Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Also on this related thread: We're way over the posting limit on this one. Let's close this thread for now. (And, in the future, please voluntarily close long threads well before I happen to stop by :-) 73, Eric /elecraft.com/ On 8/17/2018 5:13 PM, Fred Jensen wrote: Yes. Electricity cost to generate the RF that earns the revenue is a major part of the broadcast station budget. Not so much for amateurs. Since FM is constant envelope modulation, it makes sense it would have a lower overall efficiency. Even Rush Limbaugh has to take a breath occasionally on AM ... it makes no difference on FM. [:-)) 73, __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Seems like this discussion would be functional if it were ways to quiet the fans without compromising the efficiency of the cooling. Chuck Jack KE9UW Sent from my iPhone, cjack > On Aug 17, 2018, at 7:13 PM, Fred Jensen wrote: > > Yes. Electricity cost to generate the RF that earns the revenue is a major > part of the broadcast station budget. Not so much for amateurs. Since FM is > constant envelope modulation, it makes sense it would have a lower overall > efficiency. Even Rush Limbaugh has to take a breath occasionally on AM ... > it makes no difference on FM. [:-)) > > 73, > > Fred ["Skip"] K6DGW > Sparks NV DM09dn > Washoe County > >> On 8/17/2018 3:45 PM, W2xj wrote: >> Today in broadcast we generally rate transmitters by AC in to RF out. For AM >> transmitters that figure is in the low 90 percent range and the current FMs >> run at about 74% AC in to RF out. >> >> > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to c-haw...@illinois.edu __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
We're way over the posting limit on this one. Let's close this thread for now. (And, in the future, please voluntarily close long threads well before I happen to stop by :-) 73 Eric /elecraft.com/ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Yes. Electricity cost to generate the RF that earns the revenue is a major part of the broadcast station budget. Not so much for amateurs. Since FM is constant envelope modulation, it makes sense it would have a lower overall efficiency. Even Rush Limbaugh has to take a breath occasionally on AM ... it makes no difference on FM. [:-)) 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County On 8/17/2018 3:45 PM, W2xj wrote: Today in broadcast we generally rate transmitters by AC in to RF out. For AM transmitters that figure is in the low 90 percent range and the current FMs run at about 74% AC in to RF out. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Yes, it was Class C ... FM is constant envelope modulation. The ancient 50's/60's rules of thumb were: Class A: 25% - really linear Class B: 50% - linear with crossover distortion Class C: 75% - exceedingly non-linear Class AB1: between A & B, no grid current - mitigates crossover distortion Class AB2: AB1 but draws grid current - also mitigates crossover dist. For audio, Classes B and AB needed two tubes and operated push-pull. We were interested in efficiency of the PA because higher efficiency meant lower dissipation for a fixed output [10 KW]. As it was, at 90.7 MHz, the anodes were already nearly white. Again ... I do not recommend using four parallel 4-1000A's anywhere near 90.7 MHz. [:-)) The RCA Ampliphase [aka "Amplifuzz"] series of AM transmitters ran Class C through the entire RF chain. They were a bear to align ... you never wanted to start a PoP after sign-off if you'd been awake all day. The Ampliphase history is moderately interesting however, especially if you're from or in Sacramento CA. This thread however has been discussing "efficiency" of a KPA1500 in terms of output power vs drive power which isn't even remotely close to measuring efficiency. As amateurs, I can't come up with a single reason why we'd be concerned about efficiency as long as the amplifier design is solid and robust. Our A/C uses far more energy over a summer than my K3/KPA500 did all year, and I leave it on a lot. If this is all about fans and their noise, the thread needs a new subject. 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County On 8/17/2018 3:06 PM, Bill Frantz wrote: And I would guess it was running in class C, which is not linear, so only useful for certain modes (including FM). Class C can convert most of the input power to RF power. 73 Bill AE6JV On 8/17/18 at 11:48 AM, k6...@foothill.net (Fred Jensen) wrote: One 10 KW FM transmitter I helped build used four 4-1000A's in parallel and the filament power was 600 watts. Efficiency, including filament power was just over 70%. --- Bill Frantz | Ham radio contesting is a | Periwinkle (408)356-8506 | contact sport. | 16345 Englewood Ave www.pwpconsult.com | - Ken Widelitz K6LA / VY2TT | Los Gatos, CA 95032 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to k6...