[AMRadio] Re: Frequency Response
Sorry for the long winded post, but here it is.. Since the discussion is regarding distortion and frequency response, I would like to share some experience I have had with improving the fidelity of otherwise mundane audio power amplifers. Although some of the technicques presented may require some ingenuity to apply to a very large plate modulator, I feel that they have worthwhile and audible merit from the standpoint of linearity, 'tilt', and transient response. In the second case presented below, A/B tests with various CD recorded music including violin, Cuban percussion, and industrial styles, the improvements were very noticeable. Surely there is then merit for the improvement of the fidelity of the voice waveform. I would also like to suggest that a triangular wave is an excellent way to check the linearity of an audio amplifier. The proper circuit configuration around the phase inverter can make the sides of the wave obey an extremely straight 45 degree angle, to the point where the input and output signal shapes are nearly indistinguishable. 'Tuning' is done by superimposing the input and output signals on a scope and matching them. (In an amplifier with poor linearity, the sides of the triangle wave can 'bellow' out, or 'hourglass' in, just like the trapezoid RF waveform in a poorly designed or operated linear amplifier (go figure).) The first two circuits embody this method in the phase inverter circuit. I realize that many people may prefer a balanced circuit throughout, but it may not always be practical. The first two circuits also embody a cathode feedback scheme surrounding only the output tubes and the audio output transformer. This application will 'straighen up' and otherwise poor transformer quite well, although there are requirements for plenty of grid drive voltage and ample B+ voltage along with a large value filter capacitor on the plate supply. If the transformer is too small, the low frequency power output fidelity will be less improved since the transformer cannot handle the extra current demanded when correction takes place. A solution is to demand less power. This article describes the conversion of a fairly poor performing (actually bad sounding) 70W theater amplifier which suffers from lack of iron. The result is a very clear 40 watt amplifier. A method of in-circuit measurement of tube matching is shown. http://www.montagar.com/~patj/mi12188a.htm This article describes the improvements made to a decent-sounding 50 watt public address amplifier to the point where it is as faithful as a Quad or McIntosh as far as most people's ears are concerned. About 50 watts was still obtained (large iron). http://www.montagar.com/~patj/aph1050.htm This article demonstrates a method of coupling the output signal back to the grids around a transformer coupled high power (50 watt) AB2 audio stage. http://www.montagar.com/~patj/tubeart.htm For those interested in a QRP experience, this article describes an extremely linear series modulator for an 807 RF stage. http://www.montagar.com/~patj/amxmtr_dc_classamod.html Patrick
RE: [AMRadio] WTB SB-220
I have found that a good rule of thumb for using linear amplifiers on AM without burning up the tubes is the max. carrier output from the linear should be no more than half the total CCS dissipaton of the tubes. Case in point the pair of 6146's at 20-25W carrier, etc. I run my National NCL-2000 at carrier 100W output, and dissipate 300W at carrier, in a pair of 8122's. Last a lng time..
[AMRadio] SIMPSON MAINTENANCE MANUAL
Hi Don, The envelope full of 260 info and your flier arrived safely today. I sure do appreciate the time and effort that went into making copies and getting them in the mail. I have several 260s and swear by them when working with boatanchors. I recently picked up a 360 which looks the same as the 260 but with a digital readout in place of the analog meter. If you happen to have any info on this one, I would be happy to pay for copies, etc. Thanks again, you get the September Good Guy award in my book! 73, John, W4AWM
RE: [AMRadio] UPDATE: Free for SASE: Simpson 260 Repair Manual Copies
