Re: [AMRadio] AM Amps
Gary Schafer wrote: Here is a ruff rule of thumb for amps on AM: If the amp takes 100 watts to drive it on ssb then it will take 100 watts pep of AM to drive it. 100 watts pep of AM means 25 watts of carrier with 100% modulation. Kinda Sorta. Depends on the quality of the transmitter. If he reduces the carrier output power of the Ranger, then the audio output power will rise, because there won't be as much final current flowing through the secondary of the modulation transformer. Depending on the impedance match of the final to the modulator through the mod transformer, determins how much more audio will be gained (or lost) when power is reduced from the exciter. That, and the natural asymetricalness of the operators voice. Lowering the output power, more audio, a 3:1 SR (Symmetry Ratio), the 25w of carrier could contain as much as 200w PEP. In order for the linear to 'cleanly' reproduce the audio, it's going to need more than what the plates of a pair of 3-500Z's can deliver (*note: I said Cleanly) In the real world, there's likely to be some distortion, unless the carrier can be dropped down to around 10 to 12watts output of the Ranger. 73 = Best Regards, -Geoff/W5OMR
[AMRadio] AM Amps
Why not just use a coax Tee and dump half of the output power of the Ranger into a 50 ohm dummy load and the other half into the amp? Bob
Re: [AMRadio] AM Amps
Although both of these will serve to reduce the drive power and get you on the air, they are less than optimal. The problem with reducing the B+ is the max PEP goes with it. You'll want to preserve that for positive modulation peaks. As Gary Schafer sez you want to keep the driver PEP up to where the amp needs it for full output, as long as the plate dissipation is not exceeded during dead carrier. Better to keep the plate hi and pull back the screen V. A simple attenuator wastes heat, may be difficult to adjust over a wide range, and offers no improvement in modulation performance over the stock exciter running at full power, (limited positive peak capability). But, a better idea than lowering the B+. g Geoff wrote: ...Reducing the B+ level on the plate of the 6146 is another way. ...A T connector, and a dummy load works well, also. Just tossing out some more ideas.
Re: [AMRadio] AM Amps
Bob Maser wrote: Why not just use a coax Tee and dump half of the output power of the Ranger into a 50 ohm dummy load and the other half into the amp? Rangers typically deliver around 40w out of the SO-239. 20w out of the Ranger would be enough, if there were around 1000w of dissapation in the amp. A pair of 811's (even 4) ain't gonna cut it. A pair of 3-500Z's would be nice. Or a pair of 450TL's ;-) 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
Gary Blau wrote: Although both of these will serve to reduce the drive power and get you on the air, they are less than optimal. The problem with reducing the B+ is the max PEP goes with it. You'll want to preserve that for positive modulation peaks. As Gary Schafer sez you want to keep the driver PEP up to where the amp needs it for full output, as long as the plate dissipation is not exceeded during dead carrier. Better to keep the plate hi and pull back the screen V. I don't think that's what happens. http://w5omr.shacknet.nu/~wa5bxo/asyam/Amplitude%20Modulation.htm That's a great read. Everyone -should- read that. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
In a message dated 1/10/05 9:12:45 PM, [EMAIL PROTECTED] writes: Kinda Sorta. Depends on the quality of the transmitter. If he reduces the carrier output power of the Ranger, then the audio output power will rise, because there won't be as much final current flowing through the secondary of the modulation transformer. Depending on the impedance match of the final to the modulator through the mod transformer, determins how much more audio will be gained (or lost) when power is reduced from the exciter. Hmmm.. Goes without saying that however the carrier level was reduced the audio level should be concomitantly lowered to prevent over modulation. Easy to do, just reduce the mic gain control. That, and the natural asymetricalness of the operators voice. Lowering the output power, more audio, a 3:1 SR (Symmetry Ratio), the 25w of carrier could contain as much as 200w PEP. In order for the linear to 'cleanly' reproduce the audio, it's going to need more than what the plates of a pair of 3-500Z's can deliver (*note: I said Cleanly) Two hundred watts PEP on a 25 watt carrier comes out to 400% modulation. Would take some extreme speech processing to achieve this in the positive direction while limiting modulation to 100% negative at the same time. Far beyond the asymmetry of normal human speech. So, a pair of 3-500Zs running GG and giving, say, 10db gain, with 35 watts of drive would give 350 watts of carrier out and modulating at 100% with a reasonably asymmetric audio signal would give 1400 W. PEP. I have been using a 3-1000Z linear in this way for years with excellent results. Speaking of the human voice, there undoubtedly exist some levels of asymmetry depending on the speaker. I suspect, however that much of the asymmetry observed and reported is actually the product of nonlinearities in speech amplifier circuitry, particularly in the early, low-level stages. Dennis D. W7QHO Glendale, CA
