Getting Back into (Crystal) Radio sort of

I am wanting to build a good performing set with the Diodes Cor sent me. (thanx again Cor)

Slowly figuring out where I want to go with such a "simple" radio is starting to get confusing. Been looking around at a bunch of the crystal radio sites, Do it this way not that, NO!! don't do it that way either!! here's another way etc etc etc.

:wtf:

Went to one web site and they call the basic coil the "crappy coil" method.

Another site claims that PVC is better over cardboard ("you can't use cardboard for the coil form because of moisture affecting the "Q") only to find a dozen different designs using Oatmeal, Salt boxes, or even a paper towel roll for a switchable band SW rig.

Also you have sites using loose coupling of either the antenna, detector, or BOTH for "Better performance" with little or no mention of how to calculate the additional coil inductance's ( besides the tuning coil itself ) etc.

So you have the choice of the
"crappy coil"(basic air wound coil)
"Spider coil"
http://makearadio.com/coils/index.php
"Basket weave coil"
http://www.vk2zay.net/article/188
or something like one of those 1920's jobs .....
all with or without loose coupling.

Then you have the wire choices
Since D.C.C. is all but extinct

You are pretty much down to the debate of
Litz wire (for Higher Q coils)
vs
Enameled wire
Vs
Coil Diameter
vs Wire resistance
vs Freq
Vs Q.........

Of course don't forget to throw in all the different flavors of wave traps, output impedance, full wave vs 1/2 wave rectification, audio transformers, and headphone debates.....:squint:

From what I've encountered, don't both with Litz wire until you've optimized everything else. It's easily the priciest part of the "top end" crystal set.

Forms? I've tried TP tubes, oatmeal boxes, and PVC. I'll be damned, but I don't find any difference in them.

One thing I have learned, and I can't seem to figure out why nobody else has said this, but every says one end of your coil needs to be earthed. I've had much better luck attaching one coil end to one leg of a dipole, and the other end to the other leg. Then, it hit me: This is the same thing as every other receiver! Your shield/feed goes into the tank circuit of your detector circuit in your rig on the desk, so why not for your crystal rig?

I've also scrounged some diodes (schotky, I think) from a DVD player, and am getting rectification out of it. I'm also doing "full wave rectification" into two crystal earphones snuggled into an old set of stereo headphones. I do notice it's quieter, but a better sound.

I always used enameled wire, and for Medium wave could not detect a difference between that and litze wire.
Grey pvc as used here in tubing to lead the rainwater off from the gutters is H.F. proof, available here in 1/2 inch to 5 inch sizes, tip: if not sure about the H.F capabilleties, cut of small piece, put in microwave and nuke it for 10 - 30 seconds with a glass of water next to it.
If the pvc does not get warm, excellent stuff to use, also for making dipoles, isolaters etc.

http://en.wikipedia.org/wiki/Crystal_radio

Site of a Dutch chrystal radio maker.
http://www.crystal-radio.eu/
Including english descriptions, and schematic diagram, if need more translation, just ask.
From Am, to FM ;)

Quote:

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Originally Posted by PA5COR

I always used enameled wire, and for Medium wave could not detect a difference between that and litze wire.
Grey pvc as used here in tubing to lead the rainwater off from the gutters is H.F. proof, available here in 1/2 inch to 5 inch sizes, tip: if not sure about the H.F capabilleties, cut of small piece, put in microwave and nuke it for 10 - 30 seconds with a glass of water next to it.
If the pvc does not get warm, excellent stuff to use, also for making dipoles, isolaters etc.

http://en.wikipedia.org/wiki/Crystal_radio

Site of a Dutch chrystal radio maker.
http://www.crystal-radio.eu/
Including english descriptions, and schematic diagram, if need more translation, just ask.
From Am, to FM ;)

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Yup There is a lot more information to consider thanks to the interwebz available compared to when I first built one back in my teens Lol .
Gotta get the grandson ready for wrestling practice. Back in a couple hours lol.
already picked up a couple packs of enameled wire from radio shack...... litz is to pricey for my budget at the moment :)

Could have put some wire in the letter as well if i had known.... ;)
Good luck having a go at the building of the radio.
Made some for last years Jota/Joti for the group we did the radio setup.
Made some pcb's and parts solder, soldering stations and each of the builders had a licensed radio ham with them to go through the steps of building and testing.
Never seen so much happy faces when they recieved their first stations without batteries on their homemade reciever ;)
That magic will never go away.

