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Post by cbrown on Nov 17, 2014 10:05:55 GMT -5
You could buy a brand new Ameritron AL-82 (dual 3-500zg) or AL-1500 (single 3cx1500a7) for what he wants for some of those amps, and you would get a better amp. But Ameritron amps do not have cool skulls on it, so they are obviously inferior.
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Post by Night Ranger on Nov 17, 2014 10:18:01 GMT -5
You could buy a brand new Ameritron AL-82 (dual 3-500zg) or AL-1500 (single 3cx1500a7) for what he wants for some of those amps, and you would get a better amp. But Ameritron amps do not have cool skulls on it, so they are obviously inferior. You're right. What was I thinking? My bad. : ) Night Ranger
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Post by ab5ni on Nov 17, 2014 14:59:19 GMT -5
Ah. Okay. Thanks for the info, SB. Don't really follow transistorized, linear-amplifier construction practices too much. Personally, I'd only use these devices in automotive vehicles, where you don't really have to worry about finding a current source to power the things. I'm a "tube final" guy for base amplification. Makes the most sense to me and seems to be the most bang for the buck. The Texas Star series of amplifiers was also very popular in this neck of woods, by the way. I like the Texas Star amps more so than the so-called "competition" amps that the garage shop guys build, because they are biased class AB which results in far less splatter and you can actually use it on SSB without sounding all raspy. Although I am amazed at the spectral purity of that little 2 transistor Dave Made amp I use. It's actually cleaner than the old single tube Wawasee amp I was going to use on the base. Add in a little biasing, and it's a real nice little amp good for a quick 10db boost in signal. Never seen a Texas Star amp in person, but I've always heard people talking well about those amps. Never, ever read or heard a bad comment about them. I've seen the Dave Made amps on the net, but I don't really know anything about them. Did you have to add bias to the thing, or did it come from the factory that way? I've also considered making a 10 Mtr FM repeater using modified CB gear. Now I'm wondering if a Dave Made amp would be a good choice for the transmitter, especially if the thing comes from the factory biased class C? 73, Randy AB5NI
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Post by cbrown on Nov 18, 2014 9:57:37 GMT -5
Almost any CB amp will be biased Class C, except as noted the Texas Star line and the RM Italy. Some of the amp builders do build Class B amps, but its rare.
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Post by BBB on Nov 19, 2014 9:17:17 GMT -5
Now that I've seen quite a few transistorized Class C linear RF amplifiers thru the eyes of a spectrum analyzer, I can confidently say that there is a great discrepancy between the quality of the output of them. This even occurs between amps made by the same manufacturer. So the difference between a relatively linear transistorized amp and one that has many unwanted harmonics could be due to several variables including, but not limited to, component selection and in the end how well they were "tuned" at the factory before they went out the door. After all, a few of my HAM radios use the same devices like the Kenwood 430S with (2) 2sc2290's or the Yaesu FT-1000MP with 2sc2879's albeit not necessarily driven Class C. Keeping the transistors running below "saturation" is another key to keeping IMD (distortion) and splatter (harmonics) to an acceptable level so the transmitted audio is perceived as "clean." Some operators, not understanding this basic electronic fundamental, will always over-drive the amp thinking they are "getting out better" Therefore it will never sink in that the 4 pill amp they bought that was "rated" at 1000 watts PEP on the factory's web site will always sound like caca when driven beyond 200-300 watts peak on their DOSY analogue meter. I wish at least they would look up the data sheet of the transistors they are using and know what they are rated at... and then I woke up, haha. Just in case there are a few operators that want to know, here's specs on a few common transistors used in linear amps and their peak wattage ratings at acceptable IMD (distortion) levels: 2sc2879 TOSHIBA SILICON NPN EPITAXIAL PLANAR TYPE2-30MHz SSB LINEAR POWER AMPLIFIER APPLICATIONS. (LOW SUPPLY VOLTAGE USE) Specified 12.5V, 28MHz Characteristics Output Power : Po= 100WPEP Power Gain : Gp=13dB Collector Efficiency : '7 C = 35% (Min.) Intermodulation Distortion : IMD= -24dB(Max.) (MIL Standard) 2SC2290 TOSHIBA TRANSISTOR SILICON NPN EPITAXIAL PLANAR TYPE2-30MHz SSB LINEAR POWER AMPLIFIER APPLICATIONS (LOW SUPPLY VOLTAGE USE) Specified 12.5V, 28MHz Characteristics Output Power : Po= 60W PEP Power Gain : Gp=11.8dB (min.) Collector Efficiency : C = 35% (Min.) Intermodulation Distortion : IMD = - 30dB (Max.) (MIL Standard) SD1446 TransistorType Designator: 2SD1446 Material of transistor: Si Polarity: NPN Maximum collector power dissipation (Pc), Watts: 40 PEPMaximum collector-base voltage |Ucb|, V: 500 Maximum collector current |Ic max|, A: 6 Maximum temperature (Tj), °C: 150 Forward current transfer ratio (hFE), min: 2000
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Post by BBB on Nov 19, 2014 11:54:46 GMT -5
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Post by Night Ranger on Nov 19, 2014 12:35:23 GMT -5
