that the CF2 (narrow filter) is always switched in (and toss CF1!). You should not attempt any of the mods unless you feel confident in your soldering and construction skills. Also you must have all the tools and facilities to perform each modification. The mods mostly use inexpensive readily available components, resistors and capacitors. Click here to see the article list for DX-390. To remove the top and bottom covers you simply unscrew the four small black cross point screws located on the back of the receiver. I am NOT referring to sideband splatter from adjacent stations caused by the overly wide stock CF1 AM ceramic filter. Resistor R91 is just below it and should be marked with 102 (1K). The information, circuit diagrams and photos should help you easily and successfully improve the performance of your DX-394. The problem is caused by the fact that Tandy designers (or whoever) forgot one of the CF1 bias decoupling capacitors. This modification is read 1187 times. Note that there is a limit to the number of files you can download. Anyone with a schematic will note that the node at the junction of R58, R61, R62 and R64 should have a bypass capacitor to ground from this point.
Articles for: Realistic Dx 390 ModsIf the realistic Dx 390 Mods message is relate to an article, the article can be selected next to each message. Adding the.1uf capacitor around Q13's emitter resistor R91 (it already has.01uf cap across it - C81) seems to decouple the bleed through signal. Good luck and be careful - the parts are all tiny surface mount. This one may be more effective than the previous one and used together, crosstalk is reduced to an insignificant level. A Fan Club for the Tandy / Radio Shack / Realistic DX-394 General Coverage Communications Receiver. For those of you without a schematic you can find R64 by removing the bottom cover with the receiver knobs facing you. It soon acquired a poor reputation after several very negative reviews. With the bottom cover removed and the front panel knobs facing you find the silkscreen ID for Q13. It should be noted that with real strong adjacent signals there still may be some crosstalk and reducing the RF gain will help even more. Groups Radio Shack DX-394, the Forum for DX-394 Users Improvers. Here is another DX-394 modification that will further reduce adjacent channel crosstalk from strong shortwave stations (see my first mod of about a week ago). R64 is the third component to the right of D15 and has 222 (2.2K) stamped on it (you may need a magnifying glass!). Another note for those who listen to AM only on the 394 - if you swap ceramic filters CF1 and CF2 you will have a more narrow AM bandwidth for crowded band conditions.
Looking for modsThis resistor is also just below and slightly to the realistic Dx 390 Mods right of the third pin (from the left) on CF1. All that is necessary is to solder.047.2uf ceramic capacitor directly across R64 and the crosstalk will be significantly reduced. Look for the connector block CN7 and unplug this to remove the loudspeaker from the main board. It is a black surface mount transistor with three leads (2 on one side, 1 on the other) midway toward the front of the unit and left of center. Without it there is a resistive signal path through R57, R58 and R61 that bypasses the CF1 filter and causes broadband bleed through. If you have some stuff that not is listed here you can donate this by contact mods.dk.
Hints and Tips from a helpful community of enthusiasts. All credit to number Hack Code the inventors of the original DX-394 mods. Frank Cathell, tom Holden, danny Boulet, richard Putz. Bridge this resistor with.1uf.22uf ceramic capacitor (keep leads short) and you're done. Main Board Top View, main Board Bottom View.