We are moving (how many times have I said
that before) and I am going through all sorts
of junk.
I found a "Mr. Microphone" type of FM transmitter-
actually - it's called a "Sing Along." This is an extremely
low quality FM wireless mike for kids to scream into. With
a little bit of luck, their screaming might come through a nearby FM
radio. Maybe. I have also (way in the past) taken old wireless mikes -
disconnected the mike element - and fed mono line audio into them
(somewhere in the circuit board) and have come up with very HIFI mono
short range FM transitters. They didn't go far - but they sounded great.
I thought I could maybe do this with the "Sing Along." with my budget -
any port in a storm. Sometimes the "VFO" can be sort of stabilized - usually
after some drift. Whatever.
"Hey good lookin, we'll be back to pick you up later!" Remeber that quote in
the old Mr. Microphone commercial? You know. Maybe like something "good"
was going to happen later?
Well, I started to test this thing - this toy "Sing Along" FM wireless mike.
Nothing good. BLEHH! What a piece of junk! I didn't expect much, and I got even less!
A mixture of AM and FM, at very low deviation. Maybe it's broken. It's only
been sitting in the junk pile for 20 years! More to follow - like - how far does
it go? It is FCC certified, but the letters/numbers are too small for me to read.
To me, playing around with junk is fun.
Speaking of fun, I found my old Ramsey FM-10. I think I mentioned this transmitter
a few weeks ago.
A modulated free running oscillator, with a little RF "power" amplifier. From
about 1992. I put a fan on mine and a big bright red LED "power on" indicator.
(It's Cool!)
I don't know if it works, and I don't really care. Either way, it's fun.
I don't have the plastic "frequency adjust" (sp?) tool. I had one a
couple of weeks ago and threw it away. (Man!) It's also rigged for mono.
I just turned off the 19 kHz pilot (crunch went my cutters) and there you
have it.
More to follow, just for the silliness of it.
Brooce, WLP 1590 radio, relaying KDX at certain
tmes of the day and night.
(Carl does all of the anouncements. I just sit
there and eat popcorn and drink diet gingerale.
The rest of the time I play my own weird music
that only I like. I have a toggle switch. UP is
KDX. DOWN is MY JUNK. My junk. Sounds like
Wally and Beaver Clever. Here comes Eddie Haskell.
"Hi Mrs. Cleaver, what a nice hairdoo you have today.")
Years ago I had a Radio Shack wireless FM mic. I remember a pin hole you put a tuning tool inside to tune to a black frequency. It took a small watch battery but went 75 feet to a Digital Stereo around 1983.
Okay let's talk about these microphones.
To this very day I still have two of the original Mr. Microphones.
They are no longer in that silly plastic case with the orange foam ball.
But let's go back to the beginning here.
Back in the day, I purchased a Radio Shack FM91 wireless microphone.
It was the beginning of my first radio station back in 1976.
I simply planted the microphone in a sound proof cooler along with two speakers for the left and right stereo channels and then attached an SO-239 coaxial connector to the antenna wire. From there, I attached a 10 foot piece of RG-8 coaxial cable which was hooked up to a .64 wave ground plane CB antenna. Back then, I didn't know that the antenna had to be a certain wave length, but it did carry a signal for about a half mile on an outdoor FM antenna.
In later years, I realized the frequency spread of 88.1 to 92.0MHz in my area was noisy and filled with broadcast stations. I mostly used 90.1MHz, but suddenly one day when I turned the transmitter off, I noticed a dead carrier was on 90.1MHz. Long story short, WECS http://www.wecsradio.com/ a collage radio station from Willimantic Connecticut was just going on the air was covering us up.
There was no open channels in that frequency range, so I had to experiment with some values of the parts of the FM91 to change the tuning range of the tuning coil. I changed one coupling capacitor and one resistor and the range moved up to the upper FM band.
I moved to 106.5MHz. The only station that was on that channel was a religious radio station out of Boston MA. that wasn't always receivable in my area even on a large hill.
As time moved on, I bought two of those Mr. Microphones from Ronco. They transmitted something like 10 feet, that was about it.
One day I tried an experiment. I removed the circuit board from the plastic casing. I hooked the audio output of an FM mono radio that was tuned to 106.5MHz to the two poles of the circuit board that the microphone was hooked up to. I attached an SO-239 connector to the antenna circuit of Mr. Microphone. It originally used two AA batteries for power, I hooked up a 9 volt adapter so it had constant power. Finally, using 10 feet of RG-8 coax, I had it transmitting into a Citizens Band 1/4 wave ground plane antenna. This signal reached two miles line of site.
Lastly, Radio Shack sold a Science Fair AM transmitter kit. It had those springs that the parts were placed in so kids would not have to use a soldering iron. I never used the included crystal microphone when I used this kit. I did the same thing as I did with Mr. Microphone, I used an FM radio tuned to 106.5MHz and hard wired the audio output of that radio into the AM transmitter's audio input. I also powered this transmitter up using a 9 volt adapter. For an AM antenna, the building had a 25 foot television antenna tower up on the roof. I used a SO-239 connector on the AM transmitter and feed a 25 foot piece of RG-8 coax up to that tower and attached the coax to the tower by using an SO-239 connector and a copper plate that was attached to the aluminum tower using bolts so there was an electrical connection between the feed line and the tower. That signal at 1000KHz reached 1 mile line of site. I was using the tower as the actual transmitting antenna. Mind you the tower was not grounded so there was no problems with grounding out the transmitted signal.
