Thanks Brett for the reply. Yes, November 2003 QST has a 2 tube receiver described in it. I don't subscribe to QST but a friend shared the info with me. I made a copy of the article but have not really looked at it. I believe it is a real compromise, but a simple design. I don't have the info in front of me now but it uses some 12 volt filament and 12 volt plate voltage tubes. I believe they were a 12AD6 and a 12DZ6. I don't have any of these in my junk box. I do have some transformers so I guess higher plate voltage and a more common type receiving tubes is what I would rather use. Just thought I would ask what you real technicians thought of the QST article and design. Again I have never built a receiver so I am interested in starting with a simple design and getting it to work, forcing me to learn some rx theory. If there is a good schematic on a simple receiver that you would recommend, I am Interested.
Mike W0FD -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Brett Gazdzinski Sent: Thursday, November 13, 2003 6:35 AM To: amradio@mailman.qth.net Subject: RE: [AMRadio] EUREKA!!! It WORKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Mike, A modern QST? This month? Hard to see how a 2 tube receiver could be a superhet! You need a LO, a mixer (can be one tube, but that is not best), IF amp (s), detector. Without 2 stages of IF amp, and a good tube detector, it might not be great for AM, and no filter? No filter will make it rough for AM use. Most receiver designs I looked at had problems with odd IF frequencies, odd components you cant get any more like coils, or very hard to build coils in the LO with feedback windings. I could never get any design to work well as a LO except the very nice design that uses an RF choke in the cathode, two caps (220pf) to ground from the grid, cathode goes to the point between the two 220pf caps. Coil and tuning cap in parallel to ground from the grid. Coil can be switched (2 coils), or partly shorted for higher frequencies. The coil can be a slug tuned form, or almost any B+W coil stock. Tuning range is set by the value of the two 220pf caps and the size of the tuning cap. Works quite a treat as an easy oscillator without trying to wind feedback coils and so on. Its also very easy to adjust and band switch. I tried building all sorts of LO designs, and never got anything to work well except the circuit above. If you seriously plan to build a receiver, I can likely help you out with parts and a good design. I have been documenting the new receiver, and tracing out and writing down the design of the first one, so can supply easy to build circuits for each stage. When building a receiver, put things close together, all RF and IF tubes, IF transformers, terminal strips. Long wires between stages can cause serious problems. There are not that many parts in a typical stage, most go on the tube socket itself. I have a collection of 455Khz IF transformers, tube type. Coil forms and B+W coil stock is easy to get, but expensive for what you get. Lots of tube types can be used, you can use a digital frequency display or not, you need a Kiwa filter to get good performance at low cost. Its not hard at all to build a simple superhet! Brett N2DTS > > > Congrats Eddy, > > I would like to see pictures of your project. I have been > following your > posts with interest. I hope to build a receiver for my next project. > > I've not ever attempted a rx project before so still > gathering info and > looking for the simple design to start. Any comments on the 2 > tube superhet > described in QST for November? Its not a 1929 rig but may kindle the > building interest again. > > Mike > W0FD > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Eddy Swynar > Sent: Wednesday, November 12, 2003 9:56 AM > To: Amradio@mailman.qth.net; [EMAIL PROTECTED]; > [EMAIL PROTECTED]; > [EMAIL PROTECTED] > Subject: [AMRadio] EUREKA!!! It WORKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! > > > Hi All, > > Well, I am VERY happy to say that my homebrewed 12-tube 1929 > superheterodyne > receiver project IS WORKING!!!!!! > > I gave it the "maiden run" test voyage this morning---some problems > ('natch!): an open plate choke, a bad solder connection on a > bypass cap, and > not enough (and later too much!) coupling between the local > oscillator & the > detector...the usual little stuff. > > I still have to determine how many turns of the local > oscillator coil I'll > have to short out in order to make it tune the 80-meter band > (right now it > tunes from about 3.3 to 3.490-MHz---but I was wise enough > from the get-go to > employ more coil stock turns than needed, "...just in case". > It's always > easier to SHORT turns, rather than to try & ADD them later > on, after the > fact!). > > It purrs along every bit as loud as my FT-980 along side it > (the rice rocket > is relegated to the role of digital frequency meter for these > particular > tests). Signals definitely peak right up with the two pre-selector > capacitors (yup, it's a knob twiddler's delight!), & the old > British vernier > dial assembly is as smooth as silk---BETTER than anything > encountered from > either National, or Millen, surprisingly enough... > > Surprised, too, by the absence of hum, & IF feedback in the > thing---either > I'm really lucky, or I've managed to learn a trick or two in > these matters > after homebrewing for some 32 years now. :>) > > The whole package LOOKS real sexy, too---with any luck, I may > be able to > borrow a digital camera this weekend...if anyone cares to, > I'd be more than > pleased to e-mail shots of my latest "pride & joy" here to > them. Just ask! > > Now, according to Murphy's law, the darn thing should blow up > between now & > the first request for a shot...Hmmmmm. > > ~73!~ Eddy VE3CUI - VE3XZ > > _______________________________________________ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio > > _______________________________________________ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio _______________________________________________ AMRadio mailing list AMRadio@mailman.qth.net http://mailman.qth.net/mailman/listinfo/amradio
