W8EMV - Whiskey Eight Echo Mike Victor

Ball Smacker Radio eSQL "talk" from 2025-03-21

(embed a Flickr post because uploads to Typepad are failing)

First explorations of Meshtastic and some plans for bicycle portable operations

The ARROW presentation by Blake KE8SQU on Meshtastic prompted me to start exploring this LoRa-based radio protocol which operates in the 915 MHz ISM (unlicensed) band.

https://meshtastic.org

I ordered a Meshtastic radio from Rokland, their "WisMesh Pocket v2". This radio is designed as a ready-to-go portable device with a little screen, case that holds a battery, a little antenna, and generally speaking enough working parts that I should be able to turn it on and go try it out. I'll write more about it and link to it appropriately based on how well I am able to make it work.

When it arrives my initial plan is to work this into my Ann Arbor "Bike Every Park" parks challenge - throw the node in a backpack, stop at a city park, see if there's coverage there, try to make a QSO, make a suitable note, move on.

First park to try is Burns Park near my house which I know is near the node that W9TNC runs - it should be easy. From there I will start mapping out the radio terrain. My expectations are that the tops of parking structures will be good locations for 915 MHz operations, as they seem to be also for VHF/UHF. But what I don't know quite yet is what the density of stations is - the "Meshmap" suggests "not very dense" so far.

https://meshmap.net

The other thing I want to do is get a node running at home running FrozenBBS, a message board for Meshtastic.

https://github.com/kstrauser/frozenbbs

This is going to take a little more work on the hardware side; as the author writes

I have a RAK4631 radio with a RAK13800 Ethernet module, with the BBS code running on a Raspberry Pi 4 next to it. I went through a lot of false starts making this work.

The rationale for making my first node a portable one (rather than a fixed station at home) is that with the bicycle operations I can do a nice survey of the vicinity and see what is out there that could work and get a better intuitive sense for what 915 MHz propagation is like with altitude and trees figuring in. At worst, if reception is bad but I know who has a node running I can just ride close enough to be within line of sight!

Ethernet interference on 125 MHz and on 2 meters?

I'm seeing a bunch of birdies on my 2 meter radio receivers. On the Airspy HF+ SDR it looks like a bunch of bright lines. On the roll-up J-pole antenna the overall noise floor is high (S7 or even S9) which makes working simplex stations very hard, as I discovered at the last simulated repeater failure test for our weekly ARPSC net.

I was able to make a contact with Steve N8AR via the South Lyon N8SL repeater from Ann Arbor. He could hear me just fine with my Kenwood sending, but I didn't hear him on that rig. So I tuned up the Airspy receiver to hear him.

I think I figured out some of it - I have a lot of ethernet ports on a switch in the attic, and I'm seeing a very strong signal on 125 MHz which am pretty sure is gigabit ethernet modulation leaking out of the unshielded (cheap) ethernet cables.

There is also noise at home on the AM band very distinctly in front of our house under the overhead lines. Ah, city life. I will bring my radios to the park in the summertime and not have these problems.

Looks like Andy G7UHN has some suggestions with ferrite cores

http://alloutput.com/amateur-radio/ethernet-rfi-noise-reduction/

based on this presentation from Joel W5ZN

https://w5zn.org/wp-content/uploads/2024/12/Noise-The-Grim-Reaper-of-Weak-Signal-Reception.pdf

Wes N8QM had a tip for inexpensive EMF sniffers, which can be used to measure field strength. I see some of them are specially designed for ghost hunting too (!)