@foothill.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Today in broadcast we generally rate transmitters by AC in to RF out. For AM transmitters that figure is in the low 90 percent range and the current FMs run at about 74% AC in to RF out. Sent from my iPad > On Aug 17, 2018, at 11:48 AM, Fred Jensen wrote: > > Well, only if you've figured out a way to divide by zero. [:-) > > The term "amplifier efficiency" must have changed dramatically since I worked > in broadcast nearly a lifetime ago. Then, it was the ratio [expressed as a > percentage] of the RF power delivered to the 3 1/8" hardline divided by the > DC power supplied to the amplifier plate circuit. Power to the filaments was > generally excluded by manufacturers seeking to have higher efficiency > numbers. One 10 KW FM transmitter I helped build used four 4-1000A's in > parallel and the filament power was 600 watts. Efficiency, including filament > power was just over 70%. > > To measure the efficiency of a KPA1500 [or 500, or KXPA100, or KPA2] one > would measure the key down RF output and divide it by the key down DC input > power. If it was water-cooled, I suppose one should include the input power > to the pump(s), but no one ever did. SS amplifiers like the KPA(1)500 > probably run class AB or its equivalent and have substantial DC input > power even at zero RF input. > > RF output power vs RF input power defines the amplifer's transfer function, > not its efficiency. > > 73, > > Fred ["Skip"] K6DGW > Sparks NV DM09dn > Washoe County > > PS: I really don't recommend trying to get four parallel 4-1000A's to work > anything close to "well" at 90.7 MHz. Apparently, it seemed like a good idea > at the time. [:-) > >> On 8/17/2018 6:24 AM, Charlie T wrote: >> Think zero output with zero drive = zero efficiency. >> Apply some drive, read some output and the efficiency goes up from there. >> >> 73, Charlie k3ICH >> > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to w...@w2xj.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Actually a class C amplifier can be made to perform as a linear. The technology is over 60 years old but I don’t think it has ever been tried in amateur service. Sent from my iPad > On Aug 17, 2018, at 3:06 PM, Bill Frantz wrote: > > And I would guess it was running in class C, which is not linear, so only > useful for certain modes (including FM). Class C can convert most of the > input power to RF power. > > 73 Bill AE6JV > >> On 8/17/18 at 11:48 AM, k6...@foothill.net (Fred Jensen) wrote: >> >> One 10 KW FM transmitter I helped build used four 4-1000A's in parallel and >> the filament power was 600 watts. Efficiency, including filament power was >> just over 70%. > --- > Bill Frantz| Ham radio contesting is a| Periwinkle > (408)356-8506 | contact sport. | 16345 Englewood Ave > www.pwpconsult.com | - Ken Widelitz K6LA / VY2TT | Los Gatos, CA 95032 > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to w...@w2xj.net > __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
And I would guess it was running in class C, which is not linear, so only useful for certain modes (including FM). Class C can convert most of the input power to RF power. 73 Bill AE6JV On 8/17/18 at 11:48 AM, k6...@foothill.net (Fred Jensen) wrote: One 10 KW FM transmitter I helped build used four 4-1000A's in parallel and the filament power was 600 watts. Efficiency, including filament power was just over 70%. --- Bill Frantz| Ham radio contesting is a| Periwinkle (408)356-8506 | contact sport. | 16345 Englewood Ave www.pwpconsult.com | - Ken Widelitz K6LA / VY2TT | Los Gatos, CA 95032 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Sure. That's why during every QSO I ask my partner, "Can you still hear me?" If he says, "Yes", I reduce power and ask again. Eventually, we determine the minimum power necessary. Then the band changes and we start over. Kind of slows down pileups and contesting, but rule are rules, right? On 8/17/2018 11:43 AM, Lynn W. Taylor, WB6UUT wrote: Isn't there a rule about using the minimum power necessary? On 8/17/2018 11:20 AM, Wes Stewart wrote: Do they? I have a KPA500, not a '1500 but I run mine full tilt on RTTY. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