[AMRadio] Filter Choke
Tnx for the help on finding a Filter choke for my SX-71.I found a replacement choke at Tubesandmore.com that will work just fine..Keep those filiments glowing!!!..73's Ron W6MAU
Re: [AMRadio] AM Amps
73s to all, regarding Dick's problem i'd try to match 1st the Ranger's output pwr with the needed input pwr of one of the amps.The choice of the amp depends on the output pwr someone wants to push on the air.Saw a Ranger there in Ebay and think it's using something like 6L6s or anyway not high power output tubes. Playingwith the outputs B+,or grid HV or grid pollution resistance,in order to reduce or increase the output pwr and match it with amp's input it's easy.Resistances for the B+ and grid HV and a meter to measure.The greatest the 2nd grid resistance is in value the worst.It's pushing hard on limits the tube depending on the B+ and grid voltages also. Hope it helps, Chris SV1DAF. - Original Message - From: Gary Schafer [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Tuesday, January 11, 2005 6:31 AM Subject: Re: [AMRadio] AM Amps Here is a ruff rule of thumb for amps on AM: If the amp takes 100 watts to drive it on ssb then it will take 100 watts pep of AM to drive it. 100 watts pep of AM means 25 watts of carrier with 100% modulation. You will also get 25% of the carrier out of the amp from it's pep output level. If it puts out 600 watts pep (collins 30L1) then you will get 150 watts carrier out when properly set up. If it took 100 watts pep to drive it on ssb it will take 25 watts carrier on AM. To see if the tubes will handle it figure the dissipation backwards. At 150 watts output that amp should be at around 33% efficiency (if properly tuned). 150 watts divided by 33% = 454 watts plate input power. Now subtract the 150 watts of output power you are getting from the 454 watts input power and you have around 304 watts going to heat in the plates. In the case of the 30L1 divide that by 4 (the number of tubes) and that leave about 76 watts per tube in dissipation. 811A's have a 65 watt plate dissipation ratting. So you are a little over. For short transmissions you can get by with it but no long buzzard transmissions. The power supply in the 30L1 is marginal also. It will get mighty hot. The other Gary's suggestion of limiting to 125 watts carrier out (500 watts pep)gets you right in the ball park on plate dissipation. 125 divided by 33% = 378 watts input. Subtract the 125 watts and that leaves 253 watts dissipated. Divide by 4 and that is about 63 watts per tube. For proper loading on the amplifier operating at 125 watts out with carrier it should be tuned for 500 watts output pep. The drive required can be figured pretty close by first calculating the gain of the amp at 600 watts output, its rated output. If it takes 100 watts to drive it to that output power that is a gain of 6. At 500 watts out the amp will still have a gain of 6 so divide 500 by 6 which gives about 83 watts pep of drive. divide that by 4 for the carrier needed. That should be around 20 watts. Keep in mind that the amp needs to be tuned at the pep level. One way to do that is to modulate the 20 watt carrier 100% with a tone or a long hlooo and tune the amp watching a scope. Another way is to use the ssb rig with an 80 watt carrier driving the amp and tune it for max output. Then hook the AM rig up with the 20 watts drive. You can roughly check to see if you tuned the amp right by looking at the efficiency that it is running when you think you have it tuned. Calculate the input power, plate current times plate volts. Divide the output power you are seeing on the watt meter by the input power. If the efficiency is around 30 to 35% you should be in the ballpark. Any greater efficiency and it tells you that amp is not loaded heavy enough. Or you have too much drive. More than you wanted to know. 73 Gary K4FMX Gary Blau wrote: I partially disagree, but with a -big- proviso. You'll have to find a way to reduce the Ranger output to the 10-15 watt level. Maybe the nicest way to do that is a variable screen voltage control, similar to what you'll find here: http://www.w3am.com/ranger.html but I'm sure there are other methods. Just don't run the stock Ranger straight into the amp without dealing with this in some way. Don't ask the 30L1 to do more than ~125 watts carrier. The 811's can't handle much dissipation. Same is true for the SB200 and its pair of 572B's. But they both will work fine like this. I ran an SB200 like this for a long time. Bigger amps with more plate dissipation, like the Henry or SB-220 are a safer bet, but you must be very careful nonetheless. 73, g Chris wrote: Hi Dick The 30L1 would far too over stressed but the Henry would be perfect, by the way thanks for buying my Ranger, 73 Chris RICHARD W GILLESPIE wrote: I just bought a Johnson Ranger and wonder if my 30L1 or Henry 2KD would work okay. 811's in the 30L1 and a pair of 3-500's in the Henry. Thanks. Dick/K5DIC __ AMRadio
