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Re: LF: Re: Mini-Whip Antenna

from [DENNIS EASTERLING] [Permanent Link][Original]
To: <[email protected]>
Subject: Re: LF: Re: Mini-Whip Antenna
From: "DENNIS EASTERLING" <[email protected]>
Date: Sun, 16 Jan 2011 16:46:37 -0000
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References: <[email protected]> <op.vpan5am6yzqh0k@pc-roelof> <[email protected]> <op.vpat3gvlyzqh0k@pc-roelof> <04DC6D14A81F4542B1D2189A5440F3D5@DennisPC> <015d01cbb57f$1feb9d00$0201a8c0@Clemens04>
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Clemens
Thank you for your information. My homebrew untuned loops used adjacent balanced pre-amplifiers, but still suffered from local qrm. Papers I have read suggest that at lower frequencies, nearby metal objects effect the balance of unscreened loops. The screened loop I made of low loss coax, although less sensitive, enabled me to read stations on mf which were otherwise impossible, though in this case the amplifier was a grounded base followed by a grounded collector arrangement. The Wellbrook is better engineered of course, and is now steerable, so I benefit both ways. 

73 Dennis M0JXM
----- Original Message ----- From: "Clemens Paul" <[email protected]> 
To: <[email protected]>
Sent: Sunday, January 16, 2011 1:13 PM
Subject: Re: LF: Re: Mini-Whip Antenna



Dennis,

if the loop-preamp system is well balanced the loop doesn't need
screening.
E.g. the Wellbrook ALA1530 broadband loop is unshielded.
Therefore its preamp is a push-pull design.

73
Clemens
DL4RAJ
----- Original Message ----- From: "DENNIS EASTERLING" <[email protected]> 
To: <[email protected]>
Sent: Sunday, January 16, 2011 11:15 AM
Subject: Re: LF: Re: Mini-Whip Antenna



Dear Roelof and Petr

When I first tried the mini-whip I was very sceptical of its performance,
but in my circumstances, living surrounded by houses and near a main line
electric railway ((25kV) it has performed very well indeed.

I tried tuned loops of various sizes but the qrm is overwhelming in such
close quarters to the switched mode power units and machines operating in
nearby houses. Out of various loops, the wide band untuned screened loop seemed the best option, with a simple 1m loop of co-ax cable and amplifier tied to the back fence and the Wellbrook ALA1530 giving similar performance at MF, although the Welbrook is better engineered and mounted on a rotator. 
...
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