HF is sometimes Fun

That signal is actually pretty cool…

I think it’s JORN an OTHR, but it only sort of matches up.

Sometimes there was a preamble before it started, and then it would jump around frequencies a little.

They weren’t evenly spaced, the lowest I was around 6.9753 Mhz to the highest 6.9576Mhz (USB).

Around 10s between bursts too.

Don’t really know what is going on, but this is what I saved:

Recording of a single burst (USB).

Posted on

HF is not Fun

I’ve done almost nothing with HF for a while. I’m still demoralized by all the interference.

Turns out the what I was receiving wasn’t related to power supply… Or anything else I can track down.

This is what I receive on 40m with a Discone (VHF/UHF) and a Airspy HF+ Discovery.

Can just see FT8 at 7040Khz. And there is a cool looking signal at 6950Khz too.

Finally got a laptop last week. If I can replicate the interference with a small antenna I might be able to get an idea where it’s coming from.

Posted on

More HF Radio

A little more work on my magnetic loop antenna.

I switched from using a Wifi stepper to a little high torque 12v DC motor + gearbox. I really liked the Wifi Stepper, it was painless to setup and use. It was exactly what (I thought) I wanted. Unfortunately I couldn’t get enough torque at low RPM with the little steppers I had. My variable capacitor has much to large a range, and needs very fine adjustments.

I don’t know how much torque the DC motor + gearbox actually has, but it feels like a lot. Another bonus was that the motor, gearbox, and a nice PWM controller was $30 AUD from Banggood.

For testing with my SDR I also switched to using a short coax cable and a long (powered) USB cable. I don’t think I’ve seen such a clean FT8 waterfall on my PC before. There is still some RF (right next to 7.074) but it’s night and day really.

Still, no idea if I can actually hear any better, but it certainly looks clearer.

My next plan is to switch to a shielded coupling loop. Right now, it’s just a few strands of copper wire twisted together in a rough loop. I found a nice piece of cable to use a while ago, but my soldering iron couldn’t heat the large solid conductor. I bought a Chinese T12 solder iron from Banggood that should have plenty of power.

For my other noisy project, I’m pretty sure it’s USB switch mode noise. Yay.

Posted on

Noisy Waterfall

New toy, cheap antenna, and an expensive power supply.

(1.5MB png. Noise doesn’t compress well)

Viewing the whole 0-30mhz shows some, ugh, noise.

Posted on

Necrodancer PB

I said this was meant to be a place where I could look back on. So, here’s my new Necrodancer Cadence PB of 10:40.84 from 2021-01-14.

Something like 1:20 faster than my last run.

I got an amazing Dead Ringer quick kill (without knowing what I was doing, it just somehow worked) and then Boots of Leaping made a very fast Necrodancer kill too. It was a very lucky run.

I wish the replays didn’t always desync.

Posted on

Random Photos

More random stuff. First is Aura Vale Lake Park and the second is Kilcunda Surf Beach.

Posted on

Mordialloc Pier

Just a couple of random pictures from Mordialloc pier.

I need to sort out some sort of work flow for posts like this…

Posted on

4G Antenna Fun

I’ve been running Optus 4G as my primary internet connections for over a year now and most of the time it’s been fine.

This week the 2300Mhz band appeared to go down on my local tower, causing my modems to connect to another tower further away (I think). The performance was horrible and unusable.

Letting the modem decide what band to use resulted in it using 700Mhz (which honestly I didn’t know Optus even supported until I started writing this down). While it worked, it wasn’t great. I was getting about 5Mbps and latency spikes, but good enough to get stuff done.

I had a brilliant idea to get a higher gain antenna and see if I could improve my connection to this new tower so I purchased two DMM-7-38 Panorama Antennas.

Check out the amazing results on my B525 modems:

So that doesn’t look good. No difference.

I thought I was being all clever looking at the raw data, and concluded that I’d wasted my time and money. But then just ran a simple speed test using Fast

Okay, that’s more promising, how about 2300Mhz? Nope, no go, couldn’t even get DNS to work this time when connected on the 2300Mhz band.

So what does that mean?

  • The Panorama antenna is good at 700Mhz but useless at 2300Mhz?
  • The Modem lies about some of it’s stats?
  • There’s more to high quality connection than those stats?
  • 4G fluctuates too much that testing itself is unreliable?
  • I need to make (or buy) some 2300Mhz Yagi Uda’s and investigate more?

I already don’t understand HF antennas, I don’t want to start not understanding UHF antennas too.

Posted on

Time is Hard Apparently

Got my nerves together and tested the YouLoop last night with the same settings as my magnetic loop.

Thankfully it was just okay (but still amazing for the price/performance/size).

But it turns out modern computer hardware is still awful at keeping time. I noticed that my PC had drifted almost 3s in the last day. That’s too much for FT8 to cope with and I could see WSJT-X missing strong signals.

Windows does have a NTP client to keep the time updated, but it clearly only expects a low amount of drift and by default only updates once a week.

You can check the difference between your local time and real time on Windows by running:

w32tm /stripchart /computer:time.windows.com /dataonly /samples:5

I’m running NetTime with a 30min resync to see how things improve tonight. Hope no one minds me hitting the NTP server 336 times more often that normal…

Clearly the real fix is to work out how to replace my PC’s awful crystal with a GPSDO…. Or just sync using a USB GPS dongle I guess.

Posted on

New Magnetic Loop Antenna

I finally put together my small transmitting loop antenna. It’s held together with zip ties, sits on a PVC stand in my kitchen and overall is a real mess, but it’s a start and appears to (mostly) work.

Adjusting the capacitor feels almost impossible. I either need a great big reduction gearbox, or to build my own with a more reasonable capacitance range.

I tried to build a fancy coupling loop out of some nice expensive cable, but I don’t have a soldering iron powerful enough… So it’s a few strands of copper wire braided together.

It resulted in an awful SWR of 1.9 on 40m. But there are lots of things to play with.

I cannot actually (legally) transmit so I just ran some Rx tests on FT8 over 24h using a Airspy HF+ Discovery.

Was planning on running the same 24hr test using my YouLoop but I’m a little worried about the results…

Posted on