Ian, I'm sure you or I and a few others would willing criticise the sad
state of poor to middling IMD performance in ham-radio Tx equipment in
meaningful clinically objective technical reviews, but none of the
mainstream monthly ham rags who rely on advertising revenue for their
existence would dare publish our critique!
Breaking the incestuous financial nexus is problematic...a truly independent
ham radio journal is unfortunately an ironic contradiction in terms.
It would only take a few flame roastings by respected reviewers for the
equipment manufacturers to clean up their act. The downward creep in Tx IMD
specs you mention is a sad indictment; there are no easy solutions :-(
Some recent release high-end HF transceivers do have good Tx IMD specs, but
they are expensive acquisitions for the average ham hobbyist. The
widespread collapse of global economies is also not conducive for equipment
manufacturers to improve their products with the burden of additional
technical finesse and complexity required and associated hit to their
shrinking margins; it's a vexing catch-22.
73
Leigh
VK5KLT
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Ian White
Sent: Saturday, 4 May 2013 6:55 PM
To: amps@contesting.com
Subject: Re: [Amps] Pre-Distortion Linearizer
Tom W0IVJ wrote:
> As long as the transceiver manufacturers give us transceivers with poor
> IMD, it does little good to get the IMD on the amplifier good, unless you
> home brew your own transceiver.
>
Transceiver and amplifier manufacturers will continue to give us poor
IMD for exactly as long as the major equipment reviewers (ARRL, RSGB and
DARC... but mainly ARRL) continue to remain silent.
In the final years of tube transceivers, the reviews show 2-tone IMD3
performance of -35dB(pep) and better. But as solid-state PAs came on the
market, those same reviewers presided over a gradual slide into the low
30s, the high 20s and now even the mid-20s...with never a word said.
Reviewers have consistently failed to understand is that they are not
only writing for people who might be interested in buying that
transceiver or amplifier. When they fail to speak out against poor TX
performance, they are neglecting an equally important duty towards
EVERYBODY ELSE who will have to suffer on adjacent channels.
(And before the tired accusations about "commercial pressures" begin,
the underlying story is way more complex than that. The main reason why
nothing changes is technical and human: all of the reviewers have become
complicit in the present situation, and none wants to be the first to
step forward.)
73 from Ian GM3SEK
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|