Re: [AMRadio] ARRL bandwidth petition draws anti-AM'ers out of the woodwork.
have to agree W7RT need to check into a rest home for the warped. as for the ARRL what i do not understand is WHY we keep putting these fools back in office ? i keep my membership just so i can vote for the new guy each time. and stay in the dxcc program. other then that the ARRL is about useless anymore. 73 Tony wa4jqs since 1962
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
> Sharper asymmetrical clipping with sharp slope > transitions causes intermodulation and higher > order even harmonics Oops... not just even, but odd too, if positive and negative peaks are clipped. Bacon, WA3WDR
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
Hi Gary, Yes, a smooth one-sided curvature produces an even-order nonlinearity that generally produces even harmonic distortion with low intermodulation. Sharper asymmetrical clipping with sharp slope transitions causes intermodulation and higher order even harmonics, and symmetrical clipping produces odd harmonic distortion and intermodulation. My asymmetrical clipper clips positive and negative peaks, with moderately sharp slope discontinuity, although at different voltages positive and negative, so odd and even harmonics are produced. A square-law characteristic would produce some even-order harmonic distortion and some soft clipping of peaks in one direction. The closer the operating point is to zero on this curve, and the higher the signal amplitude, the more the one side gets squeezed. Most of the distortion would be second harmonic, which will cause sibilents and upper midrange sounds to cause some splatter, but sounds below 1.5 KHz will not cause splatter beyond 3 KHz from the carrier unless they go below zero on the square law curve (which is impossible, so they get cut off), or they reach overmodulation proportions. Maybe a variable-bias square law processor at low level, with a low level variable cutoff low-pass filter, would help. The diodes can remain at the modulator output to catch occasional errant peaks. I just thought about how capacitance after the diodes can cause diagonal clipping, a slew-rate limitation due to the changing impedance presented to the capacitance and the modulated stage. This would add to the distortion and splatter, because the diode action would not be what was expected, and it would be worse at higher frequecies. The capacitance itself would filter the higher frequency distortion products somewhat, but I think that the diagonal clipping would increase close-in splatter. - Original Message - From: "Gary Schafer" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, January 11, 2006 10:16 PM Subject: RE: [AMRadio] Negative Loading circuits - good, bad, or ? > Did you know that clipping an asymmetrical audio signal produces even order > harmonics where clipping symmetrical signals produces only odd order > products. > > 73 > Gary K4FMX > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Bob Bruhns > Sent: Wednesday, January 11, 2006 9:43 PM > To: Discussion of AM Radio > Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? > > Thanks, Larry, I'll be interested in that. > > I understand that one large AM network - Clear Channel, > I believe - is cutting their AM audio bandwidth to 5 > KHz to make distant AM reception better (less splash > from adjacent channels). > > I remember back in the late 60s, a little 250 watt > daytime station on 540 KHz in Islip, Long Island ran > some sort of clipping to sound louder. I don't know > about splatter, but it really didn't sound good that > way. It was pretty loud, though. > > But in amateur operation, some gentle curvature can > curb the peaks that would get sharply snipped off by > overmodulation, without a lot of splatter. Overall, it > would probably reduce the general splatter level > somewhat. Also it would be useful to have some kind of > diode and resistor to catch peaks that do overmodulate, > and keep them from making a voltage spike that could > blow the modulation transformer. But if the circuit is > being used to achieve high audio levels, then a low > pass filter ought to follow the diodes. And the > transient performance of the filter must be such that > overshoot is minimized, because overshoot would > overmodulate and splatter too. Generally a > non-overshoot filter gives a soft cutoff rather than a > sharp cutoff, unless it is complex and high order. > > I use low level asymmetrical clipping, and I can filter > that with a 3.5 KHz low-pass filter in crowded > conditions when I push the clipper hard. I > accidentally found that a side chain servo loop could > have its time constant aligned with the modulator, and > produce very good clipping control, so that's how I do > it. The clipper is really a limited amount of > extremely fast peak limiting compression, with a time > constant around a millisecond or so, riding on the > slower 0.2 second time constant of the peak limiter, > with a slower time constant coupled on a resistive > divider for some slow average compression action as > well. using a moderately complex RC network as a gain > control loop filter. Because of this time constant, > sibilents are treated with a more peak limiting action > so there is less intermodulation, and lower frequency > stuff is softly clipped. I shorten the time constant > and increase the audio drive to push this harder, > accepting some distortion for punch. When I push it > like that, I use the low-pass filter, which is just a > second-order Sallen-Key. I got a comment on how narrow > the signal was, and yet it soun
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
Hi Bacon, I understand your thinking on your clipper. As you and others stated the bottom line is spectral measurements to check for splatter. Trapizoids and "A" scopes just don't show the real results. As to the 5 kcs for Clear Channel, that is a requirement for IBOC or HD radio on AM. The digital data starts at +/- 5 kc from the carrier and extents outward for at least 15 kc, in other words the occupied BW is now 40 khz. On wideband radios you can hear the digital "hiss" thru the AM diode demod if the baseband passband is over 5 kcs. Tune to the 1st adj and you hear the hiss which sounds like an elevated noise floor and has been a real problem at night especially for the clear channel stations. That's why the FCC still has not authorized IBOC after sundown. tests at night over the last few years at WCKY (WSAI) resulted in Canada filing an objection with the US over IX so its basically stopped nighttime testing or regular use of IBOC. There are also issues with directional arrays with high Q (RSS to RMS). The array behaves so much differently on the 1st adjacent channels that IBOC either doesn't work or causes IX to stations located in the nulls. building a DA array on say 600 kcs with a 40 kcs pattern bandwidth is no easy feat. Larry . I understand that one large AM network - Clear Channel, I believe - is cutting their AM audio bandwidth to 5 KHz to make distant AM reception better (less splash from adjacent channels). I remember back in the late 60s, a little 250 watt daytime station on 540 KHz in Islip, Long Island ran some sort of clipping to sound louder. I don't know about splatter, but it really didn't sound good that way. It was pretty loud, though. But in amateur operation, some gentle curvature can curb the peaks that would get sharply snipped off by overmodulation, without a lot of splatter. Overall, it would probably reduce the general splatter level somewhat. Also it would be useful to have some kind of diode and resistor to catch peaks that do overmodulate, and keep them from making a voltage spike that could blow the modulation transformer. But if the circuit is being used to achieve high audio levels, then a low pass filter ought to follow the diodes. And the transient performance of the filter must be such that overshoot is minimized, because overshoot would overmodulate and splatter too. Generally a