Date: Thu, 12 May 2011 13:43:51 -0400
From: Jack Smith jack.sm...@cliftonlaboratories.com
Subject: Re: [Elecraft] KPA-500 Output for Input schedule?
To: elecraft@mailman.qth.net
Message-ID: 4dcc1c56.5050...@cliftonlaboratories.com
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I hope that Elecraft considers making this a published selling point in
print large enough to gain the attention of those of us who do indeed
own lower powered rigs. It presents us with another flexible option if
and when we decide to add more power. When the KPA-500 was announced, I
power output levels, which I suspect Elecraft has
done.
73,
Geoff
GM4ESD
- Original Message -
From: Wes Stewart n...@yahoo.com
To: elecraft@mailman.qth.net; G4ILOJulian julian.g4...@gmail.com
Sent: Wednesday, May 11, 2011 8:02 PM
Subject: Re: [Elecraft] KPA-500 Output
:02 PM
Subject: Re: [Elecraft] KPA-500 Output for Input schedule?
Then by definition, they aren't linear.
A graph of output power vs. input power should be a straight line. It it
isn't then it's non-linear. The practical question is how much
non-linearity is acceptable.
--- On Wed, 5/11
Hello Guy,
The short answer to the first part of your question is yes, and the generic
term for such a scheme is Predistortion. A term that has been used to
identify a Predistortion scheme which employ digital techniques is a
Digital Predistortion Linearizer (DPL), and its use can bring about
That would be a KEEN addition to a K3/KPA500 combo. Put it way out
there and give the industry yet another bone-breaking kick in the *ss.
On Thu, May 12, 2011 at 12:44 PM, Geoffrey Mackenzie-Kennedy
gm4...@btinternet.com wrote:
Hello Guy,
The short answer to the first part of your question is
Geoff list readers ...
There's an article in the current Electronics Design News, as a matter
of fact, on pre-distortion.
http://www.edn.com/article/518070-RF_predistortion_straightens_out_your_signals.php
Although aimed at cellular radio digital modulation, the concepts apply
to analog SSB
I dunno, seems more like a solution in search of a problem to me
73, Ross N4RP
On 5/12/2011 12:58 PM, Guy Olinger K2AV wrote:
That would be a KEEN addition to a K3/KPA500 combo. Put it way out
there and give the industry yet another bone-breaking kick in the *ss.
On Thu, May 12, 2011 at
It may not be valid to estimate distortion based on measuring the gain
versus power level with a CW signal. The reason is that the supply
voltage sags somewhat at maximum power, which may affect the gain. But
that doesn't affect the distortion because the supply voltage is
(nearly) constant
How so? Most hams aren't looking for linearity. The great majority
merely want to be heard and understood ... and many don't seem to care
much about the latter.If they were they wouldn't have the mic gain
and compression cranked up beyond all rational measure. Predistortion
might have
I'm a CW man, so I should keep my mouth shut, but wasn't the Class A Mode
provided by
some Yaesu (and other?) transceivers considered a selling point?
Of course their are some 'turn the gain to 11' guys, but there are also those
who care
about how they sound.
Now back to our regular bug
Let's let this thread rest for now.
73, Eric
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On 5/12/2011 8:15 AM, Guy Olinger K2AV wrote:
I would like to know if some kind of feedback (maybe complicated)
could bring about a quantum leap in linearity, like sampling the
output of the amp and feeding that back to the K3 to digitally
pre-alter the audio to cancel the distortion going
I would like to know if some kind of feedback (maybe complicated)
could bring about a quantum leap in linearity, like sampling the
output of the amp and feeding that back to the K3 to digitally
pre-alter the audio to cancel the distortion going out.
That's exactly the function of adaptive
The documentation on the Elecraft site says the KPA-500 requires 40
watts drive for full output.
Nowhere (at least not that I could find) is the minimum drive
requirement specified nor is there any schedule of output for input
such as 40 watts = 500 watts; xx watts = 250 watts, etc.
More to
Stan,
Of course it can be driven by lower power. The KPA500 is a linear
amplifier. If 40 watts in produces 500 out, then 20 in will give 250
out and 10 in will produce 125 watts. If the relationship is otherwise,
then it is not acting as a linear amplifier. The same thing should be
true
On 2011-05-11 10:16 AM, Don Wilhelm wrote:
Stan,
Of course it can be driven by lower power. The KPA500 is a linear
amplifier. If 40 watts in produces 500 out, then 20 in will give 250
out and 10 in will produce 125 watts. If the relationship is otherwise,
then it is not acting as a
Um, linear with respect to power, or linear with respect to voltage?
Linear with respect to power. Both the input and output are fixed Z
thus an increase in drive results in increases in both the current
and voltage variation which given a linear amplifier causes increases
in both current and
Don Wilhelm-4 wrote:
Of course it can be driven by lower power. The KPA500 is a linear
amplifier. If 40 watts in produces 500 out, then 20 in will give 250
out and 10 in will produce 125 watts. If the relationship is otherwise,
then it is not acting as a linear amplifier. The same
Thank you, Don. I have no experience with any kind of outboard
amplifier since I've been QRP for nearly my entire ham life, but I do
seem to recall that in 'the old days' of tube amps, there was always a
minimum drive requirement and sometimes distortion problems occured at
the lower drive
That's a linear amp in name only. Amplifying SSB should only be
done on that amp with PEP set below the point at which compression
sets in. This of course does not matter on CW or FM, one of the
common uses of such an amp. I'd be surprised if that amp would do
better than 100 watts PEP cleanly.
