Edgar,
Excellent find, thanks for posting, hope it answers Laurence’s questions.
A comment regarding the summary (last paragraph) on .pdf page 32, original document page 27: prototype transformer C_s can deviate considerably from initial design value especially if a simplified model for C_s is used in the design or design spec for the magnet wire is not controlled for insulation type and winding/layering method. If a transformer modeling tool is not available, the old Radiotron Engineer’s Handbook has some helpful models.
Note Paschal’s comment in a related context (C_a of loop) in paragraph 1, .pdf pg 40, original document pg 35:
“...it is difficult to calculate the value of C_a …easier to build and measure”.
In the case of the matching transformer, using a transformer model that has a reasonable approximation for C_s could save a fair amount of test/rewind time on the way to a VLF receiver with sensitivity of 0.5uV/m-Hz^1/2 (measured, Fig 8.5, .pdf pg 78)
Of interest in context of C_s:
Item 4, .pdf page 44, original document page 40; and last paragraph, same page
Item 2 (packing density), .pdf page 47, original document page 43
Item 4, .pdf page 47, original document page 43
Paragraph 2 (Litz wire tradeoffs), .pdf page 49, original document page 45
Last paragraph on .pdf page 52, original document page 56 (in the context of high-impedance preamps): “C_s forms a tuned circuit… (therefore) low-impedance amplifiers are a much better practical solution”
I wonder if page 38 of the original document is blank. It’s not included in the .pdf document (which is why the offset between .pdf page number and original document page number changes after original document page 37)
Thanks for posting the link; hope it answers Laurence’s questions; I had been looking for this article off and on since seeing a reference to it some years ago.
73,
Jim AA5BW
Hi Laurence,
You probably have this, but in case you do not.
http://traktoria.org/files/radio/antenna/VLF/the_design_of_broad-band_vlf_receivers_with_air-core_loop_antennas.pdf
It may not answer your questions.
Regards, Edgar
Moonah, Tasmania.