[AMRadio] AM Amps
This aint rocket science at my shack. I have a pair of trusty old 813's in grounded grid with 3200 Volts on the plates. I drive them with my Ranger all the time with no problems at all. I always tune the ranger up to full power into a either a dummy, or my dipole. THEN switch the 813's into the line and then quickly dip the ranger. It usually will dip back to about 80'mils. I leave it right there and get legal power out of the 813's. If I want to bring the Ranger back up to full power, I can and it will drive those 813's to 600 watts and sounds great. I have been using this combination for 6 years and many of you have heard me on it. If I DO bring the ranger back up to 120 mils, I have to be careful of the audio drive, as it will tend to start to distort if the gain is up to high. But if I leave the Ranger at 80 mils, it works fine and I work coast to coast! Gotta love those old 813's! 73's de W5SUM
Re: [AMRadio] Thanks
RICHARD W GILLESPIE wrote: Thanks to all for your suggestions and guidance. Great thread for getting help. Hope to talk on the air at some point with all. I gotta believe that AM is making a comeback. SSB has gotten a bit boring. Too bad AM cannot get the respect it deserves and the frequencies to go with it. Thanks again. Looking forward to hearing you on the air, Dick. There's a group of us 5-landers on 3.885 EARLY in the mornings (from 4 to 6am) and then the 'later morning' crew fires up around 8am, on 3.880. There are some other guys that might be 100 to 200 miles closer to ya, on 3.890 that you could give a listen to. Or, you could go homestead a new frequency some/anywhere else in the phone band. Seems there's a 'waste land' down below 3.850. QSO's are few and far between and mostly SSB, but I've known some AM to occur on 3.840, 3.820, and even 3.760. The point is, we don't -have- to be limited to 3.870~3.890. SSB is just another version of AM 'Phone operation, and therefore is permitted anywhere 'phone operations are allowed. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
Robert M. Bratcher Jr. wrote: If I wanted more than 100w of AM (out of my Collins 23V-3) then I'd use it for carrier only then plate modulate an amplifier with a modulation transformer (if I could find one) plus a speech amp. Then I'd run the maximum legal AM power of 375 watts. But then I run AM on the KW-1 (pure DSB AM) sometimes the KWS-1 (which does carrier plus one sideband) at the 375w limit. I'd prefer to do AM at a kilowatt but thats not legal anymore. I wonder how many AM'ers run more than the legal 375 watts? I've thought about it... Bob, there is no magic number of 375w of carrier being legal for AM. What's legal is 1500w PEP output from the transmitter. This, by the way, is damned difficult (but not impossible) to measure. If it were me, and I wanted to run a rig that wasn't covered up with neighbors (like I am!) I'd load the final to 500w DC Input and let'er run wild to where EVER the peaks went! 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
it's 500 Watts over here this limit. Chris SV1DAF. - Original Message - From: Robert M. Bratcher Jr. [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Tuesday, January 11, 2005 6:43 PM Subject: Re: [AMRadio] AM Amps At 04:31 AM 1/11/2005, you wrote: 73s to all, regarding Dick's problem i'd try to match 1st the Ranger's output pwr with the needed input pwr of one of the amps.The choice of the amp depends on the output pwr someone wants to push on the air.Saw a Ranger there in Ebay and think it's using something like 6L6s or anyway not high power output tubes. Playingwith the outputs B+,or grid HV or grid pollution resistance,in order to reduce or increase the output pwr and match it with amp's input it's easy.Resistances for the B+ and grid HV and a meter to measure.The greatest the 2nd grid resistance is in value the worst.It's pushing hard on limits the tube depending on the B+ and grid voltages also. Hope it helps, Chris SV1DAF. If I wanted more than 100w of AM (out of my Collins 23V-3) then I'd use it for carrier only then plate modulate an amplifier with a modulation transformer (if I could find one) plus a speech amp. Then I'd run the maximum legal AM power of 375 watts. But then I run AM on the KW-1 (pure DSB AM) sometimes the KWS-1 (which does carrier plus one sideband) at the 375w limit. I'd prefer to do AM at a kilowatt but thats not legal anymore. I wonder how many AM'ers run more than the legal 375 watts? I've thought about it... __ 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] AM Amps
