An amazing crystal set receiving loop on YouTube and some other ideas

I tried an experiment with a very small

loop I have.  (I have used this loop for

lots of things including CC coupling attempts.)

This loop is about 15 or 20 inches on a side. It

has multople turns of wire and is tuned with a

365 pF variable cap. 

I hooked the loop up to my crystal set without

an antenna and without a ground.  I was able

to hear our local 50 kW flamethrower.  It was

there with very low audio in the headphones,

but it was there.  So - I guess - that small

loop and the RF section of the crystal

set were able to turn on the 1N34 diode

in the crystal receiver.  What does that

take?  0.3 volts?  That's not too bad to

a small loop like that. 

Bruce, DOGRADIO, Experimenting with 1020 kHz CC now.

Bruce, I enjoy your experiments with loops and couplers and all...

These are things I have not tried to do, but I enjoy hearing about it.

If a loop like yours were tweaked and tuned to capture more and more energy from local transmitters, you might have enough voltage to light a lamp for nighttime "off the grid" living.

Am I expecting too much?

We will keep the ALPB running for that day when you have a computer to join us.

If we were a bigger organization we could send you a computer.

I wish we could do that.

Maybe someday we'll have the resources to do something like that.

When I was younger the word "loopy" was often used to describe me.

I think when KDKA first started broadcasting,

it's transmitting antenna was on the top of

some major building somewhere...  Anyway, the

story is that people in the building wound

induction coils to power light bulbs so

they would get free lighting.  At least that's

what my 9th grade science teacher said. 

Not too long ago, some major company

was trying to make a device that harnessed

power from cellphone radiation to power

what???  Uh - clocks?  thermometers?  I don't

know - but it turned out that there was a lot

less power in the air than they thought there

would be. 

Nevertheless, I didn't expect to get anything

at all from that little loop, but it did get the

one local flamethrower.  So - basically - I

had a portable crystal radio that I could

carry around.  That is cool.

Thanks for the good words Carl!

Bruce. DOGRADIO Experimenting on 1020 kHz CC now

Thanks, Bruce, for the link. The project brings to mind a question posed by one of my students. In order that our students gained hands on experience with components and soldering we had them build a Heathkit digital clock radio. These kits cost about $35 and one student asked me "Why would anyone build one for $35 when you can buy one built for $12?"

The fellow working on his crystal set could buy a radio and be done with it but many will recognize what is really going on here. It is the process and not the product he is pursuing. For example in the fourth video he is tuning and tweaking and jumping around the band listening and he is focused on getting the best reception he can and he is not concerned at all with the program content of the stations. His goal appears to be to develop the best crystal set he can rather than to sit and listen to programs or music.

In doing so, he has learned a great deal about the theory and practice of RF circuits. This happens when one pushes the technology to optimize performance and is the best way to gain knowledge.

There are those who say "I don't care how it works, just so it works when I turn it on" which is fine since not all are interested in technology. But for those who are interested in technology projects such as this radio are great learning experiences as well as a chance to discover a new application or technique to improve on the way thing are done.

Many here know this because of the quest for getting the most range from their part15 transmitters. Some don't care as long as the signal covers their house or yard but others want to push it to the limit. Both endeavors are fine depending on one's goals but much can be learned by pushing the limits through experimentation guided by theory.

It was nice to see the fellow on the videos "pushing the limits" as he did and it is obvious that he has learned a lot about the subject.

Neil

One of my first "experimental expansions" happened when I saved enough to buy a Magnavox Phonograph that had two loudspeakers in the front panel.

I discovered that with wire and some external loudspeakers I could send the music from the record-player to other rooms and out into the yard. In essence I re-discovered the public address system.

At some stage in the process I decided to see what would happen if I attached a 119VAC power cord at the voice coil of a 12" loudspeaker. Three things happened: there was a loud "POW!" noise, a wiff of smoke, and a ruptured loudspeaker.

Lesson: the power levels must be matched between amplifier and loudspeaker. A nuclear power plant is too powerful as an amplifier for a simple 3-Watt speaker.

I still am enjoying your comments. 

It's interesting, isn't it?

I like the minimalist approaches to radio

and electronics and science in general.  

And (although it's not really the same thing)

I remember being stunned by finding out how

various things worked when I was young - and

going through "my beginning" with these things.

Back then, I hooked a pretty large HI FI speaker up to a

little AM pocket radio and was really suprised

about how loud the audio was and how good it

sounded compared to the AM pocket radio by

itself.   My father thought that the final audio 

transistor in the radio would not survive driving

that big speaker.  That made sense to me also, but

there was no problem.  

I have done a lot of different fun things with radio.

In the last 40 years, I have been on all of the ham bands from 160M

to 23CM (1296 MHz.)  And I have listened from 23 kHz up to the

limits of - well - again - 1296 MHz.  The 1296 was one of the most

fun things I did in ham radio.  BUT it really wasn't my doing.  A close

friend built a 1296 FM repeater.  He was able to get his hands on 

a few 1296 FM radios dirt cheap.  So we tried that.  It was really really

hard to get it to work at all.  We finally did and with that came a big thrill.  

It wasn't the radios as much as trying to understand the reality of the

propagation up there.  Neither of us had been on that band before, and we learned

a lot about that frequency range. 

The crystal set stuff is really fun on a very basic level.  I never imagined

that it was possible to make a set up with no external ground

or antenna - especially with such a small receiving loop.  

The carrier current thing is neat, too.  For me, it's still largely

unexplored territory.  

And I have also been facinated with E skip.  (For about 40 years.)

I don't get it, and neither do a lot of scientists.  I'm not as

interested in logging DX stations on the FM BCB as in - trying

to figure out why the whole thing happened in the first place. 

Well anyway - thanks for your replies.  They are always fun!

Oh yeah - Carl - we tried the "speaker experiment" you mentioned.

(Again, about 40 years ago.)  Please please please please: NOBODY

SHOULD TRY THAT NOWADAYS.   DON'T EVEN THINK ABOUT TRYING IT.

Very Best Wishes,

Bruce, DOGRADIO - Ramping Up on 1020 kHz Carrier Current

Although, after I wrote about that crazy experiment blowing out a voice-coil, I came up with the idea that a stage production in need of explosions could just hook up a row of cheap speakers with control buttons back stage, and on the cue from the director you could have, "POW! POW! POW! POW! POW!"

If bright light bulbs were rapidly flashed on and off that would add to the effect.

Somebody write a play to go along with the sounds.

When I was about 10, I got a generator/light set for my bicycle.  Like all the kids we put baseball cards or baloons in the spokes of the wheels to make a motor sound.

I hung a speaker under my seat and hooked it to the generator.  Made a great siren sound.  A steady wail that changed frequency with speed.  Lasted a few days until the cone rattled apart.  It was an old speaker so I guess the paper cone couldn't handle the violent vibrations.