non-overshoot filter gives a soft cutoff rather than a sharp cutoff, unless it is complex and high order. I use low level asymmetrical clipping, and I can filter that with a 3.5 KHz low-pass filter in crowded conditions when I push the clipper hard. I accidentally found that a side chain servo loop could have its time constant aligned with the modulator, and produce very good clipping control, so that's how I do it. The clipper is really a limited amount of extremely fast peak limiting compression, with a time constant around a millisecond or so, riding on the slower 0.2 second time constant of the peak limiter, with a slower time constant coupled on a resistive divider for some slow average compression action as well. using a moderately complex RC network as a gain control loop filter. Because of this time constant, sibilents are treated with a more peak limiting action so there is less intermodulation, and lower frequency stuff is softly clipped. I shorten the time constant and increase the audio drive to push this harder, accepting some distortion for punch. When I push it like that, I use the low-pass filter, which is just a second-order Sallen-Key. I got a comment on how narrow the signal was, and yet it sounded clear because of upper midrange boost. The millisecond range time constant of the servo-clipper avoids a lot of high frequency harmonic generation before the audio hits the filter. Bacon, WA3WDR - Original Message - From: "Larry Will" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, January 11, 2006 7:07 PM Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? > Bacon, > > > I'll pull out a copy of the NRSC spec on the AM B'CST audio shelving > filter when I get a chance and pass along some details. > > > > Larry > > At 11:16 AM 1/11/2006, you wrote: > >Any distortion of the modulating waveform causes > >harmonic distortion and therefore splatter. The > >sharper a waveform discontinuity is, the more > >high-level harmonic energy it contains, and that > >harmonic energy becomes splatter on the air. This > >is why a low-pass filter is used in speech > >clipping systems. But the sharp clipping caused > >by overmodulation can not be filtered at the audio > >level. > > > >The extreme sharpness of clipping resulting from > >overmodulation is the reason that overmodulation > >causes so much splatter. The idea of the diode > >loading system is to produce a softer clipping > >that produces much less splatter than raw > >overmodulation. Additional diodes and resistors > >are often add
RE: [AMRadio] Negative Loading circuits - good, bad, or ?
Did you know that clipping an asymmetrical audio signal produces even order harmonics where clipping symmetrical signals produces only odd order products. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bob Bruhns Sent: Wednesday, January 11, 2006 9:43 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? Thanks, Larry, I'll be interested in that. I understand that one large AM network - Clear Channel, I believe - is cutting their AM audio bandwidth to 5 KHz to make distant AM reception better (less splash from adjacent channels). I remember back in the late 60s, a little 250 watt daytime station on 540 KHz in Islip, Long Island ran some sort of clipping to sound louder. I don't know about splatter, but it really didn't sound good that way. It was pretty loud, though. But in amateur operation, some gentle curvature can curb the peaks that would get sharply snipped off by overmodulation, without a lot of splatter. Overall, it would probably reduce the general splatter level somewhat. Also it would be useful to have some kind of diode and resistor to catch peaks that do overmodulate, and keep them from making a voltage spike that could blow the modulation transformer. But if the circuit is being used to achieve high audio levels, then a low pass filter ought to follow the diodes. And the transient performance of the filter must be such that overshoot is minimized, because overshoot would overmodulate and splatter too. Generally a non-overshoot filter gives a soft cutoff rather than a sharp cutoff, unless it is complex and high order. I use low level asymmetrical clipping, and I can filter that with a 3.5 KHz low-pass filter in crowded conditions when I push the clipper hard. I accidentally found that a side chain servo loop could have its time constant aligned with the modulator, and produce very good clipping control, so that's how I do it. The clipper is really a limited amount of extremely fast peak limiting compression, with a time constant around a millisecond or so, riding on the slower 0.2 second time constant of the peak limiter, with a slower time constant coupled on a resistive divider for some slow average compression action as well. using a moderately complex RC network as a gain control loop filter. Because of this time constant, sibilents are treated with a more peak limiting action so there is less intermodulation, and lower frequency stuff is softly clipped. I shorten the time constant and increase the audio drive to push this harder, accepting some distortion for punch. When I push it like that, I use the low-pass filter, which is just a second-order Sallen-Key. I got a comment on how narrow the signal was, and yet it sounded clear because of upper midrange boost. The millisecond range time constant of the servo-clipper avoids a lot of high frequency harmonic generation before the audio hits the filter. Bacon, WA3WDR - Original Message - From: "Larry Will" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, January 11, 2006 7:07 PM Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? > Bacon, > > > I'll pull out a copy of the NRSC spec on the AM B'CST audio shelving > filter when I get a chance and pass along some details. > > > > Larry > > At 11:16 AM 1/11/2006, you wrote: > >Any distortion of the modulating waveform causes > >harmonic distortion and therefore splatter. The > >sharper a waveform discontinuity is, the more > >high-level harmonic energy it contains, and that > >harmonic energy becomes splatter on the air. This > >is why a low-pass filter is used in speech > >clipping systems. But the sharp clipping caused > >by overmodulation can not be filtered at the audio > >level. > > > >The extreme sharpness of clipping resulting from > >overmodulation is the reason that overmodulation > >causes so much splatter. The idea of the diode > >loading system is to produce a softer clipping > >that produces much less splatter than raw > >overmodulation. Additional diodes and resistors > >are often added to provide protective loading for > >the modulator on negative peaks that would have > >been unloaded in simple diode systems or with no > >diodes at all. This protective loading reduces > >voltage spikes that can destroy the modulation > >transformer. > > > >Some distortion is still produced with the diode > >loading system, and therefore some splatter will > >result. But unless there is some other problem, > >the splatter is much less severe than raw > >overmodulation, and the high frequency products > >caused by this action can be filtered at the audio > >level. You can add a high level splatter filter, > >although that will limit your high frequency > >response. You can have a few filters or a few > >filter settings, like 10 KHz for clear conditions, > >6 KHz for intermediate conditions, and 3.5 KHz for > >crowded con
[AMRadio] FS: GalaxyV Crystal Calibrator
I have for sale a Galaxy 100 KHz crystal calibrator as used in the Galaxy III, Galaxy V, Galaxy V Mk 3, etc. Consists of a Sylvania 12ED5 tube, a NEL 100 KHz crystal, and misc parts all mounted on a small box on an octal plug. Plugs right into the chassis socket of the aforementioned transceivers. It's in good shape and should work OK but obviously will need "calibrating" and, in any case, is untested. Price is $45 including USPS Priority Mail shipping. The G V it came out of is being parted out, so if there are any G-series parts you need please let me know and we'll see what we can work out. The 6HF5s are gone. regards, Mahlon - K4OQ