The theory states that Power in = U I Power out ~ I*I*r So power-in is linear with current. Power-out is quadratic with current. Driving hard helps efficiency but hurts linearity. Max efficiency with LDMOS is about 60% with reasonable linearity and no feedback, but could be > 70% with predistortion. Higher efficiency can be obtained in class C for CW/RTTY however wideband SS designs are not suitable for class C. For low efficiency at lower power the best approach is to reduce the supply voltage. SPE gives a choice of 25V (1/3 power), 35V (half power) and 48V (full power). New 4O3A (Flex) amplifier is supposed to adjust supply voltage automatically for highest efficiency at a given power. Another choice is to use an external tuner for max power, not low SWR, as e.g. at 1/4 power the optimum output impedance is 200 Ohms not 50 Ohms. Elecraft is using a trick in KX3 where at > 12 V and 5 W another ratio is used in the final transformer, reducing power input by almost one half. Ignacy, NO9E -- Sent from: http://elecraft.365791.n2.nabble.com/ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
On 8/17/2018 11:20 AM, Wes Stewart wrote: Something to bear in mind in this discussion is that we run our equipment in ICAS, not CCS. Even in a contest situation we probably only transmit half the time. During the off (RX) time the amp isn't drawing any plate, collector or drain current, nor is it drawing much current on CW, key up or SSB between syllables. RTTY is a "continuous" mode without the syllabic breather, but it's still intermittent. Great analysis. Long-winded ragchewing on AM or keydown digital modes is probably worst case for dissipation. I don't do either, so my worst case is WSJT modes on 6M (6M because efficiency is lowest), or RTTY contesting when I'm running (that is, CQing) with few answers. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Well, only if you've figured out a way to divide by zero. [:-) The term "amplifier efficiency" must have changed dramatically since I worked in broadcast nearly a lifetime ago. Then, it was the ratio [expressed as a percentage] of the RF power delivered to the 3 1/8" hardline divided by the DC power supplied to the amplifier plate circuit. Power to the filaments was generally excluded by manufacturers seeking to have higher efficiency numbers. One 10 KW FM transmitter I helped build used four 4-1000A's in parallel and the filament power was 600 watts. Efficiency, including filament power was just over 70%. To measure the efficiency of a KPA1500 [or 500, or KXPA100, or KPA2] one would measure the key down RF output and divide it by the key down DC input power. If it was water-cooled, I suppose one should include the input power to the pump(s), but no one ever did. SS amplifiers like the KPA(1)500 probably run class AB or its equivalent and have substantial DC input power even at zero RF input. RF output power vs RF input power defines the amplifer's transfer function, not its efficiency. 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County PS: I really don't recommend trying to get four parallel 4-1000A's to work anything close to "well" at 90.7 MHz. Apparently, it seemed like a good idea at the time. [:-) On 8/17/2018 6:24 AM, Charlie T wrote: Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Yes for the US at least. However to provide effective communications, is a subjective term, therefore the entire requirement is vague. Rick nhc On 8/17/2018 11:43 AM, Lynn W. Taylor, WB6UUT wrote: Isn't there a rule about using the minimum power necessary? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Isn't there a rule about using the minimum power necessary? On 8/17/2018 11:20 AM, Wes Stewart wrote: Do they? I have a KPA500, not a '1500 but I run mine full tilt on RTTY. Something to bear in mind in this discussion is that we run our equipment in ICAS, not CCS. Even in a contest situation we probably only transmit half the time. During the off (RX) time the amp isn't drawing any plate, collector or drain current, nor is it drawing much current on CW, key up or SSB between syllables. RTTY is a "continuous" mode without the syllabic breather, but it's still intermittent. Wes On 8/17/2018 6:43 AM, j...@kk9a.com wrote: So why do most RTTY users run their amps at reduced power? John KK9A From: Charlie K3ICH Date: Fri Aug 17 09:24:18 EDT 2018 I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-bounces at mailman.qth.net On Behalf Of john at kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft at mailman.qth.net Cc: charles at k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to wes_n...@triconet.org __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to kx...@coldrockshotbrooms.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Do they? I have a KPA500, not a '1500 but I run mine full tilt on RTTY. Something to bear in mind in this discussion is that we run our equipment in ICAS, not CCS. Even in a contest situation we probably only transmit half the time. During the off (RX) time the amp isn't drawing any plate, collector or drain current, nor is it drawing much current on CW, key up or SSB between syllables. RTTY is a "continuous" mode without the syllabic breather, but it's still intermittent. Wes On 8/17/2018 6:43 AM, j...@kk9a.com wrote: So why do most RTTY users run their amps at reduced power? John KK9A From: Charlie K3ICH Date: Fri Aug 17 09:24:18 EDT 2018 I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-bounces at mailman.qth.net On Behalf Of john at kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft at mailman.qth.net Cc: charles at k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to wes_n...@triconet.org __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
