Finally ordered a NanoVNA

Finally ordered a NanoVNA and TinySA although I must say I am still confused around attenuation and the whole dB thing. Reading from the TinySA wiki

https://tinysa.org/wiki/pmwiki.php?n=Main.Transmitters

Safe measurement of the output of transmitters

Calculating with dB is not too difficult. Every factor of 10 decrease of the power of a signal reduces the dB level with -10dB

Typical output power of a transmitter

100W equals +50dBm

10W equals +40dBm

1W equals +30dBm

For best measurement of harmonics in the output of transmitters the input level of the tinySA should aim between -20dBm and -10dBm

Required attenuation between transmitter and tinySA

For 100W : between 60 and 70dB

For 10W : between 50 and 60dB

For 1W : between 40 and 50dB

The best approach is to use ALWAYS a 30dB attenuator directly connected to the tinySA and to use power attenuators to reduce the output of the transmitter to the target input level of this 30dB attenuator, that is +10dBm

So you will need these power attenuators

For 100W output: 30-40dB

For 10W output: 20-30dB

For 1W output: 10-20dB

Another option is to use a dummy load and an inline 50dB attenuating sampler. A nice example of how to build one yourself can be found here (here link is http://www.ad5x.com/images/Articles/Tap50dbRevA.pdf but no longer exists) - see below

From my reading of the above I should get a 30dB attenuator on my NanoVNA, and for a 1W rig, I would need another 20dB of power attenuation, or for a 10W rig another 20dB of power attenuation. It seems there are a bunch of cheap 2W attenuators in various steps: 1,3,6,10,15,20,30,40dB (eg 2W SMA attenuator on AliExpress) and I would also need a higher power attenuator, sort of like a dummy load?so I got a 10W SMA Attenuator at 30dB.

This was also influenced by https://groups.io/g/tinysa/topic/102097320 where Matthew Rapaport (10/22/23 #13069) writes

I have only HTs to test and transmit 1 watt. 60db of attenuation is perfect–results in 1 millionth of a watt going into the tinysa. 30db is on the radio (10 watt capacity so HT output is 1 thousandth of a watt) and another 30db (2 watt capacity) on the tinySA port. See pictures). If you’re transmitting 100 watts you’re going to need 80db attenuation to get the same 1 millionth of a watt. I would put 50 on the radio and then you can use the 30db on the port..

so I think I am in the ball park.

I did also watch another (NanoVNA as a synthesized CW signal generator) of MegawattKS informative videos where he uses a step attenuator like a AGILENT/ HP 355D STEP ATTENUATOR DC TO 1000 MHZ but these seem hard to come by. He mentions building your own?

this one https://www.arrl.org/files/file/Technology/tis/info/pdf/9506033.pdf seems like to be a big resistor network with a bunch of switches to turn various parts on/off to get desired attenuation: 1,2,3,5,10,10,10,10,10,10
you can buy one for ~$40 RF Programmable Attenuator 1MHZ-3800MHz Digital programmable RF attenuator control 0-31dB adjustable step 1dB PC controllable althought it seems to be a little limited in power
there is a thread on building your own attenuator https://www.eevblog.com/forum/projects/20db-rf-attenuator-seeking-feedback-to-improve/ has a bunch of comments and photos and circuit ideas as well as pointing to
- DC-4.0GHz RF Fixed Attenuator Radio Frequency Fixed
- and a video by https://www.youtube.com/@w2aew #91: Basic RF Attenuators - Design, Construction, Testing - PI and T style A Tutorial
- the above lead me to find https://www.youtube.com/@IMSAIGuy
  
  #545b TinySA Using Attenuators
  
  and #581 Digital Programmable RF Attenuator

Have added all the above to a watch later list on YouTube. I do feel like more of a librarian, sifting and saving a bunch of stuff for later, rather than an experimenter in RF.

regarding the lost http://www.ad5x.com/images/Articles/Tap50dbRevA.pdf it does via the web archive https://web.archive.org/web/20170124004030/http://www.ad5x.com/images/Articles/Tap50dbRevA.pdf but I have copied it for posterity archive: http://www.ad5x.com/images/Articles/Tap50dbRevA.pdf

Talking of the web archive, also found some other interesting stuff relating to the original tape measure antenna article /ham-radio/archives/pages.videotron.com_ve2jmk_tape_bm.htm.md

another tape measure antenna WebArchive: RDF2 YAGI WITH TAPE MEASURE ELEMENTS
WebArchive: THE FOX - 40 milliwatt transmitter with a bunch of cool “ugly construction” and “manhattan” build
and WebArchive: THE FOX750 - 750 milliwatt transmitter

Another interest that comes to mind is making available a bunch of software that seems to have been hidden or closed sourced. There is a big collection here https://github.com/AxiomYT/Ham-Radio-Manuals-and-hard-to-find-tools. Of particular interest seem to be: Super Morse and YagiCad. But outside of that I am also interested in Radiosonde decoding and decoding general recordings of digital signals, in real time.

