[BC] 111-c Repeat Coils...

[Burt I. Weiner]

111-C repeat coils will pass a composite (FM) stereo signal with 
excellent stereo separation.  I've used them for that and I've seen 
them pass a 100 kHz square wave as clean as a piece of wire when 
properly terminated.  Amazing transformers.

Burt

At 10:07 PM 4/6/2007, you wrote:
>From: Xmitters at aol.com
>Subject: [BC] Re:111C repeat coils
>To: broadcast at radiolists.net
>Message-ID: <c64.10af06f2.3348710e at aol.com>
>Content-Type: text/plain; charset="US-ASCII"
>
>
>In a message dated 4/6/07 11:39:29 AM Central Daylight Time,
>broadcast-request at radiolists.net writes:
>
><< The telco 111-C "repeat coils" are available on the surplus 
>market. They are
>  probably the finest audio-frequency transformers --ever. They have 
> four shield
>ed coils and the core is a toriod made of mu-metal strip. Very 
>impressive for s
>omething designed in the 1920s. The companion shunt equalizers are 
>also availab
>le although I don't remember the number. They consist of a tapped 
>inductor and
>tapped series resistors. Basically, you shunt-out >>
>
>OK, here is a dumb question. If telco copper loops are still around and 111C
>and equalizers are not considered Old Fart Engineering (see  my previous
>post/coinage of term) then why are there not companies still making 
>the 111C?
>As
>ROTL, et. al.  pointed out, Jenesn makes some nice transformers. It appears
>that the choice is either Jensen or surplus 111C. To me,  it is odd 
>if equalize
>d
>copper is still not antique technology today, that 111C type 
>performance could
>not be had without resorting to the surplus market. Seems like you could
>outfit a specialty plant in China with some knowledgeable 
>technicians, and you
>could turn out high quality affordable product. A new 111C made in the states
>would likely cost $500.00 I would guess. Just wondering.
>
>The last I looked, the companion repeat coil card for the other end of a Tel
>Labs 4008 equalized circuit, was a bit anemic at the low end as well 
>as anemic
>in the head room department.
>
>I'm sure that there are others out there besides me, that have restrictions
>about buying used stuff. What I do is, if used product is the only 
>alternative,
>
>I pay for it myself, then donate it to the station. I can only do that if the
>item costs but a few bucks.
>
>
>Jeff Glass

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at earthlink.net
K6OQK