When viewing any of our webpages (or any website for that matter), it is best to enter our (the) site at our (the) home page or the page of interest by entering it in your browser. This ensures that your browser will refresh the screen and thus present the latest version of the webpage.
Build an inexpensive radio out of an oat meal box. The pack includes 1 Spool (100 feet) #24 wire, 1 IN34 Diode, 1 100 pf Capacitor, 1 47K Resistor, 3 alligator clips, 1 ceramic, hi impedance ear piece, 56-32 by ½ machine screws, 10 6-32 nuts, 5 #6 solder lugs -- you provide the box (eat the oatmeal, it's good for you!) and an antenna. The plans for this radio are on our website at www.midnightscience.com/oat-box-project.html. Great for classes, scouting, and science fairs -- easy for kids to put together, with adult supervision.
If you need an antenna, then order the Oatbox Pack 2.
This pack includes everything in Pack 1, above, plus another spool of 24 gauge hook-up wire (100feet). The extra wire can be used to make a bigger coil, to cover more of the broadcast band, or it can be used as antenna wire. You'll need to buy and eat the oatmeal.
Attention beginners and mentors. J. K Fenton has written "Building Your First Crystal Radio," See picture and to order below.
Building Your First Crystal Radio
This small booklet is written in easy to read language for the true beginner to our wonderful hobby. It has pictures and symbols for basic parts and gives the reader basic information to get started with that first building project. 5-1/2 x 8-1/2 x 15 pages. Cat#XBGN $ 2.95.
MK484 AM RADIO KIT
No antenna or ground required!
This "MINI" kit is a subset of the MK484 AM RADIO kit and uses a small portion of the printed circuit board of that kit. The MINI features the MK484 IC, a ferrite rod antenna, a 1.5 volt regulator, a handfull of resistors and capacitors, a switch, variable capacitor, panel, chassis, and crystal radio earpiece. The set does not need an antenna or ground since it includes the ferrite rod; does not need a volume control since it has built in gain control, and the earpiece takes the place of headphones. You supply the 9V battery. The radio is set to tune the AM band.
If you wish to use the MINI with 8-ohm headphones, a bag of parts is available for purchase that includes a 386 audio IC, caps, resistors, and a volume pot with knob. We call this the Audio IC Bag-O-Parts.
MK484 AM RADIO KIT
This kit provides you with a great place to start for exploring and building kits for reception of AM broadcasts. The parts and instructions supplied with the full kit support reception of the broadcast band, roughly 550 to 1500 kHz. Increasing/decreasing the turns on the ferrite coil shifts reception down to a minimum of 180 kHz/maximum of 3,000 kHz, supported by the MK484.
The heart of the kit features the ubiquitous MK484 IC in a TO-92 transistor package coupled with our old friend, the 386-4 audio amp in an 8-pin DIP. Coupled with an external antenna, FT82-61 ferrite toroid (for tuning coil) and air-variable capacitor, the MK484 AM Radio Kit gets surprising results. The MK484 IC features stable operation and low current drain, while providing a complete RF amplifier chain, AM detection and AGC circuitry. The 4.0 by 2.5 inch PCB houses all of the electronics for the receiver except for external tuning coil, air-variable tuning capacitor, panel and chassis. Parts shipped with our full kit support reception of the standard AM band. Adding a fixed capacitor in series or parallel with the variable tuning capacitor and/or decreasing or adding turns to the ferrite core (or a combination of the two) allows for the reception at 180-550 kHz or above at 1500-3000 kHz. As with most of our kits, this one can be ordered 2 ways: 1) a Partial Kit based on the PCB and its components and 2) the Full Kit including the Partial Kit along with a laser engraved front panel, chassis, ferrite toroid and 365 uuf air variable capacitor. You must supply your own 8 to 32 ohm headphones or a small 8-ohm speaker, assembly tools, masking tape, 9 volt battery and enthusiasm! The set can be operated without an external antenna and grounding system if you use a ferrite rod or loop antenna (neither provided).
