QRP and Simple Wire Antennas
K1 Measured Performance on the 20 Meter Band

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My Station
Free Software
20 Meter Band

This is the band I have been using most often lately.  It has less QRM than 40m and is usually better performance than 40m.  I am very happy with the rigs performance on this band.  One problem that I had with the rig was on this band.  I had an intermittent "dead band" effect.  That is sometimes when I would turn on the rig 20m would be dead silent.  After some testing I was fairly convinced that I traced this back to a bad IF crystal.  I checked the solder joint on the crystal.   No problems.  I resolder it anyway.  The problem persisted.  I called Elecraft, they sent a new crystal and I have not had the problem sense.  I was real happy with the tech/product support.  Anyway.  Here's the data.


Output Power

I have included my test data for the maximum output power as a function of frequency from 14.000 MHz to 14.1600 MHz.  The results are really not that interesting in the sense that the output power is dead flat over the whole range.  At 6.0W maximum output power, the K1 is above the manufacture's advertised spec of 5.0W.  Actually, Elecraft says "Adjustable CW power output, nominally 0-5 watts or higher."  This rig lives up to that claim.  I am very happy with this result.

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Figure 1.  Maximum output power as a function of frequency for the 20 meter band.

Configuration for this test

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Figure 2.  Configuration used for the output power measurements.

I conducted this test using my SWR meter/power meter manufactured by Diesel to monitor the power.  I used my homebrew 50 ohm load.  I know that the 50 ohm load is good because I measured the return loss to be better than 20dB to 60MHz.

Just a quick note on measuring output power.  I have seen some reports of output power and there is sometimes comparison between output power into a 50ohm load and output power into an antenna.  The two measured output powers are usually different and often the result into the antenna is higher.  Now, I will give my two cents on this.  The measurement into the antenna is really the wrong way to do it, unless your antenna has extremely good SWR.  This is due to the fact that poor, or even pretty good SWR, will cause a larger voltage (voltage standing wave, hence VSWR) to be present at various points on the transmission line up to the antenna. This includes the coax between the rig and swr meter and everything up to the antenna.  Since most, if not all, swr meters measure a voltage, any increase due to SWR issues will cause a false reading.  Therefore, it is always best to measure output power into a know good 50 ohm load.  OK that is my two cents on this issue.


Maximum Tuning Range

The K1 is advertised to cover "up to 150Kz" My measured results are below.  As you can see the tuning range is well over the 150KHz soft spec.   This is another good result.

Minimum Frequency = 13.9913 MHz
Maximum Frequency = 14.1644 MHz
Tuning Range (Max Freq - Min Freq) = 173.1KHz


RIT tuning Range

I measured the RIT tuning range.  I know this is not a real big issue for some.  However, I do know that some DX stations like to work offset TX/RX.  This is when a wide RIT can be helpful.  Also, sometimes you get a contact where the other guy is off frequency by 1-2 KHz or more. This is very rare in my experience, but still happens.  Anyway the results are below.  The RIT range is about +/-4KHz.  This is typical for all four bands.

Minimum Frequency = 14.0164 MHz
Nominal (RIT off) Frequency = 14.0200 MHz
Maximum Frequency = 14.0242 MHz

RIT Lower Range =  3.6KHz
RIT Upper Range = 4.2KHz


Spectral Purity

The spectral purity of the transmitted signal was measured.  Though it may come as a surprise to some, when your transmitter is tuned to, let's say, 7.040 MHz and you transmit, you will generate a signal at 7.040MHz plus other spurious and harmonic signals at other frequencies.  Those spurious signals are not desired and in fact the level (or power level) of those undesired signals is controlled by FCC regulations.  This spectral purity test directly measures the output from the transmitter over a very broad frequency range so that one can immediately see what is actually being transmitted.  For instance, if you set your transmitter to 7.040MHz again and key it, it is likely that you will radiate some level of power at the harmonics.  Those harmonics are at 14.080, 21.120, 28.160 MHz and so on.  In addition, you may also be transmitting at other frequencies which are generated in the mixer stages, amplifiers and other non-linear elements in the transmitter.  The frequency of those components is determined by several factors one of them is the IF frequency.  These undesired signals are often called spurs which is short for spurious.

The tests on the K1 were conducted using an Advantest R3273 Spectrum Analyzer with a bandwidth of 100Hz to 26.5 GHz.  I know that that is way over the top as far as bandwidth overkill, but it was what I had available.  I had 48.2dB of attenuation between the K1 and the Advantest.

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Figure 3.  Narrow band spectral purity shows that all close in harmonics are greater than 55dB below the desired signal.  The vertical scale is 10dB/ and the horizontal scale starts at 13MHz and ends at 15MHz.  Also note that output power was set at maximum.

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Figure 4.  Wide band spectral purity plots shows that all wide band harmonics are greater than 50dB below the desired signal.  The vertical scale is 10dB/ and the horizontal scale starts at 0Hz and ends at 100MHz.  Also note that output power was set at maximum.


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