I had transferred that AM transmitter kit to a home etched circuit board I had made and moved the original plastic coil frame and tuning capacitor onto the new circuit board. All the parts were soldered in, making for a better connection over the springs the original kit used.
I no longer have that FM91, I'm not sure what happened to it. I still have the owner's manual that came with it though.
That AM transmitter is also gone, I still have two copies of the owners manual that came with the kit and could build a new one if I wanted to. I still have that tuning capacitor from the kit so that is one part that does not need to be found.
I have not looked at the owner's manual lately, but I know I drew a circuit board diagram on it, maybe if I get up into my attic, I can look through that box of service manuals I have and make a photo copy of the road map I designed, then you could create your own circuit board.
Most of the parts are easy to get if you wished to duplicate that kit.
Bruce.
I'm curious to find out how much power that Radio Shack FM Wireless mic had that you connected to a CB antenna back in the day and got a ½ mile range. I'm sure it had to be close to the Belkin FM transmitter or a little less. I'm also quite sure that the transmitter must not have had any amplification or final stage to it hence was why it didn't get hot due to the high SWR it must have had especially not using any sort of ground reflector as is on the shield of the coax. The fact too that you got so far on AM with no ground is a mystery in itself. You were able to reach ½ mile on AM with that kit is cool. Too bad the transmitter probably drifted like hell. Now if there was a way to stabilize the frequency from drift I'm sure it would be something I'd be interested in as an AM transmitter if I could get someone to put it together. I'd have to probably use a wire antenna and I would not have any way to ground it which probably would mean I would not travel very far. If the rules didn't restrict the wire length I'd put a 100 ft antenna wire on it and have a ball. It may have reached ½ mile just with that on a car Radio. Might have been fun for giggles. I'd get a Tecsun Radio just to see how far I could have made it go.
Well I guess it proves a few things here as to the mystery of how much power it may have taken on the FM side. I'd still like to know how much ERP you ended up with on FM with that Radio Shack FM microphone. God I remember the days where the students at the school for the Blind would do some of the same stuff with those FM wireless mics.
I'll get up there and dig those manuals out, I know I still have them.
This is a true story, so please take it suriously.
One day we had a hurrific thunderstorm move into the area. I was on the air using that radio shack FM91. I was sitting near a window and all of a sudden I seen a bright flash and a loud crack a split second later. We all know that means lightening hit within 20 feet of that location.
It knocked my transmitter off the air I know that. long story short, because it took several months to find out, but that lightening strike hit the cable television trunk line outside my house, which was about 20 feet away. They got complaints about weak cable signals and found the coax wire inside had been torched. At any rate, my .64 wave ground plane was about 30 feet away from ground zero and picked up enough stray current to zap the transistors of the FM91.
I ended up rebuilding a whole new circuit board and bought new parts and got things going again a few weeks later.
I never had issues with the AM transmitter kit drifting, but the FM91 did drift quite a bit. I had no frequency counter back in the day and to get back on frequency, I had a Shark stereo system that had a tuning meter on it. It had an analog tuner needle, so unlike today's digital tuners, it was hard to tell when it was on 106.5MHz, since there were no local stations on it. To get around that problem, I would hook the cable TV coax up to the stereo, the cable company was carrying the audio of one of the television stations on 106.5MHz as part of it's cable FM service. I'd tune the FM dial to where that station pegged the meter, then I'd remove the coax and turn the FM91 on and tune the FM91 until the meter pegged out. Now I knew the FM91 was back on 106.5MHz again.
I am currently doing some finishing touches on my current studio, I did do a VHS video of my former station and still have that as of today burned on DVD disc. Back then we were called WNOR. NOR is Norwich's first three letters, we also called ourselves Were Norwich's Only Rock, hence WNOR for short.
Let me be truthful here though, although the signal was very limited. Most of those devices were NOT being operated as they were intended to be by the FCC. Hence adding to the length of those device's antennas was not allowed according to the owner's manuals.
The FM91 came with a 12 inch wire dangeling from its bottom compartment, we had a .64 wave CB ground plane hooked up outdoors for the antenna.
The FM91 only has two transistors, one for the audio and one for the transmitter, so no there is no chance those transistors would ever get warm over a poor VSWR. I have no clue how much energy that one transistor put out. The Mr. Microphone only had ONE transisitor, imagine that!
Today, things are a bit different from the 1970's and 1980's when it comes to restrictions on antenna lengths.
Bruce.
It takes me a long time to read this stuff
so I'll just comment briefly for now.
To Mr. Legacy: Was the wireless mike you
had a little teeny black thing with a clip on
it that you could attach to the front of your
shirt, or something like that?
To Mr. Bruce: Facinating read - I have to go
back and look at it all again.
We in sort of in "parallel universes" I also
lived in CT and remember when WECS came
on 90.1 as well. I believe we have heard many
of the same radio stations.
I have had most of the same equipment you
worked with, but not the same sucess.
Best Wishes,
Brooce, WLP, and many other Part 15 stations
Yes. Black with a metal clip on it. Amazing how back then that the signal went further than the Belkin.
Works. Sounds OK. Fan and cool red LED
work.
It's on an empty channel.
So if it drifts a little it doesn't
matter.
There's no antenna on it so the
signal is just in the house.
Fun!
Brooce, WLP
P.S. More comments on the above soon.
I am still reading the above. It takes
me a while.
The Ramsey FM-10 has stabilzed on 90.82 MHz
and is "hanging" there.
I have to get it up to 90.9 and have it stay THERE.
Again, there is no antenna on it, so it's signal
won't interfere with anything.
I like this because I built it myself.
I found an old friend in the attic.
Brooce, WLP