wrote in :

Seeing LED's
through the lens of a nav light won't mean anything to a surveyor.


If he even looks....

On Apr 1, 11:58 am, "Capt. JG" wrote:
Isn't the point whether or not the lights are visible from the prescribed
distance?

And the right colors and properly displayed &c (see 22 and annex
I)... But, yeah.

does the CG care that they're "approved?"
I don't know the answer... just wondering.

I don't think so for uninspected vessels but the OP was talking about
spending $80 on some bulbs and was worried about the remote
possibility of RFI so I though he might be interested in the certainty
that he'd no longer have USCG approved fixtures if he installed
different bulbs... I suppose he might get into insurance difficulty
if the bulb started a fire or if he had a collision and couldn't prove
that he had legal fixtures but those seem like pretty remote issues.
A quick phone call to the surveyor that works for his insurance
company would likely reveal if there would be a problem there. It may
be that he doesn't care about USCG approval. That's cool, too.

-- Tom.

"Tony Helton" wrote in message
...

If the switching signal (PWM) is run into an inductive load in a poorly
designed circuit you could have tens or even hundreds of volts as a
transient signal. It's not the current but dI/dt that makes the voltage.
One does not need an antenna to radiate. A plain old wire can work just
fine. Since this is all so variable, it points right at the installation
factors. By the way, radio amateur QRP distances show over 1,000 miles
range with a single NAND gate as the output driver. Figure PWM waveform is
5V @ 5mA = 25mW-- 14 dBm into 50 ohm. VHF radio sensitivity typically
0.25 uV into 50 ohm ---1.25e-15 Watt or -120 dBm. Say the PWM operates at
100 kHz so the 1500th harmonic has to be down -134 dB to be undetectable
on the VHF. The Fourier expansion of a square wave PWM shows the harmonic
coefficients decreasing as 1/n, n being the harmonic number so the VHF
in-band harmonic is 1/1500 of the original signal or about 33 dB down.
That leaves about 100 dB of required attenuation (if all the DC input
power were radiated) not to interfere with the VHF. FCC requires the
harmonics to be much lower, which they are in order to comply. Automotive
testing is rigorous and thorough and it takes a real screw up to get the
thing to radiate and cause interference in the boat. The lesson here is if
you don't understand electrical installations, hire an experienced (even
licensed) technician to do the work It may save your life.

Hey Tony,

The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not 1/n
(that is for voltage). Power is proportional to voltage squared. Hence, your
1500th harmonic is down 66 dB, not 33 dB.

Amen!

Bob Crantz PhD

Bob Crantz wrote:


The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not 1/n
(that is for voltage). Power is proportional to voltage squared. Hence, your
1500th harmonic is down 66 dB, not 33 dB.

Amen!

Bob Crantz PhD

And given that you are coupling into some Gawd awful mismatched radiator
you can probably chop of at least another 30 or 40db.

Cheers
Marty

"Capt. JG" wrote in message
news:HpGdnRFII8-DLW_anZ2dnUVZ_sSlnZ2d@bayareasolutions...
Hmm.. well, I can't tell during the day when the bowlight is unlit, as
least
I don't recall being able to tell. I looked at the hi-res images of the
following, but next time I'm at the boat, I'll look again.

Isn't the point whether or not the lights are visible from the prescribed
distance? And, this would be at night of course. So, it seems to me that
if you're involved in a collision at night, and you could show that no
matter what you had was in fact visible, does the CG care that they're
"approved?" I don't know the answer... just wondering.

Is all this worry about the USCG somehow related to the fact that they are
now part of your rather scary Department of Homeland Security? Have they
unilaterally set up their own approval standards for lights? And if so, why?
The internationally accepted Colregs and, in particular, their Annex No 1
'Positioning and technical detailsabout lights and shapes' clearly states
how far lights should be visible at night and goes on to give highly
technical details about the necessary chromacity and power to achieve that.
Also it even goes on to give a warning not to have lights so bright that
they interfere with the navigators night vision. That should be enough for
anybody surely.
If you have bought decent lights,warranted by the makers to comply with
Colregs, and position them correctly is the USCG really going to stop you at
sea and check the chromacity and candlepower of the bulbs in them as long as
they are actually alight?

