Ok... Here it is:
Yeah, I know, I know... probably a hundred reasons it shouldn't work better than a round over core shield. Don't care.
What I do care about, that for those couple of 'pesky' intermittent E components that a round close shield, of foil, copper, pipe, ribbon cable... whatever variation had no effect... this does. somebody else can figure it out.... and a bumble bee can't fly.
The idea appears similar to "trough' shields for ferrites.
Did find one specific reference to this idea, where the author appears to be using the same paradigm...
attached 1990 article.
The History?
I found an 50 year old 'shorthand' note I'd scribbled when ELINT / ECM tech in SEA, possibly relating to a communications jammer or possibly a DF system.... from a discussion with a Hallicrafter's tech rep, I suspect..
...took a few minutes to decipher a couple of things, the rest is obscure, but ....
I wish I could reconstruct the conversation that elicited the 'cryptic' note, and the context of that conversation... I know that it likely had to do with a communications freq jammer, or probably our LF DF antenna. In the context of the war environment, we were constantly looking for calibration references, etc, and Hallicrafters was instrumental in both those systems, at the time,... so looking at the references I suspect we were brainstorming checkout and diagnosis for "off the cuff", quick reaction shop evaluation and or flightline troubleshooting, if you follow me.... The receiver/ transponder shop was enclosed in a Faraday Cage to keep out noise, but we needed to simulate airborne, as well as flightline, situations at times... that one rotary DF antenna was notorious for generating LF and VLF electrical noise into adjacent systems when the commutators began to fail... so we were probably looking at a "quick diagnosis" for noisy rotor. One thing that is curious is the note explicitly states that " sides= c x 10 " with some other faded and scribbled crap... and I do recall, somehow, that the c was referring to the core diameter of a ferrite rod.... I also interpret the scribblings to hint that this applied at certain frequencies, but there's no reference to which ones.... from the general context, I assumed we were discussing the bands between about 240 Hz (typical commutator noise pulses) up to about 2mHz.
The other thing I'm wondering is if one of the scribblings might say that the "thickness of the shield material" is important... can't prove that, but I suspect it strongly. The Pesky Mark I is just covered with copper foil. Both antennas are now in "Mark I" shelds... and looking fine. Prototype headed for the museum shelf.
So... there you go... I'm minus 2 or three intermittent low level E component peskies on my H field. that have pestered me for a year or so.The theories, math etc are beyond this old tired brain. Have at 'em.
Mike
