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Subject: Re: Transducer Hz - was TWL: Re: Depth sounder
From: Arild Jensen (elnav@XXX.XXX)
Date: Mon Aug 05 2002 - 01:42:26 EDT
Ron rogers wrote
> Furuno now makes some sounders that use 235Hz. They claim that it reduces
> interference from other, nearby sounders. I was not aware of the problem.
REPLY
For a more complete picture, check out Airmar and look at their catalog.
They make nearly all the ceramic transducers for all the various sounder
makers.
Transducer frequencies range from 10 Khz right up 500Khz depending on
specific applications.
As Bob Austin pointed out, some survey and research vessels use the same
transducers as recreational depth sounders.
Cross interference of multiple sounders being operated in close proximity is a
well known phenomena in tournament fishing circles where many tournament
boats congregate in confined waters. In shallow lakes the echoes bounce all
around creating spurious responses.
They also saw problems with two sounders of the same frequency operating at
opposite ends of the same boat. One for navigation and one for fish finding.
The major difference between transducers on competing brands is the
connector and sometimes the transducer housing. Fancy models may have a
speed wheel and a temperature sender included in the housing together with
the actual depth element.
It used to be that the cable length was part of a tuned circuit, but the more
recent designs( digital) does permit cable extensions and this is an indication
that cable lenght is not critical.
That in turn means that you can use an equivalent Airmar transducer.
All the new transducers that I have seen have a tag on the cable which list the
Airmar part number and the operating frequency. That is a good indication
of when you can substitute by changing the connector.
Moulded connectors cannot be opened so you need to splice the cable.
As long as the wire is spliced neatly the cable impedance is not altered much
and it should work.
If the connector can be opened, it is neater to wire direct to the pins.
regards
Arild
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