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"test" streamers

Original poster: "Terrell W. Fritz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <terrellf-at-qwest-dot-net>

Hi All,

I made a "test" streamer out of spring wire today.  It is ~0.050 inch piano
wire that is soldered and bent to the shape of a big 2.5 foot streamer.


This is my small coil with a John Freau 4x13 torroid.  The secondary was base
driven with a low-Z amp and the top signal was detected with a simple antenna a
few feet away.

The coil without the wire test streamer measured 249.68kHz.

With the streamer directly attached I got 205.86kHz.

With a 220k ohm resistor between the toroid and the streamer I get 230.86kHz.

So the direct wired streamer dropped the resonant frequency 17.55% while the
resistor series streamer drops Fo by 7.537%.  

This is very interesting in that the frequency drop is just about equivalent to
the 5-8% drop we see in real streamer loaded coils.  So my little test streamer
works :-))

I should also point out that for top voltage calculations, you NEED to account
for streamer loading or else the top terminal voltage comes out about 2X too
high.  Ideally, the streamer impedance and the coil's output impedance should
be matched for maximum power transfer.  Thus, with an equal source and load
impedance, the voltage drops by 1/2.


I need to point out that these impedances are "rough" values so feel free to
vary them a few hundred percent as needed :o))  but they get you pretty
close...  They are also "average" values that "do not" take into account
instantaneous or dynamic effects.  They are just the average of the whole
streamer effect which is far more complex.  However, the 220k +1 pF per foot of
streamer length "rough estimate" does seem to be holding up very well as a nice
streamer equivalent load to plug into models.  It also seems to hold true for
small coils like mine up to Greg Leyh's big Electrum coil.  It is great that we
are now getting more data in these matters besides just "me" :-))

One improvement to my wire streamer may be to make it out of carbon impregnated
spark plug wire which would distribute the resistance more realistically
throughout the streamer or maybe use thin tubing with water and a little copper
sulfate in it.  Right now, I am just using a 1/4 watt 220K resistor.