"Marty" wrote in message
...
Bob Crantz wrote:


The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not
1/n (that is for voltage). Power is proportional to voltage squared.
Hence, your 1500th harmonic is down 66 dB, not 33 dB.

Amen!

Bob Crantz PhD

And given that you are coupling into some Gawd awful mismatched radiator
you can probably chop of at least another 30 or 40db.

Cheers
Marty

Not all wires are bad radiators at all frequencies. Your assumption is
correct if you intend for the wire to radiate. My premise is correct if you
don't want it to. Nature always works against man's desires or more
correctly, man always works against nature.

Amen!

"Edgar" wrote in message
...

"Capt. JG" wrote in message
news:HpGdnRFII8-DLW_anZ2dnUVZ_sSlnZ2d@bayareasolutions...
Hmm.. well, I can't tell during the day when the bowlight is unlit, as
least
I don't recall being able to tell. I looked at the hi-res images of the
following, but next time I'm at the boat, I'll look again.

Isn't the point whether or not the lights are visible from the prescribed
distance? And, this would be at night of course. So, it seems to me that
if you're involved in a collision at night, and you could show that no
matter what you had was in fact visible, does the CG care that they're
"approved?" I don't know the answer... just wondering.

Is all this worry about the USCG somehow related to the fact that they are
now part of your rather scary Department of Homeland Security? Have they
unilaterally set up their own approval standards for lights? And if so,
why?
The internationally accepted Colregs and, in particular, their Annex No 1
'Positioning and technical detailsabout lights and shapes' clearly states
how far lights should be visible at night and goes on to give highly
technical details about the necessary chromacity and power to achieve
that. Also it even goes on to give a warning not to have lights so bright
that they interfere with the navigators night vision. That should be
enough for anybody surely.
If you have bought decent lights,warranted by the makers to comply with
Colregs, and position them correctly is the USCG really going to stop you
at sea and check the chromacity and candlepower of the bulbs in them as
long as they are actually alight?




These days one wonders. I just picked up my TWIC (Transportation Workers
Identification Credential). Besides the $132, they sure don't make it easy,
at least not in northern Cal. There are three offices. Two are in Oakland...
right. Couldn't find them after 2 hours of driving around when I went to
apply. They don't have a phone number... except for the 800 number, and
they're no help.

Finally, in desperation, I drove an hour out to Martinez. Still couldn't
find the place. I stopped at the Shell refinery guard shack, which was being
guarded by someone in uniform toting a friggin howitzer.

He said, and I'm not making this up, "Oh, there's no way you can find it if
you don't know where it is." And, he proceeded to give me directions to turn
on a road without a street sign, go a certain number of 1/10s of a mile,
then park and walk.

Sure, there was a sign. It was about this big: xxxx (TWIC in tiny letters).
After I found it, the process went really fast... fingerprints, retinal
scan, all about 15 minutes soup to nuts. Then, I waited six weeks and went
and picked up the card.

--
"j" ganz @@
www.sailnow.com

On Wed, 2 Apr 2008 08:19:02 -0600, "Bob Crantz"
wrote:


"Marty" wrote in message
m...
Bob Crantz wrote:


The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not
1/n (that is for voltage). Power is proportional to voltage squared.
Hence, your 1500th harmonic is down 66 dB, not 33 dB.

Amen!

Bob Crantz PhD

And given that you are coupling into some Gawd awful mismatched radiator
you can probably chop of at least another 30 or 40db.

Cheers
Marty

Not all wires are bad radiators at all frequencies. Your assumption is
correct if you intend for the wire to radiate. My premise is correct if you
don't want it to. Nature always works against man's desires or more
correctly, man always works against nature.

Amen!



There is more BS on this NG than you could shake a stick at. :-)