Don I received the envelope today with the Simpson 260 info. - Thanks for sending it along. I looked it over and will place it in my "Simpson" file for future reference. You can never have too much equipment information! I did check out your "Want" list to see if I could help you but no luck. Thanks again, 73, Chuck Kembring WB3LGG Cochranville, Pa. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Merz Donald S Sent: Tuesday, September 21, 2004 3:07 PM To: 'Amradio (E-mail); 'Baswaplist' (E-mail); 'Glowbugs (E-mail) Subject: [AMRadio] UPDATE: Free for SASE: Simpson 260 Repair Manual Copies Quick update on this: I have about 20 SASE's sitting here. I just got the copies from the printer yesterday. What a snafu. In the first go-round, they tried to hand me back uncollated, unstapled pages. I looked at it and said "what am I supposed to do with that?" Then the rains came... But all is well. I am trying to peddle a few copies on eBay to make some money to buy the kids new shoes. They haven't had any new shoes since those ones we got at the bowling alley Your SASE copies will all go out on Friday and should be in your hands Monday, 9/27. Sorry for the delay. 73, Don Merz, N3RHT -Original Message- From: Merz Donald S Sent: Tuesday, September 07, 2004 12:47 PM To: 'Amradio (E-mail); 'Baswaplist' (E-mail); 'Glowbugs (E-mail) Subject: Free for SASE: Simpson 260 Repair Manual Copies Free For SASE: Well, maybe I am the last to come across this, but I recently found a repair manual for the Simpson 260 Series VOMs. This was published by Sears, of all people, in 1976. Here are the details: "Sears Simpson 260 Meter Repair Program Division 92 Source 260" dated May, 1976. This is about 20 8.5x11 pages with many pictures and schematics. This covers all tests and repairs EXCEPT switch replacement. Switch replacement is not covered (it refers you to Simpson for a factory repair). Models covered are Series 3, 4, 5, 5P, 6 and 6P. Specifics: Lengthy troubleshooting chart, Overload Relay Adjustment, Calibration of all ranges and theory of operation. Photos show parts placement (like a Sams does) and schematics for each model are provided. Anyway, if you want a copy, just send me an 8.5x11 envelope with four 37 cent stamps on it and your address. I will stuff the envelope and mail it back to you the same day. No need to reply to this e-mail. Don't send stamps or cash--just the SASE. Address below. With any luck, the 260 will be being used by techs long after we are gone... 73, Don Merz, N3RHT 47 Hazel Drive Pittsburgh, PA 15228 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.(A) __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] WTB SB-220
Again, It would be an S1 signal above a s9/30db level noise - a barely perceivable difference. You would have to go from 100 to ~ 6,400 watts to get an S3 signal above that noise level. bob...w2ami www.qrz.com/callsign/w2ami - Original Message - From: "George Pritchard" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Monday, September 27, 2004 9:38 AM Subject: RE: [AMRadio] WTB SB-220 > When the interference is also at 30 over S9(even if it's static crashes) a > 36 dB over signal using the 400 watts helps. First put up the best ant... > Then crank-it with juice!!! > George AB2KC > 1KW 4X1 lives > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of RJ Mattson > Sent: Monday, September 27, 2004 9:27 AM > To: Discussion of AM Radio > Subject: Re: [AMRadio] WTB SB-220 > > > No matter what the spin, 100 to 400 watts is only 1 s-unit > and barely perceptible at the receiver. > A 30db/s9 signal is from a good antenna not from > 100 or 400 watts. > bob...w2ami > www.qrz.com/callsign/w2ami > > > - Original Message - > From: "Jim Candela" <[EMAIL PROTECTED]> > To: > Sent: Sunday, September 26, 2004 10:47 PM > Subject: Re: [AMRadio] WTB SB-220 > > > > Hmmm, the boys on 3878 are running 1500 watts pep plus > > on USB, and there is a 100 watt AM'er calling CQ on > > 3880. How much of an antenna would the AM'er need to > > overcome the S/N ratio? I think Astabula Bill, W8VYZ > > says it all: > > > > http://www.amwindow.org/audio/mov/w8vyz.mov > > > > Ever hear Bill running 100 watts? When Bill and Less > > K6HQI (sk) were regulars on 14286 they had to run > > heavy iron to hold the frequency. A 100 watt rig was > > seldom heard whereas a 500 watt rig (that 6db again) > > was often armchair copy, and sometimes often drive the > > QRM away. > > > > Regards, > > Jim > > > > RJ Mattson <[EMAIL PROTECTED]> wrote: > > If you can't get out consistantly with a Viking II, > > you need an antenna - > > not an amp. > > bob...w2ami > > www.qrz.com/callsign/w2ami > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net >
