KPA-1500 Efficiency As A Function of Input Power
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KPA-1500 Efficiency As A Function of Input Power
 
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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 <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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by john@kk9a.com
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: [hidden email] <[hidden email]> On Behalf Of [hidden email] Sent: Friday, August 17, 2018 9:43 AM To: [hidden email] 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 <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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by john@kk9a.com
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, [hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by john@kk9a.com
Perhaps because the power supply is the limiting factor.
Scott K9MA ---------- Scott Ellington. K9MA --- via iPhone > On Aug 17, 2018, at 8:43 AM, "[hidden email]" <[hidden email]> 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 <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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by john@kk9a.com
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, [hidden email] 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 <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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > -- Hisashi T Fujinaka - [hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by john@kk9a.com
On 8/17/2018 6:43 AM, [hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by john@kk9a.com
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, [hidden email] 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 <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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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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, [hidden email] 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 <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:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [hidden email] >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by Wes Stewart-2
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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Wes Stewart-2
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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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In reply to this post by Lynn W. Taylor, WB6UUT-3
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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: KPA-1500 Efficiency As A Function of Input Power
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Administrator
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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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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