Hello Don,
Some comments from my side in between your text below
Don Wilhelm wrote:
If I read it correctly, this 'test report' and comments were for the K2
operated without the transverter, but all the data presented was for testing
with a transverter.
**Yes, I agree. Both my K2's perform lovely under heavy contest on the
lowbands. Have no problem with its AGC behavior.
I am not certain of this individual's intent, but it would appear to me that
he was determined to present the K2 in a bad light.
** I think we cannot jump to that conclusion. I see no clear evidence of that. I 'assume'there simply was ample time for them to look into details why the test performed worse than average. I do tend to feel that some hams tend to exagarate the performance of their 'own'(home build) equipment and that in return others have a pre-biased negative tendency towards that. I try to neglect both and focus on real-life performance.
For one, I do not understand why he chose only to operate the K2 with the
preamp ON when used with a transverter - the transverter should provide all
the front-end gain needed, and turning the pre-amp on should accomplish
nothing for weak signal detection, but certainly does reduce the IF receiver
dynamic range (and thus effects his 'blocking test').
***Totally agree with you on both aspects. That at least explains the
low IP3 figures.
In addition, he used
2 borrowed K2s, and we have no information about the health of these K2s,
they may not have been operating properly. Remember that the K2 is not an
'off the shelf' transceiver, and setup and alignment is done by the
individual builder rather than on a factory assembly line. Many K2s are
operating at top performance, but many are not. Alignment and calibration
are not difficult, but we have no assurance that it was done correctly for
the K2s used.
***Yup, again agree totally. Especially the gain setting of the K2's
preamp can be altered upon your own spec. I have been succesfull on that
while matching it together with a DEM transverter.
Optimized gain setting on all stages affect both the sytem noise figure
as well as the IP3, or better said the IF overload (K2).
All in all, this report does not square with others which do document the
test setup and conditions used along with unbiased results. I refer you to
the ARRL lab test which do document their entire setup and test methodology.
Since the results in this 'report' are quite different than from other
reports,
*** Although a well documented methodology it only compares apples to
apples. It does not show wether you will hear and work the dx.
We are too much focussed on things like MDS, or in the case of this
german test the system noise figure, whereas I found that it does not
validate that lower MDS offers better reception. I noticed that internal
phase noise covers the wanted dx, especially when the band is more
crowded. So I forget about the long list of MDS measurements I performed
in the last couple of years. I use real life testing as my
qualification reference. My point is; the germans never had true RX
performance in mind. They wanted to investigate the TX performance of
nowadays 144Mhz equipment and/or transverter combo's with older stuff.
Too much noisy TX signals on the bands during contests cover all weak
stations. Local phase noise seems no design issue for the manufacturers.
Next to that they added the found system noise figure and IP3 test
results. Interesting data but the first largely depends on correct
adjustment of gain matching in all stages. The second rather too. You
need more time to set things up correctly than to throw in a couple of
transverters and some HF rigs. However I do respect there try very much;
I think they made a serious point here TX-wise and failed RX-wise.
I believe he either had malfunctioning K2s to work with or intended
to skew the report.
*** I feel uncomfortable with their blunt statements too, but see only
evidence of a lack of knowledge in their whole test procedure RX-wise.
73,
Don W3FPR
***73 Mark, PA5MW
K2; 2036 and 3323, 1x XV50
-----Original Message-----
Hello,
Taken from, the http://www.df9ic.de/tech/trxtest/trxtest.html
"The Elecraft K2 also has a low IF design using conventional VCOs
which should result in a good LO noise supression but does not.
You may compare the ARRL test results of the LO noise that
Elecraft publishes on their own website and which is closely
within our blocking test result (our measured -95 dB RX blocking
in 20 kHz offset is equivalent to -129 dBc/Hz LO noise). The high
level of TX noise shows that there seem to be design flaws
choosing too low signal levels internally. The AGC threshold is
ridiculously high (subjective impression). I also do not
understand why it uses low quality ladder crystal filters instead
of a filter from monolithic duals like any other radio does.
Overall it was the worst HF radio in the test (OK, a 144 MHz
IC910H is still worse...)."
Is the K2 + XV144 really bad combo or the others transverters are
much better?
73' SM7VZX
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