Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 18-11-2017, 15:27   #1
Registered User

Join Date: Jul 2017
Posts: 188
An OpenCPN Plugin for the new Polar Weather Satellites?

The first of four of the new Polar Weather Satellites was just launched with the promise of amazing weather data. Does anyone have the skills and desire to write a plugin to use a cheap USB software definable radio receiver and overlay the data on the chart? My coding skills are way too rusty but this could be an amazing new tool for sailors without discounting the importance of data interpretation by meterologists when available but these sats circle every 15 mins so one passing overhead in under 4 minutes at any point. Anyway, just thinking out loud. Here's the article that got.me.thinking.

Keep up the great work! Thank you.

https://www.space.com/38766-jpss1-we...h-success.html
__________________

Alberg30Shill is offline   Reply With Quote
Old 19-11-2017, 00:15   #2
Moo
Registered User

Join Date: Mar 2017
Posts: 474
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Already done. The fax plugin will receive the APT images from the satellites. The antenna is the difficult bit.

EDIT: no it seems these birds will use LRPT instead of APT; well APT has been going since the 1960s so it has probably done its time.

Details of LRPT here

The orbits are the same as the existing NOAA series by the way; circa 90 minutes rather than 15!

I find the images really useful in high latitudes less so in the tropics as I find the systems in the tropics much harder to interpret from the images.
__________________

Moo is offline   Reply With Quote
Old 20-11-2017, 07:31   #3
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 13,530
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Instructions for receiving lrpt on RTL-SDR.com

https://www.rtl-sdr.com/rtl-sdr-tuto...mages-rtl-sdr/

It appears the images can be recieved, and it is likely that weatherfax_pi can use the image, but it will be much higher resolution than the one's we are used to.
Sean may be using them now.
rgleason is offline   Reply With Quote
Old 20-11-2017, 10:37   #4
Moo
Registered User

Join Date: Mar 2017
Posts: 474
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by rgleason View Post
It appears the images can be recieved, and it is likely that weatherfax_pi can use the image, but it will be much higher resolution than the one's we are used to.
Sean may be using them now.
At least one of the Russian Meteor satellites has been transmitting LRPT for some time so somebody has probably tried it.

weatherfax_pi can use any images. There is that tutorial that I made years ago floating around somewhere.

Overlay GRIB data on satellite images in OpenCPN – Tweed's World

I'll have to revisit that to make sure that it is all still relevant with current versions.
Moo is offline   Reply With Quote
Old 20-11-2017, 12:58   #5
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 13,530
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Moo, did not connect you to Tweed's world. That would be great if you can check that tutorial.
I believe we have a link in the wiki for the PI. If not please let me know.
rgleason is offline   Reply With Quote
Old 15-06-2018, 15:54   #6
Registered User

Join Date: Apr 2015
Posts: 29
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

I know this is an old post, but I've just gotten a rtl-sdr and associated programs. I've detected both NOAA APT and METEOR LRPT signals but SNR is too low to create good images. At present I'm using a prototype Cross Dipole for an antenna.

Question; has anyone successfully implemented a system for receiving good APT and/or LRPT signals on their sailboat? What's your setup?

Below is my best image to date.
Click image for larger version

Name:	noaa-19-201806151639-mcir.jpg
Views:	68
Size:	393.2 KB
ID:	171830
W5PAD is offline   Reply With Quote
Old 15-06-2018, 16:51   #7
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again, currently in Pacific - Mexico
Boat: Sailboat
Posts: 1,266
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by W5PAD View Post
I know this is an old post, but I've just gotten a rtl-sdr and associated programs. I've detected both NOAA APT and METEOR LRPT signals but SNR is too low to create good images. At present I'm using a prototype Cross Dipole for an antenna.

Question; has anyone successfully implemented a system for receiving good APT and/or LRPT signals on their sailboat? What's your setup?

Below is my best image to date.
Attachment 171830

Here is one pic, a few minutes old, admittingly an outstanding good example. Hardware: wraase.de mx137 antenna and apt-06 decoder, Ubuntu 18.04 on Dell 7470 laptop.

