I was wondering if any one has any plans for a easy to build shortwave crystal radio. I have built a few kits but now I want to try to build something from scratch any help would be great.
thanks,
I was wondering if any one has any plans for a easy to build shortwave crystal radio. I have built a few kits but now I want to try to build something from scratch any help would be great.
thanks,
Brian
How well do they work? I never built a crystal shortwave, but have built a few regular crystal radios years ago.
What can one pick up and how does nearby AM broadcasters affect the performance?
What band ranges can one get ? 40 meters? 80 meters?
Interesting idea. I have built BC band crystal sets and they worked well for local AM stations but they did require a rather long antenna and a ground helps.
For short wave, you can take a regular BC band design and reduce the number of turns on the coil and reduce the tuning capacitor value to tune the higher frequencies. You will probably hear stations since they come booming in here after dark below 7 MHz. or so. Use a germanium diode such as the 1N34 or a galena crystal if possible. One of the "joys" of crystal sets is finding the sweet spot on the galena.
You will probably not be able to fine tune the radio since the Q will be rather low to separate the signals at these higher frequencies which will result in wide band reception but it will no doubt be fun to experiment with.
Hope this helps, and let us know what happens.
Neil
by MRAM 1500 kHz
I've dabbled a little with xtal shortwave receivers but I really had good results with a regenerative receiver.
One transistor, a tuning cap, a home-made coil and a couple other resistors and capacitors. I even have a schematic somewhere around here for a regenerative receiver that uses only a transistor, the coil, a tuning cap and an earphone. No resistors or fixed caps. Here is the PDF file.
Some of the shortwave broadcast signals are very strong at night. Usually the 5 to 10 mhz range. And if you follow the basic crystal receiver with a simple audio amp you'd be amazed at what you can pickup. The regen radio picks 'em up with very little antenna.
Hmm.. looks easy enough to build, and adapting it to output into a typical "aux" input of a home stereo wouldn't be hard..
Thinking back to Lee mentioning his part15 SW transmitter gets a good signal out across town, an interesting idea would be to make a few to give to friends or interested folks who are outside one's part15 AM or FM range as a way of having a few extra listeners if one was simulcasting on the part15 SW. Maybe make a couple spiffy looking ones and have them as a drawing/giveaway sort of thing at a local store or something as a promo idea?
Back to the original thread idea though, a crystal SW receiver might also pick up decent if the part15 SW was within a mile or two since the allowed signal strength for the SW version of part15 is considerably more generous (since it doesn't risk interfering with licensed broadcast stations, I assume).
Daniel
Thanks guys for the info! Daniel sparked my interest in part 15 sw any links to TX's or more info on that?
Brian
Receivers:
www.antiqueradio.org/econoceanic.htm
www.arcsandsparks.com/shortwaveradio.html
journeytoforever.org/edu_radio.html
www.midnightscience.com/catalog5.html
Transmitters:
Experimental broadcasting for a better tomorrow!
What about converting a hand held radio into a SWR? Is this simple to do I would like to build a SWR and convert a hand held and compare the results.
Brian
by MRAM 1500 kHz
Here is a nifty project from 1935 where you scratch make everything but the tube. You make the tuning cap, fixed cap, coils even the resistors. I really like the tuning cap. It would look great in a homebrew crystal radio.
If you wanted to make this receiver, you could probably substitue some other tube available or perhaps use a JFET transistor with the appropriate voltages.
Anyway, here is the link for the one tube regen. And if you decide not to go tube, use the same techniques to homebrew the other parts for a nice back to basics radio.
I recall years ago seeing an article in I think it was Popular Electronics on how to turn a Radio Shack "Flavoradio" into a little SW receiver by adding a tapped coil. I never got around to actually doing it because I had an old signal corps bc-10 receiver at the time and didn't need another SW receiver.
But that'd be nearly as much work when you were done as the one-transistor regen receiver that mram posted the pdf for. So I don't know as it'd be much of a shortcut to convert a hand-held AM radio and it probably wouldn't be actually cheaper if the hand-held was bought new.
Now, when I was looking at the regen pdf, what I was thinking was if one built that into a little box with a couple resistors to put the output impedance in the right ballpark and a set of RCA jacks on the back to connect it easilly to something like a home stereo? Maybe mark the spot on the dial to start looking for the friendly local part15 SW station that gave it to you? Could be a nice way to get people to tune in. The regen doesn't take much antenna, compared to what an actual crystal rig would take.
Daniel
Im not looking to take shortcuts I am just looking for more interesting projects to try. I figured these are good for me since I am at beginer level again. Until this year I haven't tinkered with building projects from scratch since my electronics class my freshmen year of high school.
That was 12 years ago and at that time I spent my lunch hour smoking pot so all the things I could have learned went up In smoke. Thats why I am here again with a clear mind trying to learn what I could have known then. So any cool radio projects would be helpful.
My two cents.
Building cool projects is lots of fun and can certainly be a learning experience. To get the most out of the experience, you should also have an understanding of basic electricity and electronics. You don't have to learn everything, but you'll be surprised how much more enjoyable project building is when you have some idea of how things work.
I'm sure if you look around on the net that you will find lots of tutorials for free. If you like books, see if you can find some of the old Heathkit course materials. They had study guides for everything from what an electron is, to ICs and digital logic. They were well written.
I hope this doesn't sound too preachy, but I believe learning never stops. I still enjoy learning new and sometimes difficult subjects, or how to use a new piece of equipment.
I have been studying up with a basic electronics book that I bought. I also have certifications for commercial closed circit cable systems which I have built for campgrounds and hotels. In that line of work though its more about how to use the right meters and isn't that challenging. Thats why now I am getting down to the nitty gritty.
So yes I agree with you 100% projects are fun but the learning is the real reward.