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
Thanks, Larry, I'll be interested in that. I understand that one large AM network - Clear Channel, I believe - is cutting their AM audio bandwidth to 5 KHz to make distant AM reception better (less splash from adjacent channels). I remember back in the late 60s, a little 250 watt daytime station on 540 KHz in Islip, Long Island ran some sort of clipping to sound louder. I don't know about splatter, but it really didn't sound good that way. It was pretty loud, though. But in amateur operation, some gentle curvature can curb the peaks that would get sharply snipped off by overmodulation, without a lot of splatter. Overall, it would probably reduce the general splatter level somewhat. Also it would be useful to have some kind of diode and resistor to catch peaks that do overmodulate, and keep them from making a voltage spike that could blow the modulation transformer. But if the circuit is being used to achieve high audio levels, then a low pass filter ought to follow the diodes. And the transient performance of the filter must be such that overshoot is minimized, because overshoot would overmodulate and splatter too. Generally a non-overshoot filter gives a soft cutoff rather than a sharp cutoff, unless it is complex and high order. I use low level asymmetrical clipping, and I can filter that with a 3.5 KHz low-pass filter in crowded conditions when I push the clipper hard. I accidentally found that a side chain servo loop could have its time constant aligned with the modulator, and produce very good clipping control, so that's how I do it. The clipper is really a limited amount of extremely fast peak limiting compression, with a time constant around a millisecond or so, riding on the slower 0.2 second time constant of the peak limiter, with a slower time constant coupled on a resistive divider for some slow average compression action as well. using a moderately complex RC network as a gain control loop filter. Because of this time constant, sibilents are treated with a more peak limiting action so there is less intermodulation, and lower frequency stuff is softly clipped. I shorten the time constant and increase the audio drive to push this harder, accepting some distortion for punch. When I push it like that, I use the low-pass filter, which is just a second-order Sallen-Key. I got a comment on how narrow the signal was, and yet it sounded clear because of upper midrange boost. The millisecond range time constant of the servo-clipper avoids a lot of high frequency harmonic generation before the audio hits the filter. Bacon, WA3WDR - Original Message - From: "Larry Will" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" Sent: Wednesday, January 11, 2006 7:07 PM Subject: Re: [AMRadio] Negative Loading circuits - good, bad, or ? > Bacon, > > > I'll pull out a copy of the NRSC spec on the AM B'CST audio shelving > filter when I get a chance and pass along some details. > > > > Larry > > At 11:16 AM 1/11/2006, you wrote: > >Any distortion of the modulating waveform causes > >harmonic distortion and therefore splatter. The > >sharper a waveform discontinuity is, the more > >high-level harmonic energy it contains, and that > >harmonic energy becomes splatter on the air. This > >is why a low-pass filter is used in speech > >clipping systems. But the sharp clipping caused > >by overmodulation can not be filtered at the audio > >level. > > > >The extreme sharpness of clipping resulting from > >overmodulation is the reason that overmodulation > >causes so much splatter. The idea of the diode > >loading system is to produce a softer clipping > >that produces much less splatter than raw > >overmodulation. Additional diodes and resistors > >are often added to provide protective loading for > >the modulator on negative peaks that would have > >been unloaded in simple diode systems or with no > >diodes at all. This protective loading reduces > >voltage spikes that can destroy the modulation > >transformer. > > > >Some distortion is still produced with the diode > >loading system, and therefore some splatter will > >result. But unless there is some other problem, > >the splatter is much less severe than raw > >overmodulation, and the high frequency products > >caused by this action can be filtered at the audio > >level. You can add a high level splatter filter, > >although that will limit your high frequency > >response. You can have a few filters or a few > >filter settings, like 10 KHz for clear conditions, > >6 KHz for intermediate conditions, and 3.5 KHz for > >crowded conditions. > > > >Some technical problems can cause extra splatter. > >If the modulator is marginally stable, it is > >possible that the dynamic change in loading > >resulting from the diode action can cause > >triggered parasitics at specific points on the > >audio waveform. This can result significant > >splatter, and it might have a distinctive resonant > >sound, which you would hear as resonances or > >co
RE: [AMRadio] I'm not an antenna expert
I would be curious as to what the fundamental resonance frequency is and what the high impedance and low impedance actually is at the feed point of the antenna without balanced line. If the feed point at the transmitter end of the line is too low, add or subtract some feed line. You can also add and subtract line from the opposite side of the antenna. You mentioned earlier about opening up the opposite end. This could be a good experiment. And also consider capacitance or inductance added where you make the cut or adding transmission line at that point with and open or closed end going nowhere except to a stick to hold it up off of the ground. It doesn't take a mathematical antenna expert to experiment You only need some extra wire. Fun Stuff John, WA5BXO -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Lawson Sent: Wednesday, January 11, 2006 10:44 AM To: amradio@mailman.qth.net Cc: [EMAIL PROTECTED] Subject: [AMRadio] I'm not an antenna expert I don't even play one on TeeVee... So, in advance of a lot of EZNec work (and I don't have the experience with that program to derive much 'good' out of it right now) - I'd like to ask what may seem to be a rather obvious HF antenna question. Due to the usual reasons - my HF antenna is a loop suspended from my backyard fence - approx 430' total, closed loop, 5' off the ground, fed by 450 ohm ladder line back into the shack, using an Ameritron ATR-15 tuner to match the system to my Valiant. The tuner and transmitter are bonded to a very heavy ground system via an 8' stake less than 3' from the gear. There is no ground system under the antenna, other than that which Nature provided - and with the current winter conditions, the ground is rather wet and conductive. This antenna system exhibits the following SWR: 160M - 1.3:1 80M - 1.1:1 40M - +3:1 20M - 2:1 15M - +3:1 10M - +3:1 The tuner capacitors end up being all-the-way-meshed on the 'misbehaving' bands - not so on 160, 80, and 20. So I'll see Y'all on 3880 and just fergit the rest. ;} No but seriously folks: obviously the feedpoint resistance is outside the tuner's ability to cope with it at various frequencies. I'm thinking the first unscientific experiment might be to go to the opposite side of the loop from the feedpoint and cut it into a big horizontal bent dipole - mainly because that will take about 45 seconds to accomplish - one of the benefits of having one's entire antenna at ahoulder-height. But I'd like to get some other opinions - I know there's an electrical Pattern here from the info - and I have some other ideas based on that. And no, I can't put up a "real antenna" so I'm pretty much comiited to making this one work as well as I can. Until I move the QTH to somewhere with a few acres and room for Lots of Wire. Cheers John KB6SCO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
Re: [AMRadio] ARRL bandwidth petition draws anti-AM'ers out of the woodwork.
