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From: parnass@ihu1h.UUCP (Bob Parnass, AJ9S)
Newsgroups: net.ham-radio
Subject: Update: eavesdropping on SCA transmissions
Message-ID: <487@ihu1h.UUCP>
Date: Sat, 23-Feb-85 17:13:03 EST
Article-I.D.: ihu1h.487
Posted: Sat Feb 23 17:13:03 1985
Date-Received: Wed, 27-Feb-85 04:17:40 EST
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 37

x
	   Update: Eavesdropping on SCA	Transmissions

     A few weeks ago, I	posed a	question about listening  to
     SCA  transmissions	on the FM commercial broadcast band.
     An	article	in _M_o_n_i_t_o_r_i_n_g__T_i_m_e_s claimed that  connecting
     a vlf receiver to an FM broadcast receiver	would permit
     SCA detection.

     Necessity being the mother	 of  invention,	 a  way	 was
     found  to	confuse	 the ICOM R71A into tuning below 100
     kHz1, and after receiving substantial inspiration	from
     Will  Martin,  Phil  Karn,	 and others I now can report
     success!

     With the R71A in the FM mode, tuned to 67 kHz,  I	con-
     nected  the  ICOM's vlf antenna input through a 0.1 ufd
     capacitor2	to the earphone	jack of	a $16 General  Elec-
     tric AM/FM	portable radio,	and can	now listen in on the
     world of SCA!

     In	the first few minutes of tuning	around,	 I've  heard
     the  Physicians' Network, Muzak, commodity	reports, and
     several data transmissions.

     Thanks again for the help!
__________

 1. Parnass, Bob, "Trick the ICOM R71A below 100 kHz", to be
    published in _M_o_n_i_t_o_r_i_n_g__T_i_m_e_s_.

 2. The	capacitor is needed with the GE	radio I	used to
    block DC.

-- 
===============================================================================
Bob Parnass,  Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414