I have listened to The Low Power Hour #19 about five times, and
so I had to talk about modulating local oscillators. Which, of course
I have listened to The Low Power Hour #19 about five times, and
so I had to talk about modulating local oscillators. Which, of course
means - taking an old radio and turning it into a transmitter.
I almost killed myself trying to do it. I figured out where the local
oscillator was in an old "All American Five" tube radio in the early
1970s. This was an AM radio.
I found the 12BE6 tube in the radio.
DON'T DO WHAT I DID - I AM LUCKY TO BE ALIVE.
SIDE NOTE:
(Oh yeah, I should have learned a safety lesson from almost
getting killed using cruddy (is it OK to say cruddy on
here?) phono oscillators - but I was a kid, so I didn't.)
Where, were we - oh yeah - so I found the 12BE6 LO tube
in the radio. I tuned it's signal in on another radio. Then - with the
"transmitting radio" on - I just started touching an antenna
wire to different areas of the tube socket until the signal
in the receiving radio got strong.
Then (a little knowledge can be dangerous) I figured out
how to audio modulate the tube. i just ran line audio into
the grid and ground, I guess. And it worked.
But there were no safeguards in place - no kind of isolation -
and I began to get very casual in my experimentation.
THEN IT BLEW UP!
I must have crossed some wires or something.
Some of you may remember the story: when I hooked my prized 1966
Sony TC-350 reel to reel deck up to a phono oscillator
and blew the tape deck up - because I didn't know the
dangers involved.
That didn't happen with the scenario that I am
chronicling here.
Instead of blowing up my prized tape deck - I
almost blew myself up in the shower of sparks
and the smoke I made.
After that the project was abandoned.
Another side note: I just looked at my prized
Sony TC-350 tape deck LAST NIGHT. (It was
repaired after the mishap.) It is now - do the math -
46 years old. It doesn't work. However - I still can't
part with it.
One other comment on THE LOW POWER HOUR # 19.
I thought it was interesting when "THE DUDE" mentioned
those paranormal experiences. I know of 5 people in
my life that had "GHOST or UFO" experiences. Including
my grandmother, who was sane, honest, and completely
reasonable the whole time I knew her. (Her departure into
the "next world" was pretty sudden.) I myself, have never heard/seen
anything like that, and I hope I never do.
You sure can hear a lot of that stuff on Coast To Coast AM,
which is on my AM radio at night. On about 15 stations.
Best Wishes,
Bruce, DOGRADIO STUDIO 2
Best Wishes,
Bruce, DOGRADIO STUDIO 2
How fast did that zap shake you out of the chair and into the air?! 😀
Great story!
RFB
First of all, I wish to register a complaint with the managers of part15.us regarding use of the word "crud."
Local oscillators have a definite allure. Back in the years when I worked for licensed full power professional radio and tv stations, and was paid to do so, I was much more interested in the local oscillator of an Eico AM radio built from a kit. I wanted so bad to modulate it. I dreamed about it. I would bring it up on dates with some of the best looking women in town. "What do you know about modulating a local oscillator?" None of them knew.
Of course today I could get a local oscillator modulated, but I'm suddenly trying to find the best looking women in town, and I'm thinking maybe they've moved.
We build our beds unmade.
Well, RFB - I don't know how fast I went away after
the big sparks and smoke. I think I got a shock and
sort of went numb emotionally. The sparking was very
frightening I remember.
And then I pulled the power, disassembled the experiment,
put the pieces away, threw the radio in the trash, and never
went near the idea of it again.
Oh yeah - when the thing was running - the audio sounded
good and the signal went a couple of hundred feet. The antenna
was a ten foot wire. I bet most of the RF was going into the power
line.
Oh well.
Bruce, DOGRADIO STUDIO 2
It's amazing what some manufactuers got away with way back when. My first AM xmtr was a Lafayette LA-23. (or KT-195...same unit..the LA came assembled, the KT was a kit)
Performance was pretty good if you added a resonant tank curcuit in the antenna line...I got about 1/4 mile out of it with no ground system at all -- just a 102" cb whip with a coil in it.