By legal power out of the 813's I assume you mean 375 watts carrier? If so there is no way the peaks are going to 1500 watts. A pair of 813's will not put out that much power in GG linear configuration. At least not very long. A pair of 813's in GG are good for about the same power out as 4 811A's. If you run them with more than 150 watts carrier out you will be flat topping with modulation, unless you keep the mod percentage very low. AT 375 watts carrier out at 33% efficiency that would require 1140 watts plate input power. That would be a plate dissipation of around 380 watts per tube! Cooked to well done in minutes! Now if you tune them so there is higher efficiency, the plate dissipation will be lower, but then your mod peaks will never reach any where near 100%. Even if your driver is modulated 100%. In AM linear service the efficiency of the amplifier must be 1/2 as much for the carrier as it is for the peaks. This is how the voltage doubles to obtain that peak power needed. Without that ratio you will have distortion and splatter. As you noted when running 600 watts carrier out you must back the modulation down. At that power level you have almost no headroom at all for audio. You are at near maximum capability of the tubes with just carrier. 73 Gary K4FMX ronnie.hull wrote: This aint rocket science at my shack. I have a pair of trusty old 813's in grounded grid with 3200 Volts on the plates. I drive them with my Ranger all the time with no problems at all. I always tune the ranger up to full power into a either a dummy, or my dipole. THEN switch the 813's into the line and then quickly dip the ranger. It usually will dip back to about 80'mils. I leave it right there and get legal power out of the 813's. If I want to bring the Ranger back up to full power, I can and it will drive those 813's to 600 watts and sounds great. I have been using this combination for 6 years and many of you have heard me on it. If I DO bring the ranger back up to 120 mils, I have to be careful of the audio drive, as it will tend to start to distort if the gain is up to high. But if I leave the Ranger at 80 mils, it works fine and I work coast to coast! Gotta love those old 813's! 73's de W5SUM __ 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] AM Amps
well all I can say is it works.. works well as a matter of fact, and has been for 6 years :) I typically run between 350 and 400 watts of carrier every day. It looks great on the scope. Modulation envelope is perfect. 100% modulation. In 6 years Ive only lost one tube, and I accidently broke that one. Ronnie - W5SUM -- Original Message --- From: Gary Schafer [EMAIL PROTECTED] To: Discussion of AM Radio amradio@mailman.qth.net Sent: Tue, 11 Jan 2005 14:34:26 -0500 Subject: Re: [AMRadio] AM Amps By legal power out of the 813's I assume you mean 375 watts carrier? If so there is no way the peaks are going to 1500 watts. A pair of 813's will not put out that much power in GG linear configuration. At least not very long. A pair of 813's in GG are good for about the same power out as 4 811A's. If you run them with more than 150 watts carrier out you will be flat topping with modulation, unless you keep the mod percentage very low. AT 375 watts carrier out at 33% efficiency that would require 1140 watts plate input power. That would be a plate dissipation of around 380 watts per tube! Cooked to well done in minutes! Now if you tune them so there is higher efficiency, the plate dissipation will be lower, but then your mod peaks will never reach any where near 100%. Even if your driver is modulated 100%. In AM linear service the efficiency of the amplifier must be 1/2 as much for the carrier as it is for the peaks. This is how the voltage doubles to obtain that peak power needed. Without that ratio you will have distortion and splatter. As you noted when running 600 watts carrier out you must back the modulation down. At that power level you have almost no headroom at all for audio. You are at near maximum capability of the tubes with just carrier. 73 Gary K4FMX ronnie.hull wrote: This aint rocket science at my shack. I have a pair of trusty old 813's in grounded grid with 3200 Volts on the plates. I drive them with my Ranger all the time with no problems at all. I always tune the ranger up to full power into a either a dummy, or my dipole. THEN switch the 813's into the line and then quickly dip the ranger. It usually will dip back to about 80'mils. I leave it right there and get legal power out of the 813's. If I want to bring the Ranger back up to full power, I can and it will drive those 813's to 600 watts and sounds great. I have been using this combination for 6 years and many of you have heard me on it. If I DO bring the ranger back up to 120 mils, I have to be careful of the audio drive, as it will tend to start to distort if the gain is up to high. But if I leave the Ranger at 80 mils, it works fine and I work coast to coast! Gotta love those old 813's! 73's de W5SUM __ 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 --- End of Original Message ---
