Red Pitaya Monitoring Station

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Daniel Wee
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Red Pitaya monitoring station

Post by Daniel Wee »

With 9V1RM relocating away from Singapore - we will need to have a monitoring station for the purpose of tracking band conditions and detecting openings. For years, Rath has been providing that service quietly for all of us but it is time for the baton to be passed along.

The Red Pitaya that 9V1RM is a good platform that allows for simultaneous monitoring, decoding of FT-8, CW, WSPR, RTTY skimming all at the same time across multiple bands. The hardware is a Red Pitaya Stem 125-14 (SGD502.96):-

https://www.mouser.sg/ProductDetail/Red ... BAvA%3D%3D

Casing (SGD87.02):-

https://www.mouser.sg/ProductDetail/Red ... ZmAhB90%3D

For the loop pre-amp, a Cross Country pre-amp (USD70 = SGD94.18):-

http://www.crosscountrywireless.net/hig ... lifier.htm

A bias tee is needed to power the pre-amp (SGD5.34):-

https://it.aliexpress.com/item/40001525 ... 8411f6a9-1

Pavel's software is ideal and we have to work out a way to get skimming going as well. This also requires a small Linux box - maybe an RP4 or similar. I could deploy the Zotac for this purpose, with the benefit of a proper i386 Ubuntu platform.

http://pavel-demin.github.io/red-pitaya ... eiver-ft8/

Total cost of this project is at least SGD688.65
Daniel Wee
Site Admin
Posts: 2409
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: Red Pitaya monitoring station

Post by Daniel Wee »

GPS module with PPS needed for FT8 timing synchronization.

http://pavel-demin.github.io/red-pitaya ... eiver-ft8/

Getting started
  • Download SD card image zip file (more details about the SD card image can be found at this link).
    Copy the contents of the SD card image zip file to a micro SD card.
    Optionally, to start the application automatically at boot time, copy its start.sh file from apps/sdr_transceiver_ft8 to the topmost directory on the SD card.
    Install the micro SD card in the Red Pitaya board and connect the power.
Configuring FT8 receiver

All the configuration files and scripts can be found in the apps/sdr_transceiver_ft8 directory on the SD card.

To enable uploads, the CALL and GRID variables should be specified in upload-ft8.sh. These variables should be set to the call sign of the receiving station and its 6-character Maidenhead grid locator.

The frequency correction ppm value can be adjusted by editing the corr parameter in write-c2-files.cfg.

The bands list in write-c2-files.cfg contains all the FT8 frequencies. They can be enabled or disabled by uncommenting or by commenting the corresponding lines.
Daniel Wee
Site Admin
Posts: 2409
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: Red Pitaya monitoring station

Post by Daniel Wee »

It appears that an impedance transformer is needed - 14:1 ratio using Mini-Circuits T14-1+ transformer. This is only true for the STEMlabs 125-14 model since the 122.88-16 models has the transformer built into the board.

https://www.minicircuits.com/WebStore/d ... l=T14-1%2B

Jumpers need to be set on the board according to this:-

https://www.redpitaya.com/159/impendance-transformer

I think you could get away with a 16:1 Coilcraft:-

https://sg.element14.com/w/c/transforme ... ransformer

Seems we can get the T14-1+ from AliExpress:-

https://www.aliexpress.com/item/1005002339595633.html
Attachments
T14-1+.pdf
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Daniel Wee
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Red Pitaya Monitoring Station

Post by Daniel Wee »

We are using the STEM 125-14 unit (14-bit ADC) but the 122-16 can also be used (16-bit). It is not clear to me if one works significantly better than the other.

1. Connect the Red Pitaya to the LAN. Insert the provided SD boot disk. Power it up via the USB port.

2. Navigate to the IP address and go to the "Application Marketplace". There install "SDR receiver compatible with HPSDR (1.0-20190527)" which should be the last one. Do NOT install the "SDR transceiver". After a while, the "RUN" option will appear. You can start the receiver by clicking run but for normal purposes, we want to automate this.

