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#11
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Odd Piece of Coaxial Cable
"Jim-NN7K" . wrote in message ... Sal M. Onella wrote: I recently handled an estate sale. Among the SK's posessions was a one-foot piece of RG-8 or RG-213 which he had carefully modified by cutting away about 3/16 inch of the jacket and braid all around the circumference of the cable, near its middle. I am not sure what use this would be to a ham. Some audio cables are made up with discontinuous shields for elimination of ground loops but I've not seen it done for RF. Ideas? All the above have merit-- One other use- in SOME installations, there is a requirement to do D.C. isolation - Removal ot part of the sheath, jumpered by a Capacitor (but if that is what this for, the cap would be in place). And, as to the first comment, such a loop would have been used as a direction Finder (the space between the broken shields was the "sense area of the loop, and, if remember right, you "Null" in the direction that the "loop" is perpendicular to. - Jim NN7K Thanks to all. I really think we have it nailed down. After the first response mentioned a small loop, I did some searching and found diagrams of loops, complete with some recommended tuning capacitors, etc. Today, I dimly recall a metal project box with three coax connectors on it. (Might still have it if it didn't sell.) My first thought was "balun" but a homemade balun doesn't have three coax connectors -- it has just one plus two non-coax connectors. THAT may have been the feed part of the loop. I don't recall if anything else was in that box. With the gap section and the feed section, then various pairs of coax jumpers would have comprised the remainder of the loop for different experimental sizes. I s'pose I should follow in the SK's footsteps and build myself a loop or two. Ain't hammin' grand?!? |
#12
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Odd Piece of Coaxial Cable
Jim-NN7K wrote:
All the above have merit-- One other use- in SOME installations, there is a requirement to do D.C. isolation - Removal ot part of the sheath, jumpered by a Capacitor (but if that is what this for, the cap would be in place). And, as to the first comment, such a loop would have been used as a direction Finder (the space between the broken shields was the "sense area of the loop, and, if remember right, you "Null" in the direction that the "loop" is perpendicular to. - Jim NN7K Actually, the active loop is the outside of the shield, and the gap is the feedpoint. Shielded loops have been discussed at great length on this newsgroup (not because they're complicated, but because they're impossible to understand until a person is willing to let go of some common misconceptions). Anyone interested in these can find the previous postings via a search at groups.google.com. Roy Lewallen, W7EL |
#13
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Odd Piece of Coaxial Cable
Roy Lewallen wrote in
treetonline: .... the feedpoint. Shielded loops have been discussed at great length on this newsgroup (not because they're complicated, but because they're impossible to understand until a person is willing to let go of some common misconceptions). Anyone interested in these can find the .... Sadly, some of the misconceptions are propagated in ARRL publications. It is understandable that people have the wrong idea! Owen |
#14
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Odd Piece of Coaxial Cable
"Roy Lewallen" wrote in message treetonline... Actually, the active loop is the outside of the shield, and the gap is the feedpoint. Shielded loops have been discussed at great length on this newsgroup (not because they're complicated, but because they're impossible to understand until a person is willing to let go of some common misconceptions). Anyone interested in these can find the previous postings via a search at groups.google.com. Well, that blows my thinking to pieces. Back to the drawing board. |
#15
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Odd Piece of Coaxial Cable
Roy Lewallen wrote:
Jim-NN7K wrote: All the above have merit-- One other use- in SOME installations, there is a requirement to do D.C. isolation - Removal ot part of the sheath, jumpered by a Capacitor (but if that is what this for, the cap would be in place). And, as to the first comment, such a loop would have been used as a direction Finder (the space between the broken shields was the "sense area of the loop, and, if remember right, you "Null" in the direction that the "loop" is perpendicular to. - Jim NN7K Actually, the active loop is the outside of the shield, and the gap is the feedpoint. Shielded loops have been discussed at great length on this newsgroup (not because they're complicated, but because they're impossible to understand until a person is willing to let go of some common misconceptions). Anyone interested in these can find the previous postings via a search at groups.google.com. Roy Lewallen, W7EL FWIW, there are several projects in the ARRL pubs, mostly for RDF, that use a short piece of coax exactly as described as a loop. -- Jim Pennino Remove .spam.sux to reply. |
#16
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Odd Piece of Coaxial Cable
wrote in message ... .. FWIW, there are several projects in the ARRL pubs, mostly for RDF, that use a short piece of coax exactly as described as a loop. I've seen some in books and on the 'net. Years ago, I did a one-week job on a Coast Guard cutter and I got to see some HF loop antennas that are standard issue for cutters. I do not recall with certainty whether they were transmit or receive or both, but I think they were both, but not at the same time, as certain USN fanwire antennas are. HRO in San Diego usually has at least one HF loop on display. "Sal" |
#17
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Odd Piece of Coaxial Cable
On Sep 6, 12:09*am, "Sal M. Onella"
wrote: wrote in message ... . FWIW, there are several projects in the ARRL pubs, mostly for RDF, that use a short piece of coax exactly as described as a loop. I've seen some in books and on the 'net. *Years ago, I did a one-week job on a Coast *Guard cutter and I got to see some HF loop antennas that are standard issue for cutters. *I do not recall with certainty whether they were transmit or receive or both, but I think they were both, but not at the same time, as certain USN fanwire antennas are. HRO in San Diego usually has at least one HF loop on display. "Sal" Ive seen sensors for SWR made his way. Slide a wire under the shield from each end and termiate them in the middle with a resistor. Jimmie |
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