This guy is VERY short sighted if he thinks AM is going to be a big problem. He hasn't heard ANYTHING until he has heard the band-polluting garbage waiting in the wings from the digital modes that ARRL wants to be used from DC to Daylight! The pests that push Winlink/Pactor on amateur radio have demonstrated their careless, hazardous operation for a few years now. I will no longer to pay to help ARRL destroy amateur radio with their foolish, ill-considered bandwidth proposals and the dishonest claim that they have adequately consulted radio amateurs before making this proposal. It has been roundly rejected by the vast majority of hams in discussions in a variety of forums. Yet they blindly press on! I don't place much greater hope in FCC any more. But we should all let them know how disgusted we are with the proposal. Your opinion may vary. My mind is made up. Yes, the behavior of the anti-AMers is absurd too! They need to get something other than air between their ears! On Wed Jan 11 14:02:11 PST 2006, Donald Chester <[EMAIL PROTECTED]> wrote: > Proceeding: RM-11306 Type Code: CO > Date Received/Adopted: 01/10/06Date Released/Denied: > Document Type: COMMENTTotal Pages: 1 > File Number/Community:DA/FCC Number: > Filed on Behalf of: Richard L. Tannehill > Filed By: > Attorney/Author Name:Document Date: > Complete Mailing Address: > 5410 W. diana Ave. > Glendale, AZ 85302 -4870 > Brief Comment > > I agree with the ARRL petition for regulation by bandwidth, and > support it, with one major exception. > The League claims that their plan does not favor one mode over > another. Not true. It favors AM-DSB > operators. It would allow for 9 KHz AM modulation, in bands which > otherwise are limited to 3.5 KHz. > These include the lower HF bands, which are quite crowded at > times. The solution is simply to > restrict AM-DSB to above 28.5 MHz. (10 meters & above) Amateurs > and the league have been > upset in the past over wide-SSB modulation, meant to improve > audio quality. AM is no different from > this. It is an old modulation that adds nothing to advancing the > technological art, and should be > confined to bands where there is ample spectrum available. > > Richard L. Tannehill P.E. - W7RT > > ARRL Life Member > (45-years amateur licensed) > > > ___ > > This message was typed using the DVORAK keyboard layout. Try it > - you'll like it. > http://www.mwbrooks.com/dvorak/ > http://gigliwood.com/abcd/ > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > >
Re: [AMRadio] I'm not an antenna expert
In a message dated 1/11/06 10:07:04 AM, [EMAIL PROTECTED] writes (in part): > But the question I still have is - what do you think of modifying the > Loop into a dipole - I'm going to try it anyway, just for the halibut - > John Good idea. Antennas experiments are fun! > but I have also thought of replacing the ladder-line with coax and a balun > at the feed point - dunno yet. > Quick and dirty, just try grounding one side of your ladder-line at the input end and feeding the other side off the single ended output of your ATU and see what happens. SWR figures might be better (but could also be worse). Line will probably radiate too if you do this but so what? I ran delta loops this way for several years with good results. Dennis D. W7QHO Glendale, CA
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
Bacon, I'll pull out a copy of the NRSC spec on the AM B'CST audio shelving filter when I get a chance and pass along some details. Larry At 11:16 AM 1/11/2006, you wrote: Any distortion of the modulating waveform causes harmonic distortion and therefore splatter. The sharper a waveform discontinuity is, the more high-level harmonic energy it contains, and that harmonic energy becomes splatter on the air. This is why a low-pass filter is used in speech clipping systems. But the sharp clipping caused by overmodulation can not be filtered at the audio level. The extreme sharpness of clipping resulting from overmodulation is the reason that overmodulation causes so much splatter. The idea of the diode loading system is to produce a softer clipping that produces much less splatter than raw overmodulation. Additional diodes and resistors are often added to provide protective loading for the modulator on negative peaks that would have been unloaded in simple diode systems or with no diodes at all. This protective loading reduces voltage spikes that can destroy the modulation transformer. Some distortion is still produced with the diode loading system, and therefore some splatter will result. But unless there is some other problem, the splatter is much less severe than raw overmodulation, and the high frequency products caused by this action can be filtered at the audio level. You can add a high level splatter filter, although that will limit your high frequency response. You can have a few filters or a few filter settings, like 10 KHz for clear conditions, 6 KHz for intermediate conditions, and 3.5 KHz for crowded conditions. Some technical problems can cause extra splatter. If the modulator is marginally stable, it is possible that the dynamic change in loading resulting from the diode action can cause triggered parasitics at specific points on the audio waveform. This can result significant splatter, and it might have a distinctive resonant sound, which you would hear as resonances or concentrated spectral points in the splatter on a sideband receiver tuned some distance from the carrier. Negative feedback can cause problems if gain and phase margins are exceeded, which often happens at frequency extremes, and this can result in triggered parasitics even if diode loading is not used. If there is a modulator stability issue at high audio frequencies, it can cause splatter. Excessive modulation of the screen grid of a plate-modulated tetrode or pentode modulated stage can cause sharp distortion too. You can see a kink at about 85% negative when this occurs, and that means you have a waveform discontinuity that can cause significant splatter that can not be filtered at the audio level. The typical circuit of the screen dropping resistor going to modulated B+ should be modified for better linearity. A good job can be done by simply connecting the top of the screen dropping resistor to unmodulated B+ and allowing the screen grid to self-modulate, but the best arrangement uses a resistive divider supplying the screen from modulated B+ and unmodulated B+. Screen-choke systems are self-modulating and do not exhibit that distortion. Class C Optimization for Ultra Low Distortion http://www.amfone.net/AMPX/71.htm The self-modulated screen grid http://www.amfone.net/AMPX/98.htm Remember also that your receiver can be listening to a really strong signal while you are testing in the shack. The splatter that you hear on that strong signal in the shack may be mild on a normal signal on the air, and the receiver can be adding to the problem is it is overloading. Bacon, WA3WDR - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, January 11, 2006 8:22 AM Subject: RE: [AMRadio] Negative Loading circuits - good, bad, or ? > Dennis, > > > > I've had good results with the "three diode" circuit too. Earliest > > reference to the scheme I can find is in QST, October 1956 > > using 866 rectifiers. > > Covered again in ER #3, July 1989, this time with solid state > > diodes. > > I did not say I had good luck with the circuit, although it looks > like it works on the scope, and on the mod monitor, it results > in a very wide signal. Not much point in running it if you go > 50Kc wide... > > > > > > Don't believe the type of diodes used would have any > > significant effect on > > this. Splatter is generated in the PA tank circuit when > > plate voltage is > > suddenly cut off on the audio negative half cycle. Same > > splatter would be > > produced if the PA was being fed straight off the secondary > > of the mod transformer. > > The 3 diode circuit is supposed to prevent the plate voltage > from going to zero. I use variacs on the power supply so I can set > the point at which the circuit starts working, and no matter if I > set it to 95, 90, or 85% I get splatter if the audio would exceed > 100% negative, so the circui
RE: [AMRadio] ARRL bandwidth petition draws anti-AM'ers out of thewoodwork.