RE: [AMRadio] AM Amps
When I run the pair of 813 rig, its doing 600 watts carrier out, and I limit my negative modulation to about 90% I used to run it to over 2000 watts pep, 2500 judging by how hard the watt meter pinned. That was when I used negative cycle loading, which did not work fast enough to prevent splatter as I found out. Now days I think the pep gets up to about 1700. My voice does not show a lot of asymmetrical waveform on any transmitter, although it used to go higher before I got the berringer and new microphone. Figuring in the old uncalibrated swan wattmeter, some swr, maybe I am even legal. Since the FCC changed it to a pep reading, all you got to do is get a stingy pep meter as far as I figure. Maybe run the carrier to 1500 watts and have a broken pep section on the watt meter? Could anyone tell the difference between 1500 watts pep, and 2000 watts pep at some distant location? My 80 meter antenna is somewhat crappy anyway, and someone running 1000 watts pep with a better antenna could sound a lot louder than me... Maybe it should be effective radiated power, in that case I am way legal. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Robert M. Bratcher Jr. Sent: Tuesday, January 11, 2005 11:43 AM To: Discussion of AM Radio Subject: Re: [AMRadio] AM Amps At 04:31 AM 1/11/2005, you wrote: 73s to all, regarding Dick's problem i'd try to match 1st the Ranger's output pwr with the needed input pwr of one of the amps.The choice of the amp depends on the output pwr someone wants to push on the air.Saw a Ranger there in Ebay and think it's using something like 6L6s or anyway not high power output tubes. Playingwith the outputs B+,or grid HV or grid pollution resistance,in order to reduce or increase the output pwr and match it with amp's input it's easy.Resistances for the B+ and grid HV and a meter to measure.The greatest the 2nd grid resistance is in value the worst.It's pushing hard on limits the tube depending on the B+ and grid voltages also. Hope it helps, Chris SV1DAF. If I wanted more than 100w of AM (out of my Collins 23V-3) then I'd use it for carrier only then plate modulate an amplifier with a modulation transformer (if I could find one) plus a speech amp. Then I'd run the maximum legal AM power of 375 watts. But then I run AM on the KW-1 (pure DSB AM) sometimes the KWS-1 (which does carrier plus one sideband) at the 375w limit. I'd prefer to do AM at a kilowatt but thats not legal anymore. I wonder how many AM'ers run more than the legal 375 watts? I've thought about it... __ 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] AM Amps
In a message dated 1/11/05 12:14:43 PM, [EMAIL PROTECTED] writes: well all I can say is it works.. works well as a matter of fact, and has been for 6 years :) I typically run between 350 and 400 watts of carrier every day. It looks great on the scope. Modulation envelope is perfect. 100% modulation. In 6 years Ive only lost one tube, and I accidently broke that one. I have to agree with Gary. You're seeing 1600 watts PEP and 400W of carrier OUT with a pair of GG 813s??? Does not compute! Just curious, are you talking about 400W INPUT power to the linear under carrier only condx maybe? If so, this would work out to about 133W carrier OUT and each 813 dissipating about 133W which would make more sense. Dennis D. W7QHO Glendale, CA
Re: [AMRadio] AM Amps
At 04:21 PM 1/11/2005 -0500, you wrote: In a message dated 1/11/05 12:14:43 PM, [EMAIL PROTECTED] writes: well all I can say is it works.. works well as a matter of fact, and has been for 6 years :) I typically run between 350 and 400 watts of carrier every day. It looks great on the scope. Modulation envelope is perfect. 100% modulation. In 6 years Ive only lost one tube, and I accidently broke that one. I have to agree with Gary. You're seeing 1600 watts PEP and 400W of carrier OUT with a pair of GG 813s??? Does not compute! Just curious, are you talking about 400W INPUT power to the linear under carrier only condx maybe? If so, this would work out to about 133W carrier OUT and each 813 dissipating about 133W which would make more sense. Dennis D. W7QHO Glendale, CA I'm with Dennis and Gary. To run a linear amplifier at 375 watts of carrier and 100% modulation, you will need around 800 watts of plate dissipation. For a short time a number of years ago, I tried running an AF-68 and a 4-1000A linear amplifier. I could never get more than around 450 watts of carrier and stay linearI didn't need a heater in the shack either. 73, Darrell, WA5VGO 73, Darrell, WA5VGO
Re: [AMRadio] AM Amps