On 8/17/2018 6:43 AM, j...@kk9a.com wrote: So why do most RTTY users run their amps at reduced power? Because they don't understand how amplifiers work. :) 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
I'm running at reduced power because I keep getting into my RemoteRig hardware at higher power (at least on 20M). On Fri, 17 Aug 2018, j...@kk9a.com wrote: So why do most RTTY users run their amps at reduced power? John KK9A From: Charlie K3ICH Date: Fri Aug 17 09:24:18 EDT 2018 I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-bounces at mailman.qth.net On Behalf Of john at kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft at mailman.qth.net Cc: charles at k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to ht...@twofifty.com -- Hisashi T Fujinaka - ht...@twofifty.com BSEE + BSChem + BAEnglish + MSCS + $2.50 = coffee __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
KK9A wrote: "...if the heat generated is approximately the same with all power levels, why do RTTY ops use lower power..." First, the heat generated is not actually approximately the same with all power levels. To a first crude approximation, the heat generated is made up of two components. One component is due to such things as biasing for linearity, and is approximately constant whenever the amp is in transmit (it's still non-zero, but quite a bit smaller, when the amp is in standby), and the other component is related to the actual signal being generated, and is approximately linear with output power. At low output powers, the first component dominates, while at higher powers the second component becomes significant. The power consumption efficiency goes from zero at zero power (some mains current being used but generating zero output) to a maximum when the signal-related component is largest compared to the constant component, i.e. at maximum power. Second, what is dissipated is the accumulated heat energy, not power. Heat removal processes are far slower than output power changes, so effectively they integrate the thermal power generation over a significant time interval. If the instantaneous power is the same in two modes, but the duty-cycle factor for one mode is twice the duty factor for the other mode, then the signal-related component of the energy to be dissipated in a given time period will be twice as high for the high-duty mode. The total energy to be dissipated will not be as much as twice as high because of the constant component, but it will still be higher in the higher duty cycle mode. Depending on the thermal design of the amplifier, that may or may not be enough of an increase to require derating. 73, Rich VE3KI __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Folks - Let's keep it polite and non-personal. Eric Moderator /elecraft.com/ On 8/17/2018 10:27 AM, j...@kk9a.com wrote: What is the Oh Jeeze about? I found K5UA's efficiency data surprising that the amp dissipates nearly the same amount of heat regardless of power level. Your comment was "I really do NOT understand why this data is so surprising." You obviously know much more about RF amplifiers than I do. I subscribe to this list to learn. So, my next question was if the heat generated is approximately the same with all power levels, why do RTTY ops use lower power. I am assuming that heat is what destroys finals or other amp components. Perhaps there is a power supply limitation or that tube amps have a more linear efficiency so lower power really means less heat. Of course RTTY has a higher duty cycle than CW and SSB, that was not my question. The RTTY duty cycle is the same whether you run 500 watts or 1500. If the amplifier heating is about the same at both power levels due to higher efficiency at higher power than why not use the maximum power for RTTY (assuming that you have an antenna and coax that can handle it)? John KK9A Sent via the Samsung Galaxy 7 edge, an AT&T 4G LTE smartphone. Charlie K3ICH wrote: Oh Jeeeze... Almost ALL amps in current use are NOT rated for continuous power output. Only the most recent SS amp builders which use devices themselves rated for 3x or 4X their rated output would dare to specify 100% duty cycle. Only a few tube type amps are rated at 100% duty cycle too and they also use severe over-kill in their PA devices, such as a pair of 8877's or maybe three, 3-500ZG's etc. I would venture to say that 85% of the current amplifiers in use today are NOT rated for 100% duty cycle, so THAT's why they back off on the RTTY output. 