Brett, you should do a photoessay on the building of this dream receiver. Dave, W3ST Secretary to the Collins Radio Association Publisher of the Collins Journal www.collinsra.com ----- Original Message ----- From: "Brett Gazdzinski" <[EMAIL PROTECTED]> To: <amradio@mailman.qth.net> Sent: Monday, November 03, 2003 8:34 AM Subject: RE: [AMRadio] FW: Homebrew receiver
> The ARRL handbook went with those like crazy, in the 1960's. > I don't think I have any 7360 tubes. I did not look hard > for them in the junk box. I DID look in the antique electronic supply > catalog, > and they wanted about $50.00 each I think! > > I should look in the junk box, since I may have some of these tubes, > I got a BUNCH of industrial tubes with numbers out of some old > sat com military stuff, many 7 and 9 pin tubes, the very nice > black tube shields, and even a bunch of those big triodes(6sa7?). > > I cant say just how quiet those tubes are, since I never used one. > Anyone know of a receiver that actually uses a 7360 as a mixer??? > > > In the first home brew receiver I built, I used a 6SA7, but unlike other > designs, it used a tube with three grids, injecting the antenna > signal into the control grid, the LO into the suppressor grid. > > Most designs I looked at had 4 grids when separate injection was used, > and would be in the very noisy category. > > This circuit was based on the Scott SLRM receiver I have. > > Mixer noise seems very very low on the homebrew, lowest of any > receiver I have ever tried. > I am not sure how important the noise figure is on 80 and 40 meters, > on higher bands, I know its important, but I don't go up there. > > On comparison to very weak signals on a very clear quiet band, > the homebrew will copy someone who is VERY weak, but give clear > copy, on the R390a, I might not even be able to tell there is a signal > there! > > I have not compared the homebrew directly to the Scott or the SX17, > but they have bandwidth problems, going quite wide at 60 db down. > That will likely add noise. > > For homebrew #2, I went with a 6ah6 in circuit design b in the handbook > (1961?), control grid gets the antenna signal, the LO is injected > into the cathode, suppressor grid is grounded, screen grid has > screen voltage on it. > Its supposed to be quiet. > I can also inject both signals into the control grid, I may try > both designs to see which works best. > > The receiver is moving along well, all the metal is cut, drilled, > punched, and I will paint the chassis on this receiver. > > The B+W coil stock arrived, the filters arrived, this receiver will > have selectable bandwidth, 4.5Khz and 5.5Khz. > > The LO coil (B+W coil stock) is mounted in a small metal box along > with the band switch (shorts out some of the coil) along with > the 40 meter tune cap, to adjust the 40 meter frequency, so I can > set it up like homebrew #1, switching between 160, 80 and 40 meters > has the receiver go to 1880, 3880, and 7290 when I change bands. > > The coil has been tested in the LO circuit for calibration... > > I broke down and bought a dremel tool, easy to make square holes > for things like relays, power cord plug in (with filter), digital > frequency display, etc. > > I need to find a good aluminum primer for painting the chassis. > > Brett > N2DTS > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] Behalf Of Donald Chester > > Sent: Sunday, November 02, 2003 11:02 AM > > To: amradio@mailman.qth.net > > Subject: RE: [AMRadio] FW: Homebrew receiver > > > > > > > > >I am not sure how much the RF amp adds to the noise level. > > >A well designed rf amp section can actually reduce noise levels. > > >Noise mostly comes from mixers, and overall tube counts. > > >All mixers add some noise, some designs are much better than others, > > >and the more there are, the more noise you get. > > > > > >I used single conversion, with a quiet mixer setup, and > > >used two tuned circuits of very high Q in the input, > > >along with resonant dipole antennas for 80 and 40 meters, > > >so I don't get any images or other problems, as signals > > >out of band are attenuated very much before making it to > > >the mixer. > > > > I think the best mixer designed ever developed used the 7360 > > or similar beam > > deflection tube. I'd like other opinions on the subject, if > > anyone thinks > > there is anything else that actually surpasses the > > performance of these > > tubes in mixer service? > > > > Don K4KYV > > > > _________________________________________________________________ > > See when your friends are online with MSN Messenger 6.0. > > Download it now > > FREE! http://msnmessenger-download.com > > > > _______________________________________________ > > 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