Gary Schafer wrote: By legal power out of the 813's I assume you mean 375 watts carrier? Why assume something that is false?? That statement is -designed- to put you on edge, Gary. Perhaps it's just my perception, but it simply appears as if you're not paying attention. NO WHERE does it say that 375w of carrier is the 'legal' limit. The LEGAL limit is 1500w PEP output. It's just a point of reference, that if you modulate a 375w signal with a sine-wave to 100% audio, then you will reach 1500w pep output. The truth of the matter is, we don't -speak- in sine-wave. Our voices are rather asymetrical. Some of us have voices that are rather 'peaked'. In order for the audio amplifying equipment to properly modulate 375w of carrier, instead of needing to only be 50% of the carrier, or 187.5w of needed audio, you -might- wind up needing an audio system with the capability of producing upwards of 600w of AUDIO. (ref: http://w5omr.shacknet.nu/~wa5bxo/asyam/Amplitude%20Modulation.htm) THIS IS NOT TO SAY that you'll be pushing your positive peaks that high, but in order to keep your signal clean, and well within good engineering practice, you certainly don't want any flat-topping or distortion. Anything in the audio system that does -not- allow your audio to be clean and free of distortion then, by definition, wouldn't be operating within good engineering practice. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
I'm with Dennis and Gary. To run a linear amplifier at 375 watts of carrier and 100% modulation, you will need around 800 watts of plate dissipation. For a short time a number of years ago, I tried running an AF-68 and a 4-1000A linear amplifier. I could never get more than around 450 watts of carrier and stay linearI didn't need a heater in the shack either. 73, Darrell, WA5VGO Darrell, do you still have the powersupply for the AF-68? I have one here, that I got from Larry/CFJ a couple of years ago, and I've been wanting to put that thing mobile for so long, that I'm about ready to build an AC-input power supply, and plug it into my 600w DC-AC inverter. Thanks. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
Geoff wrote: Gary Schafer wrote: By legal power out of the 813's I assume you mean 375 watts carrier? Why assume something that is false?? That statement is -designed- to put you on edge, Gary. Perhaps it's just my perception, but it simply appears as if you're not paying attention. NO WHERE does it say that 375w of carrier is the 'legal' limit. The LEGAL limit is 1500w PEP output. It's just a point of reference, that if you modulate a 375w signal with a sine-wave to 100% audio, then you will reach 1500w pep output. The truth of the matter is, we don't -speak- in sine-wave. Our voices are rather asymetrical. Some of us have voices that are rather 'peaked'. In order for the audio amplifying equipment to properly modulate 375w of carrier, instead of needing to only be 50% of the carrier, or 187.5w of needed audio, you -might- wind up needing an audio system with the capability of producing upwards of 600w of AUDIO. (ref: http://w5omr.shacknet.nu/~wa5bxo/asyam/Amplitude%20Modulation.htm) THIS IS NOT TO SAY that you'll be pushing your positive peaks that high, but in order to keep your signal clean, and well within good engineering practice, you certainly don't want any flat-topping or distortion. Anything in the audio system that does -not- allow your audio to be clean and free of distortion then, by definition, wouldn't be operating within good engineering practice. While I'm at it, I'll say, again, that if I wasn't covered up with neighbors, I'd run my rig at around 500w DC Input (around 1500v @ 350mA), make sure that the modulator was capable of cleanly modulating the signal, and let the positive peaks float up to wherever they like, -as long as- my negative peaks don't pinch/cut the carrier. If it's 2500w PEP, then so be it. (where'd I leave my black cowboy hat and six-shooter? ;-)) As it is, with neighbors on *ALL* sides of me, during the day-time, I limit the power output of the 250TH final to 100w OUTPUT (and probably reaching 500+wpep out) and between midnight and 6am, it's at 200w carrier (around 800wPEP out, w/o cutting the carrier off, with negative peaks) 73 = Best Regards, -Geoff/W5OMR (aka: AM Outlaw) (p.s. Does anyone (other than K4KYV) remember the phrase: When AM Kilowatts are outlawed, then Outlaws will run AM Kilowatts!?)
[AMRadio] AM Amps
I wonder if I could drive my 3CX3000 Lineeaar with my Valiant. H. Bob
Re: [AMRadio] AM Amps
Joe Crawford wrote: I just found a pair of 450TL's. Trying to find sockets for them and some HK-254's. Joe W4AAB Rangers typically deliver around 40w out of the SO-239. 20w out of the Ranger would be enough, if there were around 1000w of dissapation in the amp. A pair of 811's (even 4) ain't gonna cut it. A pair of 3-500Z's would be nice. Or a pair of 450TL's ;-) 73 = Best Regards, -Geoff/W5OMR I could might help on the sockets...
