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LF: Loop problem revealed?

To: [email protected]
Subject: LF: Loop problem revealed?
From: "J. B. Weazle McCreath" <[email protected]>
Date: Thu, 26 May 2005 11:04:04 +0100
Delivery-date: Thu, 26 May 2005 12:03:25 +0100
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----- Original Message -----
From: "Steve McDonald" <[email protected]>
To: <[email protected]>
Sent: Wednesday, May 25, 2005 11:47 PM
Subject: LF: Re: Re: Loop antenna problem


J.B. - what rx are you using with the loop?  Another thought....could
there
be a problem with the coax cable? ...old? ...moisture? ....shield open at
the connector?

Steve / VE7SL

Hi Steve, LFers,

I'm using a TS-440SAT.  I've checked the feedline with an MFJ-259
antenna analyser, and with a 50 ohm dummy load at the antenna end,
it shows as being OK from 1.7 mHz. to well above 4 mHz., but what
it is at the LF frequencies may be another matter.  With that in mind, I
tried a new temporary feedline and saw no improvement.

I think that Jim, M0BMU, is onto something when he suggested that
the pickup loop is loading down the antenna.  There's a short pigtail
lead of RG-213 from the junction box on the loop to the hardline I'm
using as the feeder. When I connect that pigtail to a 50 ohm dummy
load, the signal strength as monitored by a portable LF radio near
to the loop goes all to h..l.

With the pickup loop disconnected, the tuning of the main loop is
very sharp and signals tuned in on the portable LF rx jump way up
in strength when I tune the loop thru resonance.  This indicates to
me that the main loop is working fine and has pretty good Q.
I'm going to try the transformer approach tonite.

73, J.B.




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