Poor Mans' Electronics Web Page

Crystal radio

How to use it:

Connect the random wire antenna lead-in to the Hi-Z antenna terminal. Connect the ground wire to the ground terminal. Connect one or two high impedance earphones to the earphone terminals. I have found that using both ears to for listening helps to pick out weak signals.

Tune the variable capacitor until a local station is heard. Stations during the day up to 20 miles away should very discernable. More distant stations during the day or skip stations at night may be more challenging. Most radio stations are required to shut down or reduce power at night when skip conditions occur. Skip is when radio waves bounce of the ionosphere and travel much further than they can during daylight hours.

If you have several strong stations in your area, you may pick up more than one station at a time no matter how carefully you tune the radio. To improve on the selectivity of the radio, reduce the capacitance of the 330 uuF trimmer capacitor. The smaller the capacitor the more selective the radio is but the sensitivity will diminish. Thus, you must trade the ability to separate signals with volume.

On the other hand, if you are having difficulty hearing stations because of their distance, you may increase the capacitance of the trimmer or even replace it with a direct connection.

Click here to hear an mp3 clip of the reception of a local station on this neat little crystal radio connected to a random wire antenna and a good ground system. I routed the signal from the earphone connection into the microphone input of my computer's sound card to record this clip.

    Stations Picked up with the Crystal Set
              from Winfield, WV

I connected a high impedance digital VOM across the
earphone connections to record the peak output voltage
that each of the following stations produced. Since the
crystal set has no calibrated dial, the frequency
was determined from the WHAM radio log once I got the
call letters.

Station   Freq. KHz   Location            Signal Level mV
-------   ---------   --------------	  ---------------
CJBC      860         Toronta, CAN        190
KMOX      1120        St. Louis, MO       206
WBBM      780         Chicago, IL         145
WTAM      1100        Cleveland, OH       477
?         ?           Chinese!            176
WRVA      1140        Richmond, VA        117
WBZ       1030        Boston, MA          428
WHAM      1180        Rochester, NY       234
WFAN      660         New York, NY        298
WABC      770         New York, NY        245
WLS       890         Chicago, IL         196
WLUP      1000        Chicago, IL         229
WCHS      580         Charleston, WV      427
WBT       1110        Charlotte, NC       307
WVTS      950         Charleston, WV      101
WCBS      880         New York, NY        262
KYW       1060        Philadelphia, PA    320
WOKU      1080        Hurricane, WV        96

Notes: WTAM produced nearly a half a volt when skip
was right. Also picked up a chinese speaking station. I
believe there is a station in upper New York somewhere
that broadcasts in Chinese all the time. I don't think
I was picking up skip from China.

Poor Man's Electronics Web Page

Crystal radio