Quote:

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Originally Posted by PA5COR

Could have put some wire in the letter as well if i had known.... ;)
Good luck having a go at the building of the radio.
Made some for last years Jota/Joti for the group we did the radio setup.
Made some pcb's and parts solder, soldering stations and each of the builders had a licensed radio ham with them to go through the steps of building and testing.
Never seen so much happy faces when they recieved their first stations without batteries on their homemade reciever ;)
That magic will never go away.

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Could you repeat the name of the type of diode you're using and does it have a modern equivalent?

Man, now this is what I call a crystal radio! The guy's an artiste with wire.

http://www.crystal-radio.eu/Im000475.JPG

Thanks for the link, Cor.

Quote:

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Originally Posted by KJ6BSO

Man, now this is what I call a crystal radio! The guy's an artiste with wire.

http://www.crystal-radio.eu/Im000475.JPG

Thanks for the link, Cor.

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Yes! That was the first one I clicked on!

BAT85, ultra low noise Schottky diode.
I got a batch from Phillips for next to nothing.
Sharing them with the people here who desire to use them, so they find a good home where they will be actively used and not stay in a box here till i become S.K. ;)
Place your (free) order

Yep the guy knows his stuff ;) that';s why i put the link in.
http://www.rfmicrowave.it/catalogo/eng/A.pdf
Datasheet for the Schottky diodes for the technicaal buffs ;)
Use for detector diode, mixer diode, switching diode with low noise and low capacity in the ON state, ( replacing my switching diodes in the bandfilters in the FT 847's), replaces most diodes with germanium, generally lower voltage drop, lower noise.

Schottky diodes (also known as hot carrier diodes) are semiconductor diodes with a low forward voltage drop and a very fast switching action, the low forward voltage leading to increased efficiency. While standard silicon diodes have a forward voltage drop of about 0.6 volts, Schottky diodes voltage drop at forward biases of around 1 mA is in the range 0.15 V to 0.46 V, which makes them useful in voltage clamping applications and prevention of transistor saturation, due to the higher current density in the Schottky diode. Schottky diodes are suited for switch mode power supplies and high frequency DC to DC converters. This devices are intended for use in low voltage, high frequency inverters, free wheeling and polarity protection applications.

Quote:

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Originally Posted by KG4CGC

Could you repeat the name of the type of diode you're using and does it have a modern equivalent?

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http://www.mouser.com/Search/Refine....ord=630-1N5711
http://www.mouser.com/Search/Refine....rd=610-CDSH270

I was wondering if these are the same thing.

The BAT 85 is 30 volt 0.2 Amp, 500 MHz
Look in the link i provided for the range of Schottky diodes and the replacements ;)

Quote:

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Originally Posted by PA5COR

BAT85, ultra low noise Schottky diode.
I got a batch from Phillips for next to nothing.
Sharing them with the people here who desire to use them, so they find a good home where they will be actively used and not stay in a box here till i become S.K. ;)
Place your (free) order

Yep the guy knows his stuff ;) that';s why i put the link in.
http://www.rfmicrowave.it/catalogo/eng/A.pdf
Datasheet for the Schottky diodes for the technicaal buffs ;)
Use for detector diode, mixer diode, switching diode with low noise and low capacity in the ON state, ( replacing my switching diodes in the bandfilters in the FT 847's), replaces most diodes with germanium, generally lower voltage drop, lower noise.

