I've built many of these over the years. This same outfit has offered this kit for decades. Helped my bosses daughter build one about 25 years ago for a school science project and my own kids built a couple of them. Dangerous as all heck with the exposed voltages, but I've seen these put into nice wood or aluminum boxes, etc. You could sure build one into an old record player and make your own wireless phonograph:
https://www.tubesandmore.com/products/kit-wireless-transmitter
TIB
From reply 11
Unless the campus property is rather large and the intended reception area is rather small and near the center of the campus, Part 15 AM stations can have better results when operating under §15.219 than §15.221.
From reply 14
...this transmitter WAS on a LARGE campus of ½ mile. ...
___________
Illustration - For an FCC-compliant Part 15 AM station using 1650 kHz, located at the center of a square-shaped campus having opposite sides separated by ½ mile, and average earth conductivity, the following fields could legally exist at the borders of that campus nearest to the transmitter:
- 14.5 µV/m when operating under §15.221 ("Campus Broadcasting")
- about 400 µV/m when operating under §15.219
I could talk forever about phono oscillators.
Actually, I HAVE done that on this board in
past years. ...Probably too many stories.
I had the Lafayette "phono oscillator"
transmitters. And very dangerous to use as
I'm sure you all know. (Also inferior to the
Knight Kit rigs.)
I had the Lafayette 990177 unit that used
a 12BE6 and a 35W4. There is a video of
one of those on YouTube. Later, I had the
Lafayette KT-195 unit. It was a real dog
(mine was anyway.) It had a 36AM3B rectifier
and 2 50BM8s for audio and RF. I believe MRAM
took a KT-195 and rebuilt it so it was safe and
really useable as a transmitter. I think he modified the
entire audio chain. The KT-195 was a kit. The
"already built version" had a different model number.
It was the LA-320. These units were dangerous and
didn't work well, but they changed my life forever.
They were the first transmitters I owned in my life
that sent a radio signal more than just a few feet.
Well, no - that's wrong. I had had 2 100 mW CB
walkie talkies before that. But, for some reason,
putting out a signal on AM radio was much more
exciting.
Brooce, Part 15, Hartford, CT
So when I took my Lafayette KT-195 on
1600 kHz (roughly) and my Lafayette
991077 phono oscillator on 540 kHz (roughly)
and tried to combine the two transmitters for
stereo (using 2 different radios for receive)
things didn't go quite the way I thought they
would go.
I think the Lafayette KT-195 had AC voltage on
the chassis whether it was on or off. The 990177
phono oscillator had voltage on the chassis when the
AC plug was plugged in "the wrong way." All or
most of you reading this will know exactly what I
mean. And chassis ground on each unit was
also the ground for the audio cables that were plugged
in. The source of music for these two transmitters
was my Sony TC-350 reel to reel deck. Too bad it
was in the middle of everything. I plugged in one
transmitter and got the left stereo channel going
through the "left" radio. As I went to plug in the
AC power for the "right" transmitter to radio (with
all other cables hooked up) - things happened
quickly. It seemed that I never even got
the AC plug into the outlet. When I was plugging
it in (or trying too) a gigantic flash of light seemed
to come right out of the AC wall outlet. It seemed
to light up the inside of the whole wall socket as it jumped
to the plug to complete the path. I jumped back
and took the AC plug and cord with me in that
direction. It only took that fraction of a second
to blow up a chain of audio transistors in the Sony
deck. My priced reel to reel was ruined. (It WAS
later repaired.)
Live and learn. I'm glad that I continued to be alive
after that doomed experiment. I was 14 years old then.
Those of you who (at about the same time - the late
1960s or early 1970s) - were using "multi-project boards"
for AM BCB transmitting sure had safety on your side. I
wish I had known about the transistor and battery AM
transmitters then. Even if they did not go as far as
the vacuum tube transmitters, I would have preferred them.
Also, the KT-195 FMed very badly. In the "center" of
the received signal on the radio, where the signal was
the strongest - there was no audio. The audio was off
on the sides of where you would tune. So center carrier was
on 1600. Audio was on 1597 and 1603 or there abouts.
Also, my KT-195 seemed to put out many spurs and
strange transmitter "products," although many of them
could have been the fault of the radio I was using.
It turned out that most (or almost all) of the
transmitted power was actually in the "Marine Band"
- as it was called then - around 2100 to 2400
kHz. That was going about 1/3 mile - well -
to a good receiving installation anyway. (A Knight Kit
R-100 receiver with a 90 foot outdoor wire antenna.)
My transmitting antenna was just sitting on the cellar
floor (how about that?)
Dangerous and crazy - yes - but these were still very
exciting times. I "transmitted" on about 1600 for a
long time - many months at least - until my friend
at the receiving end stumbled upon the 2100 kHz
signal and realized it was coming from my house.
LOL!
Brooce, Part 15, Hartford, CT