73, Charlie k3ICH -Original Message- From: elecraft-bounces at mailman.qth.net On Behalf Of john at kk9a.com Sent: Friday, August 17, 2018 9:43 AM To: elecraft at mailman.qth.net Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power So why do most RTTY users run their amps at reduced power? John KK9A From: Charlie K3ICH Date: Fri Aug 17 09:24:18 EDT 2018 I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-bounces at mailman.qth.net On Behalf Of john at kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft at mailman.qth.net Cc: charles at k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to eric.swa...@elecraft.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Not sure why that's a surprise. It's a linear amp ... the bias point is what draws the current, and therefore essentially determines the dissipation. There's nothing remarkable about it. Amplifier 101. Dave AB7E On 8/16/2018 10:17 PM, char...@k5ua.com wrote: Thanks for the replies. Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) 10w 29a 52.7v 1528w 375W 375/1528 = 24.5% 1205w 15w 37a 52.7v 1950w 620w 620/1950 = 31.7% 1335w 20w 43a 52.6v 2262w 861w 861/2262 = 38.0% 1413w 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. Charles K5UA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to xda...@cis-broadband.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Perhaps because the power supply is the limiting factor. Scott K9MA -- Scott Ellington. K9MA --- via iPhone > On Aug 17, 2018, at 8:43 AM, "j...@kk9a.com" wrote: > > So why do most RTTY users run their amps at reduced power? > > John KK9A > > > From: Charlie K3ICH > Date: Fri Aug 17 09:24:18 EDT 2018 > > > I really do NOT understand why this data is so surprising. > It all seems to me to be perfectly normal with the amplifier's highest > efficiency occurring at near max output. > Which curiously, I would assume, is the way the amp was designed. > > Think zero output with zero drive = zero efficiency. > Apply some drive, read some output and the efficiency goes up from there. > > 73, Charlie k3ICH > > > > > -Original Message- > From: elecraft-bounces at mailman.qth.net mailman.qth.net> On > Behalf Of john at kk9a.com > Sent: Friday, August 17, 2018 8:57 AM > To: elecraft at mailman.qth.net > Cc: charles at k5ua.com > Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power > > Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) > at lower power would keep the fan from running as much. I knew that > efficiency changed with output power but I did not expect that it was this > significant. If your data is correct there is 1000++ watts of heat to > dissipate no matter what power level you use. > > John KK9A > > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to k...@sdellington.us __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Yes yes and yes. Amps are designed with the fixed output matching network chosen for a value of impedance and energy transfer to be at "rated power". Running any amp at reduced power then does not confirm to the design of the output matching network and the efficiency decreases. You aren't doing any favor to yourself, the amp, or others to run the amp otherwise. 73 Bob, K4TAX On 8/17/2018 8:24 AM, Charlie T wrote: I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of j...@kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft@mailman.qth.net Cc: char...@k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A From: charles k5ua Date: Fri Aug 17 01:17:49 EDT 2018 Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) 10w 29a 52.7v 1528w 375W375/1528 = 24.5% 1205w 15w 37a 52.7v 1950w 620w620/1950 = 31.7% 1335w 20w 43a 52.6v 2262w 861w861/2262 = 38.0% 1413w 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. Charles K5UA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to pin...@erols.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to rmcg...@blomand.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
I've said this and measured this for years with tube type amps, where as
I hear hams say they are running reduced power to "save the tubes".
That's HOGWASH. Determine the efficiency at reduced power vs. rated
power. The excessive heat at reduced power has to go somewhere.
I view running an amp, tube or solid state types, at reduced power is
much like driving with your right foot on the accelerator and the left
foot on the brake {US style} and wondering why your gas mileage suffers
and your brakes wear out.
Tune it up, load it up, and run that sucker at full power. After all,
that's why you have an amp.
73
Bob, K4TAX
On 8/17/2018 8:11 AM, ANDY DURBIN wrote:
"There was a similar post about the KPA500 in the last year or so. Elecraft
responded that the amp was designed for 500 Watts running less was less efficient and
running amp at low power was doing it no favors."
