I wish to install a 2nd depth sounder.

I have a Raytheon ST60 series sounder and a Navman 450 combo paddle-wheel log
and depth. The Raytheon is already in use but I wish to install the Navman depth
transducer as a backup and a check. It also will measure greater depths than the
Raytheon which sometimes comes up with shallow depths in turbulent water - when
the chart says 3,000 metres. I don't want to adjust its sensitivity.

Questions - Will there be interference to either or do both filter out through
being different wave lengths or somesuch?

How far apart do they have to be?

What else haven't I thought of?

Peter Hendra wrote:
I wish to install a 2nd depth sounder.

I have a Raytheon ST60 series sounder and a Navman 450 combo paddle-wheel log
and depth. The Raytheon is already in use but I wish to install the Navman depth
transducer as a backup and a check. It also will measure greater depths than the
Raytheon which sometimes comes up with shallow depths in turbulent water - when
the chart says 3,000 metres. I don't want to adjust its sensitivity.

Questions - Will there be interference to either or do both filter out through
being different wave lengths or somesuch?

How far apart do they have to be?

What else haven't I thought of?

You're right in the raymarine depth sensor not being much good in deep
water; mine craps out at about 150-160m (guess it's about 500 feet
that's the real limit) and the behaviour at the boundary is not very
good. It can take a while for it to register "LAST" instead of "DEPTH".

--
Kees

If both sounders use the same frequency, which they probably will, then yes
they will interfere with each other.
A sounder works by measuring the time it takes for the signal to travel from
the transducer to the bottom and back. If two sounders are operating at the
same frequency they have no way of determining which signals return they are
receiving.


"Peter Hendra" wrote in message
...
I wish to install a 2nd depth sounder.

I have a Raytheon ST60 series sounder and a Navman 450 combo paddle-wheel
log
and depth. The Raytheon is already in use but I wish to install the Navman
depth
transducer as a backup and a check. It also will measure greater depths
than the
Raytheon which sometimes comes up with shallow depths in turbulent water -
when
the chart says 3,000 metres. I don't want to adjust its sensitivity.

Questions - Will there be interference to either or do both filter out
through
being different wave lengths or somesuch?

How far apart do they have to be?

What else haven't I thought of?

"BrianR" wrote in message
...
If both sounders use the same frequency, which they probably will, then
yes they will interfere with each other.
A sounder works by measuring the time it takes for the signal to travel
from the transducer to the bottom and back. If two sounders are operating
at the same frequency they have no way of determining which signals return
they are receiving.


If that was the case wouldn't you expect to see interference when sailing in
close proximity to other vessels with echo sounders running? I never saw any
sign of this

"MGP" . wrote in message ...

"BrianR" wrote in message
...
If both sounders use the same frequency, which they probably will, then
yes they will interfere with each other.
A sounder works by measuring the time it takes for the signal to travel
from the transducer to the bottom and back. If two sounders are
operating
at the same frequency they have no way of determining which signals
return
they are receiving.


If that was the case wouldn't you expect to see interference when sailing
in
close proximity to other vessels with echo sounders running? I never saw
any
sign of this



A quick review of the physics involved:
+ speed of sound in water is roughly 1493m/s in fresh water and 1533m/s in
sea water
+ round trip time for "interesting" depths ( 100m) is less than 150ms
+ the energy of the echo obeys an inverse square law, so the return is much
weaker than
the signal generated by the transducer

Taken together, this means the sounder operates in pulse mode so as not to
drown out the echo and that pulses must be at least 150ms apart to allow for
the round-trip time even in shallow water. For the example earlier in this
thread of 3km charted depth, round trip time is of the order of 4 seconds.
To make the transmitted pulse as efficient as possible (both equipment power
wise and snr), a short duration, high amplitude is required. For sake of
argument, assuming a 5ms pulse, this gives a maximum duty cycle of the
transmitter of about 3% for 100m and 0.13% for km. At this point it begins
to become clear that the interference problem postulated above would require
the sounders on nearby boats (or multiple sounders on a single boat) to be
both in phase and using the same pulse rate if the sounders are using any
form of signal processing (e.g. averaging successive readings and/or range
gating). As the maximum depth resolution of the sounder increases, the duty
cycle decrease further reduces the probability of collision.

Additional refinements ala CSMA (carrier sense multiple access) are left as
an exercise to the reader.

