Crystal Radio Magic

[xee2]

Just remembered there is also a strong resonant point at 7MHz that I played with. Does this change anything?

I doubt that your signal generator will put out enough power to interfere with anything unless you have neighbors within a 100 feet and then they would need to have a radio tuned to the frequency you are using (unlikely).

[jake]

Just remembered there is also a strong resonant point at 7MHz that I played with. Does this change anything?

[xee2]

So I went outside soldered into a ground wire and set to work. With 1 turn, 1/2" flat copper stock primary. Tried different arials, different hights, and so on and so on. Got it down to 1620(heard it on the radio 15' away) with a big aluminum salad bowl. , I went back to no terminal and put on my big fat 2 turn primary. Started testing with this when


A small white exlporer sticker on side said "Texas Communicat........." Could not read the whole thing. Pulled into my driveway waved nicely at me then drove off nice and slow....

There is a company called "Texas Communications" that runs communication services and it may have been one of their trucks. but still It did not feel right.

Did I break a rule?? FCC or other??

Function Generator signal level never went past 1/3. and was usually all the way down..

BK Precision 4017A, 10mHz, 10v(max) p-p into 50ohm, minium .25v p-p across my scope.

You broke no rules. He probably pulled into your driveway by mistake and then realized he was not where he should be.

[jake]

Oooops!!!



So I went outside soldered into a ground wire and set to work. With 1 turn, 1/2" flat copper stock primary. Tried different arials, different hights, and so on and so on. Got it down to 1620(heard it on the radio 15' away) with a big aluminum salad bowl. , I went back to no terminal and put on my big fat 2 turn primary. Started testing with this when


A small white exlporer sticker on side said "Texas Communicat........." Could not read the whole thing. Pulled into my driveway waved nicely at me then drove off nice and slow....

There is a company called "Texas Communications" that runs communication services and it may have been one of their trucks. but still It did not feel right.

Did I break a rule?? FCC or other??

Function Generator signal level never went past 1/3. and was usually all the way down..

BK Precision 4017A, 10mHz, 10v(max) p-p into 50ohm, minium .25v p-p across my scope.

[xee2]

As far as the Standing wave. Should there be one along the lenght of the wire?

For parallel resonator or self resonant coil:
When the resonator is at resonance there will be a standing wave on the inductor wire with a peak voltage measured across the ends. Note that this is an RF wave not DC. Best way to measure this is with scope using very small capacitor as probe. There will be multiple peaks if the resonator is resonating at a harmonic of fundamental resonator frequency.

[madhatter]

[QUOTE=jake;189683][QUOTE=madhatter;189674]Not sure I understand what you're after, could you explain a bit more?

As far as the Standing wave. Should there be one along the lenght of the wire?

jake, jastermake @ yahoogroup

I'm going to be a bit lazy here and point you to this, Standing waves and resonance : TRANSMISSION LINES it may help answer some questions, if you've got more after, let me know.

the length, are you referring to the physical wire length or the length of the coil? there is also the issue of electrical length. gets more involved with RF and transmission, esp here since C is no longer a fixed value.

[jake]

[QUOTE=madhatter;189674]Not sure I understand what you're after, could you explain a bit more?[Quote]

As far as the Standing wave. Should there be one along the lenght of the wire?

Also this is going to be frustrating, but all leads will impact the L&C of the circuit, I found that by using the coil itself it's a better compramise then adding in wire length. the leads and LED also effect the circuit too, it's a big balance game.

Yes, Yes, and Yes I noticed that.

A wise man once said "we were going to need a new set of tools to work with these new concepts" or something along those lines. Once I realized I could easily light an led I thought that it could make a handy dandy indicator. THEN..

I get my hands on a 10MHz function generator. I start testing and messing but lacking a fuctional ground I can only take my results as mere observations of a crystal radio and NOT a TRT. What did I learn....that leads are the enemy. Thats when I made the leap form FWBR to AV plug and that made all the difference. Thanks to all those who helped with that. No leads and 1 point of contact. That makes a nice little indicator. With that indicator I can touch the coil at any point. And it appears to make very little change to the resonant frequency. The change I do see is usually caused by me holding the AV plug. BUT I cant get the AV plut to light on a stick.

jake, jastermake @ yahoogroup

[madhatter]

Yes, you are correct. However one can use the Hertzian waves to tune their secondary, just like we are doing with the function generator. LEDs make pretty good HF indicator lights.