Although for Radiosonde there seems to be this https://github.com/dbdexter-dev/sondedump

git clone git@github.com:dbdexter-dev/sondedump.git dbdexter-dev-sondedump
cd dbdexter-dev-sondedump
mkdir build && cd build
cmake ..
# errored, I didn't have cmake
brew install cmake

cmake ..
# errored, it wanted portaudio, or I could turn it off
cmake .. -DENABLE_AUDIO=OFF
make
./sondedump ~/gqrx_20240224_234742_401500000.wav
    [decode.c:177] Autodetected: RS41
    (U4824694) [ 3486] -17.8'C  11%    37.73016S 145.16373E   9847m    27.1m/s  84'  +2.5m/s
    (U4824694) [ 3487] -17.8'C  11%    37.73013S 145.16403E   9850m    26.4m/s  83'  +3.2m/s
    (U4824694) [ 3488] -17.9'C   6%    37.73011S 145.16432E   9854m    25.8m/s  84'  +4.8m/s
    (U4824694) [ 3489] -17.9'C   6%    37.73009S 145.16461E   9858m    25.9m/s  85'  +3.4m/s
    (U4824694) [ 3490] -18.0'C   6%    37.73007S 145.16490E   9862m    26.3m/s  85'  +3.8m/s
    ...

# found out I could
brew install portaudio
rm -rf ../build/*
cmake ..
make
./sondedump --audio-device 0
# will listen to microphone? but did not seem to work when I played a recording
afplay ~/gqrx_20240224_234742_401500000.wav

will need to work out how to treat GQRX as input stream?

also was interesting that you can put in your coordinates to get “relative (az, el, range)” presumably https://en.wikipedia.org/wiki/Horizontal_coordinate_system:

az - Azimuth
el - Elevation
range - distance?

./sondedump -h

Usage: ./sondedump [options] file_in
   -a, --audio-device <id>      Use PortAudio device <id> as input (default:
                                choose interactively)
   -c, --csv <file>             Output data to <file> in CSV format
   -f, --fmt <format>           Format output lines as <format>
   -g, --gpx <file>             Output GPX track to <file>
   -k, --kml <file>             Output KML track to <file>
   -l, --live-kml <file>        Output live KML track to <file>
   -r, --location <lat,lon,alt> Set receiver location to <lat, lon, alt>
                                (default: none)
   -t, --type <type>            Enable decoder for the given sonde type.
                                Supported values:
                                    auto: Autodetect (default)
                                    c50: Meteolabor SRS-C50
                                    dfm: GRAW DFM06/09
                                    imet4: InterMet iMet-4
                                    ims100: Meisei iMS-100/RS-11G
                                    m10: MeteoModem M10/M20
                                    mrzn1: Meteo-Radiy MRZ-N1
                                    rs41: Vaisala RS41-SG(P,M)
   -T, --tui                    Enable TUI display

   -h, --help                   Print this help screen
   -v, --version                Print version info

Available format specifiers:
   %a      Altitude (m)
   %b      Burstkill/shutdown timer
   %c      Climb rate (m/s)
   %d      Dew point (degrees Celsius)
   %f      Frame counter
   %h      Heading (degrees)
   %l      Latitude (decimal degrees + N/S)
   %o      Longitude (decimal degrees + E/W)
   %p      Pressure (hPa)
   %r      Relative humidity (%)
   %s      Speed (m/s)
   %S      Sonde serial number
   %t      Temperature (degrees Celsius)
   %T      Timestamp (yyyy-mm-dd hh:mm::ss, local)
   %x      Decoded XDATA

TUI keybinds:
   Arrow keys: change active decoder
   Tab: toggle between absolute (lat, lon, alt) and relative (az, el, range)
   coordinates (requires -r, --location)

how about routing some audio to be the input using https://existential.audio/blackhole/

give email and download via link - I got 2 ch version
install
go to Audio MIDI Setup - as per https://existential.audio/blackhole/support/#system
- create a Multi-Output Device for sound and blackhole 2ch
under System Settings > Sound change the output to be the multi-output device
now playing with afplay will decode when running ./sondedump against the BlackHole 2ch device

./sondedump

==============================
Please select an audio device:
0) BlackHole 2ch
1) MacBook Pro Microphone

will listen to the Radiosonde tomorrow and then it’s a question of switching it to a RasPi - for portability and safety for the computer(a RasPi is cheaper to replace)

Update to run sondedump just run

git clone git@github.com:saramic/ham-radio.git
cd ham-radio/experiments/in_radiosonde_sondedump

make
make build
make demo

# to clean up
make clean