Re: 'Updated' NRC 4' Loop


I envy anyone whose indoor RF environment is quiet enough to get any
actual benefit out of something like this. For most of us I would
suppose all the digital hash from home electronics would make a loop
like this, regardless of size, fairly useless. Loops like this ruled
DX in the '60s and '70s, but are definitely old school today when
outdoor antennas are a necessity for most. Not that you couldn't mount
the thing on a rooftop and motor-tune the variable capacitor (or use
varactor tuning) I guess.

What I remember of the big NRC loop (as demonstrated by the late great
Gordon Nelson, WA1UXQ) is that, in many urban settings, the use of the
FET amp is "overkill": too much gain, likely to overload receivers if
not be overloaded itself. The use of the FET amp with its very high
input impedance does give fantastically sharp Q (tuning selectivity)
nearly to the point of regeneration. The beast really shines in rural
very-low-noise locations. In the city, I'd say chuck the amp and go
with a passive pick-up link that is relatively loosely coupled. You'll
have less gain and Q than with the FET amp but far fewer spurs /
overload. A 4' square loop will still provide a lot of sensitivity,
even if just passively coupled.

Mark Connelly, WA1ION - Billerica, MA

--- In ultralightdx@..., Brandon Jordan <>
I see that the latest version of the NRC Antenna Reference Manual Volume
1 features the plans for the original NRC 4' FET Altazimuth loop antenna
with digitally enhanced drawings and updated material sources.

Since I now have a large shack with plenty of room for a 4' loop, I am
thinking about finally making one of these. Has anyone made one of these
loops lately? How much different, if at all, are the plans in this
updated manual from the original?


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