Schottky diodes (also known as hot carrier diodes) are semiconductor diodes with a low forward voltage drop and a very fast switching action, the low forward voltage leading to increased efficiency. While standard silicon diodes have a forward voltage drop of about 0.6 volts, Schottky diodes voltage drop at forward biases of around 1 mA is in the range 0.15 V to 0.46 V, which makes them useful in voltage clamping applications and prevention of transistor saturation, due to the higher current density in the Schottky diode. Schottky diodes are suited for switch mode power supplies and high frequency DC to DC converters. This devices are intended for use in low voltage, high frequency inverters, free wheeling and polarity protection applications.

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I figured that since I am using such a "Hot" Diode that it deserved a "decent" crystal radio wrapped around it :) .

So instead of the typical single tapped coil I want to do something a little more advanced. I'm planning on loosely coupling the antenna And perhaps the detector circuit BUT I am not finding any info on calculating the additional coils needed.

The actual tuning coil is no problem, standard math formula....now finding the info on the antenna or detector coupling coils is another story.

Most of the designs of the Dutch maker come with schematics including number of windings and diameter of the coil former.
Trial and error will bring you the optimum result, to many variables to give a detailed number.

Will have to pop off a few more to another member, will do it this week.
Soon we will have our own chrystal radio club ;)

Quote:

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Originally Posted by PA5COR

Trial and error will bring you the optimum result, to many variables to give a detailed number.
Soon we will have our own chrystal radio club ;)

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Kewel

looking around for info and parts etc I came across some good sites.

On "that other" site somebody posted a link for coil forms at
http://www.westernsierraradio.com/products.html
But they are a bit pricey especially for a 1 trick pony.

I found another establishment with comparable forms at a lot better price along with a lot more parts
http://peeblesoriginals.com/

So far these are some of the better sites I have found

Here is a site on Crystal DXing that I haven't had a chance to go through yet
http://homepage.ntlworld.com/lapthorn/xtal.htm

Also this place has been around for ages and has a newsletter
http://www.midnightscience.com/index.html

Another useful link
http://www.crystalradiosupply.com/index1.html

This one has quite a bit of info to browse
http://www.crystalradio.net/

Quote:

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Originally Posted by kd8dey

On "that other" site somebody posted a link for coil forms at
http://www.westernsierraradio.com/products.html
But they are a bit pricey especially for a 1 trick pony.

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Continuous grommets, sometimes called caterpillar grommets, are a good, cheap way to make air wound coils.

Hello.

I was told that "this" would not work or "that" was better when building crystal radios.
It is just as bad as having an "elmer".
I built 5 crystal radios following plans I could find and based on what I could find for parts.
All worked just fine.
A few months later this dufus ham shows up and asks me for "his parts".
I aks him what parts and he says the there was a charge for his advice.
I pointed out that I took none of his advice and produced the drawings I did of the material I copied.
My very first experience of US hams.
The French ham I met who showed me woodworking helped me build all of the cabinets and forms needed.
I was called into the principals office, the gent argued that I had stolen from him.
I requested a complete and detailed explanation of what it was that I had stolen.
One week later I presented the 5 complete and working crystal radios, complete with spare parts I had fabricated.
It was clear that none of this was anything like what he brought, it was so much better!
Headphones? how about 5 pairs of rebuilt ones with modern omnimagnet diaphragms?
This is a very thin sheet of very magnetic alloy that produces a massive increase in volume over common sheet steel that is used.
You will find this in some horn speakers but can make your own easy enough.
And, speaking of speakers, I built a pair of them also. ;)
I later built a "phono ocillator" with one tube, a TV sweep tube!
Proper filtering was applied and so it ran clean, but there was zero chance it was within part 15 output specs!
This was a new tube I got cheap with the idea that I was to get my ticket soon.
There was a 4 transistor circuit driving this tube, all built inside the chassis of an old 5 tube AC/DC farm radio that was rebuilt for operation from AC from a TV transformer.
You could pull the back cover and everything looked normal, transistor circuits were under the chassis and the output tube was inside the battery box.
Turn it on and it worked like any radio, to transmit you would push the volume/power knob in.
I could carry it everywhere as it looked like any radio.
I got the idea from East Germany, where converting car radios to 2 way service must have been a national pastime. ;)