Here is an example of measured PA dissipation for a KPA500:
https://www.dropbox.com/s/bq0v2740t3iztnj/KPA500%20PA%20DISS%20for%2040%20meters.pdf?dl=0
73,
Andy k3wyc
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Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Because the effect of power dissipation over time is temperature increase. RTTY has a high duty cycle (100% when you are transmitting), compared to 50% for CW and usually something less for SSB (it depends on the amount of compression). So more heat is produced when you run RTTY, which the amplifier's cooling system has to get rid of. If the cooling system can't get rid of it, the temperature rises dangerously and components fail. In the case of the KPA1500, it would seem that there is more power dissipated BY THE FINALS at somewhat reduced power levels. But there are other components, such as the lowpass filters, which also dissipate some power, due to unavoidable losses. This dissipation increases as the power output increases. These components would thus get hotter with higher power, and they would be more stressed. This is a good reason to run less power with RTTY with some amplifiers. I think the designers of the KPA1500 took this into account, and you will be fine following the published spec. 73, Victor, 4X6GP Rehovot, Israel Formerly K2VCO CWops no. 5 http://www.qsl.net/k2vco/ On 17/08/2018 16:43, j...@kk9a.com wrote: So why do most RTTY users run their amps at reduced power? John KK9A __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Oh Jeeeze... Almost ALL amps in current use are NOT rated for continuous power output. Only the most recent SS amp builders which use devices themselves rated for 3x or 4X their rated output would dare to specify 100% duty cycle. Only a few tube type amps are rated at 100% duty cycle too and they also use severe over-kill in their PA devices, such as a pair of 8877's or maybe three, 3-500ZG's etc. I would venture to say that 85% of the current amplifiers in use today are NOT rated for 100% duty cycle, so THAT's why they back off on the RTTY output. 73, Charlie k3ICH -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of j...@kk9a.com Sent: Friday, August 17, 2018 9:43 AM To: elecraft@mailman.qth.net Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power So why do most RTTY users run their amps at reduced power? John KK9A From: Charlie K3ICH Date: Fri Aug 17 09:24:18 EDT 2018 I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-bounces at mailman.qth.net On Behalf Of john at kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft at mailman.qth.net Cc: charles at k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to pin...@erols.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
Charles, It is just like your car. You get great gas mileage at certain speeds and driving methods. Worse is at lower speeds, stop and go, and 55 -65 Mph is a good speed for having an efficient mileage car. However, 70-80 is worse on the mileage. Everything has a sweet spot. Nothing is for free as it takes power to do work or in this case to output RF. The front end of the process always has some requirements to get things moving that do little for you, but you got to have them. Does this make any sense? I don't mean to a smart, I am just trying to relate this in a different way that you are probably familiar with. I don't operate RTTY, but it is one of the hardest modes on the equipment similar to AM or FM. I would guess it is a duty cycle requirement, so the equipment doesn't melt down or to not create splatter issues. RTTY equipment needs to be properly adjusted for decoding similar to FT8. Bill, K8ZCT -- Sent from: http://elecraft.365791.n2.nabble.com/ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
For those curious about the reasons for high power draw at low power out, it might be useful to review the handbook discussion of amplifiers, and the characteristics of class A, B, and C designs. 73 Bill AE6JV -- Bill Frantz| There are now so many exceptions to the 408-356-8506 | Fourth Amendment that it operates only by www.pwpconsult.com | accident. - William Hugh Murray __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
I really do NOT understand why this data is so surprising. It all seems to me to be perfectly normal with the amplifier's highest efficiency occurring at near max output. Which curiously, I would assume, is the way the amp was designed. Think zero output with zero drive = zero efficiency. Apply some drive, read some output and the efficiency goes up from there. 73, Charlie k3ICH -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of j...@kk9a.com Sent: Friday, August 17, 2018 8:57 AM To: elecraft@mailman.qth.net Cc: char...@k5ua.com Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Interesting data, Charles. I assumed that running the KPA1500 (or KPA500) at lower power would keep the fan from running as much. I knew that efficiency changed with output power but I did not expect that it was this significant. If your data is correct there is 1000++ watts of heat to dissipate no matter what power level you use. John KK9A From: charles k5ua Date: Fri Aug 17 01:17:49 EDT 2018 Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) 10w 29a 52.7v 1528w 375W375/1528 = 24.5% 1205w 15w 37a 52.7v 1950w 620w620/1950 = 31.7% 1335w 20w 43a 52.6v 2262w 861w861/2262 = 38.0% 1413w 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. Charles K5UA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to pin...@erols.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
