Hi Brett, I sure would appreciate some more info re. those "Kiwi" IF filters...!
Where do you buy them...? What are their different bandwidths...? Do they have a website...? Hope to hear from you soon, with thanks in advance! ~73~ Eddy VE3CUI - VE3XZ ----- Original Message ----- From: "Brett Gazdzinski" <[EMAIL PROTECTED]> To: <amradio@mailman.qth.net> Sent: Tuesday, October 21, 2003 2:39 PM Subject: [AMRadio] RE: new home brew receiver progress > I am making good progress on the new receiver. > I have tried lots of circuits for the local oscillator, > and have come up with a good circuit. > Its very hard to build a good stable oscillator without > complex coils with feedback windings. > > I found a circuit in the Bill Orr handbook, out of the C-W man's receiver > that uses one untapped coil, one side goes to ground, a variable cap across > the coil to ground, an RF choke in the cathode, and a pair of caps > in series from the grid to ground, the center (between the caps) > goes to the cathode for feedback. > > I tried various coil types, various size ceramic slug tuned forms > with various gauge wire on them, pre made phenolic slug tuned forms > that I unwound some wire from till I got to the correct frequency, > large ceramic coil forms, and B+W coil stock. > > The best results are from the B+W coil stock, a much higher > Q coil, gives less harmonics out. > > I changed the design some, instead of using the 6U8, I used a 6C4, > since the ARRL handbook says a separate oscillator tube results > in a more stable receiver. > 2nd harmonics are down more than 45 DB with the B+W coil, much less with > some of the others, some generate harmonics out to 60 Mhz > or so! > The oscillator keeps working down to as little as 10 volts on the plate, > and I may run it at 75 volts. > I just tack parts together on the workbench, hooked up to > the old heathkit variable high voltage power supply, > so the finished product should actually work better, with > short wires and a sensible layout. > > To switch between 80 and 40 meters, all I need to do is > short part of the coil to ground. > One end is always connected to ground, and a tap to > ground will give 40 meters, I tested it, and it works well, > no drop in output, no increase in harmonics. > I plan on putting the coil and switch in a small box to isolate > it. > > I think the mixer tube will be a 6AH6, and I will try to inject > the osc into the cathode. > If that does not work well, I can inject it into the grid. > The ARRL 1967 handbook has lots of good info about > this sort of mixer stuff on page 99. > > I think the IF amps will be 2 or 3 6BZ6 tubes. > The same handbook gives circuits and values for various tubes. > > I have a circuit for the low distortion detector, and the S meter > amp, but have to change from octal tubes to 7 or 9 pin > tubes, from a 6SN7 for the S meter circuit, and the detector needs > a diode, and a triode, like the 6SN7. > > I may be able to drive the S meter directly with an IF > amp plate current, like the Gonset G76 does. > I found a nice S meter from an old heathkit receiver > on E bay a while ago. It can be lit up from the back, a nice touch, > and its only an S meter, not out of a transceiver with plate current > and so on.. > > I have the chassis, the side supports and front panel, > the IF transformers, the digital frequency display, the tuning cap > and various reduction drives, nice ceramic tube sockets, the antenna > tuning coil forms, loads of VR tubes, and all the other tubes. > > The Kiwi filters have not arrived yet, and I may need to buy a > power transformer, to give 200 volts out with choke input, > and filament windings. > > Its really getting to be ham radio season, with building and > operating, and I am having FUN! > > > Brett > N2DTS > > > _______________________________________________ > AMRadio mailing list > AMRadio@mailman.qth.net > http://mailman.qth.net/mailman/listinfo/amradio >
