Nice! Did you find that the current was very erratic or was it stable?
On Wed, Jun 26, 2019 at 1:00 PM Bert Hickman <bert@xxxxxxxxxxxxxxxxxxxxx>
wrote:
> 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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> >>
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