Weatherfax_pi Recievers: RtlSDR + SSB radios

[Franziska]

Originally Posted by sailorF54

Yes, a shielded cable in the vicinity of electronic appliances is useful not necessarily up to the shroud. Note that the length of wire from the receiver to the shoud is part of the antenna length.
Sorry, no idea whether (clamp-on) ferrites are useful.

I'll forgo the ferrites then and use the shielded cable. Another great answer. We'll get there.
I'll install this in Mai.
Should I remove the shield for the distance outside (far from other electrics).

[sailorF54]

Originally Posted by Franziska

I'll forgo the ferrites then and use the shielded cable. Another great answer. We'll get there.
I'll install this in Mai.
Should I remove the shield for the distance outside (far from other electrics).

Don't bother if, as I understand, the distance to the shroud is only a few m long
PS a coax antenna is only mandatory when transmitting where you have to have a 50 ohm matching impedance between the transmitter output and the antenna

[Franziska]

Originally Posted by sailorF54

Don't bother if, as I understand, the distance to the shroud is only a few m long
PS a coax antenna is only mandatory when transmitting where you have to have a 50 ohm matching impedance between the transmitter output and the antenna

Yes, about 2.5m from receiver parallel to electric cables, than going through deck and up inside the shroud.
So I'll use a standard normal insulated cable for the whole run. Multistrand or wire?

[sailorF54]

Originally Posted by Franziska

Yes, about 2.5m from receiver parallel to electric cables, than going through deck and up inside the shroud.
So I'll use a standard normal insulated cable for the whole run. Multistrand or wire?

IMHO, does not matter. Take a marine grade to have good insulation against moist, salty, air, with a diameter that will fit the plug to your receiver set...

[Franziska]

Originally Posted by sailorF54

IMHO, does not matter. Take a marine grade to have good insulation against moist, salty, air, with a diameter that will fit the plug to your receiver set...

Thanks and have a happy Easter.

[SCarns]

This is an exciting thread. Unfortunately, even though I’m a certified marine electronics installer, I’ve never had a good grasp at SSB or Ham radio concepts.

I’ve discussed this in various thread with both Rick and Sean, but there is definitely a disconnect between SDR and OCPN WeFax. I originally got a Nooelec Ham-it-up set up, but Sean didn’t feel that package would work. He recommended a standard RTL-SDR V3 dongle, which I have.

Based on the above, I gather that i need to bridge the gap between SDR radio app and OCPN WeFax. I had hoped to use a virtual audio connection using VB-Audio Virtual Cable on my Mac, but ran out of steam and got side-tracked with more important projects.

I’m happy this is being revisited. Can anyone confirm I’m on the right track here? Perhaps it’s time to take another shot at this…

Anyone have something similar working? Sean had said he only made it work with a radio receiver with an audio out to his PC, keeping it simple.

[Kelkara]

I never got as far as using the OCPN plugin ...

I started using a Ham It Up SDR dongle running through FLDigi and a virtual audio cable to JVComm software ... It worked but I got poor results. The problem was my laptop which produced vast amounts of RFI which swamped the SDR signal.

I then moved to a Tecsun 660 radio, and it wasn't much better, the laptop was still the problem. So I switched to using my phone running HF Weatherfax app, and the results were much better, but still not good.

Finally I realised that the remaining RFI was coming from the 12V-6V power adapter I was using to power the radio ... running the radio off batteries finally deliverd good results.

Unfortunately despite trying all kinds of plugs and adapters I haven't managed to work out how to plug the audio directly from the radio into the phone, so I have to listen to all the beeping as the fax is received.

So my experience is of no help to people trying to use OCPN, but it is a cautionary tale about RFI ... my laptop turned out to be completely useless for this purpose.

[rgleason]

Kellara thank you for your post. It reminded me of how I had been using Weatherfax HF and found it pretty satisfactory. I used a short double ended audio connector cable from ADVID to get it from the rtl-sdr into the phone which I still have. I also made up the connectors necessary to connect to 75 ohm coax home made antenna that I hung up high on the mast.