Thanks for the input, we need to save AM ON ALL HF BANDS BRAD KB7FQR -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of W5OMR/Geoff Sent: Wednesday, January 11, 2006 2:18 PM To: Discussion of AM Radio Subject: Re: [AMRadio] ARRL bandwidth petition draws anti-AM'ers out of thewoodwork. Donald Chester wrote: > Proceeding: RM-11306 Type Code: CO > Date Received/Adopted: 01/10/06Date Released/Denied: > Document Type: COMMENTTotal Pages: 1 > File Number/Community:DA/FCC Number: > Filed on Behalf of: Richard L. Tannehill > Filed By: > Attorney/Author Name:Document Date: > Complete Mailing Address: > 5410 W. diana Ave. > Glendale, AZ 85302 -4870 > Brief Comment > > I agree with the ARRL petition for regulation by bandwidth, and > support it, with one major exception. > The League claims that their plan does not favor one mode over > another. Not true. It favors AM-DSB > operators. It would allow for 9 KHz AM modulation, in bands which > otherwise are limited to 3.5 KHz. > These include the lower HF bands, which are quite crowded at times. > The solution is simply to > restrict AM-DSB to above 28.5 MHz. (10 meters & above) Amateurs and > the league have been > upset in the past over wide-SSB modulation, meant to improve audio > quality. AM is no different from > this. It is an old modulation that adds nothing to advancing the > technological art, and should be > confined to bands where there is ample spectrum available. > > Richard L. Tannehill P.E. - W7RT > > ARRL Life Member > (45-years amateur licensed) Who does he think invented Class D/E? Engineers that were -not- hams? I'm not sure what the percentage is, but I think it's actually fairly high, that the number station engineers (for lack of a better term, in today's times) who do work in radio/broadcasting, are also ham radio operators. In 1996, I was introduced to a Class E 40m amplifier, that looks no bigger (if not smaller) than the two transistor, solid-state amp I use for mobile operation, and the Class E amp used 1 device. 12v @ 50amps, I think, for something like 500w CW. In the late 1990's, John/WA5BXO was using solid-state circuitry to directly drive the grids of a Class B modulator. Now, that was some radical thinking, and the old timers let him know about it... that is, until they heard it. They were convinced. For someone to say that there's no advancement in the 'old modulation', with "nothing to advancing the technological art", my reply is "go back and do your homework, before such a blanket statement is made. 45 years as a ham... probably got a ticket when he around 20'ish.. I'm reminded of a new-classic, favorite, one-liner... "Why is it that the narrowest of minds, are found in the fattest of heads?" --- 73 = Best Regards, -Geoff/W5OMR __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
Re: [AMRadio] ARRL bandwidth petition draws anti-AM'ers out of the woodwork.
Donald Chester wrote: Proceeding: RM-11306 Type Code: CO Date Received/Adopted: 01/10/06Date Released/Denied: Document Type: COMMENTTotal Pages: 1 File Number/Community:DA/FCC Number: Filed on Behalf of: Richard L. Tannehill Filed By: Attorney/Author Name:Document Date: Complete Mailing Address: 5410 W. diana Ave. Glendale, AZ 85302 -4870 Brief Comment I agree with the ARRL petition for regulation by bandwidth, and support it, with one major exception. The League claims that their plan does not favor one mode over another. Not true. It favors AM-DSB operators. It would allow for 9 KHz AM modulation, in bands which otherwise are limited to 3.5 KHz. These include the lower HF bands, which are quite crowded at times. The solution is simply to restrict AM-DSB to above 28.5 MHz. (10 meters & above) Amateurs and the league have been upset in the past over wide-SSB modulation, meant to improve audio quality. AM is no different from this. It is an old modulation that adds nothing to advancing the technological art, and should be confined to bands where there is ample spectrum available. Richard L. Tannehill P.E. - W7RT ARRL Life Member (45-years amateur licensed) Who does he think invented Class D/E? Engineers that were -not- hams? I'm not sure what the percentage is, but I think it's actually fairly high, that the number station engineers (for lack of a better term, in today's times) who do work in radio/broadcasting, are also ham radio operators. In 1996, I was introduced to a Class E 40m amplifier, that looks no bigger (if not smaller) than the two transistor, solid-state amp I use for mobile operation, and the Class E amp used 1 device. 12v @ 50amps, I think, for something like 500w CW. In the late 1990's, John/WA5BXO was using solid-state circuitry to directly drive the grids of a Class B modulator. Now, that was some radical thinking, and the old timers let him know about it... that is, until they heard it. They were convinced. For someone to say that there's no advancement in the 'old modulation', with "nothing to advancing the technological art", my reply is "go back and do your homework, before such a blanket statement is made. 45 years as a ham... probably got a ticket when he around 20'ish.. I'm reminded of a new-classic, favorite, one-liner... "Why is it that the narrowest of minds, are found in the fattest of heads?" --- 73 = Best Regards, -Geoff/W5OMR
[AMRadio] ARRL bandwidth petition draws anti-AM'ers out of the woodwork.
