After checking my zinc anode, I'm fairly certain I'm getting
accelerated erosion of my shaft zinc anode when transmitting Sailmail
e-mail via my HF radio and PacTOR modem.

Sailmail and the PacTOR modem drive the HF radio (an ICOM IC-M710)
fairly hard.

Does everyone transmitting with a PacTOR modem suffer accelerated
erosion of their zinc anodes? Or is this something specific to my
installation (and can be corrected)? If the latter, what should I look
for and correct?

Cheers

Bil

Bil wrote:
After checking my zinc anode, I'm fairly certain I'm getting
accelerated erosion of my shaft zinc anode when transmitting Sailmail
e-mail via my HF radio and PacTOR modem.

Sailmail and the PacTOR modem drive the HF radio (an ICOM IC-M710)
fairly hard.

Does everyone transmitting with a PacTOR modem suffer accelerated
erosion of their zinc anodes? Or is this something specific to my
installation (and can be corrected)? If the latter, what should I look
for and correct?

Cheers

Bil

How is your rf ground set up?
Gordon

On Sun, 27 Jan 2008 16:49:11 -0800 (PST), Bil
wrote:

After checking my zinc anode, I'm fairly certain I'm getting
accelerated erosion of my shaft zinc anode when transmitting Sailmail
e-mail via my HF radio and PacTOR modem.

Sailmail and the PacTOR modem drive the HF radio (an ICOM IC-M710)
fairly hard.

Does everyone transmitting with a PacTOR modem suffer accelerated
erosion of their zinc anodes? Or is this something specific to my
installation (and can be corrected)? If the latter, what should I look
for and correct?

Cheers

Bil

Hi Bill,

Why do you think that your problem is due to using the HF radio?

Chuck

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Thanks for your responses.

For Gordon: the RF ground/counterpoise is a copper foil which - I
think - is connected to the engine block.

For Chuck: I've not noticed the same erosion of the anode when in any
of three different marinas and connected to shore power, including for
months at a time. I've only noticed the erosion after passages that
have included daily Pactor modem work. I renewed the shaft anode 3
months ago, found it erosion free 6 weeks ago before leaving a marina,
and found significant pitting when I checked it two days ago after
entering a marina (with 6 weeks of passage making and no shore power
connection in between checks).

Bil

Bil wrote in news:4593e5ee-8dc2-463a-bd1d-
:

After checking my zinc anode, I'm fairly certain I'm getting
accelerated erosion of my shaft zinc anode when transmitting Sailmail
e-mail via my HF radio and PacTOR modem.

Sailmail and the PacTOR modem drive the HF radio (an ICOM IC-M710)
fairly hard.

Does everyone transmitting with a PacTOR modem suffer accelerated
erosion of their zinc anodes? Or is this something specific to my
installation (and can be corrected)? If the latter, what should I look
for and correct?

Cheers

Bil


You must send an awful lot of email.....

You may want to disconnect the tuner ground from the underwater propulsion
and zincs and go to a ground screen system inside the hull. Start right
under the tuner and just lay out a roll of chicken wire screen along the
hull as big as you can. This forms a series capacitor with the seawater
outside the plastic the other plate. If your screen has a large enough
area against the hull, (The bigger the better), the RF to ground flows
through this series capacitor's "hull dielectric" into the sea....without
direct contact with the zinc protected underwater metals. With no
RF current flowing through the zincs....the RF problem bypasses it right
through the hull.

Bil wrote:

Thanks for your responses.

For Gordon: the RF ground/counterpoise is a copper foil which - I
think - is connected to the engine block.


That probably "grounds" your electrical system to the water through the
propeller shaft.

Go figger...

For Chuck: I've not noticed the same erosion of the anode when in any
of three different marinas and connected to shore power, including for
months at a time. I've only noticed the erosion after passages that
have included daily Pactor modem work. I renewed the shaft anode 3
months ago, found it erosion free 6 weeks ago before leaving a marina,
and found significant pitting when I checked it two days ago after
entering a marina (with 6 weeks of passage making and no shore power
connection in between checks).

Bil

On Sun, 27 Jan 2008 18:22:55 -0800 (PST), Bil
wrote:

Thanks for your responses.

For Gordon: the RF ground/counterpoise is a copper foil which - I
think - is connected to the engine block.

For Chuck: I've not noticed the same erosion of the anode when in any
of three different marinas and connected to shore power, including for
months at a time. I've only noticed the erosion after passages that
have included daily Pactor modem work. I renewed the shaft anode 3
months ago, found it erosion free 6 weeks ago before leaving a marina,
and found significant pitting when I checked it two days ago after
entering a marina (with 6 weeks of passage making and no shore power
connection in between checks).