I believe most every electrical device and piece of equipment will have some type efficiency curve for power in and power out. A motor sitting at idle is using power, but doing almost no real work. However, at no load it is still using watts. Typically a motor has the best efficiency at around 75% load or so. I am sure an amplifier or any electronic device is similar to a motor or transformer. There are always "no load losses", that you need to have regardless of the load on the device or output of the device. Also, I am not sure you are looking at the entire picture with your numbers. I see that you are multiplying the DC amperes x DC volts. In reality, the power supply has to make that DC power, and it also has some electrical power loss. You should really use a power meter on the 240V feed from your panel to get the exact input power required for the KPA-1500. That is why Elecraft recommends a 20A feeder at nominal 240V input. The range of the power supply is 195V to 250V. At maximum power output of the amp there will be less amperes used at 250V than 195V but it will require the same input power. There is a maximum power dissipation hard fault @ 2050 watts. So, that would say if you are dissipating 2050 watts, and putting out 1500 watts RF, that would require 3550 watts of input power. At 240V that is about 15 amps and at 195V that is over 18 amps. You don't want to run it that high or at that efficiency. You need to make some changes in your setup to keep below that level. The calculations are even worse for the "efficiency" using the power used on the 240V side, but that is what you are really paying for in your monthly electric bill. What you did probably is close enough for discussion and Elecraft metering reflects those numbers, but it is worth noting there are many factors that enter into an "efficiency" calculation. Loading the amp into a dummy load gives you one set of data. However, the better your antenna matches at each frequency without needing the tuner, the less heat the tuner will create doing it's job to match to 50 ohms, so the amp can put out maximum power. Of course, if your antenna has a high SWR, because of it's electrical design, you are just making heat somewhere, and not putting your power used to good RF output production for getting your station heard on the airwaves. Bill, K8ZCT -- Sent from: http://elecraft.365791.n2.nabble.com/ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
It's normal. Even at zero output, (keyed ON but with no drive power) the idling current required to obtain linear class amplification will cause significant power dissipation in the final, regardless if its solid or hollow state. 73, Charlie k3ICH -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of char...@k5ua.com Sent: Friday, August 17, 2018 1:18 AM To: elecraft@mailman.qth.net Subject: [Elecraft] KPA-1500 Efficiency As A Function of Input Power Thanks for the replies. Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power. The following table illustrates the relationships between exciter power, voltage, current, power-in(voltage x amps), power-out, efficiency, and dissipated power. The following test was made with the KPA-1500 into a dummy load and readings from the KPA-1500 utility software. (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) (Dissipated Pwr) 10w 29a 52.7v 1528w 375W375/1528 = 24.5% 1205w 15w 37a 52.7v 1950w 620w620/1950 = 31.7% 1335w 20w 43a 52.6v 2262w 861w861/2262 = 38.0% 1413w 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w The remarkable thing is that DISSIPATED POWER appears to be relatively constant from 375w output through 1825w output. This implies the KPA-1500 will need to dissipate nearly the same amount of heat at low power output as at high power output, if I am interpreting the data correctly. I would like to know from Elecraft if this is normal behavior. Charles K5UA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to pin...@erols.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
" Upon further testing, I have found that the efficiency of the KPA-1500 is varies greatly with driving power." That's the reason SPE amps have a power range selection choice setting. (Me thinks) 73, RoyK6XK __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 Efficiency As A Function of Input Power
There was a similar post about the KPA500 in the last year or so. Elecraft responded that the amp was designed for 500 Watts running less was less efficient and running amp at low power was doing it no favors. With the KPA500, so many wanted 1500 W so now you have it, you want to run less? Sent from my iPhone ...nr4c. bill > On Aug 17, 2018, at 1:17 AM, char...@k5ua.com wrote: > > Thanks for the replies. > > Upon further testing, I have found that the efficiency of the KPA-1500 is > varies greatly with driving power. The following table illustrates the > relationships between exciter power, voltage, current, power-in(voltage x > amps), power-out, efficiency, and dissipated power. The following test was > made with the KPA-1500 into a dummy load and readings from the KPA-1500 > utility software. > > (Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin) > (Dissipated Pwr) > 10w 29a 52.7v 1528w 375W375/1528 = 24.5% 1205w > 15w 37a 52.7v 1950w 620w620/1950 = 31.7% 1335w > 20w 43a 52.6v 2262w 861w861/2262 = 38.0% 1413w > 25w 47a 52.6v 2472w 1060w 1060/2472 = 42.8% 1451w > 30w 51a 52.6v 2682w 1227w 1227/2682 = 45.7% 1420w > 35w 53a 52.5v 2782w 1380w 1380/2782 = 49.5% 1412w > 40w 55a 52.5v 2887w 1497w 1497/2887 = 51.9% 1382w > 45w 56a 52.5v 2940w 1600w 1600/2940 = 54.4% 1313w > 50w 57a 52.5v 2992w 1703w 1703/2992 = 56.9% 1315w > 53w 59a 52.5v 3097w 1825w 1825/3097 = 58.9% 1306w > > The remarkable thing is that DISSIPATED POWER appears to be relatively > constant from 375w output through 1825w output. This implies the KPA-1500 > will need to dissipate nearly the same amount of heat at low power output as > at high power output, if I am interpreting the data correctly. I would like > to know from Elecraft if this is normal behavior. > > Charles K5UA > __ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to n...@widomaker.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
