[Test-Equipment] Hilborn Loop

[Richard Knoppow]

----- Original Message ----- 
From: "Miles B. Anderson, K2CBY" <k2cby at optonline.net>
To: "Test Equipment Mailman" 
<test-equipment at mailman.qth.net>
Sent: Tuesday, October 16, 2007 10:09 AM
Subject: [Test-Equipment] Hilborn Loop


>I recently had a Leeds Northrop galvanometer bridge on my 
>bench -- the kind
> that the phone company engineers used in years past to 
> measure cable
> resistances.
>
> In a moment when I had nothing better to do I read the 
> instruction card
> pasted inside the case cover. There was a detailed 
> discussion of the
> Wheatstone Bridge, the Murray loop test and the many 
> varieties of the Varley
> loop (Varley must have been a busy guy!).
>
> There was also a note that the galvanometer switch could 
> be set to a
> position allowing its use in a "Hilborn loop." No further 
> mention of Mr.
> (Ms.?) Hilborn or his (her) loop. No success with Google.
>
> Anybody got any idea what a Hilborn loop is or what it 
> does?
>
> Miles Anderson, K2CBY
> 16 Round Pond Ln
> Sag Harbor, NY 11963
> (631) 725-4400
> e-mail k2cby at optonline.net
>
    I think I have the same unit, mine is a model 5430-AM-1 
I also got curious about the Hilborn loop. I found a pretty 
good explanation in a downloadable handbook at:

http://www.dielectrictechnologies.com/doclib/T272_OpManual_07.pdf

    The various test connections, like the Murray and Varley 
loops, are usually covered in books on telephone or 
telegraph technology. Some very old ones are available for 
download as PDFs from the Google books search. These are 
mostly old enough to be in the public domain. These days a 
book must be nearly as old as a dinosaur to be safe.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk at ix.netcom.com