Big problem with this AC/DC rig, was that there was no such thing as a "polarized plug" in the 60s, and you had a 50/50 chance of putting the plug in the wall the wrong way, and having the chassis hot with 115vac! Fortunately I never touched anything connected to the chassis and ground at the same time, but used to wonder why I was getting shocked when I would have one hand on a metal mike and the other on a metal turntable. YOW!!
An engineer from the local RCA plant told me the secret. "Connect a wire from the chassis to ground with a light bulb in the middle. Then put in the plug. If the light bulb lights, put the plug in the wall the other way. The bulb won't light, and you'll know you're safe."
Well, It worked, and I didn't electrocute myself with that thing.
Can you imagine the flak if a safety hazard like that got on the market today? I can hear the stampede of lawyers already!
I still have the two main pieces of
my second Part 15 AM station from
1968. Neither work, but in the other
room in my "collection" is a Lafayette
KT-195 and a Sony TC-350 reel to reel
deck that was made in 1966.
I can't part with them!
And what you said is absolutely true!
Bruce, DOGRADIO STUDIO 2
Hey, I had a KT-195 back in 1963. It did OK but then I built a 1 transistor oscillator/broadcaster and it was even better. Not the original, but I still have one.
The REMCO CARAVELLE was the start for my PART 15 adventures in 1962. I have three of these.
A always wanted a Caravelle...don't know why I never got one. They had the coolest TV commercial: "Attention upstairs radio -- Take down this message!" Before my LA-23 (KT 195) I had a 2 transistor AM rig made by International Semiconductors. The company named it "Station F U N". How corny is that?! It worked about as well as those 2 transistor radios of the early sixties. Maximum range was about 20 feet! With that experience to guide me, I figured the 3 tube KT-195 would do a LOT better than that, and I was right. If I had it today and used a good groud system, I bet its' range would equal the Rangemaster! (If only it had PLL frequency control instead of that cheap LC curcuit! But no such animal existed way back then)
So mram1500 -- How far did your 1 transistor broadcaster go? I think it's amazing it beat the KT 195. Mine was the envy of the neighborhood!
The Caravelle did (does) really look cool, especially when you're only 10 years old. Wow, big desk mic, morse code key, AM receiver too! But not a great performer. The biggest problem I had was frequency stability and the range was about 50 feet.
Once you set the frequency you'd better not move or let go of anything connected to it. Otherwise, the signal would move way off channel.
The KT-195 was the first "kit" I built. For a 10 year old I guess I did OK. It worked much better than the Caravelle but again the range was not much more than 100 feet even on a long wire. It needs that tank circuit added as mentioned.
Then I found a book at the library, Harry Zarchy - Using Transistors. It was a collection of simple transistor circuits and there it was, 1 transistor a couple resistors and capacitors and a coil. Built it on a piece of wood. Ran on a 6 volt battery. The signal covered a city block, maybe 500 feet.
I still have the schematic scribbled down somewhere and I'll probably put one together to tinker with.
Part of the reasons for changing the electrical standards to grounded and polarized outlets is because of these issues of getting zapped by appliances and other devices plugged into the AC outlets.
The devices had the right idea...ground the cabinet to the neutral of the AC line, which is tied to an Earth ground outside at the drop. Problem was that after the service drop, the wiring in the home or building went whichever way it got wired..following no standard. It was very common to see a cluster of outlets all wired backwards from each other, making things even worse.
I remember someone once telling me "ahh..AC has no polarity, it don't matter which way you plug that in!".
I believe it was someone messing around with one of those Knight kits. Interesting that a few days later the fella says "umm...well ignore what I said earlier about AC having no polarity!". HA HA.
What I cannot figure out is the manufacturers and design engineers KNEW that having a metal cabinet tied directly to one side of that AC voltage pair, and without a polarized plug and wiring behind the outlets, that sooner or later someone is bound to plug that in backwards and make that metal cabinet intended to be a ground become HOT, but for many many years this is how things were built and wired up.
I also wondered WHY would they even tie the metal cabinet to the power cord anyway..unless that power cord had a ground wire in it. Makes no sense..never did..still doesn't.
I'm glad the NEC changed its standards and we have safer wiring in our homes as well as safer power grids above our heads and below our feet.
Tip for future tinkering on old stuff: An isolation transformer will keep the hair combed down and pants dry!
Or change out that old unit's non-polarized plug with a polarized plug!
Gotta love them good ol days!
RFB