In the late 90s, while in high school, I built an FM transmitter and with a few friends ran a weekend pirate ration station. (AMF - Anonymous Mother ....)
The kit was sold by a company called Ramsay Electronics. It was 1 watt and with the right antenna (which was quite visible on the roof of my friend's house. They lived right at the top of a hill) it did a good job of covering our small town. There was a brief time when we would get word of several house parties all tuning in when we started to play more dance music late at night. There would be requests from people all through the week at school to play this or that, or call a certain number because someone wanted to say something. This time also coincided with the very first MP3s and I was a "Vice President" of an irc "courier" group, so we could get all the latest stuff!
It only lasted one school year and my friends loved the notoriety, but I used to just sit there and day dream about the audio passing through the low and high pass filters that I had been constantly tweaking, and then being modulated and then re amplified before being pushed out. I still get an excited sensation just thinking about it.
We had a baby monitor that apparently broadcasted on AM, a cassette player, and a lot of shouting and we weren't afraid to use it :p. I'm not sure it even worked outside the confines of our own house.
The output of the original Ramsey kits was about 25 mW, which was FCC-compliant. The one watt kits used a MRF557 transistor (rated for up to 1.5 watts) and were definitely illegal to operate in the U.S. without a license. They were sold in the U.S. as "export" models for overseas use only. I may be wrong, but I think this eventually got them in hot water with the FCC and led to them discontinuing the kits.
As a teen in the early 80s I played with many FM transmitter kits, but liked one in particular (can't recall the brand, possibly Amtroncraft) which used a MRF237 and was rated 5W. I didn't have a FM antenna nor a VHF SWR meter to make one and test it, but I thought: "27*4=108, my mobile CB antenna should resonate...". So I put that CB antenna on the balcony, turned on the TX with an audio oscillator as input then called a friend living roughly 2Km away and his home on the other side of the building (no line of sight) asking him to tune his FM radio to my tx frequency, and he got the beep loud and clear. I couldn't believe that, I just had to hear it with my own ears, but I thought the beep would draw too much attention, so I connected the input to the stereo, put on a record (by KISS if memory serves), then went out and as fast as I could with my boombox walked to my friend's house and further; At some point the 1st side of the record ended so I was left with the carrier alone, but that was a success.
I had too much fear of operating it however; the seventies were gone, piracy was being taken very seriously and our equivalent of the FCC, then my father, would spank my ass badly If I was caught, so after a few other tests I put that transmitter in a drawer and pretty much forgot about it.
You are right! I actually grew up in Canada and the Ramsay kit shipped from Rochester NY if I remember correctly. 1 Watt was very clearly labeled for Export Only, although still not legal in Canada.
I believe they do still sell the 1watt through distributors (I guess downloading the compliance risk?), at least they did 5 or 6 years ago last I looked.
A friend of mine bought the transmitter from an AM radio station that went out of business to use as a ham radio transmitter... how they managed to shove it into his basement is beyond me. He ran it on its low power setting, and everyone loved the quality of his audio.
One night I tuned into the most beautiful-sounding AM signal I ever heard in a two-ham QSO (on 80 or 40?). One of the guys was a gear-fanatic using pro gear and a top-grade mike. I'd never heard such AM voice quality. The other guy had a much newer, commercial ham rig, and the difference was so obvious.
Spark gap transmitter were (one of?) the first form of radio broadcasting: https://en.wikipedia.org/wiki/Spark-gap_transmitter . Since it is not very selective - its signal spreads through the whole spectrum - its use is forbidden today; think a single radio station which transmitter over all frequencies, like you can turn the dial and it will always interfere and you can't get rid of it.
Because tuning was a known "phenomenon" and having the possibility of using the radio spectrum for multiple transmission was desirable, efforts began to make transmissions more selective so they wouldn't pollute the whole radio spectrum.
Radio pioneers didn't have anything close to modern small, powerful, solid state, very close to sine oscillators at the time. They had to use what was available so they could modulate their transmission. In a simplified model, a radio transmission be thought of as an antenna whose electric potential varies with the sine of time at, for AM broadcasts, the order for hundred of kilohertz. This oscillation is then "multiplied" by the signal one want to transmit. Better results occur when the "transmitted signal" (think about it as something close to a payload) has a much lower frequency than the "carrier": the frequency at which the potential of the antenna would oscillate to transmit a constant value.