I do have a RTL-SDR dongle on board, as well as a ASUS tinkerboard or RPI3s etc, but just haven't gotten around making it work with APT. The APT-06 receiver only does the NOAA APT, not Meteor LRPT. So getting the RTL_SDR to work with APT and LPRT, before all NOAA APT satellites have failed would be a goal.


Cheers


Dirk
Attached Thumbnails
Click image for larger version

Name:	noaa-18-06152318-mcir-noexif.jpg
Views:	61
Size:	170.0 KB
ID:	171832  
LeaseOnLife is offline   Reply With Quote
Old 15-06-2018, 18:38   #8
Registered User

Join Date: Apr 2015
Posts: 29
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

The MX137 is on my list of things to consider. In trying to get my set up working I've noticed that antenna height above ground plane (water in this case) makes a noticeable difference in signal strength. I also verified this using 4nec2 antenna modeling. Have you tried the MX137 at different heights?

I'm using Windows 10 and the following s/w for LRPT: Orbitron, SDRSharp (w/ two plugins), and lrptdecoder. To receive APT I've added Wxtoimg and VBCable to the above suite.
W5PAD is offline   Reply With Quote
Old 15-06-2018, 19:03   #9
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again, currently in Pacific - Mexico
Boat: Sailboat
Posts: 1,266
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by W5PAD View Post
.... I've noticed that antenna height above ground plane (water in this case) makes a noticeable difference in signal strength. I also verified this using 4nec2 antenna modeling. Have you tried the MX137 at different heights?
......

I have not! Is there an optimum range? Mine is roughly 3.5m above sea level, when not heeled.
LeaseOnLife is offline   Reply With Quote
Old 15-06-2018, 19:27   #10
Registered User

Join Date: Apr 2015
Posts: 29
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by LeaseOnLife View Post
I have not! Is there an optimum range? Mine is roughly 3.5m above sea level, when not heeled.
Here is a quick list of vertical antenna patterns for different heights (value in meters in upper left corner, ex h=4). I only included ones that would give better horizon to horizon coverage. At 3.5 m there are a few deep nulls. You can try raising and lowering by 0.5 m and see what happens. Keep in mind these are ideal patterns and the real world is most definitely different.
Click image for larger version

Name:	Picture1.png
Views:	69
Size:	334.6 KB
ID:	171839
W5PAD is offline   Reply With Quote
Old 16-06-2018, 04:05   #11
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again, currently in Pacific - Mexico
Boat: Sailboat
Posts: 1,266
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by W5PAD View Post
Here is a quick list of vertical antenna patterns for different heights (value in meters in upper left corner, ex h=4). I only included ones that would give better horizon to horizon coverage. At 3.5 m there are a few deep nulls. You can try raising and lowering by 0.5 m and see what happens. Keep in mind these are ideal patterns and the real world is most definitely different.
Attachment 171839

Thank you, these nulls show up as gray bars persistently, I have an explanation now. Lowering the antenna will bring it in the shadow of solar panels. For now, I can live with the nulls, now that I understand them better. When time and material permits, I can play with it more. Thanks again!
Dirk
LeaseOnLife is offline   Reply With Quote
Old 16-06-2018, 04:25   #12
Registered User

Join Date: Apr 2015
Posts: 29
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by LeaseOnLife View Post
Thank you, these nulls show up as gray bars persistently, I have an explanation now. Lowering the antenna will bring it in the shadow of solar panels. For now, I can live with the nulls, now that I understand them better. When time and material permits, I can play with it more. Thanks again!
Dirk
You're welcome.

I meant to ask if the drop outs always occurred, and if so it would confirm the model to a certain extent.

Are you familiar with turnstile antennas? Something that's been rattling around in my head is to modify the MX-137 into a turnstile. If I understand the MX-137, it's a cross dipole. The difference between a cross dipole and a turnstile are the reflective elements. The reflective elements essentially creates an artificial ground plane. By adding reflective elements the beam pattern would become more like the first two plots and could eliminate the nulls. If you're so inclined when you have time to play around with the antenna, try adding reflective elements in addition to varying the height. I'd be very interested in your findings.
W5PAD is offline   Reply With Quote
Old 16-06-2018, 07:14   #13
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again, currently in Pacific - Mexico
Boat: Sailboat
Posts: 1,266
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by W5PAD View Post
... By adding reflective elements the beam pattern would become more like the first two plots and could eliminate the nulls. If you're so inclined when you have time to play around with the antenna, try adding reflective elements in addition to varying the height. I'd be very interested in your findings.