Proceeding: RM-11306 Type Code: CO Date Received/Adopted: 01/10/06Date Released/Denied: Document Type: COMMENTTotal Pages: 1 File Number/Community:DA/FCC Number: Filed on Behalf of: Richard L. Tannehill Filed By: Attorney/Author Name:Document Date: Complete Mailing Address: 5410 W. diana Ave. Glendale, AZ 85302 -4870 Brief Comment I agree with the ARRL petition for regulation by bandwidth, and support it, with one major exception. The League claims that their plan does not favor one mode over another. Not true. It favors AM-DSB operators. It would allow for 9 KHz AM modulation, in bands which otherwise are limited to 3.5 KHz. These include the lower HF bands, which are quite crowded at times. The solution is simply to restrict AM-DSB to above 28.5 MHz. (10 meters & above) Amateurs and the league have been upset in the past over wide-SSB modulation, meant to improve audio quality. AM is no different from this. It is an old modulation that adds nothing to advancing the technological art, and should be confined to bands where there is ample spectrum available. Richard L. Tannehill P.E. - W7RT ARRL Life Member (45-years amateur licensed) ___ This message was typed using the DVORAK keyboard layout. Try it - you'll like it. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
Bacon, As usual your explanations are correct. Broadcast AM stations gave up on high level negative clipping long ago because of splatter out 50 kcs or more even before the almost universal switch to Class D systems. The best high level plate modulated system while pretty good as in the BTA-1R RCA still can't hold a candle to the low IM and harmonic distortion and carrier phase modulation of modern Class D transmitters. They are real good to 110% and quite acceptable to 125% + mod even with the VERY tight rules on splatter in the AM broadcast service. The audio band input filters ahead of all transmitter audio are typically 9-11 poles starting at around 8 khz rolling down to about 30 dB at 9 kcs. Larry W3LW At 11:16 AM 1/11/2006, you wrote: Any distortion of the modulating waveform causes harmonic distortion and therefore splatter. The sharper a waveform discontinuity is, the more high-level harmonic energy it contains, and that harmonic energy becomes splatter on the air. This is why a low-pass filter is used in speech clipping systems. But the sharp clipping caused by overmodulation can not be filtered at the audio level. The extreme sharpness of clipping resulting from overmodulation is the reason that overmodulation causes so much splatter. The idea of the diode loading system is to produce a softer clipping that produces much less splatter than raw overmodulation. Additional diodes and resistors are often added to provide protective loading for the modulator on negative peaks that would have been unloaded in simple diode systems or with no diodes at all. This protective loading reduces voltage spikes that can destroy the modulation transformer. Some distortion is still produced with the diode loading system, and therefore some splatter will result. But unless there is some other problem, the splatter is much less severe than raw overmodulation, and the high frequency products caused by this action can be filtered at the audio level. You can add a high level splatter filter, although that will limit your high frequency response. You can have a few filters or a few filter settings, like 10 KHz for clear conditions, 6 KHz for intermediate conditions, and 3.5 KHz for crowded conditions. Some technical problems can cause extra splatter. If the modulator is marginally stable, it is possible that the dynamic change in loading resulting from the diode action can cause triggered parasitics at specific points on the audio waveform. This can result significant splatter, and it might have a distinctive resonant sound, which you would hear as resonances or concentrated spectral points in the splatter on a sideband receiver tuned some distance from the carrier. Negative feedback can cause problems if gain and phase margins are exceeded, which often happens at frequency extremes, and this can result in triggered parasitics even if diode loading is not used. If there is a modulator stability issue at high audio frequencies, it can cause splatter. Excessive modulation of the screen grid of a plate-modulated tetrode or pentode modulated stage can cause sharp distortion too. You can see a kink at about 85% negative when this occurs, and that means you have a waveform discontinuity that can cause significant splatter that can not be filtered at the audio level. The typical circuit of the screen dropping resistor going to modulated B+ should be modified for better linearity. A good job can be done by simply connecting the top of the screen dropping resistor to unmodulated B+ and allowing the screen grid to self-modulate, but the best arrangement uses a resistive divider supplying the screen from modulated B+ and unmodulated B+. Screen-choke systems are self-modulating and do not exhibit that distortion. Class C Optimization for Ultra Low Distortion http://www.amfone.net/AMPX/71.htm The self-modulated screen grid http://www.amfone.net/AMPX/98.htm Remember also that your receiver can be listening to a really strong signal while you are testing in the shack. The splatter that you hear on that strong signal in the shack may be mild on a normal signal on the air, and the receiver can be adding to the problem is it is overloading. Bacon, WA3WDR - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, January 11, 2006 8:22 AM Subject: RE: [AMRadio] Negative Loading circuits - good, bad, or ? > Dennis, > > > > I've had good results with the "three diode" circuit too. Earliest > > reference to the scheme I can find is in QST, October 1956 > > using 866 rectifiers. > > Covered again in ER #3, July 1989, this time with solid state > > diodes. > > I did not say I had good luck with the circuit, although it looks > like it works on the scope, and on the mod monitor, it results > in a very wide signal. Not much point in running it if you go > 50Kc wide... > > > > > > Don't believe the type of diodes used would have an
RE: [AMRadio] Negative Loading circuits - good, bad, or ?
I use the one mentioned earlier, it used tubes and was in an old QST. The variac is on the power supply that provides the voltage to the RF deck when the carrier is cut off. This circuit uses 3 diodes, a load resistor, and the power supply. Some circuits use a voltage dropping resistor instead of a power supply, but there is no easy way to adjust the point at which you want the loading to start at. You can also use a panel meter on the power supply (current) to show how hard you are into the loading... Brett N2DTS > > Brett, > > What circuit are you using? The ones I referenced don't > call for variacs or > auxiliary power supplies. > > Dennis D. W7QHO > Glendale, CA
Re: [AMRadio] I'm not an antenna expert
