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 <radio75a3@msn.com> 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: w2pm@aol.com
> > Date: Sun, 17 Jun 2012 11:52:38 -0400
> > To: radio75a3@msn.com
> > CC: topband@contesting.com; tshoppa@wmata.com
> > 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 <radio75a3@msn.com> 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: tshoppa@wmata.com
> > >> To: topband@contesting.com
> > >> 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
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