Re: [AMRadio] Frequency Response
Exactly. However, if you intend to employ significant audio clipping as a means of peak control and loudness enhancement, the low freq response should ideally extend well below that to better accommodate the flat topped waveforms without substantial elevation of their peak level caused by the tilt. But again, this is only ham radio and your rule of thumb is a great one. If everyone's rig passed that test we'd be talking about something else. g Donald Chester wrote: > > >By 'tilt' I mean the observable tilting of the top and bottom of a > >square wave (or resulting modulated envelope) caused by low frequency > >roll off and non constant group delay through the transmitter in > >question. > > That's why the transmitter frequency response, including transformers, > should be essentially flat at least one octave above and one octave below > the actual range of frequencies you plan to transmit. > > For example, if you intended to limit your audio response to 150-4000~, the > audio chain should test flat from 75 to 8000~. > > Don k4kyv
RE: [AMRadio] WTB SB-220
When the interference is also at 30 over S9(even if it's static crashes) a 36 dB over signal using the 400 watts helps. First put up the best ant... Then crank-it with juice!!! George AB2KC 1KW 4X1 lives -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of RJ Mattson Sent: Monday, September 27, 2004 9:27 AM To: Discussion of AM Radio Subject: Re: [AMRadio] WTB SB-220 No matter what the spin, 100 to 400 watts is only 1 s-unit and barely perceptible at the receiver. A 30db/s9 signal is from a good antenna not from 100 or 400 watts. bob...w2ami www.qrz.com/callsign/w2ami - Original Message - From: "Jim Candela" <[EMAIL PROTECTED]> To: Sent: Sunday, September 26, 2004 10:47 PM Subject: Re: [AMRadio] WTB SB-220 > > Hmmm, the boys on 3878 are running 1500 watts pep plus > on USB, and there is a 100 watt AM'er calling CQ on > 3880. How much of an antenna would the AM'er need to > overcome the S/N ratio? I think Astabula Bill, W8VYZ > says it all: > > http://www.amwindow.org/audio/mov/w8vyz.mov > > Ever hear Bill running 100 watts? When Bill and Less > K6HQI (sk) were regulars on 14286 they had to run > heavy iron to hold the frequency. A 100 watt rig was > seldom heard whereas a 500 watt rig (that 6db again) > was often armchair copy, and sometimes often drive the > QRM away. > > Regards, > Jim > > RJ Mattson <[EMAIL PROTECTED]> wrote: > If you can't get out consistantly with a Viking II, > you need an antenna - > not an amp. > bob...w2ami > www.qrz.com/callsign/w2ami __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
Re: [AMRadio] WTB SB-220
No matter what the spin, 100 to 400 watts is only 1 s-unit and barely perceptible at the receiver. A 30db/s9 signal is from a good antenna not from 100 or 400 watts. bob...w2ami www.qrz.com/callsign/w2ami - Original Message - From: "Jim Candela" <[EMAIL PROTECTED]> To: Sent: Sunday, September 26, 2004 10:47 PM Subject: Re: [AMRadio] WTB SB-220 > > Hmmm, the boys on 3878 are running 1500 watts pep plus > on USB, and there is a 100 watt AM'er calling CQ on > 3880. How much of an antenna would the AM'er need to > overcome the S/N ratio? I think Astabula Bill, W8VYZ > says it all: > > http://www.amwindow.org/audio/mov/w8vyz.mov > > Ever hear Bill running 100 watts? When Bill and Less > K6HQI (sk) were regulars on 14286 they had to run > heavy iron to hold the frequency. A 100 watt rig was > seldom heard whereas a 500 watt rig (that 6db again) > was often armchair copy, and sometimes often drive the > QRM away. > > Regards, > Jim > > RJ Mattson <[EMAIL PROTECTED]> wrote: > If you can't get out consistantly with a Viking II, > you need an antenna - > not an amp. > bob...w2ami > www.qrz.com/callsign/w2ami
Re: [AMRadio] WTB SB-220
It probably was Bill's voice and audio that drove the QRM away. Pete, wa2cwa On Sun, 26 Sep 2004 19:47:10 -0700 (PDT) Jim Candela <[EMAIL PROTECTED]> writes: > Ever hear Bill running 100 watts? When Bill and Less > K6HQI (sk) were regulars on 14286 they had to run > heavy iron to hold the frequency. A 100 watt rig was > seldom heard whereas a 500 watt rig (that 6db again) > was often armchair copy, and sometimes often drive the > QRM away. > > Regards, > Jim Get your name as your email address. Includes spam protection, 1GB storage, no ads and more Only $1.99/ month - visit http://www.mysite.com/name today!
