[amsat-bb] Mount Carmel HS ARC marine buoy deployed and transmitting

[Don KB2YSI]

That is a really cool sounding project and thank you for sharing your
process!

On Thu, Jul 16, 2020, 19:50 Greg via AMSAT-BB <amsat-bb at amsat.org> wrote:

> Great idea and thanks for sharing the technical details.
>
> Greg
> N3MVF
>
> On Jul 16, 2020, at 7:20 PM, GEO Badger via AMSAT-BB <amsat-bb at amsat.org>
> wrote:
>
> Very cool Phil.. Thanks for sharing that.
> As an ex-employee of MBARI, I can tell you that we threw a lot of stuff in
> the water that took more development time and cost than yours with similar
> results.
> ---
> Ciao baby, catch you on the flip side
> 73 de W3AB/GEO
>
> http://www.w3ab.org
>
> You can say "over", you can say "out", you just can't say "over and out".
>
>    On Thursday, July 16, 2020, 03:48:27 PM PDT, Phil Karn via AMSAT-BB <
> amsat-bb at amsat.org> wrote:
>
> Over the past year, Randy, KQ6RS and I have mentored the MCHSARC in
> designing and constructing a simple marine buoy that was deployed from
> the R/V Sally Ride this morning about 700 km off the coast of southern
> California. It is up and transmitting WSPR on 20m using the callsign
> KQ6RS, and is being received all over the US and into Canada and Brazil.
>
> The electronics is the 20m WSPR version of the WB8ELK "pico tracker"
> that has been flown quite a few times (including by us) on long duration
> balloons. We removed the solar panels and substituted 21 ordinary
> alkaline D-cells wired to supply 4.5V. We estimate battery lifetime will
> be 6 months.
>
> The basic design was inspired by Bob, WB4APR, at the US Naval Academy.
> Physically, the buoy is just a 5' section of 4" PVC pipe, ballasted at
> one end to float vertically in the water. The top is closed by a sewer
> pressure test plug I found at Home Depot; it has a bolt in the center
> that acts as a convenient feed-through and mounting point for the
> antenna, a stainless steel CB whip with a matching network designed,
> tested and carefully tuned by Randy. We use the sea as a counterpoise,
> but to avoid direct metal/seawater contact we lined the inside of the
> pipe with copper tape to form a capacitive connection. We probably spent
> too much time on this; Randy even modeled the electrical fields in the
> seawater with a professional RF analysis package.
>
> In our first flotation tests in Randy's swimming pool we found that the
> ballasted pipe, by itself, was remarkably stable in pitch, roll, sway
> and surge but oscillated a lot in heave (up and down). To damp this
> Randy added cross arms at the water line to add drag in the vertical
> direction. (It wasn't our intent to mimic a religious icon but that's
> where the physics went.) Tuning the antenna required sea water, so Randy
> did it from a dock on Mission Bay here in San Diego.
>
> We tried to make this thing as rugged as we could. (My favorite saying
> to the students was that the sea *always* wins in the end, but we can
> delay that long enough to be useful.) Everything inside is held in place
> with epoxy or polyurethane foam. Randy reinforced the sewer plug with a
> PVC end cap with a hole cut in the center. Although the antenna is
> stainless steel, Randy covered it with a type of heatshrink with a
> waterproofing compound inside. Activation was by removing an external
> magnet placed over a parallel pair of normally closed magnetic reed
> switches. (Using two instead of one was my idea.) We even argued how to
> guard against the crew forgetting to remove the magnet before
> deployment. Randy found some adhesive that would dissolve and let the
> magnet fall away; I suggested a big REMOVE BEFORE FLIGHT tag and a float
> that would pull it away if it was tossed into the water.
>
> That left the problem of deployment. We couldn't just drop it close to
> the coast because it would quickly wash back up on the beach. We needed
> a boat ride. We were originally going on a NOAA vessel in April, but
> that trip was cancelled due to the pandemic. Randy secured a trip on the
> R/V Sally Ride, a research ship operated by Scripps Institute of
> Oceanography and home ported here in San Diego.
>
> This map shows the "lawn mowing" pattern they follow to measure and
> sample sea water off southern California. We were deployed early this
> morning at the most southwestern point shown here:
>
> https://calcofi.org/cruises/2020-cruises/calcofi-2007sr.html
>
> First report was at 12:52:30 UTC this morning from 29 51.25N, 123
> 37.50W. That's grid square CL89eu, which I figure is pretty rare for
> grid hunters. The current carried us east into CL89fu at 20:32:30. This
> is a little surprising since we thought the currents in that area are to
> the southwest. But that's why you do science!
>
> You can track us on aprs.fi here:
>
> https://aprs.fi/#!call=a%2FKQ6RS-1&others=1&timerange=604800&tail=3600
>
> We also show up on wsprnet.org
>
> http://wsprnet.org/drupal/wsprnet/map
>
> Because of the funky way Bill encodes position in WSPR (which was never
> designed for this), you'll see some weird-looking callsigns (like
> 0W7NFU) in addition to KQ6RS.
>
> This was our first buoy, just to get our feet wet (ha ha). Now to think
> about what we want to put in our *second* buoy. Two-way links, satellite
> tracking, sensors, the works. But remember the "second system" effect...
>
> 73, Phil
>
>
>
>
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