Bil

So we can rule out the shore power connection.

I'd be inclined to rule out the HF rig as the culprit since from the
perspective of galvanic currents it looks the same whether you are
operating it or not. The HF rig would be a player only if you had a
completely isolated DC ground system, in which your prop and shaft
were not connected galvanically (by wire) to your DC ground. Such a
system is rare on older boats but is beginning to appear on some new
boats. As far as I know, there are no known cases of 150 watt radios
accelerating zinc erosion via RF.

The interesting variable in your situation appears to be the boat's
motion. At rest in a marine, no problem. Underway, rapid erosion. Some
of that erosion is simply due to the motion of the water relative to
the prop. The faster you go, the faster the zinc will erode. Whether
this could explain the problem depends on how long your passages were
and how fast you were moving and past experience.

Another possibility is that while underway, some piece of electrical
equipment is energized that is off while you are at the marina. If
this "appliance" is faulty, say with the positive wire shorting to the
bilge water, you could be setting up a condition for accelerated
erosion of your zinc. Next question might be how does your recent
experience with zincs compare with previous passages?

Chuck

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I note that this is a shaft anode.

Many consider that this is good enough but note that some gearboxes do not
have a good electrical connection through them, some are intermittent, it
depends on the design and I suspect the fluid (oil or ATF).

I consider that a hull anode is essential as well as a shaft anode, if there
is no positive connection from the shaft to the engine etc.

An alternative is a set of slip rings from the hull anode wiring system to
the shaft, then no shaft anode is needed and the hull anode can be large
enough to last a long time.

Alec


"larry" wrote in message
...
Bil wrote in news:4593e5ee-8dc2-463a-bd1d-
:

After checking my zinc anode, I'm fairly certain I'm getting
accelerated erosion of my shaft zinc anode when transmitting Sailmail
e-mail via my HF radio and PacTOR modem.

Sailmail and the PacTOR modem drive the HF radio (an ICOM IC-M710)
fairly hard.

Does everyone transmitting with a PacTOR modem suffer accelerated
erosion of their zinc anodes? Or is this something specific to my
installation (and can be corrected)? If the latter, what should I look
for and correct?

Cheers

Bil


You must send an awful lot of email.....

You may want to disconnect the tuner ground from the underwater propulsion
and zincs and go to a ground screen system inside the hull. Start right
under the tuner and just lay out a roll of chicken wire screen along the
hull as big as you can. This forms a series capacitor with the seawater
outside the plastic the other plate. If your screen has a large enough
area against the hull, (The bigger the better), the RF to ground flows
through this series capacitor's "hull dielectric" into the sea....without
direct contact with the zinc protected underwater metals. With no
RF current flowing through the zincs....the RF problem bypasses it right
through the hull.

On Mon, 28 Jan 2008 14:33:00 -0000, "Alec"
wrote:

I note that this is a shaft anode.

Many consider that this is good enough but note that some gearboxes do not
have a good electrical connection through them, some are intermittent, it
depends on the design and I suspect the fluid (oil or ATF).

I consider that a hull anode is essential as well as a shaft anode, if there
is no positive connection from the shaft to the engine etc.

An alternative is a set of slip rings from the hull anode wiring system to
the shaft, then no shaft anode is needed and the hull anode can be large
enough to last a long time.

Alec


While there is merit to these suggestions, the fact remains that the
OP's zinc is eroding rapidly. This can only occur with a good
electrical connection. If the zinc is simply dropped into seawater,
unconnected to anything, it will last much longer than any of us! ;-_

Chuck

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Followup to msg on Sun, 27 Jan 2008 16:49:11 -0800 (PST), Bil
:
(Original msg on bottom)

I use a lot Pactor winlink SSB and I have not any accelation on the
standard zinc corrosion.
Important note may be : I have no connection between ground straps and
boat negative (engine body) neither the TX is grounded to negative or
to strap, just the antenna tuner goes to gnd strap.
Counterpois is based on two external plates + boat keel,tanks etc
coupled via capacitors

Hope it helps
Manlio
ik2rau



After checking my zinc anode, I'm fairly certain I'm getting
accelerated erosion of my shaft zinc anode when transmitting Sailmail
e-mail via my HF radio and PacTOR modem.

Sailmail and the PacTOR modem drive the HF radio (an ICOM IC-M710)
fairly hard.

Does everyone transmitting with a PacTOR modem suffer accelerated
erosion of their zinc anodes? Or is this something specific to my
installation (and can be corrected)? If the latter, what should I look
for and correct?

Cheers

Bil