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 Post subject: First time crystal radio build
PostPosted: Apr Mon 12, 2021 1:22 am 
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Location: New Hampshire
I wanted to make a simple crystal radio that is under 10$ (if
possible) think variable capacitor, copper wire, detector, etc. however
I have a germanium transistor I got from a scrap board and I was
wondering if I could use it for a detector? if so what 2 leads would I
use as the anode and the cathode?
also, the tuning cap I am using is from an old
transistor radio is this the right amount of picofarads?
any tips you could give would also be of help.
thanks,
henry


Last edited by whfh99 on Apr Mon 12, 2021 7:41 pm, edited 1 time in total.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 1:36 am 
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Henry

Yes, just use emitter and base of the germanium transistor. The extra lead can be left floating.

Tuners are usually specified at 365 pf but just about anything will work. Less capacity range and you won't cover the entire broadcast band. Use what you have. Don't buy a lot of parts. With a crystal set a wide range of parts will work.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 12:06 pm 
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Norm Leal wrote:
Henry

Yes, just use emitter and base of the germanium transistor. The extra lead can be left floating.

Tuners are usually specified at 365 pf but just about anything will work. Less capacity range and you won't cover the entire broadcast band. Use what you have. Don't buy a lot of parts. With a crystal set a wide range of parts will work.


thank you,
you answered my question exactly now I have a new one, is there anything I can use instead of the copper wire antenna? I was looking at the prices of some of the rolls and who needs 20 pounds of wire?.... I know I am probably going to have to buy a low impendence earphone I am ok with that but still if there is anything I have laying around in the shop that would work i would use it.
thank you
henry


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 4:26 pm 
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For a crystal radio you need a HIGH impedance earphone, something like this https://www.amazon.com/Piezoelectric-Im ... B071JWPTT9. A low impedance earphone is what you use on your phone, or tablet.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 5:42 pm 
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+1 on the headphones. You want HI impedance and if you get a piezo type, it will need a resistor across the headphone leads.

http://makearadio.com/misc-stuff/piezophones.php

MakeARadio is a great site for simple (and complex) radio projects. http://makearadio.com/crystal/index.php

You will need copper wire for the coil, or buy some kind of vintage/commercial coil.

I have used galvanized electric fence wire for antennas. Not as good as copper, but cheap. You don't need 20 lbs and should be able to buy shorter rolls. The gauge depends on how long you want to stretch it out. Long runs will need heavier gauge, or the wire will sag/break.

Ming Mak is an avid crystal radio builder and also has an Ebay store selling Litz wire for coils and various crystal radio parts. https://www.ebay.com/str/mkmak222litzwi ... 7675.l2563

Rich


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 6:13 pm 
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thank you both,
I meant to write high impendence my mistake. I guess I was looking in the wrong spot for the copper wire I was looking on Walmart and the prices were insane but where you directed me to the prices were better.
I have some electric fence wire but it is currently being used maybe I can use that as an antenna? I also have some wire with clips on it that could be an antenna. have some brass rod I could stick into the ground, could I use it as a ground?
I am going to order the wire and the earphone soon.
thanks,
henry

p.s thanks rich for the link to the site it is a great site with lots of plans I think there is one on there I might base this build off of.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 7:59 pm 
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As a kid when we discovered crystal radios, we would find and take apart transformers or motors for their wire. We would climb up the telephone pole and string it to our club house.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 9:05 pm 
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Mike Toon wrote:
As a kid when we discovered crystal radios, we would find and take apart transformers or motors for their wire. We would climb up the telephone pole and string it to our club house.

sounds like fun however, I don't think I will be using telephone poles for antennas!


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 9:07 pm 
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whfh99 wrote:
Mike Toon wrote:
As a kid when we discovered crystal radios, we would find and take apart transformers or motors for their wire. We would climb up the telephone pole and string it to our club house.

sounds like fun however, I don't think I will be using telephone poles for antennas!

You can use a Slinky... :wink:

Image

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Mon 12, 2021 9:12 pm 
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not a bad idea I will have to look around for one...


