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?
" 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
__
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:
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
"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
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
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
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
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
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
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
Thanks to all who responded to my query. I have since connected the HM-10 XD to
the K3S and have found that the following settings work well for both the HC4X
and HC5X cartridges. MC FP H, mic menu setting, and Mic gain 30. I continue to
use the same transmit EQ settings as I used for the the
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.
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
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
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
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|
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
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
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
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Elecraft mailing list
Home:
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
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
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
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,
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
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
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?
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
The issue is discharge curve. A very good LiFePO4, LiIon, or Lipoly
battery will have a very flat discharge curve, maintaining its terminal
voltage under load right up to near total discharge. At that point, the
terminal voltage will adopt the glide angle of a brick at which point my
K2
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:
And with that, let's close this thread now before it veers into a discussion pro
and con on the legality of running different power levels.
In general, in the interest of keeping list volume under control and discussions
polite, we prefer FCC rule and policy discussions, along with other
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
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
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
While running the KPA1500 in the SARTG tonight, I noticed that the temp
reading drops about 10C when transmitting. min fan speed 1.
Seems to be related to power - at 1500W it's pretty close to 10C. At
lower powers, it's less of a difference. I don't recall seeing that
before.
Normal?
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
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
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?
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
Howie this is excellent data. Thank you for your work in this area.
The table really clearly shows the tradeoffs between cost, weight, volume,
capacity and everything else. Alkaline batteries do pretty well for themselves,
although I'm not sure why the voltage for 8 cells is listed at only 9.6
The actual FCC regulation (47 CFR 97.313) reads:
“An amateur station must use the minimum transmitter power necessary to carry
out the DESIRED communications” (my capitalization).
In operating my own station I assign primary importance to the term “desired
communication” and secondary
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
I noticed this problem shortly after getting my 1500 back in May. I only see
this problem on 40 mtrs for some reason. I've never seen a 10 degree
fluctuation but itis regularly 6 degrees and has approached 8 degrees. I only
work cw for the most part. I see it all the time when the duty
Yea, I was on 40m also. So there's a second data point.
Did not notice it before - but having watched it pretty consistently
tonight, I will know what to look for on other bands. Tonight was the
first night I had the chance to run it on RTTY and want to be sure the
thing is ready for prime
Like many of us of a certain age, I have started wearing hearing aids
(actually I first tried one 20 years ago but since my hearing on one ear
was still pretty good at the time I gave up on it soon after). Now I
have issues in both ears and am essentially deaf in one so I got aids
with CROS
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