OK, that I can do I think: add reflective elements 1/4 wavelength = 54.7cm below the MX137. What length should these reflectors be? Usually it should be 1/4 wavelength, but since the MX137 uses 1/8 wavelength antennas, would 1/8 be the right choice (also easier to mount on a boat). Is orientation of the lower cross critical, in line with the crossed elements above?
LeaseOnLife is offline   Reply With Quote
Old 16-06-2018, 14:09   #14
Registered User

Join Date: Apr 2015
Posts: 29
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by LeaseOnLife View Post
OK, that I can do I think: add reflective elements 1/4 wavelength = 54.7cm below the MX137. What length should these reflectors be? Usually it should be 1/4 wavelength, but since the MX137 uses 1/8 wavelength antennas, would 1/8 be the right choice (also easier to mount on a boat). Is orientation of the lower cross critical, in line with the crossed elements above?
My educated guess is the MX137 uses rubber ducky elements. While the physical length may be short, the electrical length is actually 1/2 wl (tip to tip). The lower elements should also be 1/2 wl.


The separation between the upper and lower elements isn't critical. A closer separation favors more receive gain straight up while a wider separation favors more receive gain towards the horizon. If you have time you can try different separations between 20-70 cm to see which gives adequate performance.

Regarding orientation. Every design I've seen on the web has the reflective elements in line with the main elements. I ran the model twisting the angel in 5 deg increments and the beam pattern did not change. This was a little surprising. One thing I did not check is if the polarization remained RHCP through out the rotation. I'd start with the elements in alignment, and again if you have time play with it and see what happens. Note, the reflective elements should not be electrically connected to each other.

Another thought that I'm not sure how to model is to use rubber duckys for the reflective elements. Maybe I'll research how the model and build them.
W5PAD is offline   Reply With Quote
Old 17-06-2018, 13:36   #15
Registered User
 
LeaseOnLife's Avatar

Join Date: Apr 2008
Location: out cruising again, currently in Pacific - Mexico
Boat: Sailboat
Posts: 1,266
Re: An OpenCPN Plugin for the new Polar Weather Satellites?

Quote:
Originally Posted by W5PAD View Post
My educated guess is the MX137 uses rubber ducky elements.
correct!

Quote:
While the physical length may be short, the electrical length is actually 1/2 wl (tip to tip). The lower elements should also be 1/2 wl.
That won't work for me, I made a home-built cross dipole with 1/2 wl, it worked well in the backyard, but couldn't fit on the boat.

Quote:
The separation between the upper and lower elements isn't critical. A closer separation favors more receive gain straight up while a wider separation favors more receive gain towards the horizon. If you have time you can try different separations between 20-70 cm to see which gives adequate performance.

Regarding orientation. Every design I've seen on the web has the reflective elements in line with the main elements. I ran the model twisting the angel in 5 deg increments and the beam pattern did not change. This was a little surprising. One thing I did not check is if the polarization remained RHCP through out the rotation. I'd start with the elements in alignment, and again if you have time play with it and see what happens. Note, the reflective elements should not be electrically connected to each other.
Thanks!

Quote:
Another thought that I'm not sure how to model is to use rubber duckys for the reflective elements. Maybe I'll research how the model and build them.
That would help, 1/2 wl is just not feasible, that is why I bought the MX137. Rubber duckies from aircraft VHF would probably be a close enough match.
__________________

LeaseOnLife is offline   Reply With Quote
Reply

Tags
enc, opencpn, plug, satellite, weather

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Plugin Polar edelvoilier OpenCPN 122 19-07-2019 17:40
Polar Plugin questions RHarriss OpenCPN 7 11-08-2017 20:06
Opencpn 4.4.0 - Weather Routing "Grib Plugin Not Supported" TiOlivier OpenCPN 7 22-07-2016 06:22
opencpn weather routing plugin not found usodimare OpenCPN 8 26-08-2015 13:26
Polar View / Polar Com Digital Map Software tomj Navigation 1 17-05-2011 19:24

Advertise Here


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:12.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×

ShowCase vBulletin Plugins by Drive Thru Online, Inc.