On Wed, 11 Jan 2006, W5OMR/Geoff wrote: There's no law that says you have to run full power output, to tune SWR on an impedance matching device... Ooops - I should have clarified that - I do not run full power to play with the tuning - actually I run the minimum I can get the Valiant to put out, by decreasing the coupling to as little as possible, and tuning the transmitter up at that output - usually 20-30 watts. THEN I load 'er up to full blast. I'd just as soon use a solid state rig, that has SWR protection in it... slowly adjust the impedance matching device, until you get full output of the ricebox, and minimum standing wave ratio. Then, DON'T TOUCH IT! Just switch rigs, and tune the transmitter to that setting. it's resonant. Except that I don't seem to be able to achieve much in the way of 'resonance' on the affected bands - the tuner settings get very 'squirrely' and of course the transmitter tuning goes wildly off as those adjustments are made - as opposed to the bands where the antenna/feedline is "happy" - then it's stable, and an easy matter to arrive at a logical setting for the system. One of the drawbacks to the pseudo-NVIS arrangment is that it is like a 'searchlight' directed straight up to a cloud-deck in the sky - the light is diffused back down, as opposed to a more directional distribution of radiated flux - so I really need to have an electrically efficient antenna system as I can, give my particular constraints. But the question I still have is - what do you think of modifying the Loop into a dipole - I'm going to try it anyway, just for the halibut - but I have also thought of replacing the ladder-line with coax and a balun at the feed point - dunno yet. Cheers John KB6SCO
Re: [AMRadio] I'm not an antenna expert
In a message dated 1/11/06 9:18:50 AM, [EMAIL PROTECTED] writes: > I'm afraid of what I'm doing to the > tuner/transmitter at that amount of reflected power. > John, What kind of a tuner are you using and where are you measuring the SWR? Dennis D. W7QHO Glendale, CA
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
In a message dated 1/11/06 5:26:15 AM, [EMAIL PROTECTED] writes: > The 3 diode circuit is supposed to prevent the plate voltage > from going to zero. I use variacs on the power supply so I can set > the point at which the circuit starts working, and no matter if I > set it to 95, 90, or 85% I get splatter if the audio would exceed > 100% negative, so the circuit seems to do no good. > Brett, What circuit are you using? The ones I referenced don't call for variacs or auxiliary power supplies. Dennis D. W7QHO Glendale, CA
Re: [AMRadio] I'm not an antenna expert
John Lawson wrote: On Wed, 11 Jan 2006, Brian Carling wrote: Should work great for close in work, out to about 200-500 miles. Well, except for the bands where the system SWR is over 3:1 - then it don't work at all ;} and I'm afraid of what I'm doing to the tuner/transmitter at that amount of reflected power. There's no law that says you have to run full power output, to tune SWR on an impedance matching device... I'd just as soon use a solid state rig, that has SWR protection in it... slowly adjust the impedance matching device, until you get full output of the ricebox, and minimum standing wave ratio. Then, DON'T TOUCH IT! Just switch rigs, and tune the transmitter to that setting. it's resonant. otherwise, you might be loading up on some harmonic -- 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] I'm not an antenna expert
On Wed, 11 Jan 2006, Brian Carling wrote: Should work great for close in work, out to about 200-500 miles. Well, except for the bands where the system SWR is over 3:1 - then it don't work at all ;} and I'm afraid of what I'm doing to the tuner/transmitter at that amount of reflected power. Cheers John KB6SCO
Re: [AMRadio] I'm not an antenna expert
Should work great for close in work, out to about 200-500 miles. On 11 Jan 2006 at 11:43, John Lawson wrote: > > I don't even play one on TeeVee... > >So, in advance of a lot of EZNec work (and I don't have the experience > with that program to derive much 'good' out of it right now) - I'd like > to ask what may seem to be a rather obvious HF antenna question. > >Due to the usual reasons - my HF antenna is a loop suspended from my > backyard fence - approx 430' total, closed loop, 5' off the ground, fed by > 450 ohm ladder line back into the shack, using an Ameritron ATR-15 tuner > to match the system to my Valiant. The tuner and transmitter are bonded > to a very heavy ground system via an 8' stake less than 3' from the gear. > There is no ground system under the antenna, other than that which Nature > provided - and with the current winter conditions, the ground is rather > wet and conductive. > >This antenna system exhibits the following SWR: > > 160M - 1.3:1 > 80M - 1.1:1 > 40M - +3:1 > 20M - 2:1 > 15M - +3:1 > 10M - +3:1 > > The tuner capacitors end up being all-the-way-meshed on the > 'misbehaving' bands - not so on 160, 80, and 20. > > >So I'll see Y'all on 3880 and just fergit the rest. ;} > > >No but seriously folks: obviously the feedpoint resistance is outside > the tuner's ability to cope with it at various frequencies. > >I'm thinking the first unscientific experiment might be to go to the > opposite side of the loop from the feedpoint and cut it into a big > horizontal bent dipole - mainly because that will take about 45 seconds to > accomplish - one of the benefits of having one's entire antenna at > ahoulder-height. > >But I'd like to get some other opinions - I know there's an electrical > Pattern here from the info - and I have some other ideas based on that. > >And no, I can't put up a "real antenna" so I'm pretty much comiited to > making this one work as well as I can. Until I move the QTH to somewhere > with a few acres and room for Lots of Wire. > > >Cheers > > John KB6SCO > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
[AMRadio] RE: Homebrew PW Modulator
The homebrew modulator has been sold. On 11 Jan 2006 at 9:26, Brian Carling wrote: > FOR SALE: > > Neat little homebrew 15-25W modulator with pair of > push-pull 6AQ5s. Has gain control and RCA input. > No power supply. Excellent job - I did not build it, but whoever > did was an expert. Has 12AX7 preamp etc. All in nice shape. > > Available for $35.00 plus shipping
[AMRadio] I'm not an antenna expert
I don't even play one on TeeVee... So, in advance of a lot of EZNec work (and I don't have the experience with that program to derive much 'good' out of it right now) - I'd like to ask what may seem to be a rather obvious HF antenna question. Due to the usual reasons - my HF antenna is a loop suspended from my backyard fence - approx 430' total, closed loop, 5' off the ground, fed by 450 ohm ladder line back into the shack, using an Ameritron ATR-15 tuner to match the system to my Valiant. The tuner and transmitter are bonded to a very heavy ground system via an 8' stake less than 3' from the gear. There is no ground system under the antenna, other than that which Nature provided - and with the current winter conditions, the ground is rather wet and conductive. This antenna system exhibits the following SWR: 160M - 1.3:1 80M - 1.1:1 40M - +3:1 20M - 2:1 15M - +3:1 10M - +3:1 The tuner capacitors end up being all-the-way-meshed on the 'misbehaving' bands - not so on 160, 80, and 20. So I'll see Y'all on 3880 and just fergit the rest. ;} No but seriously folks: obviously the feedpoint resistance is outside the tuner's ability to cope with it at various frequencies. I'm thinking the first unscientific experiment might be to go to the opposite side of the loop from the feedpoint and cut it into a big horizontal bent dipole - mainly because that will take about 45 seconds to accomplish - one of the benefits of having one's entire antenna at ahoulder-height. But I'd like to get some other opinions - I know there's an electrical Pattern here from the info - and I have some other ideas based on that. And no, I can't put up a "real antenna" so I'm pretty much comiited to making this one work as well as I can. Until I move the QTH to somewhere with a few acres and room for Lots of Wire. Cheers John KB6SCO
Re: [AMRadio] Negative Loading circuits - good, bad, or ?
