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: [email protected] > 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 > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