• https://www.hamtronics.com/make-a-75-ohm-fm-antenna/
• Furuno Weatherfax FAX5 Antennas >$500 are good from 80kHz to 30mHz Range
• Gam Electronics Specifically Tuned to Maximize Signal Strength for Fax Reception,
  • Use RG 58 for runs less than 20 feet
  • Use RG-8X for runs over 20 feet
  • Frequency 2-30 MHz (Weatherfax / DSC) and 88-108 MHz (FM)
  https://www.landfallnavigation.com/m...x-antenna.html

One of the problems I had however was getting the rtl-sdr to work reliably (this was early rtl-sdr!!, so perhaps things have improved.)


I was able to decode some recordings and move the files into weatherfax_pi so I could view them overlayed on OpenCPN. There is also a built in copy of the NOAA/NWS Radiofacsimile schedule, and an option to download the latest copy of the schedule from the NWS website.
Google App -

• https://play.google.com/store/apps/d...hl=en_US&gl=US
• HF Weather Fax decoder for Android phones & tablet

Also for Apple -

• https://apps.apple.com/us/app/hf-wea...ax/id394199597
• HF Weather Fax Marine Radio Fascimile Decoder App for iPad iPhone iPod Touch

And here are other good threads
https://www.cruisersforum.com/forums...nna-98786.html
https://www.cruisersforum.com/forums...-a-238043.html

[rgleason]

Good post about using coax for weatherfax
https://www.cruisersforum.com/forums...ml#post3370496

and

https://www.cruisersforum.com/forums...ml#post3335541


A setup using RPI

https://www.youtube.com/watch?v=cdKhxicZHGs

[Maelruan]

I agree with SailorF54 that shielded cable is good near sources of interference - the shield acts as a "Faraday Cage" to keep interference away from the inner antenna wire.
The ferrites absorb a lot of noise which is why they are used on USB cables, charging cables, etc. You may find quite a difference in the clarity/readability of the image when you use them - e.g. less grey & numeric values can be read more easily. The OpenCPN weatherfax plugin seems to have better digital signal processing within it than any other wefax app I've used.
Best frequencies vary with the the Sun. Higher frequencies are better during daylight, lower frequencies better at night. Propagation can be checked with an app like VOAProp.
Since the optimum length for the antenna is a half/quarter wave length, an antenna tuner will electrically match a fixed length antenna to changing frequencies, and may also pre-amplify the desired signal.
The wefax transmitters with the best signals for western Europe are those of the German Weather Service (DWD) at Offenbach/Hamburg with 7878.5 khz on the dial, or 3853.5 & 13881.02 as alternatives. The UK transmitters at Northwood are not as good, but I tune them at 8038.5 and 4608.5.
DWD also have very good RTTY/SYNOP forecasts and reports which I tune at 4581.5, 7644.5, & 10099.3. The Hague (PBB) also has RTTY forecasts at 6356.5 & 8437.6. As mentioned in other threads, I use MULTIPSK to decode these.

[rgleason]

Here is a Simple NOAA/Meteor Weather Satellite Antenna: A 137 MHz V-Dipole

Also a good weather station receiver by Wraas WeSaCom-B the MX-137 antenna is for marine.

APT-06 / APT-06AD Dedicated Weather Satellite Receiver

Look at Tweed's writeup here.


Some other suitable receivers

https://wxtoimgrestored.xyz/hardware/

[Bill O]

Rick,
Thank you for posting the link for the DIY WX Sat. antenna. Seems like a much simpler build than a helical antenna.
Do have a question though if it would work on a boat since they specifically wanted the antenna V facing south and the coax pointed north. Is this needed? I'm certain no one would want to go outside to try align the antenna every time a bird was coming by to get a scheduled download.

[rgleason]

Thanks Bill, that's a good point. I imagine it could be done, but perhaps another antenna would be better.

Originally Posted by Bill O

Rick,
Thank you for posting the link for the DIY WX Sat. antenna. Seems like a much simpler build than a helical antenna.
Do have a question though if it would work on a boat since they specifically wanted the antenna V facing south and the coax pointed north. Is this needed? I'm certain no one would want to go outside to try align the antenna every time a bird was coming by to get a scheduled download.

[rgleason]

This is my goto resource

Marine Weather

There’s a app for the iPhone so that by simply placing through phone near the speaker it will receive and decode weatherfax