Partial Kit: PCB, PCB Parts & Full Manual: $39.95. Full Kit: PCB, PCB Parts, Ferrite Toroid, Air Variable 365 Capacitor, Laser Engraved Panel, Chassis & Full Manual: $64.95. You can order the MK484 IC itself on the parts page.
CRYSTAL RADIO ANTENNA KIT
This kit consists of 50 feet of #14 AWG insulated & stranded copper antenna wire, two nail insulators, two antenna insulators and an instruction and installation sheet. The instruction sheet outlines how to install and tune the antenna to resonance for the AM band.
The nail insulators mount with two wood screws and provide for wire support near the window and at a tree or eve. Weave the wire through the "claws" of the nail insulator to hold it in place. The antenna insulators may be used with rope on one side and as a tie-off for the antenna wire on the other side.
These are shown in the picture inside the 50' loop of wire.
Since the wire is flexible, you can easily feed it through on your window sill.
CRYSTAL RADIO GROUNDING KIT
This kit is ideal for use with our Crystal Radio Antenna Kit or for general station grounding. It consists of a long-lasting 2.5 by 1/2 inch galvanized ground rod, 1/2-inch brass rod clamp, ten feet of #14 Insultated Stranded copper antenna wire and an instruction/installation sheet. The grounding kit provides for an outside grounding circuit for your crystal radio. The antenna wire is very flexible, allowing you to loop it under your window and then simply closing the window.
GALENA DETECTOR KIT
Step back in time with our galena detector kit and experience the soft detection that comes from minerals. Marconi would be proud of you! Delight in the first broadcast reception using the galena with any of our crystal radio kits or as a replacement for those 1N34 diodes you may have been using.
No soldering required in this simple assembly of mechanical parts. Kit contains 2.5 by 3.4 by 3/4 unstained but predrilled wood base, mounted galena, phospher-bronze cat whisker, 3-inch brass rod, compression spring, and brass parts. Assembly time is about one-half hour. CAT # XSGDK $29.95.
See the parts page to purchase individual parts.
ABS PANELS & CHASSIS KIT
We are offering two precut ABS (low-RF-loss) panels, 5 x 6 x 1/8 and 5 x 8 x 1/8th inches. These are combined to form a radio chassis as shown in the picture at right. The 5 x 6 panel is shown as the front panel. Two wood pine rails, each 1.5 by ¾ by 8 inches long are used to hold the two ABS panels together, using wood screws.
The assembly in the picture is available as a kit, including the two panels, two wood rails, and six wood screws. Although holes are shown in the picture, no holes are predrilled in the panels or rails. The kit does include mechanical drawings showing dimensions and locations for the holes, including a drill-hole patterns for the shaft and mounting of our 365 air variable capacitors. We also offer the ABS precut panels separately, 5x6x1/8 or 5x8x1/8 inch.
INFINITE IMPEDANCE DETECTOR KIT
This kit includes parts and a small PCB to substitute a JFET circuit configured as an infinite impedance detector for the usual 1N34 diode detector. With this replacement, your crystal set will generate more volume and reduce audio distortion. Historically this arrangement was used with a triode tube in early AM radio sets. Ideal for those wishing to listen to AM with improved audio linearity. Kit replaces the diode detector in your crystal or TRF set.
Assembly time is about one-half hour. CAT # XSIDK $19.95.
JFET DETECTOR KIT
Experience some of the operational qualities of a high-impedance DX crystal set by replacing that ordinary germanium diode in your basic set with a junction field effect transistor (JFET) detector circuit. You’ll notice sharper tuning and higher volume due to the high input impedance of the JFET, which preserves the Q of your tuning coil. The 2n5484 JFET is supported by a printed circuit board (PCB), a handful of resistors, capacitors, low-current LED, 9V battery & holder, battery clip with wires, and SPDT switch. You’ll mount the parts on the 2.0 by 1.4 inch PCB, as shown on the picture. All parts required are included except for the 9V battery and any necessary hookup wire.
Manual includes schematic, step-by-step assembly instructions, and suggestions for installing the detector assembly in a crystal set in place of your diode.
