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?!?

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

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

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.

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.

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"

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