"Larry W4CSC" wrote in message
...
On Sun, 9 Nov 2003 10:08:42 +0100, "Meindert Sprang"
wrote:


That is nonsense. It all depends on proper PCB design. I HAVE measured
it,
for crying out loud!

Gee, the manufacturers that HAVE to pass FCC specs on radiation don't
know that. They spend lots of money coating cases, using metal
cabinets, and other shielding. You should go into consulting. Organ
manufacturers would love to put out digital organs and keyboards
without having to coat the whole thing in tin foil and expensive
shielded boxes with foil shielded data lines to pass the FCC tests.

Of course it all depends on the application. Certain areas just need
complete shielding where extremely low limits are required. All I am saying
is that to get something like NMEA equipment quiet and unsusceptible to HF
and VHF at reasonable levels like specified in IEC and FCC standards
applicable to that kind of equipment, it is not necessary to have everything
shielded. And I believe a lot of equipment present on the market prove this
statement.

And judging from your previous posts here in this group, the interference
problems you have had are caused by certain NMEA equipment that is
definately not FCC approved. Check the multiplexer and expander you so much
prefer: no FCC approval and well known to produce interference.

Whoa, sport! Your attack on me was about 4800 baud NMEA and it
RADIATES LIKE HELL into the HF on every boat I know of because of the
way you manufacturers treat the interconnects, dangling the 4800 baud
pulses out there in unshielded space. Quit sidestepping the issue.

I am not sidestepping the issue. I just happen to have good experience with
NMEA, without any interference on HF.

Unshielded 4800 baud data has no place around a submicrovolt HF
receiver within a few feet of its receiving antenna....

Like I said befo with properly filtered outputs, which is just mandatory
if you want to get something through the IEC of FCC tests, there will be no
problem. I mean, it is stupid to have NMEA drivers capable of running at
10Mbaud if you only have to drive 4800 baud. So with the properly
dimensioned drivers and RC networks, the slew-rate of the output datasignal
is brought back so such a low figure, that there are no significant
harmonics present over a few 100 kHz.

AS with consumer electronics, until the regulators step in to force
the manufacturers to conform to some sort of radiation standard,
nothing will change.

I don't understand what your implying here. Navigation electronics without
specific IEC945 approval falls in the same category as consumer electronics
and is therefore subject to the same EMC limits. So there ARE regulations
enforced.

But we seem to keep on disagreeing on this subject. So lets end this
discussion.

Best,
Meindert