Any distortion of the modulating waveform causes harmonic distortion and therefore splatter. The sharper a waveform discontinuity is, the more high-level harmonic energy it contains, and that harmonic energy becomes splatter on the air. This is why a low-pass filter is used in speech clipping systems. But the sharp clipping caused by overmodulation can not be filtered at the audio level. The extreme sharpness of clipping resulting from overmodulation is the reason that overmodulation causes so much splatter. The idea of the diode loading system is to produce a softer clipping that produces much less splatter than raw overmodulation. Additional diodes and resistors are often added to provide protective loading for the modulator on negative peaks that would have been unloaded in simple diode systems or with no diodes at all. This protective loading reduces voltage spikes that can destroy the modulation transformer. Some distortion is still produced with the diode loading system, and therefore some splatter will result. But unless there is some other problem, the splatter is much less severe than raw overmodulation, and the high frequency products caused by this action can be filtered at the audio level. You can add a high level splatter filter, although that will limit your high frequency response. You can have a few filters or a few filter settings, like 10 KHz for clear conditions, 6 KHz for intermediate conditions, and 3.5 KHz for crowded conditions. Some technical problems can cause extra splatter. If the modulator is marginally stable, it is possible that the dynamic change in loading resulting from the diode action can cause triggered parasitics at specific points on the audio waveform. This can result significant splatter, and it might have a distinctive resonant sound, which you would hear as resonances or concentrated spectral points in the splatter on a sideband receiver tuned some distance from the carrier. Negative feedback can cause problems if gain and phase margins are exceeded, which often happens at frequency extremes, and this can result in triggered parasitics even if diode loading is not used. If there is a modulator stability issue at high audio frequencies, it can cause splatter. Excessive modulation of the screen grid of a plate-modulated tetrode or pentode modulated stage can cause sharp distortion too. You can see a kink at about 85% negative when this occurs, and that means you have a waveform discontinuity that can cause significant splatter that can not be filtered at the audio level. The typical circuit of the screen dropping resistor going to modulated B+ should be modified for better linearity. A good job can be done by simply connecting the top of the screen dropping resistor to unmodulated B+ and allowing the screen grid to self-modulate, but the best arrangement uses a resistive divider supplying the screen from modulated B+ and unmodulated B+. Screen-choke systems are self-modulating and do not exhibit that distortion. Class C Optimization for Ultra Low Distortion http://www.amfone.net/AMPX/71.htm The self-modulated screen grid http://www.amfone.net/AMPX/98.htm Remember also that your receiver can be listening to a really strong signal while you are testing in the shack. The splatter that you hear on that strong signal in the shack may be mild on a normal signal on the air, and the receiver can be adding to the problem is it is overloading. Bacon, WA3WDR - Original Message - From: "Brett gazdzinski" <[EMAIL PROTECTED]> To: "'Discussion of AM Radio'" Sent: Wednesday, January 11, 2006 8:22 AM Subject: RE: [AMRadio] Negative Loading circuits - good, bad, or ? > Dennis, > > > > I've had good results with the "three diode" circuit too. Earliest > > reference to the scheme I can find is in QST, October 1956 > > using 866 rectifiers. > > Covered again in ER #3, July 1989, this time with solid state > > diodes. > > I did not say I had good luck with the circuit, although it looks > like it works on the scope, and on the mod monitor, it results > in a very wide signal. Not much point in running it if you go > 50Kc wide... > > > > > > Don't believe the type of diodes used would have any > > significant effect on > > this. Splatter is generated in the PA tank circuit when > > plate voltage is > > suddenly cut off on the audio negative half cycle. Same > > splatter would be > > produced if the PA was being fed straight off the secondary > > of the mod transformer. > > The 3 diode circuit is supposed to prevent the plate voltage > from going to zero. I use variacs on the power supply so I can set > the point at which the circuit starts working, and no matter if I > set it to 95, 90, or 85% I get splatter if the audio would exceed > 100% negative, so the circuit seems to do no good. > > It LOOKS like it works, I get current in the negative cycle loading > circuit, mod monitor shows the limiting working, scope looks ok, > the signal just ge
[AMRadio] FS: Homebrew PW Modulator
FOR SALE: Neat little homebrew 15-25W modulator with pair of push-pull 6AQ5s. Has gain control and RCA input. No power supply. Excellent job - I did not build it, but whoever did was an expert. Has 12AX7 preamp etc. All in nice shape. Available for $35.00 plus shipping
RE: [AMRadio] Negative Loading circuits - good, bad, or ?
Dennis, > I've had good results with the "three diode" circuit too. Earliest > reference to the scheme I can find is in QST, October 1956 > using 866 rectifiers. > Covered again in ER #3, July 1989, this time with solid state > diodes. I did not say I had good luck with the circuit, although it looks like it works on the scope, and on the mod monitor, it results in a very wide signal. Not much point in running it if you go 50Kc wide... > Don't believe the type of diodes used would have any > significant effect on > this. Splatter is generated in the PA tank circuit when > plate voltage is > suddenly cut off on the audio negative half cycle. Same > splatter would be > produced if the PA was being fed straight off the secondary > of the mod transformer. The 3 diode circuit is supposed to prevent the plate voltage from going to zero. I use variacs on the power supply so I can set the point at which the circuit starts working, and no matter if I set it to 95, 90, or 85% I get splatter if the audio would exceed 100% negative, so the circuit seems to do no good. It LOOKS like it works, I get current in the negative cycle loading circuit, mod monitor shows the limiting working, scope looks ok, the signal just gets REAL wide, no matter what rig I run. Everyone would assume it works, I did, till I got reports I was real wide and dug out the spectrum analyzer... Perhaps the very high frequency stuff gets past the circuit? I should run some tests... Brett N2DTS > > Dennis D. W7QHO > Glendale, CA
[AMRadio] a little refresher guide in email nettiquette
Hi, Geoff It's me. Thank you for your care and pedagogy but you are wrong about the way it happened: when I saw it, your ammendment was not yet there and I thought it could be a very well known reference to most of members and it would not be mentioned if not asked for. And I would like to read it! And the question was solved. In my opinion, what you added is very well know to most of members but one is somewhat free to still have a style of his own. Now, let's thank Jim Wilhite too for his fellowship! And to close it, some bandwidth will not be too excessive, in my opinion, when it concerns to main subject here: good AM ;-)) Vy 73 de Jose' - CT1AXG - Date: Tue, 10 Jan 2006 00:45:35 -0600 From: W5OMR/Geoff <[EMAIL PROTECTED]> Subject: Re: [AMRadio] AM modulation To: Discussion of AM Radio Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Jim Wilhite wrote: > Look here: > http://www.qsl.net/wa5bxo/amtech.html I imagine he was just catching up, and reading the list-mail, and saw the one message where I forgot to inclue the URL (which was immediatly done in the -next- message). A Lot of times, someone will ask the whole of the group a question. Instead of jumping in on -that- particular message, I'll read through the list, -first- to make sure it hasn't already been answered, -or-, someone elses point of view has been given (if that's what the situation requires) and one that is similar to mine has been brought to light, then there'd be no need for me to chime and and say (basically) -me, too-, unless my whole intent and purpose was to take up bandwidth. .../... __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
