Re: [PSUBS-MAILIST] retractable buoy

[Jon Wallace <jonw@psubs.org>]

Frank,

I don't think testing David's comm system in a pool is a valid test.  
I've discussed this with him before and even suggested we send some 
units to Vance or Jay so they can be tested in deep water.  David's comm 
set is based upon an acoustic element, not a carrier element.  As such, 
it is going to be affected much more by water conditions and underwater 
topography than a UQC comm set such as Cliff and Alec have been talking 
about.

My work with David and acoustic pingers in the Spring of 2008 gave a 
preview of what to expect.  In fresh water averaging 20 feet, I could 
easily discern the pinger over 1,000 feet away.  In fresh water 
averaging 50 feet, the range was cut to about 600-700 feet.  I brought 
the pinger and hydrophone to Maine for the 2008 convention and we set it 
up from the dock in Castine.  The water depth was around 10-12 feet at 
the dock and the lengthwise distance between the pinger and hydrophone 
was about 75 feet.  Those with me that day (JimK, AndyG, Lea) will 
recall that the pinger was barely audible.  That's a huge difference in 
performance and from my point of view rendered the device non-usable.  
Was it the salt-water?  Was it the topography and/or material of the 
seascape?  One thing for sure, it was not boat traffic because there was 
little traffic there at the time.  Comparatively, Andy had brought a 
couple of ultrasonic pingers from Desert Star and those worked 
tremendously well under the same conditions and exact same placement.

So there is much testing that needs to be done with 20-20k acoustic 
communications in general.  David's units really need to be field tested 
in both fresh and salt water, under numerous conditions, depths, and 
ranges (as applicable to psubbers), and most importantly the results 
recorded accurately so they can be inspected by others who can then 
decide if the units will work for the type of diving conditions they 
operate in.  It would be best if the units were tested by someone who 
has experience with professional grade equipment so that the unit could 
be rated (this would be subjective for sure) for clarity of spoken word 
as well.  I should probably dig out my pinger and hydrophone and head 
over to Hampton Beach sometime to do some more salt-water testing from 
the jetty just in case Castine was an anomaly.  The only problem is that 
its not deep water.

Many of us have heard the quality provided by the Nuyco units, which to 
my ears were crystal clear and easily on par with being on a land-line.  
If we can get Alec to Florida next July we'll have another opportunity 
to hear what some other units sound like.

Jon



ShellyDalg@aol.com wrote:
> This could be something David can work on. What kind and how long 
> would work. Could this be tested in shallow water like a swimming pool ?
> If a small enough wire could be used, a small reel and a plug-in jack 
> floating on the surface could be useful.
> Frank D.




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