Re: [AMRadio] AM Amps
Gary Schafer wrote: I know full well that there is no such thing as a 375 watt carrier limit to AM power in the FCC rules. I never said there was. Ok, good. I was just making sure ;) Too many people believe that there's some 'magical mystification' about 375w of carrier output being the 'legal limit'. I was trying to clarify Ronnie's statement about how much power he runs his 813's at when he says he runs them at legal power out. And since we don't know if Ronnie has a symmetrical voice pattern or otherwise, we can only assume it is symmetrical when discussing general power principles. Maybe he has the peaks phased so maximum peaks are in the negative direction? I don't know. Either way it appears as though he only has enough headroom for less than 50% modulation in the positive direction. Agreed, there. And, I've been to Ronnie's shack. I'm pretty sure he doesnt' do any audio shaping, or phasing, or any other audio tricks on either the Ranger or the Globe King 500 he's running there. On top of that the plate dissipation is around 380 watts per tube if the amp is tuned properly, which it can't be if it is not burning up tubes. That is the whole point, if you are paying attention. :) I was... it was just the 'legal limit' that caught my attention (yet again ;-) Maybe you could tell us how much peak envelope power would be available from a pair of GG 813's at 375 watts carrier out with 100% modulation? I'm not sure you can get more than around 1kW PEP output of a pair of 813's... and probably more like 800w. (3) in parallel would be a different story, though. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] ten-tec radio
[EMAIL PROTECTED] wrote: I am thinking about giving my ten-tec jupiter a try on am.(only base rig i have) and body using one,and can give me an idea as to how this rig will work also have 811 amp 73 Ron af4ob I was in the Ten-Tec labs Ham Shack, back in September of this year. There was a group of H'AM's on 7.290, and the reciever on the Omni 6 sounded superb! Am told that the transmit audio, with the DSP, etc will sound just as well. I think the Jupiter has those features. If the AM filter has been added, Ron, you shouldn't have any troubles, out of it. Just remember, 25% of the total output of the transciever, for 25% output of the amplifier's max. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
If you had an amp rated at 1500 pep rated for Continuous Commercial Service and were going to drive it with a Ranger, (with W3AM's modification as an example) where would you set the carrier level with no modulation? Byron, W3WKR
Re: [AMRadio] AM Amps
Byron Lichtenwalner wrote: If you had an amp rated at 1500 pep rated for Continuous Commercial Service and were going to drive it with a Ranger, (with W3AM's modification as an example) where would you set the carrier level with no modulation? Byron, W3WKR Where the 'scope showed that I had 90% negative modulation peaks. Operating your AM rig without an Oscilloscope is like driving your car at night, without headlights (Don Chester -K4KYV) 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
I'm not sure you can get more than around 1kW PEP output of a pair of 813's... and probably more like 800w. (3) in parallel would be a different story, though. 73 = Best Regards, -Geoff/W5OMR I would say you are pretty much on the mark there. I have a pair of 813's in GG also. I only run them at around 2500 volt and can get about 650 watts max out with 100 watts drive if I remember right. I ran them well over 3000 volts many years ago and got quite a bit more out of them but didn't have a decent watt meter then so I don't know exactly. 1000 watts out seems doable but they will be running around 1600 watts or more input. They will turn pretty red. Even on SSB at that power. *whew* We agree on -something- ;-) But I'm enjoying the discussion. I may not be the most articulate individual around, and I'm -far- from reminding anyone of someone whom posses articulatino, but when it comes to someone saying 375w is the limit to run to get 1500w pep output, I can't swallow that. It's a true statement, if you were to apply a sine-wave (at an arbitrary rate... say, 1kc) to 100%, but as it's been said before, we don't -talk- in sine-waves. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] ten-tec radio
I have worked a friend on AM who has a Jupiter. It sounded just fine to me, but I am not real picky on audio shaping and filtering. As I understand, the Jupiter is a software defined radio so you might want to have a qso with someone who can direct you as you make the settings for AM. With a following amp, you should do just fine, provided you don't overdrive the amp. 73 Jim W5JO - Original Message - From: [EMAIL PROTECTED] To: AMRadio@mailman.qth.net Sent: Tuesday, January 11, 2005 9:16 PM Subject: [AMRadio] ten-tec radio I am thinking about giving my ten-tec jupiter a try on am.(only base rig i have) and body using one,and can give me an idea as to how this rig will work also have 811 amp 73 Ron af4ob __ 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] AM Amps