Carl
Your diodes are on ther way since this afternoon.
Hope the mailman is a bit fast ;)

Have fun with thm,

Cor

Quote:

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Originally Posted by KJ6BSO

Continuous grommets, sometimes called caterpillar grommets, are a good, cheap way to make air wound coils.

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Quote:

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Originally Posted by PA5COR

Carl
Your diodes are on ther way since this afternoon.
Hope the mailman is a bit fast ;)

Have fun with thm,

Cor

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Okay, Cor, thanks a bunch! I'm trying to get my ten-year-old grandson interested in radio (or, for that matter, anything other than himself) and I thought building up a working radio starting from a simple crystal set might be the way to do it.

Start with a simple Chrystal set, and show" see kid, no electricity and working fine" does open his eyes.
Use a decent length of antenna wire, and a good ground.

You can go from there to more sophisticated radio's adding amplification and selectivity and speaker.
But most kids turn on from seeing actually a radio work without electricity and listening to the earphone ( Hi Impedance) to the stations.

Grabbed a couple cheap plastic cutting boards from the local dollar store to make a couple spider coil forms.
planning on using 290uh for the inductance along with a 15-410pf capacitor from peebles if still in stock.

should give me plenty of leeway to cover the entire broadcast band.

The grandson's wrestling coach does woodwork. Since I don't have any hand-tools as far working dense plastic perhaps.... :)

I was under the impression that ants only needed to use mandibles.

http://www.uploadarchief.net/files/d...o_examples.gif

Look at the last schematic diagram, the double diode detector.
More sensetivety, more output too.

Quote:

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Originally Posted by PA5COR

http://www.uploadarchief.net/files/d...o_examples.gif

Look at the last schematic diagram, the double diode detector.
More sensetivety, more output too.

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Seen those on another site :)
On that last one they list L1-L2 as 60 turns and 30 turns of litz.

I would have been better if they had listed a little more info on the coil. IF I remember correctly The tap point depends on sensitivity vs selectivity and builders usually tapped at about the top 1/3 of the coil length as the best compromise which this one follows, SO using the L/C formula and the 1/3-2/3 coil split you should be able to place it where you want it in the bands :)

Hello.

If you are into active devices you can build a tube type radio that runs on 12 volts.
http://makearadio.com/visitorsprojec...tube-radio.php
Yes, if you are so inclined you can build a 5 tube AC/DC that runs on 12 volts AC/DC
The trick is to do all of the diodes in solid state and think of the output section with a transistor in mind, or not.
Think of how a switching power supply works, it will run on DC as well as AC.
Computer supplies that have failed are very common and can be had for nothing most of the time.
This is something to think about once you want something more advanced but are concerned of safety.
I no longer connect the filaments in series and run off 110 but run everything off 12 volts with a switcher somewhere in line.
The absolute highest voltage I want to see is 48 volts nominal, something I can boost to whatever I want while limiting the current internally.
I can get up to 3 watts out of a TV sweep tube with very much safe voltages and current.
This being 1/2 of a push-pull circuit and a transistor providing up to 12 watts I can get that tube sound with transistor volume.
Dump that into a quality single cone speaker and you have it made.
Farm radios ran on as little as 32 volts and were common, in fact the conversion was sometimes done at the point of sale.
http://www.vintagetunesradios.com/an...-for-sale.html
This gives you a beseline to work with.
Note that I do not approve of anything like the "Solid state B+ supply as this is a hot chassis design.