Wow, I wish we could buy 8 pole filters in amateur radio volumes for a
wholesale price 1-5$. Or even $30-$40! They just don't exist. (But let
me know if you find some..)
Our filters -were- designed for their excellent IMD performance. Also,
we have these filters tested for IMD and passband response during
manufacture. Its always possible one can slip through, but not very often.
And the K3 -does- provide top of the line front end performance. Even if
you subtract 5-7 dB from our verified lab test numbers at the ARRL and
Sherwood you are in the top tier of all amateur rigs. Period. All of the
reviewers (ARRL, Sherwood, Radcom etc) have praised the K3 for its top
of the line performance.
Let's also remember that the IMD dynamic range numbers we are now
testing for (95-100 dB+) push the limits of many test lab set ups.
Without careful measurement technique and appropriate gear it is easy to
confuse the IMD limits of the test set up equipment with the rig. I've
personally tripped across that many times here in my lab and have helped
others clean up their lab set ups. Also, there are several methods to
test IMD dynamic range. (IMD product at MDS, at S5 etc.) With a
non-linear device like a crystal filter, the level of test signal is
critical for accurate comparisons. It does not act like a transistor
amplifier does when subjected to signals at its upper limits. We've seen
several folks (including ourselves) test at signal levels way above the
max the filter will ever see and then incorrectly try to extrapolate
back to IMD performance at expected use strong signal levels. Its easy
to get widely varying and inconsistent results when testing that way.
But the bottom line is: How does a radio perform in actual use? I'll let
our customers past and future postings speak for that. :-)
73, Eric WA6HHQ
-----
Jerry T. Dowell wrote:
The high prices of the roofing filters for the K3 and optional filters for
other rigs reminds me of a little history.
..... Drake and others had switched to Japanese suppliers since
they could get the filters for a little over $1 each, whereas his cost was
over $2 each. Note that there were no middlemen. Drake was selling their
filters for $40 or $50 each, I forget which. A tidy profit. Howard charged
me $40 for that CW filter, by the way. Inflation since that time has been about
a factor of 2.6, according to official US Government figures:
Some of us would disagree with the official numbers, putting it closer to a
factor of 10,
Nevertheless, I find it especially disturbing having to pay these modern
prices considering that the filters have apparently not been designed or
chosen for good IMD performance or advantageous group delay characteristics.
Also, some filters are reputed to have been defective. Of course, the
filters may not be totally to blame for the mediocre front end performance
of the K3 (compared with the professional-level performance that some of us
had hoped for.)
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