[BC] Our Wild TECH Youth - more memories

[Charles Lewis]

Date: Sat, 09 Jul 2005 00:00:36 -0700

From: "WFIFeng at aol.com" <reader at oldradio.com>
Subject: Re: [BC] Our Wild TECH Youth - more memories

In a message dated 07/08/2005 12:48:39 PM Eastern Daylight Time,
clewis at sto.ibb.gov writes:

 >     Even later I went into competition with the NCSU campus carrier
 >      current station with a home brewed 6AG7 & 6L6 carrier current setup
 >      in my room that covered two large dorms that were fed from a single
 >      transformer vault.

Cool! By "competition", you DON'T mean that you zero-beat their carrier, and
stepped on them, right? You just found another spot on the dial, and offered
"alternative programming"?


        No, I would never have interfered with them. I tuned up on a
        frequency about 40 kHz above them near the low end of the band.

        I mostly just played albums or a stack of 45's on my changer. We
        did have a little fun with the microphone a few times.

        The oscillator was variable, no crystal. To overcome a tendency
        of the oscillator to FM, I ran the it at half frequency. Carrier
        current transmitters are usually set up to work low in the band.
        One weekend I decided to experiment with a higher frequency to
        see what effect it might have on coverage and unwanted radiation
        at a distance from the dormitories.  I found 910 kHz to be a
        nice clear frequency and tuned up there. Then I took my portable
        radio for a walk through the halls of the two dormitories to
        check coverage.

        Reception was not noticeably different until I visited the snack
        bar in the basement of the dorm next door to mine that was also
        well covered since it was on the same transformers. When the
        attendant heard the music on my radio he let out an expletive.
        He said he couldn't get rid of that @#$ radio station I was
        listening to.  He proceeded to show me that he could tune from
        one end of the dial to the other on the snack shop's radio and
        still hear the same thing.

        It dawned on me immediately that I my chosen frequency was 2 x
        455 kHz. My oscillator was running at 455 kHz, and there was
        enough RF getting through at that frequency that it was coupling
        into the 455 kHz i.f. stages of his radio!  I had a captive
        audience!  I didn't let on that I knew where the transmission
        was coming from, but I got off 910 kHz as soon as got back to my
        room.

>        I modulated it using a very large reverse connected audio line to
 >      voice coil transformer driven by a Heathkit Williamson mono hi-fi
 >      amp (KT-88s?).  What happened to that pile of junk after it proved
 >      its point at NCSU is another long story.

Cool! I'm interested in that "long story"!


        OK.  Here's the other long story about the junk transmitter.

        After the junk transmitter accomplished its goal of showing that
        something so crummy (one of its crowning touches was a PA coil
        wound on a toilet tissue roll and supported well above the
        chassis where it waved around on its leads so as to be very
        visible) could sound better than the horribly distorted,
        unlistenable campus radio station's AM signal, It found a new
        home at the nearby State School for the Blind.  I had a teen
        aged ham friend there whom I visited often.  When, I told him
        about my BC band carrier current exploits, he begged me for the
        transmitter.

        One weekend, I took the transmitter over to him and set it up
        for carrier current operation.  He and his friends fed audio to
        the modulator through a cheap little Calrad high impedance audio
        mixer.  They had a couple of Talking Book record players and a
        Calrad crystal mike hooked to the mixer.  They sounded  very
        professional with this cheap and simple setup.  The carrier
        current transmitter covered the dorm nicely, and they began to
        have a ball playing radio station.

        Some weeks later, I happened to tune across the AM dial and
        found a strong and decent sounding new radio station around the
        middle of the dial.  Imagine my shock when they identified as
        being at the school for the blind!  I immediately called to see
        what was going on.  It turned out they were not satisfied with
        just covering their own boy's dorm.  They wanted the chicks on
        campus to hear them also.  They had abandoned permissible
        carrier current and were using an outdoors tree supported wire
        antenna fed against the building pipes as ground.   They had
        moved higher in the band to get more efficiency with the
        relatively short antenna.

        I spoke to them of the FCC and asked them not to link me with
        this illicit operation in any way.  They said they were not
        worried at all about the FCC.   They continued their broadcasts
        for some time.  It seems I recall hearing they did eventually
        get a communication from the FCC just telling them to knock it
        off.  These events were in the early 60's.  The FCC was more to
        be feared by transgressors back then, but these kids knew they
        would get some leeway.

        Those kids at the school for the blind were incredible.  They
        always amazed me.  I have stories about that too.

        A couple of years laterI built a little more sophisticated
        carrier current transmitter with crystal control that used two
        crystals, a story in itself,  and put it to more legitimate use
        in my college dorm.   But that's another long story.

        For anyone unaware, carrier current stations utilize the
        building's AC wiring as a lossy radiating transmission line. 
        When operating properly, it will not be heard far from the
        building on a good radio.  It is akin to the systems used at
        places like amusement parks that employ slotted, leaky coaxial
        transmission lines positioned along roadways to transmit
        information to arriving vehicles.  It used to be common on
        college campuses.  Some used one transmitter brute force feeding
        the campus wiring, not a good solution.  Some used a single
        transmitter feeding numerous couplers around the campus via long
        coaxial lines.  Some, like NCSU at the time, had numerous lower
        powered transmitters located at dorm groups and fed audio from
        the studio by wire. 

        Most later went to low power licensed FM transmitters, but in
        the early 60's AM was still king in most places.  Lots of people
        then still had AM only radios.  (Anyone remember when WKIX
        dominated the market in Raleigh with top 40 style programming? 
        WAYS in Charlotte?)