This is normal from theory. Input power increase as I*U. Output power
increases as I*I*R. So at half input power one quarter output power. At 1/4
input power 1/16 output power.
Two ways around, none implemented in KPA1500. Change transformer windings
like in KX3, which is harder to do at high
I would be concerned about reducing voltage for SSB and TX IMD. The NXP 1K50H
devices are only biased at 1 amp each which is a bit low for optimal IMD as it
is. SSB IMD could be improved by increasing bias to 2 amps per device. Since
the bias is only present during TX the waste heat increase
Yes, I read the same. Lowering the PA voltage might be a bit difficult...
73, Roy K6XK
On 11/13/2020 8:27 AM, Howard Sherer wrote:
Reading the display on the KPA 1500 at various RF output levels shows an
efficiency as follows on 40M into a dummyload:
300W 23%
500W 27%
1000W 42%
Reading the display on the KPA 1500 at various RF output levels shows an
efficiency as follows on 40M into a dummyload:
300W 23%
500W 27%
1000W 42%
1300W 48%
1500W 52%
1600W 54%
Have other owners seen results like this? Do you think a firmware and menu
item could be developed to
The bias would do nothing for low power.
Low power can be implemented in two ways, with different taps at final
transformer (KX3), and with different supply voltage (Expert amps). The
first one is hard at a KW level. The second one requires power supply with
different voltages. If the power
I would like to see the KPA-1500 have a "Medium Power" setting with optimized
bias for that power level so the amp could be operated at 750-watts output and
good efficiency. While the KPA-1500 can operate FT and RTTY contests at 1,500
watts, I believe the amp operated at 750-watts with an
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
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
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:
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
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
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
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
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
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?
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
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
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
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?
-
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 t
18 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 w
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:
, 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
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
y 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
lf 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
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.
th.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.
an.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 fr
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
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
-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
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
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
Thanks to all that commented. Just wanted to make sure this was normal
operating behavior. Seemed counter-intuitive but now I think I
understand it. Maybe will run a "Time to Temp" test running low power
vs. high power. Just curious.
Charles K5UA
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|
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
"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:
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
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
-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
" 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
__
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?
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
I would think these RF input versus RF output numbers are reasonable.
Everyone's setup will vary for all bands.
I haven't looked at the KPA-1500 Utility in a while, but "real" efficiency
of the amplifier is a different calculation. Amp efficiency is Power Input
versus Power Output, and per
There's no way 40W drives exactly 1500W on all bands. Here's what I get
into a DL (no tuner). Power measurements based on the LP100 which was
calibrated by Larry last year - not what I would call a current cal but
certainly better than a generic Bird. Feed with a key-down in CW, with
the
Are you saying it took exactly 40W input on each band to produce 1500W out..
I find the gain of the amp very different from band to band. For
example on 80M mine takes 32W to produce 1500W into a dummy load, and
15M it takes 47W to produce 1500W in to a dummy load. That's a
variation of
Just wondering, how much power will the KPA-1500 put into a dummy load?
73 Darrell AB2E
From: elecraft-boun...@mailman.qth.net on
behalf of char...@k5ua.com
Sent: Wednesday, August 15, 2018 10:40 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] KPA-1500
Just curious what other users of the KPA-1500 see as the efficiency
reported by the KPA-1500 utility app.
The following efficiencies are being report by my KPA-1500 utility app
by band into a dummy load running 40 watts input and 1500 watts output:
80M CW: 61%
80M SSB: 64%
40M CW: 54%
49 matches
Mail list logo