I have personally experimentally verified non-interference in shallow (10m)
fresh water operating a Raymarine ST-60 tridata and a Humminbird ID 120 with
transducers located within 2m of each other on the same boat.

I have an ST50 and an old B&G Hornet depth sounder in my boat and they don't
seem to interfere with each other. The transducers are less than 12 inches
apart. The B&G is just a backup that I would use in case the ST50 died.
Even if interference were occuring, in this case it would not be an issue.
Perhaps you are in the same position.

"Peter Hendra" wrote in message
...
I wish to install a 2nd depth sounder.

I have a Raytheon ST60 series sounder and a Navman 450 combo paddle-wheel
log
and depth. The Raytheon is already in use but I wish to install the Navman
depth
transducer as a backup and a check. It also will measure greater depths
than the
Raytheon which sometimes comes up with shallow depths in turbulent water -
when
the chart says 3,000 metres. I don't want to adjust its sensitivity.

Questions - Will there be interference to either or do both filter out
through
being different wave lengths or somesuch?

How far apart do they have to be?

What else haven't I thought of?

"Gordon Wedman" wrote in
news:XrWAe.150070$on1.146205@clgrps13:

I have an ST50 and an old B&G Hornet depth sounder in my boat and they
don't seem to interfere with each other. The transducers are less
than 12 inches apart. The B&G is just a backup that I would use in
case the ST50 died. Even if interference were occuring, in this case
it would not be an issue. Perhaps you are in the same position.



We run a B&G Network Depth instrument about 6" from a Garmin 185's sonar
transducer, too, aboard "Lionheart". Doesn't seem to both it at
all....until the damned bubbles when the sailing is good get under the
Garmin's transducer and set off its depth warning alarm....

--
Larry

This jerk called my cellphone and was nasty.
Continental Warranty -- MCG Enterprises -- Mepco-
24955 Pacific Coast HWY Suite C303
Malibu California 90265
888-244-0925
Fax: 310-456-8844
Email:
Read about them he
http://www.ripoffreport.com/view.asp...3&view=printer

I have a 50/200, another 50/200 and a 120 (Khz units). The 120
(digital depth) rarely gets interference but the 50/200s are VIDEO units
and I will see significantly more screen clutter when they are operated
at the same frequency. It won't change the digital readouts on them
but it will make the digital depth unlock and not display the number.
Bottom still shows pretty clearly as a line on the display.



J. Michael Milner wrote:
"MGP" . wrote in message ...

"BrianR" wrote in message
. ..

If both sounders use the same frequency, which they probably will, then
yes they will interfere with each other.
A sounder works by measuring the time it takes for the signal to travel
from the transducer to the bottom and back. If two sounders are

operating

at the same frequency they have no way of determining which signals

return

they are receiving.


If that was the case wouldn't you expect to see interference when sailing

in

close proximity to other vessels with echo sounders running? I never saw

any

sign of this




A quick review of the physics involved:
+ speed of sound in water is roughly 1493m/s in fresh water and 1533m/s in
sea water
+ round trip time for "interesting" depths ( 100m) is less than 150ms
+ the energy of the echo obeys an inverse square law, so the return is much
weaker than
the signal generated by the transducer

Taken together, this means the sounder operates in pulse mode so as not to
drown out the echo and that pulses must be at least 150ms apart to allow for
the round-trip time even in shallow water. For the example earlier in this
thread of 3km charted depth, round trip time is of the order of 4 seconds.
To make the transmitted pulse as efficient as possible (both equipment power
wise and snr), a short duration, high amplitude is required. For sake of
argument, assuming a 5ms pulse, this gives a maximum duty cycle of the
transmitter of about 3% for 100m and 0.13% for km. At this point it begins
to become clear that the interference problem postulated above would require
the sounders on nearby boats (or multiple sounders on a single boat) to be
both in phase and using the same pulse rate if the sounders are using any
form of signal processing (e.g. averaging successive readings and/or range
gating). As the maximum depth resolution of the sounder increases, the duty
cycle decrease further reduces the probability of collision.

Additional refinements ala CSMA (carrier sense multiple access) are left as
an exercise to the reader.

I have personally experimentally verified non-interference in shallow (10m)
fresh water operating a Raymarine ST-60 tridata and a Humminbird ID 120 with
transducers located within 2m of each other on the same boat.