You might have to forward this Bill. I'm not on CQ contest.
> The simple way around this problem is to find inexpensive
> narrowband crystal filters in the 45-70 MHz IF range which would
> plug into the first IF of current generation radios. Of course this
> is not that simple since this could defeat some of the wideband
> mode features (e.g FM) of those radios. Perhaps Inrad could
> provide these filters as an interim solution.
Bill and all,
With virtually no increase in product cost or basic design structure, it is
possible to correct almost all of the major problems. This goes for horrid
SSB IM transmitter performance and exceptionally poor CW transmitter
performance, not just receivers. All the components required for good
performance are already in the radio, they are just not being used
correctly.
Since the 1970's, inexpensive very tough mixers and IF amplifiers have been
available. The ~70MHz first IF required for use of broadband front-end
filters does not need to cause problems. With any amount of care at all in
design, filters could be located after two or three mixers and exceed
whatever we might reasonably require.
The real root of the problem is close-spaced performance is largely ignored.
This is almost certainly because published measurements and reviews do not
properly highlight bandwidth and performance problems. For many years radios
have been tested at spacings outside the roofing filter bandwidth, only
those results are published in reviews. Even radios with known severe
problems are not taken to task by our representatives.
The result of this is everything looks good. Consumers and manufacturers
totally miss design errors hampering close-spaced performance. There isn't
any incentive for manufacturers to watch performance, so they won't. Many
radios that have received good reviews won't even pass basic FCC technical
standards. We are stuck with the results, and have little control of the
situation unless the ARRL, JARL, RSGB, and so on step up to the plate for
members instead of coddling manufacturers with reviews that make poorly
performing radios or sloppy RF designs appear acceptable and
"state-of-the-art".
It isn't the receiver or transmitter expense or technology or location of
filters causing the problem. It is the demands of acceptable technical
standards that are causing the problems. Our membership organizations have
set the performance bar very low in reviews, and manufacturers have quite
naturally adjusted to barely pass the test. The important thing is no one
says anything bad about the design flaws so they sell radios and spend money
advertising, not that flaws are corrected.
Watch how long it takes, if ever, to see the bandwidth of transmitters
clearly published in reviews (as was promised nearly a year ago), and how
long it takes our technical publications to correct "optimum CW waveforms"
that are actually poor waveshapes. Within a few years of that time,
performance will improve.
73 Tom
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