antenna<\/a> itself plus noise to find out because I live in town and there’s potential noise sources all around. I couldn’t use the antenna plus signals because the ionosphere compromises the source-directionality of signals that pass through it, and it’s an HF-only antenna. (I suppose I could have spent most of the day delving into the physics of it, and coming up with the answer, but that would have taken most of the day and I just wanted a quick answer.)<\/p>\nChecking on-line wasn’t very helpful. I found articles claiming that both<\/em> the null and the lobes were “in the plane of the loop”! Part of the issue, I think, is that there are different geometries of loop antennas. What one would tend to think of as the “plane” of a large, flat, air-core loop is perpendicular to what one would tend to think for a compact, multi-turn ferrite loop stick antenna.<\/p>\nA simple experiment with one of my old tube radios (which have a large, flat air-core loop antenna for the medium-wave broadcast band) and KVI’s signal on 570 KHz povided the answer: for “flat” loop antennas with a large diameter and low number of turns, the null is along the plane the loop exists in.<\/strong> It was pretty definitive: when I got the radio aligned so I had difficulty hearing KVI, its back (on which the loop is mounted) was aligned directly on a line running from KVI’s Vashon Island transmitter to me.<\/p>\nSo there you have it.<\/p>\n
Note that the while the peaks of a loop antenna are very broad, the nulls are by contrast very sharp. I’ve noticed this when nulling out interference; a slight bump on the HF loop antenna (changing its position by mere inches) often makes a significant difference.<\/p>\n","protected":false},"excerpt":{"rendered":"
I’ve been wondering that, since I’ve been using it to null out noise sources, yet I had long forgotten what the pattern of such antennas is. I couldn’t just use the antenna itself plus noise to find out because I live in town and there’s potential noise sources all around. I couldn’t use the antenna […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[],"class_list":["post-1906","post","type-post","status-publish","format-standard","hentry","category-radio"],"_links":{"self":[{"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=\/wp\/v2\/posts\/1906","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1906"}],"version-history":[{"count":0,"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=\/wp\/v2\/posts\/1906\/revisions"}],"wp:attachment":[{"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1906"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1906"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blackcap.name\/blog\/new\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1906"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}