This is the one I run in my car. It is suppose to have a five pole Chebyshev filter built in, and it is class AB. So far it works great on transmit, but the receive preamp transistor appears to be breaking down. 75 watts output on AM with four watts in the medium power setting, and 200+ watts on sideband with 12 watts in on the high power setting. I snapped some ferrite chokes on the B+ wire to keep RF from exiting that way. Blue faced Palomar 350 with two 2sc2879's Front www.shadowstorm.com/cb/palomar-350/Palomar-350-front.jpgInside cover www.shadowstorm.com/cb/palomar-350/Palomar-350-inside.jpgStay away from the black faced Palomar Elite amps. They are not made by the same people. I had alot of problems with my black faced Palomar 300 Elite. I finally tossed it in the garbage. Night Ranger
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Post by ab5ni on Nov 19, 2014 12:37:48 GMT -5
Now that I've seen quite a few transistorized Class C linear RF amplifiers thru the eyes of a spectrum analyzer, I can confidently say that there is a great discrepancy between the quality of the output of them. This even occurs between amps made by the same manufacturer. So the difference between a relatively linear transistorized amp and one that has many unwanted harmonics could be due to several variables including, but not limited to, component selection and in the end how well they were "tuned" at the factory before they went out the door. After all, a few of my HAM radios use the same devices like the Kenwood 430S with (2) 2sc2290's or the Yaesu FT-1000MP with 2sc2879's albeit not necessarily driven Class C. Great post, BBB! I'm pretty sure it is safe to say here that Kenwood and Yaesu went the extra mile, making damn sure their rigs were spectrally pure and then some, especially when they both knew that they'd eventually have to go through the ARRL's engineering lab and review . A non-passing grade from them could mean a complete failure in sales, without doubt. Unfortunately, the CB crowd doesn't have something like this (as far as I know), and these "manufacturers" can get away with almost anything. It takes a certain mindset and curiosity to understand these thing, BBB. We know this stuff because we like to know how things work under the hood and enjoy reading. Unfortunately, the vast majority of people hate reading and just want their "things" to work and not worry about how they do the things they do. They just want to sit back and operate. This is the mindset we're dealing with when we see DOSY meters, 50W rigs driving 4W-input, two-transistor amplifiers -- add infinitum . 73, Randy AB5NI
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Sandbagger
Administrator/The Boss
Posts: 6,245
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Post by Sandbagger on Nov 19, 2014 18:30:50 GMT -5
Now that I've seen quite a few transistorized Class C linear RF amplifiers thru the eyes of a spectrum analyzer, I can confidently say that there is a great discrepancy between the quality of the output of them. This even occurs between amps made by the same manufacturer. So the difference between a relatively linear transistorized amp and one that has many unwanted harmonics could be due to several variables including, but not limited to, component selection and in the end how well they were "tuned" at the factory before they went out the door. After all, a few of my HAM radios use the same devices like the Kenwood 430S with (2) 2sc2290's or the Yaesu FT-1000MP with 2sc2879's albeit not necessarily driven Class C. Great post, BBB! I'm pretty sure it is safe to say here that Kenwood and Yaesu went the extra mile, making damn sure their rigs were spectrally pure and then some, especially when they both knew that they'd eventually have to go through the ARRL's engineering lab and review . A non-passing grade from them could mean a complete failure in sales, without doubt. Unfortunately, the CB crowd doesn't have something like this (as far as I know), and these "manufacturers" can get away with almost anything. It takes a certain mindset and curiosity to understand these thing, BBB. We know this stuff because we like to know how things work under the hood and enjoy reading. Unfortunately, the vast majority of people hate reading and just want their "things" to work and not worry about how they do the things they do. They just want to sit back and operate. This is the mindset we're dealing with when we see DOSY meters, 50W rigs driving 4W-input, two-transistor amplifiers -- add infinitum . I think we are all in agreement that there are those who pretty much link their manhood to the wattmeter readings in their shacks. The higher the needle goes, the bigger "man" they perceive themselves to be. To imply that their Dosy meters are way off, is taken as a personal insult. To quote from the Toshiba device datasheet in contradiction to what the garage shop amp makers claim for power output, or to even hint that spurious emissions are responsible for the (false) higher power readings, is akin to calling the cops on the neighbors keg party. You're the killjoy, the buzzkill, the wet blanket, or worse, the snotty know-it-all ham. But while it can bring a chuckle, every now and then, to see some of the more extreme examples of idiocy at work, in the process of "zero-five'ing" their amps, it's probably not a good idea to harp on it ad-nausium, as it starts to get old. Eventually we'll start to sound like a bunch of old yentas gossiping at the fence......
