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Crystal Receiver CR-1 Crystal Heathkit Brand, Heath Co.; Benton Harbor MI, build 1958, 11 pictures, 1 schematics, United States of America, tubes. Heathkit CR-1 Crystal Radio and Miller 595 Tuner Information. This page gives the circuit and pictoral description of the famous Heathkit CR-1 crystal radio. It was a double tuned crystal radio from the 1950's with a series tuned primary that had a 365 pf variable capacitor and selectable additional capacitance on the center selector switch.
Your story about the Heathkit CR-1 reminded me of the Futura 3 Transistor radio I got for Christmas that I used to listen to the Los Angeles Dodgers baseball games at night, using the earphone. One day, someone borrowed the Futura and broke the case. The CR-1 would be no exception. Miller introduced their crystal tuner, on which the CR-1 was based, as a hi-fi tuner. Hi-fi was a big deal in the 1950s, and AM broadcasters played classical and jazz music, as FM was still in its infancy.
Links Heathkit CR-1 Crystal clear Radio stations and Miller 595 Tuner Info This web page provides the outlet and pictoral description of the well-known Heathkit CR-1 crystal radio. It has been a double tuned crystal radió from the 1950's i9000 with a collection tuned main that experienced a 365 pf adjustable capacitor and selectable additional capacitance on the center selector change. In my opinion, it would have been more logical to possess produced the center change for varying the inductance and making use of a tapped primary coil. Here is a picture of the inside of of the unique CR-1. Another picture displaying the inside of the initial Heathkit CR-1. Notice the square pinkish mica capacitors, the configuration of the central antenna switch, the 'cable knit' look of the coils windings, and the long screws holding the section to the thréaded stubs that are recessed heavy into the cabinet.
Anyway the coils, ski slopes as 'transformér' in the diágram, had been both injury on a ferrite fishing rod and the secondary coil was component of a container with the 365 cover and the gérmanium diode for thé detector circuit. They do not provide details of the coil design but with a little testing you can get into the BC band tuning range. Here is the original circiut: This shows the pictoral diágram of the inside of the place: First Prototype In my 1st building task reproduction I used a toroidal primary rather of a fishing rod. An Amidon FT 114-61 was my option for the core, and 45 changes of 24 GA enamel wire for the secondary gets the detector container in the sports event. (Amidon't webpage is ). I utilized 30 moves of the exact same wire would on the exact same toroid for the primary with taps át 3, 6, 9 15, 24, and 32 spins. I utilized the center selector change to differ the inductance of the principal instead of changing in additional capacitors.
The little package is definitely a Radio stations Shack component #270-1805 that can be just about exactly the exact same size as the first enclosure. The front panel can be produced of lightweight aluminum, so it acts as a typical surface, but the anténna and one óf the headphone joining posts require to end up being insulated from it making use of little fiber washers to prevent those binding content from making electrical contact with the board. The radio was originally sold either with or along aspect a pair of 4000 ohm Trimm Acme headphones. They had been only center of the street for awareness and a great old pair of Brandes Superior or American Electric powered 509-Watts's would be much more sensitive. Right here can be a shot of the major components on the ground.
The rotary switch, diode, and container are from Radio stations Shack. The variable caps had been acquired from the Xtal Set Culture. The coil is defined above and I obtained the older mica capacitors from my rubbish container. I ended up using a different coil and no padder capacitors even though. One challenge had been to touch a few of the openings on the top encounter of the variable caps to enable them to become mounted to the top panel using 6-32 screws. Treatment must become taken to prevent harming the capacitor and to keep the steel shavings out of the golf ball bearing mechanism. OK, right here is usually the finished CR-1 clone.
This very first attempt offers the binding content spaced a bit too close up. I didn't have an primary to copy, just photos. I furthermore tried a few of different coil constructions and the a single I decided on has 45 works of 24 GA wire for the tuned secondary, and the major is drawn on as noted above. Inside it will be pretty easy. Just the 2 variable caps, the rotary switch wired up to the toroidal coils, and the diode can be seen from the capacitór to the binding blog post on the much still left.
I hooked it upward and measured 6 regional stations in the 1st minute in the daytimé, and with á great pair of earphones obtained 7 local people and another 4 out of condition stations on the first night. If I actually obtain a keep of an authentic, I will write-up a evaluation of the performance. Okay, I obtained a loan of the first Heathkit CR-1 and right here can be what I found. The initial CR-1 has a very much more definite dual tuned effect than my spinóff.
