Bob Markus wrote:
I agree, does not seem likely. I'm a ham and lots of experience with VHF.
Cannot explain it and I do not know why. But we could not receive with the
Nav. lights on.

LED lights are generally pulsed to save power. Crude electronics plus a
long wire antenna up the mast radiating like crazy all the way fronm DC
to almost light. A few turns through a ferrite ring at each end of the
cable would probably help but there is no substitute for proper EMC
filtering. YMMV.

"Chris Newport" wrote in message
...
Bob Markus wrote:
I agree, does not seem likely. I'm a ham and lots of experience with
VHF. Cannot explain it and I do not know why. But we could not receive
with the Nav. lights on.

LED lights are generally pulsed to save power. Crude electronics plus a
long wire antenna up the mast radiating like crazy all the way fronm DC to
almost light. A few turns through a ferrite ring at each end of the cable
would probably help but there is no substitute for proper EMC filtering.
YMMV.

Meindert, Terry, Chris
Thanks for the info. Didn't know they would take something simple and
complicate it. Switched to save power? How much power are we trying to
save anyway? Maybe go back to oil lamps?
And then we find out there's interference with the VHF.
Sheesh...........what progress.

"Gordon Wedman" wrote in message
news:Naa5f.17849$y_1.2003@edtnps89...
Meindert, Terry, Chris
Thanks for the info. Didn't know they would take something simple and
complicate it. Switched to save power? How much power are we trying to
save anyway?

Ok, I'll do some math: A typical high-power LED draws 500 mA at 3V. If I use
a ballast resistor to connect this LED to a battery at 12V, 9V will drop
across the resistor at 500mA, which produces 4.5Watts of heat, which is
quite substantial. The total power drawn from the battery is 6 Watt.

With a switched regulator, there is (hardly) no voltage drop, so the power
the LED uses (3V * 500mA = 1.5Watt) is the same as the power drawn from the
battery. So more efficiency and the regulator also compensates for varying
battery voltage which results in longer LED life. LEDs are quite picky on
the proper voltage. 1/10th of a volt more than specified can shorten their
lifespan from 50,000 hours to a few 100. This regulator prevents this.

Meindert

On 2005-10-19 07:13:06 +1000, "Meindert Sprang"
said:

"Gordon Wedman" wrote in message
news:Naa5f.17849$y_1.2003@edtnps89...
Meindert, Terry, Chris
Thanks for the info. Didn't know they would take something simple and
complicate it. Switched to save power? How much power are we trying to
save anyway?

Ok, I'll do some math: A typical high-power LED draws 500 mA at 3V. If I use
a ballast resistor to connect this LED to a battery at 12V, 9V will drop
across the resistor at 500mA, which produces 4.5Watts of heat, which is
quite substantial. The total power drawn from the battery is 6 Watt.

With a switched regulator, there is (hardly) no voltage drop, so the power
the LED uses (3V * 500mA = 1.5Watt) is the same as the power drawn from the
battery. So more efficiency and the regulator also compensates for varying
battery voltage which results in longer LED life. LEDs are quite picky on
the proper voltage. 1/10th of a volt more than specified can shorten their
lifespan from 50,000 hours to a few 100. This regulator prevents this.

Meindert

Don't forget that the LED is a current device. By that I mean light
output is a function of forward current. Hence to get even illumination
from multiple LEDs it is imperative that each LED be driven via a
current regulated source. It is not sufficient to parallel them up in
series with a dropping resistor.

Sometimes simple things are complex.

--
Regards,
John Proctor VK3JP, VKV6789
S/V Chagall

"John Proctor" wrote in message
news:2005101923295216807%lost@nowhereorg...
Don't forget that the LED is a current device. By that I mean light
output is a function of forward current. Hence to get even illumination
from multiple LEDs it is imperative that each LED be driven via a
current regulated source. It is not sufficient to parallel them up in
series with a dropping resistor.

Indeed. It's better to connect them in series (3 x 3V) and regulate the
current though that. Needs only one regulator.

Meindert

"Meindert Sprang" wrote in message
...
"Gordon Wedman" wrote in message
news:Naa5f.17849$y_1.2003@edtnps89...
Meindert, Terry, Chris
Thanks for the info. Didn't know they would take something simple and
complicate it. Switched to save power? How much power are we trying to
save anyway?

Ok, I'll do some math: A typical high-power LED draws 500 mA at 3V. If I
use
a ballast resistor to connect this LED to a battery at 12V, 9V will drop
across the resistor at 500mA, which produces 4.5Watts of heat, which is
quite substantial. The total power drawn from the battery is 6 Watt.

With a switched regulator, there is (hardly) no voltage drop, so the power
the LED uses (3V * 500mA = 1.5Watt) is the same as the power drawn from
the
battery. So more efficiency and the regulator also compensates for varying
battery voltage which results in longer LED life. LEDs are quite picky on
the proper voltage. 1/10th of a volt more than specified can shorten their
lifespan from 50,000 hours to a few 100. This regulator prevents this.

Meindert

Not to be argumentative but.........
It seems to me that a typical masthead lamp uses about 20 watts. So with
the simple LED setup we are going from 20 watts to 6 watts. Not good enough
though.
We have to add some electronics to get it down to 1.5 watts (and add $$$ to
the cost). Oh by the way, you can't transmit on your VHF now.
It just seems that some companies are gold plating the faucets and then not
doing a proper job of it too boot.
Lastly, how big is a 5 watt resistor? I don't think this is all that much
heat. What about the heat from the 12 and 20 watt cabin lamps?

"Gordon Wedman" wrote in message
news:Nbv5f.26865$yS6.2060@clgrps12...
Not to be argumentative but.........
It seems to me that a typical masthead lamp uses about 20 watts. So with
the simple LED setup we are going from 20 watts to 6 watts. Not good
enough
though.
We have to add some electronics to get it down to 1.5 watts (and add $$$
to
the cost). Oh by the way, you can't transmit on your VHF now.

If done properly, it shouldn't be a problem.

Lastly, how big is a 5 watt resistor? I don't think this is all that much
heat. What about the heat from the 12 and 20 watt cabin lamps?

Have you ever touched a 12 watt bulb when lit?
To give you an indication, I have some electronics here with a voltage
regulator. this regulator is one of those components of 1/2" in width and
3/4" in length, with a metal tab that can be screwed to a heatsink. In this
design, the regulator burns 1.2 Watt. Without heatsink, it hurts when you
touch it. 5 Watts is enough to solder.

Meindert

On 2005-10-20 01:56:05 +1000, "Meindert Sprang"
said:

"John Proctor" wrote in message
news:2005101923295216807%lost@nowhereorg...
Don't forget that the LED is a current device. By that I mean light
output is a function of forward current. Hence to get even illumination
from multiple LEDs it is imperative that each LED be driven via a
current regulated source. It is not sufficient to parallel them up in
series with a dropping resistor.

Indeed. It's better to connect them in series (3 x 3V) and regulate the
current though that. Needs only one regulator.

Meindert

Unfortunately that approach does not allow for component spread.
Statistically a batch of random LEDs will exhibit a reasonable spread
in current to deliver equivalent luminosity. This is where the problem
lies with using LEDs for backlight on displays etc. Where the
illumination level must be even individual regulators are a must. In
the case of marine lighting where you are mearly interested in the
agregate light output a series connected string and regulator will
suffice.

--
Regards,
John Proctor VK3JP, VKV6789
S/V Chagall