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Softrock Lite 6.2
Adventures in Electronics and Radio
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K2 Performance Measurements with and
Without Buffer Amplifier
I've completed a suite of tests on my K2 (SN 05689)
assembled by Frank, W6NEK, with and without a prototype buffer interface
amplifier installed. My K2 has the following options:
- SSB option
- 100 watt power amplifier
- Noise blanker
Rather than post several dozen spectrum analyzer plots
and other data points, I'll summarize the results and show an illustration
or two.
The results are:
1. The buffer amplifier produces no meaningful change in the K2's
performance; and
2. My K2's performance is similar to the ARRL's measured performance (better
in some respects, never worse) and meets all relevant FCC rules and
regulations for spurious emissions. |
| The following shows the main
configuration for testing intermodulation and transmitted spurious and
harmonics. Generally, I used an HP 8558B spectrum analyzer, with a home made
A/D converter and software to capture the data in a form amenable to
computer publishing.
During the tests, a prototype Z91 was connected to the
buffer amplifier output and ran in normal scan mode.
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The spectrum analyzer plot at the right shows the stock
K2, operating at 100 watts, CW mode, 7.1 MHz.
The strongest spurious response is -58 dB below the transmitter output
power.
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The plot at the right shows the K2, with the buffer
amplifier board installed, otherwise operating identically with the plot
shown above.(The bottom plot has an extra 20
dB series attenuation, so the reference levels are 20 dB different to
compensate.)
The strongest spurious response is -62 dB below the
transmitter output power.
There are very slight difference in the emitted
spectrum, but these are not significant. In both cases, the levels are far
below the FCC's -43 dB limit.
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| Received and transmit phase noise are
unchanged after installing the buffer amplifier. |
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