The 2 knobs for tuning the ANT and DET circuits seem to track pretty closely with each additional and both need to become tuned to the same rate of recurrence farily dramatically to obtain reception. It will be easy to skip a station by not getting the tuners coordinated. I discovered it best to shift the DET call a little then mop the ANT button back and forth a little tó zero in ón the place if there had been one there.
The outlet gurus e-mailed me and correctly predicted that my routine would fairly much function as a solitary tuned outlet. The inductance tap switch generally varied the selectivity and I found the 9 turn faucet to be great for both level of sensitivity and selectivity. There has been some apparent tuning impact of the ANT variable cap at the higher frequency finish of the dial but the DET tuner do most of the tuning. It has been, however, extremely delicate and tuned extremely sharply in any case. In reality the quantity was louder across the entire frequency variety than the on the unique CR-1, and I has been able to obtain a couple of weaker channels that I couldn't get to on the real CR-1. Therefore general I have always been very content with the efficiency but I will consider another one to attempt and clone the coils and efficiency of the unique a little more closely. Next Version After a lot of advice and numerous coils afterwards, I believe I obtained pretty near to the authentic performance.
The secret is definitely the coils. I have always been informed the authentic offers 2 little ferrite cores in it instead than 1 long one so, I played around with with different sizes of cores combined with different amounts of changes on the coil and after that zeroed in on the proper spacing between thé 2 cores. The spacing between the coils could be sized from outside but the stuff inside the cardboard tube has been impossible to find out without damaging the coils. It appears like the primary can be about 1/4 in . diameter and éxtends just to thé outer edges óf the coiI windings when yóu look into thé ends of thé tube. If anyoné understands the precise original specifications please let me understand. Anyhow, I has been able to choose up the same channels with this version as with the initial.
After numerous efforts and evaluation of an original coil and X-ray right here is definitely what I ended up with. I utilized 21/44 Litz wire for thé windings. The anténna coils was about 140 moves with a 9/16 in . slug inside thát part for abóut 335 uH inductance. The space between the coils was 10 mm or about 7/16 inches. The detector coil had about 90 converts with a 9/16 in .
long slug insidé that and méasured 240 uH. On some of the coils, I tried bringing out a faucet about 30 converts from the stator finish of the winding for the detector faucet. Hard to state if this made and recognizable difference, not significantly if any. This coils appeared to duplicate the performance of the original in both awareness and seIectivity. Any closer spácing of the coiIs and you obtain too very much coupling and the tuning will get very broad.
Here is usually a front side content label that I produced on some slim acetate plastic material, imprinted the Heathkit logo on it, ánd glued on tó the front side of the aluminum -panel. I marketed a several of these obviously introduced as home made clones, though I possess occasionally seen my radios show up for sale on Ebay promoted as a legitimate Heathkit, which should be obvious that they are usually not. Notice the brief smooth Phillips mind screws, the lettering which is clearly different than the primary, and the coil inside can be clearly hand twisted as opposed to the organised machine turning of the originals. Furthermore take note the circular modern ceramic chip capacitors and the multiposition switch.
If you operate across one óf my radios getting goes by off as an primary, you can relate the seller to this page, but the radió itself, unless damaged, should work just as properly as the real point, and there were just a dozen or so ever produced, so they are usually quite uncommon certainly! Addendum 5/29/01 Unravelling the techniques of the CR-1 coil, or The CR-1 coils Shown This is definitely an real X-ray óf a Héathkit CR-1 coil. As you notice, it offers the 2 coils each with its own individual ferrite slug. The greatest I can measure, each slug will be about 13 mm or about 1/2 in . long by 1/4 inch diameter. The parting between the slugs can be 7/16 inches.
It appears like the sIug in the bigger (antenna) coil is not quite based under the coil. I feel not certain if this had been intentional or not. Anyhow it has been useful to understand how it has been made so one might get a better idea of how to create a copy. The Amidon R61-025-400 primary can be reduce into the 1/2 inch lengths for usé in constructing á coil Iike this one. l will publish further information as I advance with this task. (i am sorry this connected site has been removed, but will attempt to relocate it) This is certainly a hyperlink to a web page with more information about another famous crystal radio, thé Miller 565 / 595 Tuner. This was my next task.
Crystal Radio Station
The modified schematic can be proven below.