Topband: Receive loop observations

[James Rodenkirch]

Doggone it, Don...I'd seen that presentation before - simply forgot about using a xfmr to couple unbalanced coax to balanced rcv antenna....good on ya for sending that on -- need to find a Fair-rite 61 core.....hihi


________________________________
From: Don Kirk <wd8dsb at gmail.com>
Sent: Friday, April 1, 2016 2:02 PM
To: James Rodenkirch
Cc: Top Band Contesting
Subject: Re: Topband: Receive loop observations

Hi Jim,

I know my following info does not directly answer your question, but I do think it's important regarding feedline isolation.

I suggest you take a look at the recommendations of N6RK regarding the use of a matching transformer to feed tuned shielded loops as it isolates the feedline from the antenna (shield of coax not tied directly to the loop).  I use the N6RK matching transformer method on my loops of similar design and think it makes the most sense regarding feedline isolation, and maintaining proper balance of the antenna.

Here is a link to his paper, and his matching transformer is shown on page 30 and 33 of his paper.
http://www.n6rk.com/loopantennas/pacificon.pdf

73,
Don (wd8dsb)

73,
Don (wd8dsb)

On Fri, Apr 1, 2016 at 3:04 PM, James Rodenkirch <Rodenkirch_LLC at msn.com<mailto:Rodenkirch_LLC at msn.com>> wrote:
I have installed a receive loop (  http://www.qsl.net/kc2tx/  ) and finished measuring and observing...


Measurements:


VSWR --- 1.7 @ 1.830

ZO ----- 77 at 1.830


Observation:


Following ON4UN's comments regarding needing a preamp or not, measured S1 to 2 noise level with antenna connected during mid-day, S0 with dummy load connected.


During evening hours, notice some improvement - S2 drop in noise level when switching from xmt antenna (inverted U) to the loop - but not hearing much in the way of receive signals (e.g., hear a fairly strong signal from the west coast on the xmt antenna, nothing on the loop and I have it oriented east/west).


I'm uncertain if a low noise amp will help my cause (thoughts??)


I do not have a common mode choke installed, yet...will one make that much difference?


The loop is located about 60' away from the Inverted U and radials.


Comments/suggestions appreciated.



Thank you, in advance, for constructive, relative to what I have now, replies....non-"constructive" means I can't erect a BOG, Beveridge or Waller Flag so don't ask why I didn't go that route.


71.5/72 de Jim Rodenkirch K9JWV
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