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Yahderhey

Crystal Swl

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I recently got into building crystal recievers. They are nothing fancy, but I think thats the point. Just wondering how many of you do this and how do you get a good ground? The radio I'm working on now could be small enough to carry out into the field without to much trouble, however I don't know what kind of antenna or ground I'll need. Please keep in mind most of what I build is made of junk and readily available materials. Also, did I mention I'm not a hammie? Thanks.

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I built one as a kid. I had a long wire along the roof of the house and a wire out the second floor window to a water pipe for group. Because the radio is powered by the signal, you need a really good antenna. I think the rule is the more wire you can get in the air the better.

 

I'll leave the question on ground for those who have more experience, if you you can find a metal water pipe that's in the ground, I'd take that over most anything else.

 

As for performance, my radio could pick up the bigger AM stations in the area. Given it's sensitivity (or lack of it) I don't think it could ever do Shortwave. However, I have heard of those who did build such radios to pick up distant stations, so your mileage may vary.

 

You may want to consider "cheating" and use a small audio amplifier to use more comfortable closed-air headphones and overcome the weak volume that you'll get from a purely signal powered earphone. Since you plan on being portable, that will help you overcome local sounds.

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Check out this Cigar Box Crystal set. It is a portable unit that works very well. I built one a couple of years ago. The antenna is also the tank inductor. I have been building crystal radios for a few years, not so much since I started geocaching :( . The Xtal Set Society has a lot of good on-line resources. The Crystal Set Handbook is a great resource.

 

On grounding, don't count on a water pipe being ground if you live in a newer home. The best bet is the copper stake next to the cable tv connection to your house. National electrical code requires that all electrical outlet have a connection to ground, that doesn't mean yours do.

 

On antennas, ALWAYS make sure you have a spark arrestor on your antenna. Any decent antenna will attract electrostatic discharges, the typical crystal set is almost directly connected to the antenna. This is not intended to scare you just to make sure you are safe.

 

Hope this is of some help.

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I've built a set that actually picks up SW. In fact I've heard a station in Birmingham, AL from my home in Wisconsin. The problem is that the local AM station bleeds over everything on the dial even with a wave trap. I thought if I could get out in the boondocks a little I might be able to hear more stations. Maybe I'll research loop antennas.

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I've built a set that actually picks up SW. In fact I've heard a station in Birmingham, AL from my home in Wisconsin. The problem is that the local AM station bleeds over everything on the dial even with a wave trap. I thought if I could get out in the boondocks a little I might be able to hear more stations. Maybe I'll research loop antennas.

You need to work on the selectivity of your set. Usually you trade selectivity for sensitivity. The loop antenna in the cigar box set is directional which helps with selectivity.

 

Getting out in the boonies does help. We had some great times listening to am broadcast' from Mexico and LA up in the Sierras. You can buy a copper ground stake from a building supply store, this helps a lot with sensitivity.

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I've built several, and usually have parts laying around.

 

I have built them with Cub Scouts, and still do wtih Boy Scouts occasionally.

 

I did use one at camp once, using a galvanized water pipe as a ground. I used a simple random wire throw up in a tree as an antenna. It worked, at least on a few of the high-power stations around L.A.

 

The scouts loved it, since there were no batteries.

 

I think they are a great way to learn about RF energy!

 

Dave_W6DPS

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There is a guy (ham operator) near where I live who has been building all sorts of crystal radio receivers. He keeps some of them, and sells others. He has even devoted a web page to them.

 

They can be fun and a good learning experience for anybody of any age. :D

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