What large antenna works best for a crystal radio? - Videokarma.org TV - Video

jbivy · #1 03-01-2012, 06:07 PM

Im running what looks like a giant square with an X that connects the corners. Roughly 50'x20', with a copper cable that runs to the ground and is connected to a piece of rebar thats pounded 3' in the ground.

Ive found i actually have better reception with JUST the ground hooked up to where the antenna should be. Ive no idea why this is going on.

An uncle said the box with an X in it was a great antenna for crystal radios, but apparently its not working for me or for this location.

Im running the antenna between the house and garage, so ive a decent size place to make a large one.

Which antennas have you had the best experience with?

Reece · #2 03-02-2012, 05:52 AM

"More wire, up higher" is the usual mantra for crystal set antennas. I never used any fancy designs but just a single long wire, as long as the property would allow, and as high as I had attachment points. Be sure your antenna ends have good insulators. The one I have now is No. 14 insulated wire, black plastic insulation, bought off the reel at Lowe's. The end insulators are classic glass ribbed ones. The lead in wire is the same as the antenna. It goes from the top of the chimney about 30 ft. high out to a metal TV pole about 20 ft. high, total length 60 ft. Your X antenna as long as it's supported by insulators should be fine. Mine works great for all radios, xtal included.

Jeffhs · #3 03-02-2012, 01:26 PM

I've had two crystal sets in my life, one constructed on a piece of wood (as a Cub Scout project), the other a "Remco" crystal radio, both from the '60s. I used a 50' long wire antenna and was able to hear the local station (0.5 kW) three miles away on both sets. The Remco radio also picked up, to my surprise, after the local station had signed off for the night, a 5kW station from Cleveland. Never did hear any other Cleveland stations on either set; my having heard the 5kW station I mentioned must have been a fluke. I lived in an eastern Cleveland suburb (15 miles from downtown) at the time.

jbivy · #4 03-02-2012, 01:48 PM

Well im very well insulated, im using some "screw in" glass insulators at all four points. 16 gauge insulated wire for my "box with an x inside".

but WHY am i pulling in stations better with my antenna hooked to the ground than my HUGE antenna?

Reece · #5 03-03-2012, 08:35 AM

There are crystal sets and then there are crystal sets. Some have two or more tuned circuits and ceramic insulated tuning capacitors, litz wire coils, matching transformers and sensitive headphones, and get DX like a superhet. Could you post a picture and a schematic of your set?

stusnyder · #6 03-03-2012, 09:12 AM

Quote:

Originally Posted by jbivy

but WHY am i pulling in stations better with my antenna hooked to the ground than my HUGE antenna?

Every crystal radio I ever had, instructions said to hook it up to a cold water pipe that was in the ground.

old_coot88 · #7 03-03-2012, 11:10 AM

Quote:

Originally Posted by jbivy

...but WHY am i pulling in stations better with my antenna hooked to the ground than my HUGE antenna?

How long is the wire running from the radio to the ground connection?

jbivy · #8 03-03-2012, 04:04 PM

Quote:

Originally Posted by old_coot88

How long is the wire running from the radio to the ground connection?

Roughly 20' feet, a 2nd floor window to the ground and wrapped around a piece of rebar thats been pounded deeply into the ground.

DavGoodlin · #9 03-06-2012, 03:43 PM

JB, That ground seems to be a like a vertical antenna (like a car whip) terminated to a high-impedance ground plane at the bottom. Not surprised it works either.
Maybe it's tuned just right for what you're receiving.

I had a Radio Scrap crystal set kit 40 years ago. IIRC, it used a tunable coil, 1N64 diode, resistor and earphone. The ground was connected to a plate screw on a nearby receptacle and the antenna was 20 ft of 22 ga stranded insulated wire. It got all three local stations (10 miles - 1/5 kW)almost simultaneously, you could sort of tune it so one would be louder that the other 2.

old_tv_nut · #10 03-06-2012, 04:33 PM

Quote:

Originally Posted by jbivy

Im running what looks like a giant square with an X that connects the corners. Roughly 50'x20', with a copper cable that runs to the ground and is connected to a piece of rebar thats pounded 3' in the ground.

Ive found i actually have better reception with JUST the ground hooked up to where the antenna should be. Ive no idea why this is going on.

An uncle said the box with an X in it was a great antenna for crystal radios, but apparently its not working for me or for this location.

Im running the antenna between the house and garage, so ive a decent size place to make a large one.

Which antennas have you had the best experience with?

Do you have both a ground and an antenna connection to the crystal set, or only a single antenna connection? You need both. A sketch of your setup would help.

jbivy · #11 03-06-2012, 05:45 PM

im using 365pf poly film air variable capacitors (instead of the 280's that the design called for), a 1n34 diode, a .001 cap, a 350uf coil (i had it so i used it). Instead of headphones (im a bit deaf) im using a tiny headphone amp that powers a 2" speaker. Im getting one station in wonderfull, with a bit of bleeding of another on it.

and of course i have both the ground wire and antenna hooked up. The results were pretty lousy. On a lark i connected the antenna to the ground as well and it got far better reception. The "ground" can be disconnected without much loss. Im just baffled at this point.

Im debating changing out the coil for a roller coil. I hope that adds some more selectivity. http://www.ebay.com/itm/251004411630...84.m1438.l2649

leadlike · #12 03-06-2012, 08:52 PM

I've had a similar problem with my electric radios. When I first setup my antenna/ground wires (antenna was an outdoor longwire, ground was a lot like yours) I found that poor ground connection quickly turned the ground wire into a pretty effective antenna. I suspected a problem with grounding, so I poured warm salt water over the ground rod, soaking the earth real good. With that done, my ground rod worked-well, long enough for me to determine that was the problem.

jbivy · #13 03-06-2012, 08:56 PM

Quote:

Originally Posted by leadlike

I've had a similar problem with my electric radios. When I first setup my antenna/ground wires (antenna was an outdoor longwire, ground was a lot like yours) I found that poor ground connection quickly turned the ground wire into a pretty effective antenna. I suspected a problem with grounding, so I poured warm salt water over the ground rod, soaking the earth real good. With that done, my ground rod worked-well, long enough for me to determine that was the problem.

Well im in washington state, my ground is always damp. I pounded a piece of rebar perhaps 3 feet into the ground, ground the top of it with a grinder and wrapped it really well with my ground wire and then taped that up with duct tape.

Maybe the fact its 20 feet long, from a 2nd floor window to the ground, is why its a more effective antenna.

old_coot88 · #14 03-06-2012, 09:18 PM

Quote:

Originally Posted by jbivy

...Maybe the fact its 20 feet long, from a 2nd floor window to the ground, is why its a more effective antenna.

Plus, since it's vertical, it's more sensitive to the vertically-polarized waves from the BCB towers (vertical radiators emit vertically-polarized waves).

Reece · #15 03-07-2012, 06:38 AM

Here's a great site. The site owner has built lots of crystal sets with amazing results, and they are built with outstanding craftsmanship. I learned a lot from him. He's carrying on in the tradition started by his grandfather who made and sold crystal sets to jewelers in the 19-teens (article on those sets towards the end of the website.)

http://www.hobbytech.com/crystalradio/crystalradio.htm