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Tue 13, 2021 1:00 am 
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just bought the copper wire and the earphone parts will come soon tomorrow when it's light out I will post a picture of my hand-drawn schematic.
thanks, for all the help so far I have a feeling this will be really cool!
-henry


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Tue 13, 2021 11:23 am 
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Welcome to the world of crystal radios! I was bitten by the bug a long time ago. Still no vaccine available! My 2 cent's worth.. nothing like ,copper wire in the air, higher the better, a really nice set to build with out using litz wire is a (pretty good crystal set) as described on Al Klase's website. It uses common components, and really works well, I bought the coil wire and coil forms at Home Depot. And make sure you build the tuner for it as it makes it come alive. Plus you'll learn about double tuning front ends and coupling. I enclosed his link and my rendition of his radio I built a long time ago. Have fun, also performance depends on how many AM stations are close to you and RFI issues. PerryAmicangelo Kingsford Michigan.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Tue 13, 2021 12:11 pm 
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ballroad wrote:
Welcome to the world of crystal radios! I was bitten by the bug a long time ago. Still no vaccine available! My 2 cent's worth.. nothing like ,copper wire in the air, higher the better, a really nice set to build with out using litz wire is a (pretty good crystal set) as described on Al Klase's website. It uses common components, and really works well, I bought the coil wire and coil forms at Home Depot. And make sure you build the tuner for it as it makes it come alive. Plus you'll learn about double tuning front ends and coupling. I enclosed his link and my rendition of his radio I built a long time ago. Have fun, also performance depends on how many AM stations are close to you and RFI issues. PerryAmicangelo Kingsford Michigan.

hello, thanks for the kind words!
below is a hand-drawn schematic (excuse the bad drawings) that I made it is very simple and thanks for the tip. I really like the radio you made how come it uses two variable tuning capacitors? I think that one might be my next build... I get stations from Boston and new york at night often and sometimes even Mexico if the conditions are good.
thanks,
henry


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Tue 13, 2021 6:15 pm 
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It has two tuning caps as it's two separate units. Something about not loading down tank circuit, all I know is if you tune a station, then pull the two apart it really makes the signal louder and sharper.... another site to dig into is The Radio Forum, lots of good info, Crystal radios can be very involved and a lot of the info is way above my intelligence....

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Last edited by ballroad on Apr Tue 13, 2021 7:25 pm, edited 1 time in total.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Tue 13, 2021 6:34 pm 
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ballroad wrote:
It has two tuning caps as it's two separate units. Something about not loading down tank circuit, all I know is if you tube a station, then pull the two apart it really makes the signal louder and sharper.... another site to dig into is The Radio Forum, lots of good info, Crystal radios can be very involved and a lot of the info is way above my intelligence....


oh, that makes sense I am sure it has good performance.


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Wed 14, 2021 11:01 pm 
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Well all the parts came today. I'm excited to get building!
However I have a quick question I know I was told to use The Base and emitter Of the transistor as the Detector However Which one Should I wire To the earphone?(schematic above) Also I am assuming that the base is in the middle of the transistor And the emitter Is on what side? (See picture)
Thanks,
Henry


And also Did I Wrap The copper wire around the tube right? Its a bit tangled on the ends...


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Wed 14, 2021 11:17 pm 
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It's all about experimentation, Henry.

Usually the collector element of a Transistor is identified in some way, such as a tab on the case, dot, or it's spaced a ways away from the base and emitter. The base is normally the center element. Try the two closer leads both ways, as it will only work wired in one direction. A Diode is like a one-way valve.

AFA the coil, it may work that way, but I would like to see it wound correctly on both ends, for both electronic and visual performance and looks.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Wed 14, 2021 11:21 pm 
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fifties wrote:
It's all about experimentation, Henry.

Usually the collector element of a Transistor is identified in some way, such as a tab on the case, dot, or it's spaced a ways away from the base and emitter. The base is normally the center element. Try the two closer leads both ways, as it will only work wired in one direction. A Diode is like a one-way valve.

AFA the coil, it may work that way, but I would like to see it wound correctly on both ends, for both electronic and visual performance and looks.


ok yes, the collector lead has a triangle on its side. will try both ways.
and I will try my best to fix the coil. is the amount of wire I have on the roll too much or just right?


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 Post subject: Re: First time crystal radio build
PostPosted: Apr Wed 14, 2021 11:26 pm 
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whfh99 wrote:
is the amount of wire I have on the roll too much or just right?

That usually cannot be determined visually. Did you follow a specific circuit, or just randomly wound the coil? Regardless, try it.

A normal schematic would have the number of turns specified, as well as the diameter of the coil form.

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 Post subject: Re: First time crystal radio build
PostPosted: Apr Wed 14, 2021 11:33 pm 
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fifties wrote:
whfh99 wrote:
is the amount of wire I have on the roll too much or just right?

That usually cannot be determined visually. Did you follow a specific circuit, or just randomly wound the coil? Regardless, try it.

A normal schematic would have the number of turns specified, as well as the diameter of the coil form.

this all coming out of my head...so I will try it.


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