The power switch, bias pot and LED can be mounted on the board or on your set’s front panel with wires running to the board if desired. The 9V battery clip leads insert at connector 3 (CONN3) at left; earpiece or headphone leads insert at CONN2 at right, and your paralleled coil and tuning cap tank leads insert at CONN1 at bottom left.
JFET AM CRYSTAL RADIO KIT
This AM crystal set is built around a Junction Field Effect Transistor (JFET) and when coupled with a separate antenna tuner performs a good bit like a Hi-Z DX set. Hi-Z sets generally make use of Litz coils, HI-Z diode, matching transformer, and sound-powered phones. With this set, you experience some of the same results but at less cost and procurement time. Background material on this set can be found in the May and July 2011 newsletters of The Xtal Set Society.
This set uses a 3.5-inch PVC formed 250 microhenry (uH) coil, consisting of 61 turns of # 24 plastic coated wire. Our standard 365 uufd air variable capacitor is placed in parallel with the coil to resonant it at the desired AM band frequency. A 2 by 1.4 inch printed circuit board (PCB) is provided for the detector. The source-follower output of the detector can drive a crystal ear piece or old-style high impedance headphones, such as a Baldwin pair. The high impedance of the “gate” input of the detector helps to preserve the Q of the input coil, thus preserving selectivity that would otherwise be reduced by the load of a simple 1N34 and phones. The “source” output voltage maintains most of the signal level presented by the tuned circuit too, thus providing a bigger signal to the phones than with a diode detector. The result is generally better selectivity and volume than with a simple low-cost set. For weak signal reception, best results are obtained when using a good antenna and an antenna tuner that is lightly coupling to your crystal set.
AM BAND ANTENNA TUNER KIT
This AM Band Tuner will work with most any crystal radio set. Tuners are attached to the antenna and inductively couple the signal captured into your crystal radio set. By adding the tuner to your station, selectivity and volume can generally be improved.
The backside of the tuner is shown at right. A dual-gang 365 pf capacitor is used to resonate the tuner coil and the antenna system as a whole. The result is an increase in the signal gleaned from the antenna and coupled to the set magnetically. The tuner uses a 6 by 5 inch front panel and a 6 by 8 in chassis. Two switches are used to configure the tuner. In addition, a nylon shaft is added to the tuning capacitor to reduce “hand capacity” while tuning. Kit time is less than one hour experienced builder and should add performance to your crystal radio station.
XS-402 The Little Wonder Crystal Radio Kit
Our “Little Wonder” is a super starter kit for kids and beginning adult builders! It tunes the entire broadcast band. The extra large solder pads make it easy for beginning builders to have a successful first radio. There are only a few solder joints, and the pads are spread out making it clean and simple to assemble. The “Little Wonder” was designed especially for the XSS by our founder, Grampa Phil, WØXI. We tried to combine everything we’ve learned about building radios with beginners and kids to create a radio that everyone can build the first time. There is no coil to wind, a high resonant frequency molded choke have been used in place of the coil. A nice photo diagram is included showing all the parts and their placement on the printed circuit board (PCB) . This radio is perfect for parents and grandparents to build with kids. It is also priced right for classroom use, and can be used to teach basic radio theory, soldering, and handling of electronic parts and PCB’s. Kit includes a high impedance crystal earplug. A super performer and a great little kit; you’ve got to have one! XS402 $18.95.
XS-500 Basic Crystal Radio
The XS-500 Basic Crystal Radio is a tapped-coil crystal set, designed for those who wish to wind their own coil and for solder or non-solder assembly. Set tunes the AM broadcast band and requires, as usual, an antenna and grounding (antenna wire not included). One-hundred foot wire spools are available via mail order or our web site. We like the assembly flexibility of this set: a bit of a challenge in winding the coil and the alternative for non-solder assembly. This basic kit includes a pre-drilled wood base, pre-drilled PVC coil form, 50 feet of enamel wire, 1N34 detector diode, ear piece, capacitors and a resistor, alligator clips, Fahnestock clips, 6-32 mounting hardware, and manual. Cat # XS500 $19.95.