Geoff wrote: I'm not sure you can get more than around 1kW PEP output of a pair of 813's... and probably more like 800w. (3) in parallel would be a different story, though. 73 = Best Regards, -Geoff/W5OMR I would say you are pretty much on the mark there. I have a pair of 813's in GG also. I only run them at around 2500 volt and can get about 650 watts max out with 100 watts drive if I remember right. I ran them well over 3000 volts many years ago and got quite a bit more out of them but didn't have a decent watt meter then so I don't know exactly. 1000 watts out seems doable but they will be running around 1600 watts or more input. They will turn pretty red. Even on SSB at that power. *whew* We agree on -something- ;-) But I'm enjoying the discussion. I may not be the most articulate individual around, and I'm -far- from reminding anyone of someone whom posses articulatino, but when it comes to someone saying 375w is the limit to run to get 1500w pep output, I can't swallow that. It's a true statement, if you were to apply a sine-wave (at an arbitrary rate... say, 1kc) to 100%, but as it's been said before, we don't -talk- in sine-waves. 73 = Best Regards, -Geoff/W5OMR But it is also true for voice modulation if you are talking about modulation peaks at 100% positive. Modulation is modulation. 73 Gary K4FMX
[AMRadio] BW Butterfly caps
Does anyone have the values of the different 'Butterfly' capacitors? I now have 3... one in the final, and 2 extras (with HDVL jackbars) that I'm going to build something with (someday). CX49A is one. CX-82B is the other. I think the CX-46 is what's in the rig. Thanks for any info. Google came up empty. 73 = Best Regards, -Geoff/W5OMR
Re: [AMRadio] AM Amps
Hey Geoff: Since there's already a screen at hand, why not use it to your advantage in this case by making it variable to allow clean adjustment of output power? It just seems like what the doctor ordered for driving a linear, that's all. As for your second question, I should have clarified that I was not thinking of a simple phase inversion aimed at impressing the highest voice peaks to the negative modulation direction, (the primary idea of the article) but taking it to an extreme of radically reducing the positive peaks by some means (such as very agressive positive peak clipping, or unplugging the positive tube in your push pull modulator!). Of course, simply inverting the phase in and of itself will not hurt quality in any way. But while aggressive positive limiting of some sort would allow higher carrier power before reaching the PEP limit of 1500watts, it will also increase distortion. How bad or tolerable it might be depends on a lot of variables and the limiting techniques employed. If you just want the most intense 'communications quality' result possible from the rig at hand, then it might make some sense. But in the real world, how much of a potential benefit is at stake here? Even wildly asymmetrical voices aren't going to buy more than several dB relative difference between positive and negative peak voltages, an amount that can easily be made up for with modest audio limiting. Since some sort of negative peak limiting should be used anyway to protect from carrier pinch off, some amount of that asymmetry is going to be given up right there. Finally, if your voice doesn't happen to be wildly asymmetrical, you're out of luck anyway. A lot of AM hams don't seem to use any negative peak control other than the mic gain pot, and many don't even have a scope to monitor for carrier pinch off, so a lot of this is like counting pixies on the head of a pin. FWIW my prejudice is looking at this as a broadcast engineer, which may be a bit different than some AM ops. Not better, just different. That prejudice steers me toward high audio quality, consistently very high average modulation levels (loudness) being almost always more useful than modest increases in carrier power, and a paranoid fear of negatively overmodulating. I admit to impatience with low power stations that do not agressively modulate to make up for it, which is common. Sorry. My object is to rattle the speaker on the other end, and make the station easy to listen to no matter what power level is in use. But, clearly hams can operate successfully without concerning themselves with any of this and still have a ripping good time. We're all looking for our own buzz. g Geoff wrote: ...I'll be the first one to admit that I'm 'weak' when it comes to pentode/tetrode design/operation. I like triodes. Their easier to work with, and require fewer power supplies. Less can go wrong. ...Why wouldn't it sound as good? You've just reversed the 'phase' of the audio if you, say, switch the grid caps on the modulators, or switched the plate caps on the modulators, even reversing the polarity of the microphone would have *basically* the same effect. Yes, your positive peaks would reduce, and you can run the carrier level back up. At 1500wPEP output (as John so eloquently described in his article) with his rig and voice, he would have to keep his rig at 220w input (around 160w of carrier out) to keep within the 1500w limit. Inverting the audio phase, he could probably run 1000w of carrier, with PEP audio to 1500w, still have the same QUALITY of audio, -and- probably be heard better, due to the lack of interference from the 160w carrier, to the 1000w carrier. It just wouldn't sound -as loud-.
