Peter Chadwick wrote:
>
>Steve G8IZY said:
>
>
> >Maybe... if rig reviewers in Rad Com, QST etc.paid
> > more attention to these sort of design defects,
> >then things would improve. A tall order? - possibly
> > the magazines would just lose advertisers!
>
>The advertisers are and publishers are in a cleft stick though
> - they heavily rely on each other. In point of fact, relatively
>few amateurs have any problem with these design faults.
>
The problem with reviews is that they can only test systematically for
*known* aspects of performance. It's much less certain whether they pick
up any other defects that are specific to one particular rig. Also,
reviews come out when the rig is very new, so they don't have the
benefit of wide user feedback.
Even so, I agree that initial ALC overshoot is a common enough problem
that it should be added to every review lab's schedule of tests.
>Mark commented:
>>It seems so ass-backwards to push for better RX
>>performance with higher dynamic range, better filtering etc
>
>It's taken a good few years to get the improvements, though.
And the older rigs are still around for 10-20 years or more.
>It always interests me as to why spurious responses (both
>internal and external) don't receive more attention
>(sorry for the pun!), as they contribute to reception failure
>- just as IMD and phase noise do, and with increasing DDS
>use, can become a major problem. They are, after all, a
>special case of phase noise.
>
The difficulty with DDS spurs is that the amplitudes and frequencies
change (pseudo) randomly with frequency. It would take a computer-
controlled rig and signal generator - or alternatively, take forever -
to do a thorough search on an HF transceiver. A few token measurements
are all you're likely to get for a magazine review.
In many ways it's better to read the reviews, and then wait several
months and monitor the DXcluster and discussion groups for the rig
you're thinking of buying... and AMPS of course, unless you plan to run
barefoot forever.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|