Before I spend $60 to$80 to replace the masthead tri-color bulb with an LED
equivalent, I am wondering what the consensus is here about interference
between LEDs and VHFs (or other electronics). Are there certain LED lights
that are superior or worse in this respect? What in-use experience can
anyone relay?

--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://home.comcast.net/~kerrydeare

On Mar 30, 1:44 am, "Armond Perretta"
wrote:
Before I spend $60 to$80 to replace the masthead tri-color bulb with an LED
equivalent, I am wondering what the consensus is here about interference
between LEDs and VHFs (or other electronics). Are there certain LED lights
that are superior or worse in this respect? What in-use experience can
anyone relay?

It will always be at least a potential problem with PWM current
regulators. Shielding that works adequately in automotive lights may
well not be good enough for marine service. "Practical Sailor" has
received complaints as recently as this year. I'd suggest using a
portable AM radio to test your unit for RF before installing. If you
want to avoid the PIA of testing you could insist on lights that are
not PWM regulated. An acquaintance of mine runs a shop in Fiji that
makes LED lights. Obviously, he's an interested party but I think he
is very, very honest. Here is his description of the problem:
http://www.bebi-electronics.com/regulator.html.

-- Tom.

On Sun, 30 Mar 2008 16:29:05 -0400, wrote:

wind my watch, even if it was already broken.
I have ,a Rolex mechanical, not electric, watch that has to be wound.
Rolex invented the self winding watch in 1939, but mine doesn't. There
are many that I wouldn't trust to wind it. It is actually easy to
screw up, unlike with most mechanical watches.

Casady

On Mar 30, 10:29 am, wrote:
A potential problem is not a problem. That's like saying all gasoline powered
cars have the potential to explode in a ball of flames at any moment. How many
manufacturers of LED units are using pulse width modulation regulators, and of
those, which ones ACTUALLY have a problem? When it comes to technical
information that is trustworthy, I wouldn't let the amateurs at Practical Sailor
wind my watch, even if it was already broken.

Whatever. PS is perfectly capable of passing on reports of problems.
You might look over http://www.ssca.org/DiscBoard/viewto...t=2687&start=0
or do a little search.

-- Tom.

On Mar 31, 12:34 am, wrote:
Try hehttp://ogmtechnical.blogspot.com/

Thanks for that link. Speculating between the lines and being a tad
skeptical of company self-reporting it sounds like they may have unit
to unit differences in RFI and hence a manufacturing/QA problem. PWM
regulators are made in the gazillions for the automotive market. As I
recall the gent in the PS letter was quoted as saying (more or less)
"gee we've installed countless LEDs in cars and we never have had a
problem with RFI there, it must be a user thing." But, boats aren't
cars. Rather like gasoline engines that need to be modified for
marine use with things like spark arrestors and bilge blowers because
of potential problems in boats, LEDs for marine use should take
particular care with RFI because of potential problems. PWM
regulators are great but because of their timing circuitry are
potential RFI emitters.

By the way, some remarks that Roger made have reminded me that
changing the bulb in your nav lights from the manufacturer's tested
type to anything else will take the lamp out of compliance. I'm not
lawyerly enough to know what having non-USCG approved lighting does
to a skipper's liability. It is likely that many LED bulbs will not
comply with Annex I section 8 despite being visible at the ranges
required by rule 22... It's also likely that USCG stamped LED lamps
don't meet annex I.8...

-- Tom.

wrote in message
...
On Mar 31, 12:34 am, wrote:
Try hehttp://ogmtechnical.blogspot.com/

Thanks for that link. Speculating between the lines and being a tad
skeptical of company self-reporting it sounds like they may have unit
to unit differences in RFI and hence a manufacturing/QA problem. PWM
regulators are made in the gazillions for the automotive market. As I
recall the gent in the PS letter was quoted as saying (more or less)
"gee we've installed countless LEDs in cars and we never have had a
problem with RFI there, it must be a user thing."

It most certainly is.


But, boats aren't
cars. Rather like gasoline engines that need to be modified for
marine use with things like spark arrestors and bilge blowers because
of potential problems in boats, LEDs for marine use should take
particular care with RFI because of potential problems.

No, the wiring in boats should be done as carefully as in cars. If the
regulator can pass FCC emissions for cars, it should be passing for boats.
But in some cases they don't because the wiring in too thin and too long for
the intended use. The supply feed wires, rather than being low impedance
become a high impedance (inductive) and do a great job of acting as an
antenna for any noise on them. For the most part boat wiring is the
sloppiest crap in the world. Here are some boat wiring tips:

1. Use adequate gauge wire. The feedline resistance, depending on the
current it carries, should be 1/2 ohm or less.

2. Use twisted pair type wiring to reduce emissions and susceptibility.

3. Don't dump all you ground currents into the same wire. Use a single
ground wire for each fixture. Don't daisy chain grounds. Keep the ground
impedances low.

