Gee Ed, didn't mean to flip your switch. Grid voltage here is 125 AC loaded, I have seen carbon zinc batteries @ 1.15 volts out of the package.
None of this is really critical, but any amateur should use good engineering practice, or did I misread some rules? 73 Jim de W5JO ----- Original Message ----- From: "Edward B Richards" <[EMAIL PROTECTED]> To: <[email protected]> Cc: <[email protected]> Sent: Tuesday, August 24, 2004 2:53 PM Subject: Re: [AMRadio] Test Equipment Recommendation > I think you guys are getting carried away with technicalities. We are not > space laboratories, we are amateurs. Look at your license. Nearly all > VTVM's use a 12AU7 and a 6AL5. They are available in abundance. I have > about 50 of each. Any good used tube will be aged. Even if recalibration > is required we are talking about removing 2 screws and adjusting 3 pots. > Not an all day job. Re calibration, Heathkit used a fresh zink-carbon > battery for a terminal voltage of 1.55 volts. I use a fresh alkaline > battery with a terminal voltage of 1.62 volts. It works for me. For ACV > if you don't have another meter or a friend that does, wait for early > morning when the electrical grid is lightly loaded and calibrate your ACV > for 122 VAC. You will be in the 5% accuracy of the VTVM. > > 73, Ed Richards K6UUZ > > > On Tue, 24 Aug 2004 11:43:39 -0500 "Jim Wilhite" <[EMAIL PROTECTED]> > writes: > > When considering a VTVM one should look at one thing in particular, > > tube > > replacement. The Senior Voltohmyst uses a 6AL5 and a 12AU7 . > > Finding tubes > > is not a problem, but for reasonable accuracy the right tube is. > > > > According to the manual for the Voltohmyst, the tubes must be > > thoroughly > > aged. For example, to age the 12AU7 the grids and cathodes are > > connected to > > B- and the heathers be operated at 6.3 volts for approximately 12 > > hours > > before installation. The tube can be installed then left turned on > > for > > about 36 hours then the instrument must be re-calibrated. If the > > second > > method does not provide proper results, the first method should be > > followed. > > The 6AL5 can just be aged by leaving it on for about 36 hours, but > > then > > re-calibration must follow. > > > > While neither of these methods are particularly difficult, how many > > of us > > have standard sources to calibrate our meters? It seems to me a > > good modern > > Fluke meter might be the best choice. They are not easily destroyed > > nor go > > out of calibration easy. Some are sensitive to high RF fields which > > blow > > the input protector. I have had that trouble with a Fluke 77. > > Most, if not > > all provide a high impedance input and are rugged. > > > > Granted using them to tuned for peak resonance is difficult, Sears > > sells a > > dual digital/analog meter with high impedance. They are not > > terribly > > expensive and can provide both digital and analog readings. > > > > 73 Jim > > de W5JO > > > > ----- Original Message ----- > > From: "Merz Donald S" <[EMAIL PROTECTED]> > > To: "Discussion of AM Radio" <[email protected]> > > Sent: Tuesday, August 24, 2004 9:21 AM > > Subject: RE: [AMRadio] Test Equipment Recommendation > > > > > > > Really? Is this the best recommendation that we can come up with? > > Every > > one of these that I see is awfully beat up after 30-50 years. And > > these were > > not especially high quality units to begin with. > > > > > > On the other hand, I don't know what else to recommend. I am using > > an old > > Radio Shack Micronta VTVM, probably from 1970. I've had a Simpson > > 303 (these > > do not age well--to be avoided) and the RCA VoltOhmyst in several > > different > > flavors, plus several other brands. The Micronta has delivered the > > most > > reliable, accurate service of any of them. But I can't really > > recommend that > > because nobody could ever find one. > > > > > > Given the advanced age of the VTVMs that survive today, this > > actually is a > > harder question than it first seems. > > > > > > 73, Don Merz, N3RHT > > > > > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] > > > [mailto:[EMAIL PROTECTED] Behalf Of Edward B > > Richards > > > Sent: Monday, August 23, 2004 11:27 PM > > > To: [EMAIL PROTECTED]; [email protected] > > > Subject: Re: [AMRadio] Test Equipment Recommendation > > > > > > > > > Bill; > > > > > > Go to that auction place and buy a Heathkit VTVM. There are > > usually a lot > > > of them listed. All are 11 megohm input impedance. Then buy an RF > > probe. > > > The later VTVM's have a phone jack input and so do most RF probes. > > Also > > > known a demodulator or scope demodulator. Good luck > > > > > > 73, Ed Richards K6UUZ > > > > > > > > > On Mon, 23 Aug 2004 19:30:22 -0600 (GMT-06:00) Bill Pancake > > > <[EMAIL PROTECTED]> writes: > > > > Would appreciate a recommendation as to make and model of a VTVM > > that > > > > will come with an rf probe that is suitable for using when > > working > > > > on boatanchor gear. I just need an idea of what to look for. > > > > Thanks, Bill, [EMAIL PROTECTED] > > > > > > > > > > > > ______________________________________________________________ > > > > AMRadio mailing list > > > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > > > Help: http://mailman.qth.net/mmfaq.html > > > > Post: mailto:[email protected] > > > > > > > > > > ______________________________________________________________ > > > AMRadio mailing list > > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > > Help: http://mailman.qth.net/mmfaq.html > > > Post: mailto:[email protected] > > > > > > The information contained in this e-mail may be confidential and > > is > > intended solely for the use of the named addressee. > > > Access, copying or re-use of the e-mail or any information > > contained > > therein by any other person is not authorized. > > > If you are not the intended recipient please notify us immediately > > by > > returning the e-mail to the originator.(B) > > > ______________________________________________________________ > > > AMRadio mailing list > > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > > Help: http://mailman.qth.net/mmfaq.html > > > Post: mailto:[email protected] > > > > > > > > > > > > ______________________________________________________________ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:[email protected] > > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > >