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Sandbagger
Administrator/The Boss
Posts: 6,245
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Post by Sandbagger on Nov 19, 2014 18:54:34 GMT -5
Sure looks like that amp was the victim of overdrive, or it took off in oscillation. All of the feedback resistors are cooked, which doesn't bode well for the condition of the rest of the amp.
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Post by ab5ni on Nov 19, 2014 21:59:27 GMT -5
Great post, BBB! I'm pretty sure it is safe to say here that Kenwood and Yaesu went the extra mile, making damn sure their rigs were spectrally pure and then some, especially when they both knew that they'd eventually have to go through the ARRL's engineering lab and review . A non-passing grade from them could mean a complete failure in sales, without doubt. Unfortunately, the CB crowd doesn't have something like this (as far as I know), and these "manufacturers" can get away with almost anything. It takes a certain mindset and curiosity to understand these thing, BBB. We know this stuff because we like to know how things work under the hood and enjoy reading. Unfortunately, the vast majority of people hate reading and just want their "things" to work and not worry about how they do the things they do. They just want to sit back and operate. This is the mindset we're dealing with when we see DOSY meters, 50W rigs driving 4W-input, two-transistor amplifiers -- add infinitum . I think we are all in agreement that there are those who pretty much link their manhood to the wattmeter readings in their shacks. The higher the needle goes, the bigger "man" they perceive themselves to be. To imply that their Dosy meters are way off, is taken as a personal insult. To quote from the Toshiba device datasheet in contradiction to what the garage shop amp makers claim for power output, or to even hint that spurious emissions are responsible for the (false) higher power readings, is akin to calling the cops on the neighbors keg party. You're the killjoy, the buzzkill, the wet blanket, or worse, the snotty know-it-all ham. But while it can bring a chuckle, every now and then, to see some of the more extreme examples of idiocy at work, in the process of "zero-five'ing" their amps, it's probably not a good idea to harp on it ad-nausium, as it starts to get old. Eventually we'll start to sound like a bunch of old yentas gossiping at the fence...... With this conversation, at least some of them might find their way here, read a bit, and better inform themselves', SB. As far as the chuckling is concerned, I tend to agree that we might be taking some of this stuff too seriously. The only solution I can see is that we have to address all the layman in terms they understand -- in other words, tone down the tech talk a bit and explain the tech terms we use -- or we'll eventually push them away, with most of them becoming insulted and such. 73, Randy AB5NI
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Post by ab5ni on Nov 19, 2014 22:20:38 GMT -5
This is the one I run in my car. It is suppose to have a five pole Chebyshev filter built in, and it is class AB. So far it works great on transmit, but the receive preamp transistor appears to be breaking down. 75 watts output on AM with four watts in the medium power setting, and 200+ watts on sideband with 12 watts in on the high power setting. I snapped some ferrite chokes on the B+ wire to keep RF from exiting that way. Blue faced Palomar 350 with two 2sc2879's Front www.shadowstorm.com/cb/palomar-350/Palomar-350-front.jpgInside cover www.shadowstorm.com/cb/palomar-350/Palomar-350-inside.jpgStay away from the black faced Palomar Elite amps. They are not made by the same people. I had alot of problems with my black faced Palomar 300 Elite. I finally tossed it in the garbage. Night Ranger That amp looks like it is well made, NR, and they even bothered to have a custom board built for the thing. As far as the preamp goes, I'd just rip the one in there out and replace the thing, although there is the possibility that it's good and over driving an RF amp in the frontend of your rig. You could easily test this by putting a liner-taper pot before the pre-amp circuit and find the right setting for driving the the amp's RF amp, or you could add the pot after the preamp and tone it down a bit before feeding the signal the the Rig's RF amplifier. In either case, you'd find out if using the pre-amp is even worth using with your rig. In most rigs, the thing will probably just over drive the rig's RF amplifier and add a LOT more noise, increasing the noise floor significantly. 73, Randy AB5NI
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