[BC] Xmitters at aol.com

[Dana Puopolo]

111C's also worked great for splitting audio to multiple studios. Years back,
I connected one winding to the output of a medium powered stereo receiver (a
Pioneer SX-434), and used the other three windings to distribute air monitor
to three separate studios. Worked great.

-D

------ Original Message ------
Received: Mon, 09 Apr 2007 03:06:46 AM EDT
From: "Milton R Holladay Jr." <miltron at mindspring.com>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Subject: Re: [BC] Xmitters at aol.com

According to Bell System practice, part of your second paragraph is not
precisely correct.  The pair of windings that go to the line should be wired
in parallel on both ends, to help overcome the line capacitance.
A specific set of the windings is designated LINE (I believe it is 1 & 2 and
5 & 6) and the other set is designated DROP (3 & 4 and 7 & 8  ?)and is wired
600/series or 150/parallel to match the customer's needs. This is the case
no matter which end of the circuit it is on.
This arrangement should be flat to 15,000Hz for a quarter mile or more,
depending on cable type; maybe several miles if you had old timey open wire
lines.
The 23A was the equalizer for 8kHz, and the 16816 for 5, 8, & 15 kHz,
succeeded by the 20159
I believe Barry has official data posted for at laest the 111C.  I have seen
one old one in a cast iron case...................
M
----- Original Message ----- 
From: <RichardBJohnson at comcast.net>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>;
<broadcast at radiolists.net>
Cc: <RLO2L at aol.com>
Sent: Friday, April 06, 2007 9:37 AM
Subject: Re: [BC] Xmitters at aol.com


>
> The telco 111-C "repeat coils" are available on the surplus market. They
are probably the finest audio-frequency transformers --ever. They have four
shielded coils and the core is a toriod made of mu-metal strip. Very
impressive for something designed in the 1920s. The companion shunt
equalizers are also available although I don't remember the number. They
consist of a tapped inductor and tapped series resistors. Basically, you
shunt-out
> the low frequencies the same amount as the high frequencies have been
shunted-out by the line capacitance. A one-mile long physical pair, with no
side-legs or stubs can be equalized to over 100 kHz, so equalizing it to 15
kHz is a no-brainer. You won't need any amplification, the line-loss after
equalization will be less than 10 dB.
>
> You connect your  station's audio feed at the studio to the outgoing 111-C
"coil" primary. You make the primary by connecting any two coils in series.
You connect the other two series-connected coils to the phone line. At the
transmitter, you connect another "coil" the same way. On the telco side, you
connect will your shunt equalizer but don't connect it yet. Since you
probably don't have a helper at the studio, you go to the studio and send 15
kHz. You go back to the transmitter and measure the signal, it will probably
be about 9 dB below  what you are sending from the studio. Write this down!
Then you go back to the studio and send the exact same level at 100 Hz. Then
you go to the transmitter and connect the equalizer. You leave the resistor
in its default (mid) position, and you adjust the taps on the inductor to
reduce the 100 Hz level to the level of the 15 kHz tone previously measured
and written down. You should be able to get it within 1 dB.
>
> The result will be an equalized "program channel A," in telco lingo. For a
mile-long line, you will certainly
> have it equalized well enough for AM, perhaps even FM. In a previous life
I was able to equalize stereo pairs to 15 kHz, although I needed a Langevin
EQ-257-A  equalizer. It had a multi-turn wirewound potentiometer in series
with
> the inductor.
>
> --
> Cheers,
> Richard B. Johnson
> Read about my book
> http://www.AbominableFirebug.com

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