Then by definition, they aren't linear.
A graph of output power vs. input power should be a straight line. It it isn't
then it's non-linear. The practical question is how much non-linearity is
acceptable.
--- On Wed, 5/11/11, Julian, G4ILO julian.g4...@gmail.com wrote:
If it does that
Perhaps that Mirage amp is intended for FM? Not all amps need to be linear.
Peter W0LLN
On Wed, May 11, 2011 at 2:02 PM, Wes Stewart n...@yahoo.com wrote:
Then by definition, they aren't linear.
A graph of output power vs. input power should be a straight line. It it
isn't then it's
You can read the detailed description at the link I gave. In fact, it claims
to have active bias for improved SSB linearity. So it is definitely
intended for SSB use.
I agree that a graph of output power vs. input power should be a straight
line. But I don't believe there is a linear amplifier
Julian,
From the words of Bob Freiss (the designer) on 9/8/2010 --
The KPA500 requires 30 to 40 watts for full output. With 10 watts of drive
the output will be around 200 watts or a little less.
It's very easy to measure the 1-tone gain compression characteristics of an
amplifier. The desired result is a graph of Pout vs. Pin, with Pin on the
horizontal axis and Pout on the vertical.
So what one needs to do is set Pin to the amp, and measure Pout into a dummy
load. If you do this for
Stan,
Allow some variation to antenna variations also.
This on 15M, swr is 1.0:1
2W = 30W out
2.5W = 40W
3w = 50w
3.5w = 60w
4w = 70w
4.5w = 75w out
5w = 80w
5.5w = 90w
6w = 100w
6.5w = 110w
7w = 120w
7.5w = 130w
8w = 150w
8.5w = 160w
9w = 170w
9.5w = 180w
10w = 190w
11w = 200w
12w = 225w
Adding gain calculation ...
2W = 30W 11.8 dB
2.5W = 40W 12.0 dB
3w = 50w 12.2 dB
3.5w = 60w 12.3 dB
4w = 70w 12.4 dB
4.5w = 75w 12.2 dB
5w = 80w 12.0 dB
5.5w = 90w 12.1 dB
6w = 100w 12.2 dB
6.5w = 110w 12.3 dB
7w = 120w 12.3 dB
Joe, I believe your hypothesis (extrapolation to high power) will be verified
once someone makes higher power measurements.
Regards,
Al W6LX
From: Joe Subich, W4TV li...@subich.com
The numbers look about right including the decreased gain at low level
(as
Joe,
325W @ 15W drive
410W @ 20W drive
490W @ 25W drive
510W @ 26W drive
530W @ 27W drive
560W @ 28W drive
580W @ 29W drive
600W @ 30W drive
630W @ 31W drive
650W @ 32W drive
675W @ 35W drive
690W @ 37W drive
700W @ 40W drive
Is this still about right for your calculations.
Gary
On 12 May
Joe,
Just to clarify, the last measurements were on 28.447.44 (a clear frequency
here at the moment), SWR is 1.1:1, tri-band yagi.
On 12 May 2011 08:40, Gary Gregory garyvk...@gmail.com wrote:
Joe,
325W @ 15W drive
410W @ 20W drive
490W @ 25W drive
510W @ 26W drive
530W @ 27W drive
560W
The RFsensing on the K3 is a real trick. The frst 'dit' may suffer a mild
truncation on band change, but this only happens if you don't press a band
button prior to transmitting.
Low power band changing does occur with 1W on CW. Tested it just now with a
band change from 10M to 15M
Maybe this is
Adding the calculations below ... it's obvious that a lot of
care went into the design - the gain is flat +/- 0.2 dB from
8 to 35W in (150 to 650W out). The 1 dB compression point
looks to be somewhere above 700W.
I don't think I would make a habit of running the KPA-500 at
less than 150 W or
Gregory garyvk...@gmail.com
To: Joe Subich, W4TV li...@subich.com
Cc: elecraft@mailman.qth.net
Sent: Wed, May 11, 2011 3:46:57 PM
Subject: Re: [Elecraft] KPA-500 Output for Input schedule?
The RFsensing on the K3 is a real trick. The frst 'dit' may suffer a mild
truncation on band change
:57 PM
Subject: Re: [Elecraft] KPA-500 Output for Input schedule?
The RFsensing on the K3 is a real trick. The frst 'dit' may suffer a mild
truncation on band change, but this only happens if you don't press a band
button prior to transmitting.
Low power band changing does occur with 1W on CW
Adding a power gain and rounding to nearest two digit integer,
considering accuracy of measuring device (rarely more than two
significant digits), it is safe to say that the amplifier keeps its
linearity to 650 watts. The variability at 325 and 410 is most likely
the measuring instrument's
While those results are very good, I would like to point out that it
is from a sample of one KPA500. I would suggest that an allowance of
10% be considered over the entire population of KPA500s just due to
component tolerances giving rise to some unit to unit variation. Even
using the 10%
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