Getting Back into (Crystal) Radio sort of

[kd8dey]

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.



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.....

[KC2UGV]

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.

[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 ;)

[kd8dey]

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 ;)

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 :)

[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.

[KG4CGC]

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.

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

[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.

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

[kd8dey]

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.

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.

[NQ6U]

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



Thanks for the link, Cor.

[KG4CGC]

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



Thanks for the link, Cor.

Yes! That was the first one I clicked on!