4. Solder, don't crimp!

5. Put ferrite chokes at the electronics box to reduce conducted EMI. Shunt
the supply lines with filters caps were practical. Increase the common mode
rejection on supply lines.

6. Don't loop wires into coils, keep paths as short as possible.

PWM
regulators are great but because of their timing circuitry are
potential RFI emitters.


It's not the regulator that is emitting, it is the wiring feeding into it.

wrote in message
...
On Mon, 31 Mar 2008 12:19:50 -0700 (PDT), "
wrote:

On Mar 31, 12:34 am, wrote:
Try hehttp://ogmtechnical.blogspot.com/

Thanks for that link. Speculating between the lines and being a tad
skeptical of company self-reporting it sounds like they may have unit
to unit differences in RFI and hence a manufacturing/QA problem.

Sounds more like there are variables in how they are installed.


Bingo! We have a winner!

PWM
regulators are made in the gazillions for the automotive market. As I
recall the gent in the PS letter was quoted as saying (more or less)
"gee we've installed countless LEDs in cars and we never have had a
problem with RFI there, it must be a user thing." But, boats aren't
cars. Rather like gasoline engines that need to be modified for
marine use with things like spark arrestors and bilge blowers because
of potential problems in boats, LEDs for marine use should take
particular care with RFI because of potential problems. PWM
regulators are great but because of their timing circuitry are
potential RFI emitters.

The current used to power an LED mastlight is TINY. Even if the regulator
WERE a
bit noisy, it would be so weak that it likely wouldn't have any effect at
all
unless maybe the regulator was mounted directly on the antenna whip. The
regulation in my anchor light is completely surrounded by the grounded
metal
bayonet base.

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.




By the way, some remarks that Roger made have reminded me that
changing the bulb in your nav lights from the manufacturer's tested
type to anything else will take the lamp out of compliance. I'm not
lawyerly enough to know what having non-USCG approved lighting does
to a skipper's liability. It is likely that many LED bulbs will not
comply with Annex I section 8 despite being visible at the ranges
required by rule 22... It's also likely that USCG stamped LED lamps
don't meet annex I.8...

The USCG doesn't test devices and approve them. They publish standards,
and a
laboratory tests your product and charges you a fee to attest that it
meets the
standards. If you have an unapproved device and it becomes an issue in
court,
you can still retroactively have the device examined and declared
compliant.

Good info on the retroactive part. You can't do that for FCC.


A kerosene lamp is perfectly valid as an anchor light as long as it meets
the
standards. No actual "pre-approval" is needed to use it. You just have to
have
confidence that it can meet the criteria. My LED anchor light is USCG
approved
because I say it is. No one has asked me to prove it, but I'm sure I could
hire
someone to validate my claim if it was ever needed.

Meanwhile, just hope that when you have to defend your unit with a stamp
of
approval on it from some lab, the opposition doesn't take the wind out of
your
sails by claiming it was partially obscured by a blob of bird **** on one
side
and therefore didn't meet the standards at the time of the incident.


Let's put windshield wipers on all navigation lights!

Good info on the retroactive part. You can't do that for FCC.

FWIW the CFR is he
http://ecfr.gpoaccess.gov/cgi/t/text...6:1.0.1.3.17.2

or http://tinyurl.com/ypv4ld. A mariner can not certify a light as
USCG approved at any time but a non USCG approved light may be in
compliance with COLREGS.

-- 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

wrote in :

On Sun, 30 Mar 2008 07:44:14 -0400, "Armond Perretta"
wrote:

Before I spend $60 to$80 to replace the masthead tri-color bulb with
an LED equivalent, I am wondering what the consensus is here about
interference between LEDs and VHFs (or other electronics). Are there
certain LED lights that are superior or worse in this respect? What
in-use experience can anyone relay?

The interference, if any, would be caused by any integral voltage
regulator. Even if the unit you use has integral regulation, that
doesn't mean it will cause any interference. Some earlier LED units
supposedly had some sort of shielding problems, but it was not a
universal problem with LED tri-colors. I recently noticed that
"Lopolight" is now fully approved for use worldwide.

I have an LED masthead lamp that was a simple bayonet base replacement
for the incandescent. No problems with interference whatsoever.

I believe that there's an extensive discussion of this in the SSCA.ORG
forum.

-- Geoff
www.GeoffSchultz.org