Now, early broadcast really worked around the technology available at the time. To oscillate the electric potential of the antenna, they resorted to eletromechanical methods. Very interesting solutions were developed: https://en.wikipedia.org/wiki/Spark-gap_transmitter#Rotary_g...
> Spark gap transmitter were (one of?) the first form of radio broadcasting
AFAIK this is also the reason the German language uses the word funken for transmitting wireless broadcasts, derived from Funke (spark). And of course the corresponding noun Funk, often embedded in typical, lengthy noun constructs.
The German company Telefunken also has a couple mentions in the Wikipedia article you linked to, as one of the early manufacturer of commercial radio equipment.
I actually made a spark gap "receiver" when I was a kid following some plans I found. I used a rubber tube with a metal rod in one end, then filled partially with iron filings I made from filing a pipe, then stuck another metal rod to plug the other end of the tube slightly compressing the filings. I then placed a LED, resistor and battery in series with the device. If the LED turns on, flick the device until it is off. Then place next to my gas stove and click the gas spark igniter. If all goes well, the spark will iron align some of the iron filings to create a conductive path and the LED will turn on. Flick again to turn off.
The first job I ever had was at a Radio station, where we were transitioning away from Harris 90 automation to an AudioVault/BEI controlled automation.
The only reason I got the job is because I could figure out how to use the interface: the other two kids from high school who went with me couldn't manage to record audio from the interview.
I remember so many late nights running football, basketball, and other games during the summer...only to turn around and do an afternoon game the next day, then my usual 4-midnight station rotation, all while making around $5/hour.
Caltech had a pirate station when I was there, naturally dubbed "KCAL". The equipment was all custom designed and built by the local EEs. What I remember most about it was the lovingly machined panels made for it. It was a beauty. I wonder whatever happened to it.
Signal generators (common test equipment) can also be used as broadcasters. I recall doing this a long time ago with an old HP 8640B. It has both AM and FM modulation. Not much output power, but the output power is adjustable so that you can experiment without creating issues for anyone else.
My father was a radio DJ and so I grew up after school in local radio stations during the 80s and 90s. I hope someone else gets a kick out of seeing this old radio broadcasting equipment.
I definitely get a kick out of seeing it, very nostalgic. I had a few shows on my college radio station (88.5 WRUR in Rochester, NY) back in the early 90's, including the 9am news slot on Friday mornings and a brutal 3-6am slot on Wednesday mornings where I did whatever the heck I wanted (nobody was listening at that hour anyway).
I'm currently at WRUR. It is not the same as it was in the 90s but we're still here. If you have any cool stories I'd love to hear them. They are a little more strict these days.
I was back on campus about two years ago and the studio was almost unrecognizable, although the rest of Todd Union looked about the same! Yeah, we weren't very strict back in those days. You just had to do so many hours in the AM booth and then you were given access to the FM studio. So you just did your AM time by playing album sides while you did your homework; nobody was listening to AM anyway.
Not too many exciting stories. I got the opportunity to sub for somebody in the 5pm Friday slot one week. I had no idea what the slot was, but I just went in and did my 3am show. The phone lines quickly lit up with people saying, "What the hell is this Sh#!? You're complete crap. Where's the Jazz hour?" Lol. On the other end of the spectrum, one of the UR bus drivers recognized my voice and told me he loved my 9am news slot and always tuned in. I always did the top stories off the AP feed and then finished with some weird off-the-wall story, before turning it over to my buddy to do the sports.
Today if you head to SDF or some tildes you can DJ online to a streaming server, among other geeky stuff inside (those are public Unix machines to learn and share).
I'm currently working on getting a retired Broadcast Electronics 2100C cart machine from my old college radio station and as I expected the parts appear to be very hard to come by. If anyone has a suggestion/lead I'd be grateful.
The kit was sold by a company called Ramsay Electronics. It was 1 watt and with the right antenna (which was quite visible on the roof of my friend's house. They lived right at the top of a hill) it did a good job of covering our small town. There was a brief time when we would get word of several house parties all tuning in when we started to play more dance music late at night. There would be requests from people all through the week at school to play this or that, or call a certain number because someone wanted to say something. This time also coincided with the very first MP3s and I was a "Vice President" of an irc "courier" group, so we could get all the latest stuff!
It only lasted one school year and my friends loved the notoriety, but I used to just sit there and day dream about the audio passing through the low and high pass filters that I had been constantly tweaking, and then being modulated and then re amplified before being pushed out. I still get an excited sensation just thinking about it.