I haven't checked the K3 speech processor accuracy yet, but will get to
it shortly. I did run a power check with carrier though. I calibrated my
K3 internal meter against my LP-100, and verified it against my HP 438A
power meter. The calibration was done according to the manual at 5W and
50W on 20m. Here are my results for requested powers of 5W, 10W, 50W and
100W for three bands, plus 120W on 20m...
160m 5.1 9.7 51.0 95.3
20m 5.0 9.5 50.0 94.1 110.8 (120W)
10m 4.8 9.1 48.5 91.0
It looks like the coupler in the K3 has a little falloff in response
with rising frequency, and a little non-linearity. This would be
expected. When the dust settles, they could probably add a little code
to compensate for this in the firmware. That's the beauty of firmware ;-)
Mine may not be fully representative, since I had a slight amount of
damage to a T/R switch component on my KPA3 (self inflicted during
installation. I substituted a part, but am awaiting the correct one).
But since the ratios below 12W and above 12W seem to track, I think
these are probably typical (12W is the switching point between low power
final and high power final for those who don't know). BTW, my output on
20m tracks yours pretty well.
73,
Larry N8LP
Message: 4
Date: Mon, 04 Feb 2008 19:45:10 -0500
From: Bill Tippett <[EMAIL PROTECTED]>
Subject: [Elecraft] K3 SSB average power output
To: [email protected]
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset="us-ascii"; format=flowed
N8LP's LP-100 has a function for evaluating
Peak to Average performance of speech processors. SSB
isn/t of much interest to me until 10 meters comes back
so I haven't played with this mode in the LP-100. Larry
has a K3 on order and maybe he will compare the K3
speech processor to others when he gets his K3.
73, Bill W4ZV
See LP-100 at http://telepostinc.com/
* Peak to Average ratio screen. Allows accurate checking
and setting of compression in your speech processor.
Peak-to-Average Mode
This mode lets you determine the average power in a signal by taking
40,000 samples/second, and compares this to the peak power in
the signal. The result is displayed as a ratio in dB. I provide a
couple test tones, which are available on my website at
http://www.telepostinc.com/Files/two-level-tone-loop3.zip and
http://www.telepostinc.com/Files/loud_tone.zip. The loud tone is used to
set the maximum power and proper ALC range (with processing OFF). The
two-level tone is used to determine the peak-to-average
ratio of the output signal. It can be played back on your PC, or
converted to mp3 and played on a portable player. It can be played over
a speaker into the microphone, or directly into the mic input. The
two-level tone provides alternating loud and soft tones with 20 dB
difference in level. This tone should provide the following
Peak-to-Average ratios vs. effective compression ratio.
Compression Ratio Peak-to-Average Ratio
0dB 5.2dB
5dB 5.6dB
10dB 3.6dB
15dB 2.2dB
20dB 0dB
I plan more test tones with different characteristics in the future,
which is why I decided to keep the display as Peak-to-Average as
opposed to Compression, which would only be accurate with one test
signal. I will provide additional tables such as the one above with
the additional test signals
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