Topband: Receiving loops

[W2PM]

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