Passive Audio CW Filter Kit
We're pleased to announce our Passive Audio CW Filter Kit. It was inspired by our enthusiasm for non-powered – no batteries or power supplies required – electronics. The kit features a 250 Hertz (Hz) bandwidth, 700 Hz center-frequency, 8-ohms in, 8-ohms out audio filter, designed for CW operation. A bypass switch allows for bypass and in-line reception comparison. The unit installs between your receiver's headphone jack and headphones or speaker. Assembly for experienced kit builders is less than an hour. The kit consists of eleven parts, including three high-mu ferrites, quality PCB and black plastic case. Instructions are included for changing the filter bandwidth to 500 Hz for CW or 1500 Hz for SSB; for either of these frequency bandwidths the number of winding per core must be changed and a different set of capacitors purchased.
The kit can accommodate other center frequencies and bandwidths. To calculate the number of turns for the cores (coils) and the capacitor values required download these files: manual addendum and filter calculator spread sheet (xls).
CW REGEN FILTER, (Alias: The Scrubber)
This kit was inspired by the inhibiting galactic noise encountered when listening to HF CW. Many proficient CW operators turn the AF gain full on and manage the audio signal and noise with internal rig filters and the RF gain knob. Even with these techniques band-limited cosmic static is present along with some man-made noise. There isn’t much one can do to copy CW notes that are simply too weak; but, one can scrub away a portion of the static that makes its way into our consciousness with an audio regenerative filter. (See the feature article on the CW Scrubber in November, 2012 CQ Magazine.)
For example, when tuned to a quiet spot on 30-meters, regen’s output shows a reduction in noise compared to the signal at the phone jack of the receiver. In bypass mode one simply listens to what the rig has to offer. In scrubber mode, the multiple-op-amp filters and regen work together to remove a majority of the remaining white noise. The processed signal sounds clean with a slight echo-chamber quality. For most this is an improvement, reducing stress and improving copy.
For experienced kit makers, assembly and alignment is about two hours. You can use a meter or scope to align the filters and the audio delay line. If you have neither of these you can align the filter by ear.
Download tuning by ear instructions by clicking on this link.
Download those instructiions by clicking here. If you don't have a signal generator, you can use CW from your rig, a code oscillator or download 600, 700, and/or 800 Hz wavefiles from our "downloads" webpage. In addition, you’ll supply the connectors and cabling for your specific radio and the following tools and supplies: pliers, cutters, knife or wire stripper, soldering iron & solder, masking tape and your enthusiasm! The filter can be supplied with a well regulated and grounded +12VDC supply or 9V battery. A well grounded station is necessary when external high gain audio-based accessories are added to prevent or substantially reduce any “ground loop” interference.
The populated PCB fits in a plastic case that is W 3.700, H 1.450, and L 6.100 inches.
XS-W Crystal Set
This is our smallest crystal set yet, measuring 1.5 by 2 by 0.5 inches. It’s small enough to wear on your wrist, and includes jacks for plugging in an antenna and ear piece. Set is tuned by selecting a set of capacitors wired in parallel with the miniature molded coil. Kit is constructed by soldering the parts onto the printed circuit board provided. Plugs to match the jacks, along with an ear-piece are provided. As with all sets, it requires an antenna, not provided.
Cat # XS-W,
For QRP Amateur Radio use. This kit and our passive CW filter kit were inspired by our enthusiasm for non-powered - no batteries - electronics. The “smart” dummy load, assembled on a 1-1/4 by 4-1/2 inch PCB, features a 10-watt dummy load with power levels acheived denoted by four LEDs. The circuit includes six 3-watt metal film resistors, four detector diodes, four zeners, four LEDs, and bias resistors. The four LED circuits denote power achieved: 1, 2, 5, or 10-watts. The signal measured supplies the power. No batteries Mom! Assembly time is about 25 minutes. Coax with PL-259 connector not included. Kit Price, $19.95.