So whats you take on my standing wave question? last page

Not sure I understand what you're after, could you explain a bit more?

Also this is going to be frustrating, but all leads will impact the L&C of the circuit, I found that by using the coil itself it's a better compramise then adding in wire length. the leads and LED also effect the circuit too, it's a big balance game.

[jake]

The crystal radio project is to recover Teluric currents, not hertzian waves. This is why ground is THE most important part of the project.

recovering hertzian waves and magnifying them to power LED's etc.. is nothing new, novel but not what Eric was going for.

Diodes, 1N34A have a very low FW voltage, and a high 50V breakdown. 1N60 is nearly twice as high in forward voltage with a lower 40v breakdown, although the 1N60 is supposedly mfg to higher tolerances.

a ground impedance of 1ohm or less is going to be the biggest and for most an impossible requirement.

Yes, you are correct. However one can use the Hertzian waves to tune their secondary, just like we are doing with the function generator. LEDs make pretty good HF indicator lights.

So whats you take on my standing wave question? last page

[madhatter]

The crystal radio project is to recover Teluric currents, not hertzian waves. This is why ground is THE most important part of the project.

recovering hertzian waves and magnifying them to power LED's etc.. is nothing new, novel but not what Eric was going for.

Diodes, 1N34A have a very low FW voltage, and a high 50V breakdown. 1N60 is nearly twice as high in forward voltage with a lower 40v breakdown, although the 1N60 is supposedly mfg to higher tolerances.

a ground impedance of 1ohm or less is going to be the biggest and for most an impossible requirement.

[xee2]

One previous setup it was making the radio louder when I hooked it up.

Your house radio resonator and the crystal set resonator are mutually coupled. See ... AM Radio with wireless Loop Antenna - YouTube

[jake]

@ jake

I calculated the field strength voltage 5 miles away from a 1,000 watt transmitter to be 0.03 volts per meter. This is a rough calculation but gives approximate value to be expected. You are getting much more out. I am impressed with your design. I worked several years as an antenna engineer developing very advanced antenna designs, so it takes a bit to impress me.

For a 10,000 watt transmitter this increases to about 0.10 volts per meter.

After I did the calculations the hard way, I found an online calculator that gives about the same answers:

Volt per meter and power density calculator


EDIT: A tuned antenna will suck up the RF energy much like an electronic vacuum cleaner, so I would expect your antenna to produce more than the ambient volts. It is actually possible to measure the lack of signal behind a tuned antenna which shows it has absorbed energy from an area much larger than itself.

Just noticed this edit:

Right now it does nothing to a radio when I plug hook up the secondary but I can still light the led.

One previous setup it was making the radio louder when I hooked it up. I think it was when I grounded it to the house ground but the led would just fliker every once in a while.

This is where the extra coil and ring capacitor come in to play. I dont want to change the wire length, coil hight or coil diameter. So all I have is capacitance and I have tried: a 3 turn 505pf variable air cap. A 112pf HV air cap. and a couple of other crystal radio/pocket radio caps and they just dont do much of anything across the secondary.

[jake]

FM anyone?

@loadstone,

Have you ever tried power recovery with an FM station??

[Loadstone]

@ Jake....i have used 1N34's but in my clip they are a different type...i think 1n60.....
I started off getting low voltages and refined it until i can get up to 28 volts out @ 500 ua.....not much power but i can run various small devices or charge batteries now.
It's all fun....i also tinker with the capacity versus inductance ect....teaches you alot!
Scotty.

[jake]

@ loadstone

NICE!

Wish I had seen that earlier. Tried earlier on to get a joule thief to work but failed. Then I got good light from the coil directly and dropped that idea. I'm borrowing a function generator so I'm spending my time working with that. I'll eventually get a thief to steal radiowaves.

Did you ever work with 1N34 germanium diodes? How do thay compare to the ones in the video?