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 DelibertKB3FJO
> 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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