3. Follow the instructions on https://www.hamsci.org/n6tv-red-pitaya- ... mmer-hdsdr and modify the rc.local file.
- note that once you do this, the way to stop the receiver is to run the script:-

Code: Select all

/opt/redpitaya/www/apps/sdr_receiver_hpsdr/stop.sh
The following link is also useful:

https://www.scivision.dev/red-pitaya-hp ... ver-setup/

This link gives some more information about the Red Pitaya setup. especially for skimming:

https://sm7iun.se/redpitaya/ft8skimmer/
Daniel Wee
Site Admin
Posts: 2409
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: Red Pitaya Monitoring Station

Post by Daniel Wee »

Okay, a few non-obvious things about getting this all going. 9V1RM was using not one, but three Red Pitayas to get all that decode. One dedicated for FT8, another for WSPR, and another for CW/RTTY/WebSDR. That's a LOT of hardware that I wasn't aware of. The CW skimmer server was running on an i8700 Windows machine too. We're going to have to just start with FT8.

Secondly - when preparing the SD-card for FT8 decode, according to

https://pavel-demin.github.io/red-pitay ... eiver-ft8/
https://sm7iun.se/redpitaya/ft8skimmer/

You get the latest file not from the page link, but from the github link:-

https://github.com/pavel-demin/red-pita ... s/releases

This is the same for both 125-14 and the 122-16 boards. You just have to pick different files for the start up.

After you extract the contents to a FAT32 formatted SD-card, you will need to edit some files before you put it into the Red Pitaya because that image is non-editable from inside the Red Pitaya shell. You can't even change the password permanently.

Then copy the startup.sh from the /apps/sdr_transceiver_ft8 directory to the root directory. Additionally, you need to edit

/apps/sdr_transceiver_ft8/upload-ft8.sh

to provide the callsign and grid for pskreporting.

After you put the card into the Red Pitaya - it still will not start until you navigate to the IP address with a browser. I might be doing something wrong but we need to solve a few of these problems. Can't have it needing a manual re-start every time.

**UPDATE** It does start up by itself, eventually. The thing starts by a cron cycle so it may take a while before it starts up. When it does start up, eventually, you will see the BLUE LED light up, next to the GREEN power LED.
Daniel Wee
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Posts: 2409
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Re: Red Pitaya Monitoring Station

Post by Daniel Wee »

The plan now is to just set the Red Pitaya up alone, with a wire to a loop antenna and the pre-amp, along with a bias-Tee to send power up. I think we also need a fan to keep the Red Pitaya ventilated and cool. Beyond this, we will have to think about keeping RFI out, which means choking the power and feedlines - probably with some FT240-31 or -43s.

This was recommended:-
https://sg.element14.com/fair-rite/2631 ... 2631803802
Daniel Wee
Site Admin
Posts: 2409
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Re: Red Pitaya Monitoring Station

Post by Daniel Wee »

The Pavel SD-card runs things from RAM disk, meaning that all changes will not persist through a reboot. In order to make changes stick, they need to be committed to disk using:-

Code: Select all

lbu commit -d
There also seems to be a way to make the SD card writable with "rw" and read only with "ro" after changes are made. For more information, including getting WiFi up and running here:-

http://pavel-demin.github.io/red-pitaya-notes/alpine/
Daniel Wee
Site Admin
Posts: 2409
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: Red Pitaya Monitoring Station

Post by Daniel Wee »

Power is supplied through a PTH08080WAZ power module. I had to use really heavy gauge wires to supply power to the board due to inordinate voltage droop (4.2V!!) using regular hook-up wires. This is fed through TP10 so as to take advantage of the fuse.

https://redpitaya.readthedocs.io/en/lat ... xtent.html
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Daniel Wee
Site Admin
Posts: 2409
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: Red Pitaya Monitoring Station

Post by Daniel Wee »

Remaining work to be done:-

1. Integrating the bias-T into the casing
- coax from SO-239 to bias-T and from bias-T to the Red Pitaya
- the mounting might have to use double sided tape since board has no mounting holes
- removal of BNC and barrel socket power connectors

2. Copper block for FPGA
- polishing of surfaces
- getting the thermal interface right, either with adhesive or paste
https://kianhuatmetal.com/contact-us/

3. Potential power or connected LED

4. Spraying casing black
- wet sanding surfaces

5. Linear 12V 1A power supply
Attachments
bias_tee.jpg
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Daniel Wee
Site Admin
Posts: 2409
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Loop antenna for broadband monitoring

Post by Daniel Wee »

We're using the Cross Country Loop+ LNA for a loop, modified to have a cutoff just above 50MHz.

http://www.crosscountrywireless.net/loo ... lifier.htm

Some loop information and ideas:-

http://www.crosscountrywireless.net/car ... ntenna.htm
http://www.lz1aq.signacor.com/docs/loop ... c-loop.php
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