General radio ⁽¹²⁾

Here is a quick and dirty comparison between the Behringer UMC204HD + PA0RDT mini whip and the Airspy HF+ Discovery and YouLoop looking at a similar amount of spectrum from 0 up to 96kHz or so. First the UMC204HD: And the Airspy: This was not done in any scientific fashion, it's just to show that the soundcard method works ok but is not as good as the Airspy. No surprises there and this is no criticism of either method. I can see the utility of the soundcard method when coupled with the vlfrx-tools package as all manner of analyses become possible. I have only just started reading about that.

Another new toy arrived today. A Behringer UMC204HD "2x4, 24-Bit/192 kHz USB audio/MIDI interface". I had been reading about the use of soudcards for VLF reception and the raves about the UMC202HD - the 204 model has the addition of a MIDI interface as well which may be useful and one came up at the right price (ok, I missed several of the 202 models on eBay so grabbed this 204 one buy-it-now!) I did experiment previously with the built-in soundcard on the Linux PC but got very poor results, quite possibly due to a lack of perseverence (fiddling) on my part. Anyway, I took the advice of the many raves. And it works!I installed the excellent vlfrx-tools package plus an additional package vtlivesgram. Running vtcard and vtcat piped into vtlivesgram results in a very useful display: The trace above shows peaks where I see them using the Airspy HF+ Discovery / YouLoop combination which provided my first ever reception of SAQ. The results are limited when compared to the Airspy but that is to be expected. Here, the Behringer input is simply the output from a PA0RDT mini whip in the loft, plugged directly in via a 1/4" jack.

After having ditched Meshtastic, for now at least, I had a fiddle with two of the LoRa modules with a view to repurposing them. And there they are. The first is a LoRa APRS r/o iGate, listening on 439.9125MHz, and the second is a receiver for radiosondes listening around 400MHz. Nestled under a 70cm ground plane in the shack is, of course a good way to ensure nothing is ever received unless it is very close! However, it is destined for greater things... although at the end of the day it's just me fiddling. The LoRa APRS map is at https://lora.ham-radio-op.net/ The radiosonde one stands a better chance of actually receiving something, especially as it is currently connected to the 70cm big wheel antenna in the loft. See https://sondehub.org/ The plan is to connect these two along with the module running TinyGS to a common antenna currently in the loft. They will be connected using a Crosscountry Wireless multicoupler which is due to arrive in a day or so.

For me, and this is in no way intended to persuade people not to dabble, Meshtastic was the usual 'new shiny' that I like to fiddle with, but it was just that. A bit of radio fun for little outlay using devices I can redeploy. In our wider area it seems to have snowballed and become rather congested. While I can see the point, I have many other radio bits and bobs to play with and having yet two more antennas in the loft was rather overdoing things. I had to seriously think exactly what I had used it for and it came down to occasionally saying 'good morning', answering when people ask if anyone is receiving them, and... well, I am struggling to find anything else. Of course I stress that is what I had used it for, not taking away from what others are doing. It is a neat idea. So both nodes have been switched off.

Both my 868MHz and 433MHz nodes are being odd today. I had been looking into the data that arrives when '--noproto' is sent to the node and, typically there is a fairly constant stream of data. But today, despite both being power cycled there is no data at all. Odd, because when I ask the 868Mhz node for its nodelist it is being updated. Maybe it's something in the new firmware but for now I've been fiddling enough and it's time to take a step back. I have not had any successful traceroutes today, I responded to a couple of requests and got no reply. It's made worse by the fact that, having moved the nodes in the loft they are now out of BLE range. Both are connected to a Raspberry Pi via USB so I can access the nodes that way but for client use I use my mobile node assuming that the node in the loft will relay everything - maybe not. And for 433MHz I only have the one node anyway. Mind you, it is raining and I suspect that is making a fairly decent shield for 868MHz, and I have yet to see any activity…