[AMRadio] 813 tx


Jim candela jcandela at prodigy.net
Sun Oct 31 08:17:44 EST 2004



Chris, You mentioned broadcasting music to entertain an audience. If the
truth be known, some of us on this reflector may have at one time or another
done this. I can only speak for myself however. :)

I once had a kilowatt AM rig where with 1000 watts DC input I got 850 watts
carrier output (about 1983). On a particular Saturday night I installed a
600 watt movie projector bulb as a "dummy" load at the top of my 40 foot
tower. The rig loaded really nicely into that bulb. Wanting to see how it
looked with modulation I needed a modulation source to modulate the rig
while I was outside looking at the light. So my first CD player was put to
use playing some Beatles music. It was amazing how bright that bulb was, and
how much neighborhood illumination resulted. I had to quit when the
neighbors started coming by... I wonder how far that thing radiated RF....

About 10 years earlier when I was a freshman in college, I set up a 80 meter
ham station in my dorm room. For an antenna I used a 10' whip out the window
with a loading coil, and the aluminum window frame was my counterpoise. I
did work a few hams on AM using my Lear T30 transmitter (4 - 6L6's + 6SN7,
and 6SJ7). I was received more by the dorm inhabitants on their TV sets and
stereo amplifiers however. They shut me down. About this time I was
experimenting with transistors. With a simple transistor gain tester I
noticed that the readings would vary when moving the leads of the transistor
tester. I had several computer boards, and some of these early silicon
transistors made excellent VHF oscillators. I conjured up a two transistor
100 Mhz transmitter (MO and PA), and amplitude modulated the oscillator. The
amplifier was class C, so most of the AM was gone, and FM was the dominate
modulation. Listening to this on a quality FM receiver startled me when I
discovered that the quality was excellent. I guess that we had maybe 100 mw
RF output, and with a dipole on the roof of a 3 story building, this thing
really got out good. This was the beginning of WRFP, Radio Free Puterbaugh.
Every Friday and Saturday night we had a dorm sponsored radio station with
full campus coverage. Requests would come into the front desk, and with
dozens of students making their LP's available (remember vinyl?), we had a
full fledged radio station with pre-recorded commercials. So what started
out as a ham with a TVI and RFI problem turned into a full fledged radio
station. The same folk that were mad at me were now actively working on the
broadcasting! We did this for several months before the novelty wore off.

Regards,
Jim

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of CHRIS PAPAIOANNOU
Sent: Thursday, October 28, 2004 12:36 PM
To: Discussion of AM Radio
Cc: gpritchard at comtechpst.com
Subject: Re: [AMRadio] 813 tx


Legendary tube!About 20-25 yrs ago saw a rack mount homebrew 813 rig in a
fellow's house..p.s and tx in different pi aluminium chassis one above the
other...6L6 the oscillator tube,an 807 like buffer and 2 of those 813
"babes"in parallel like p.a
The p.a tubes were fed with 1200V on plate,was using an 100 W
modulator-amp,and had a long wire about 300 feet long...
I still remember it after all this time gone..
Btw saw a ham from AZ today morning while was searching in the intrnet who
has used the tube self-oscillated.A well homebrew rig..and a surprise for me
who have never seen this tube working in this way be4.
73,Chris,SV1DAF.
----- Original Message -----
From: "George Pritchard" <gpritchard at comtechpst.com>
To: "'Discussion of AM Radio'" <amradio at mailman.qth.net>
Sent: Thursday, October 28, 2004 5:45 PM
Subject: RE: [AMRadio] 813 tx


> I had one of those rigs as a kid BEFORE I WAS A HAM. I used it on CB
> modulated with 811A's. Then I found out about Amateur Radio. A backwards
> experience. Years later I parted it out, unknowing it was so well
> documented. I actually traced that thing out and drew the schematic at 16
> years old. The rig sat at the high school in a corner for years... The
> instructor gave it to me to male room at the end of June. I spent my
summer
> vacation that year on the CB band with that thing. Some of that rig is
here
> and there in the shack, sort of a ghost. When I saw it in the 1956
handbook
> I bought at a fest... I almost had tears. It WAS the one I had.
> George
> AB2KC
>
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of CHRIS PAPAIOANNOU
> Sent: Tuesday, October 26, 2004 5:02 AM
> To: Discussion of AM Radio
> Cc: peter A Markavage
> Subject: Re: [AMRadio] 813 tx
>
>
> tnx Pete..
> Chris,SV1DAF.
> ----- Original Message -----
> From: "peter A Markavage" <manualman at juno.com>
> To: <amradio at mailman.qth.net>
> Sent: Tuesday, October 26, 2004 9:02 AM
> Subject: Re: [AMRadio] 813 tx
>
>
> > Here's some:
> > http://www.amwindow.org/tech/htm/813/813.htm
> >
> > http://www.remote.arrl.org/tis/info/pdf/5401011.pdf
> >
> > http://www.remote.arrl.org/tis/info/pdf/5610033.pdf
> >
> > http://www.remote.arrl.org/tis/info/pdf/57hb192.pdf
> >
> > Doing a "Google" search on "813 transmitter" turned up 49 hits.
> >
> > Pete, wa2cwa
> >
> >
> > On Tue, 26 Oct 2004 06:44:32 +0300 "CHRIS  PAPAIOANNOU"
> > <amateur at ipnet.gr> writes:
> > > 73 to all group's members around,
> > > i'm new in this list.My name is Chris,my call is SV1DAF and i'm
> > > located in Athens,Greece.
> > > I'm not new in AM..20-25 years ago there was too much AM activity
> > > here,with homemade tube rigs,in the MW band.Was illegal but there
> > > was.Then most of the "amateurs"became hams with legal activity in
> > > the ham bands.The rest of them left the radiowaves.
> > > Not long ago i started homebrewing again after long time.My homebrew
> > > rigs now are:
> > > 1)6V6/807 crystal controlled where the 1st tube is the oscillator
> > > tube and the 2nd one the pa one.
> > > 2)6J5/EL34
> > > I prefer plate modulation and the reasons are known and clear,and
> > > i'm using an amp with 2 EL504s like output tubes.These are sweep
> > > tubes.
> > > I'm now searching for a tx drawing with an 813 tube like pa tube.Any
> > > replies will be too much appreciated.
> > > Tnx for the attention paid to my introduction,
> > > 73,Chris,SV1DAF.
> >
> > ________________________________________________________________
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