are
HAM radio guys that use RF ammeters, and there are even plans to build
your
own, however, I wonder how accurate it would be (due to dirty EMI and
irregular current draw)? Has anyone tried this? Or is there a better
way
to
ensure the tune is spot on other than observing for best streamer
production?
Thanks,
~Dan
Kansas City area...where the ground might be starting to dry out, but
only
a little bit
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