Agreed. Wasn't sure of which. On my flags and pennants I have no shield pick up which I account to both using well designed 16:1 transformers with isolated windings and having the coax run under ground much of the route back inside.
Sent from my iPad On Jun 17, 2012, at 16:09, Arthur Delibert <[email protected]> wrote: > Thanks. I wasn't referring to a magnetic loop that uses the shield for > pickup. I was referring to the outer shield on the coax that runs from any > antenna to the shack. If you use an antenna that was chosen for its specific > directional and/or low-noise properties, and you don't isolate that antenna > from the outer shield of the feedline, the shield itself becomes part of the > antenna, spoils the directionality and picks up additional noise. > > Art Delibert > KB3FJO > > > From: [email protected] > > Date: Sun, 17 Jun 2012 11:52:38 -0400 > > To: [email protected] > > CC: [email protected]; [email protected] > > Subject: Re: Topband: Receiving loops > > > > If you are referring to a magnetic loop the problem is not the pickup from > > the shield - that is the conductor for picking up the signals - all signals > > including noise. The issue with a magnetic loop would be imbalance and that > > would be due to improper construction where the sides of the loop either > > way of the gap would not be equal or how you connect or install the tuning > > capacitor. Close proximity to a conducting surface would also affect the > > directivity. But even with a poorly constructed mag loop you should still > > get the null but it may not be symetrical or as deep as it should be. > > > > Sent from my iPad > > > > On Jun 16, 2012, at 10:36, Arthur Delibert <[email protected]> wrote: > > > > > > > > Tim -- If the suggestions from others don't entirely do the trick, here's > > > another thing to consider: The outer conductor on your coax might be > > > picking up local noise and/or destroying the pattern of your receiving > > > antenna. I DX the AM broadcast band with whatever antennas I can fit into > > > my suburban backyard. I was getting poor results with a pennant until I > > > put Radio Works T-4 line isolators at both ends of the coax. Suddenly the > > > antenna began to behave as expected. Hope this helps. Art DelibertKB3FJO > > >> From: [email protected] > > >> To: [email protected] > > >> Date: Sat, 16 Jun 2012 13:28:38 +0000 > > >> Subject: Topband: Receiving loops > > >> > > >> I want to try a new receiving antenna for the summer Stew Perry. Last > > >> winter was my first foray onto 160M and I really felt like an alligator. > > >> I could work everyone I could hear, with just 100W. I think that means I > > >> need a better receive antenna. If you look at my score in the winter > > >> Stew Perry I think I did great QSO-number wise, but my average distance > > >> was very poor, I'm guessing typical alligator. > > >> > > >> I have tried pennants and K9AY's over the winter with little success. > > >> Compared to my transmitting antenna (A "T" with a poor radial system) > > >> most signals were still better, S/N wise, on my transmitting antenna. I > > >> feel like I must've been doing something wrong. Still the fact that a > > >> few signals came in on the loop with by ear much better S/N, maybe I was > > >> on the right track and just didn't try hard enough. > > >> > > >> I will be trying a small tuned magnetic loop tonight (e.g. the last one > > >> at http://www.w8ji.com/magnetic_receiving_loops.htm with the 9:1 > > >> transformer) . And maybe a terminated beverage but I'm limited to about > > >> 150'... well maybe I could run something longer down the driveway as > > >> long as I clean it up before the sun comes up and the neighbors see. > > >> > > >> I was fairly impressed with small tuned magnetic loops when I was doing > > >> some BCB DX'ing several years ago. I wasn't comparing with beverages or > > >> anything. > > >> > > >> Tim N3QE > > >> _______________________________________________ > > >> UR RST IS ... ... ..9 QSB QSB - hw? BK > > > > > > _______________________________________________ > > > UR RST IS ... ... ..9 QSB QSB - hw? BK > > _______________________________________________ > > UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
