Re: [IRCA] IRCA Loop update 3

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

Had some time so I made another loop this afternoon.  Got a couple lengths
of 1" copper tubing and four elbows.  Cut the tube into four pieces of about
five feet each.  Prepped the ends, assembled into a square, slipped a toroid
with six turns of #16 over one tube and soldered it up.

Overall signal was down a little from the ten foot previous version as
expected.  The DX Engineering preamp came in yesterday, so the lower gain
wasn't a problem.  Right now it's hung by a rope from a rafter in my
breezeway.

Rotating it showed a good symmetry of the pattern.  A null of a station has
the loop aimed the same way when turned 180°.

Was able to get clear audio off WSBS-860 which has been a difficult catch
here in the past.  Local WPRO could be nulled down to the same S meter
reading as the adjacent 640 station in Springfield, MA.  One thing I noticed
is that the loop is not affected by hand capacitance.  You can grab the loop
to null a station, and taking your hand off doesn't change the null at all.
Probably due to the extremely low impedence of the loop.

I really need to make a good azimuth/elevation mount base for it.  That will
make better nulls likely.

I did try using the phasor with the outside 10' loop.  Good nulls could be
had on some stations, though not all.  I think that needs some further
thought.

So far I'm much happier with this untuned loop over the usual multiturn
tuned loop such as the 4' ELAZ commonly used.  Sure is quicker and easier to
build and far less fragile.

Craig Healy
Providence, RI


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