Tuesday, November 24, 2020

WSPR Watch updates - now running on Apple Silicon

With the dawn of Apple Silicon, it's now possible to run the iOS version of WSPR Watch directly on a Mac. It works very well and looks pretty much the same as the macOS version I made with Catalyst. Here's the two side by side:

The native iOS version is the one on the left. For now, I'm leaving the Catalyst version in the App Store for people who haven't moved to Apple Silicon yet.

There have been a few bug fix releases recently. One issue was that the map stopped working on macOS Catalina, not because of something I did but because of a change in Xcode. If your map isn't showing, grab the latest version.

Monday, November 23, 2020

Some examples of recent spam or phishing SMS messages

 Seems legit?

That's over a few months. Clearly my name and phone number is on a list somewhere.

MacBook Air M1 - great but not totally plain sailing

As a developer, I wanted to make sure that my software runs well on the new Apple Silicon so I ordered a MacBook Air with the M1 chip as soon as they were announced.

Overall, I'm extremely happy with the battery life and performance of Apple's CPUs, but as an early adopter of both the new Big Sur operating system and the new hardware, I have run in to a few issues which I want to share.

Migration Assistant

Out of the box I tried to use migration assistant to copy over the configuration from my existing MacBook Pro. Because my existing Mac is on macOS 11.0.1 and the new machine came with the slightly older macOS 11.0, Migration Assistant said it couldn't migrate until the machine was updated. Consequently I had to complete a clean setup and do the upgrade.

Upgrade stalled

The software upgrade from 11.0 to 11.0.1 stalled about three quarters of the way through the progress bar. I left it for several hours with the mouse pointing at the progress but there was no movement. I had to long press the TouchID power button to force a reboot. On restart it seemed to finish ok but I'm a little concerned that some part of the install might not have been completed.

I fared better than some who ended up with an un-bootable machine. Apple has a support note on how to recover from this situation by making a bootable recovery disk on another machine.

External Samsung T5 SSD problems

A Samsung T5 SSD which works perfectly on other machines fails to mount or work reliably on the Air M1. I'm not alone in finding this. Heavier USB-C cables seem to help and upgrading the drive's firmware has improved, but not totally fixed the issue.

The Samsung software is terrible by the way. There is a theory that the M1 Macs are not providing enough power for some external drives but older, larger, drives are working for me so I'm not convinced that's the root cause.

Good things

The initial tasks to be done on a fresh macOS install sometimes bring a machine to its knees for a day or two. Spotlight indexing, iCloud syncing, photo analysis and (in my case), installing Xcode, are all heavy tasks. The M1 Air handled all this and stayed cool while sipping battery.

The keyboard is a big improvement over the one in my current MacBook Pro which has one of the much maligned low profile keyboards.

TouchID on a Mac is a new experience for me and is wonderful. I wish they'd do FaceID.

This MacBook Air is Apple's entry level machine and it out performs most of the current Intel based range. 24 hours in, the 8 CPU cores are mostly idle.

I can't wait to see what they do with the higher end machines.

Thursday, November 19, 2020

After getting to 20 days of zero COVID cases, a van trip

We moved to Victoria (Australia) just as COVID was ramping up and this state has had quite a strict and lengthy lockdown which has worked. After being limited to travel within just 5km of home, that was lifted to 25km and now the state is open. I took up a kind offer from old friend Richard who has recently purchased a property in Drummond. Naturally, being a considerate guest, I slept in the van.

The van has been parked under cover for some time and a few days ago I discovered that, despite taking it for a weekly drive, the deep cycle "house" battery was very flat. It was showing 3V and at that low voltage the relay which connects it to the alternator had, correctly, declined to do that. I should have noticed.

Something must have been draining the battery slowly even though everything was off. Happily after a slow charge it doesn't seem to be too damaged.

It was sunny both days and the battery quickly charged and was able to run the fridge over night without any trouble.

I have read that connecting the house battery suddenly to the car's alternator isn't as gentle on it as being charged from solar through a charge controller so for now I'm parking it in a sunny spot and have disconnected the alternator relay.

Speaking of solar.. Richard's place is completely off grid and has an impressive solar system built over many years back to a time when panels were so expensive that it made sense to have them steered to follow the sun.

The house is wired for 48V, although it's hard to find lights for this voltage. There is an inverter to provide 240V AC as well. The fridge is gas though.

We hung out a dipole for 40m and had a tune around. Very low noise location, just the ticking of my charge controller. We heard VK7, VK4 and a bit of VK2. 

Friday, November 06, 2020

Antenna noise canceller working well against bad switching supply noise on 40m.

HF noise is an increasing problem that plagues hams in the suburbs. Switching power supplies, solar inverters and plasma TVs are all culprits.

Here I'm plagued by occasional bad interference on 40m (but really all over HF) that I think comes from a switch mode power supply used by a neighbour. I've just built the antenna noise canceller by Terry, VK5TM and it seems to work very well.

Noise cancellers work by taking a sample of the noise, inverting the phase, matching the level with the signal and mixing them - thus cancelling the noise but leaving the signal. Here's another example where I switch it in and out:

Here's the part of the circuit that controls the phase of the noise signal that is then amplified and mixed with the main antenna signal:

I bought the board and kit of parts (AU$55) and it is a very professional package. The parts are well presented and I found none missing.

The board is excellent quality.

The kit went together smoothly following Terry's instructions. The only fault was mine, when powered up the relays didn't click even though the transmit LED came on - I had missed a solder joint on one of the coils.

I purchased a metal box from Jaycar, part HB5442, 120x61x102mm and the project fits well with plenty of room for wiring.

To effectively cancel noise you need a sense antenna that picks up the noise but not the signal. In my case I'm using a 20m dipole on the fence line as the sense antenna and an end fed for 40m for the signal. I think that having a sense antenna that doesn't pick up the band I'm wanting to receive might be a reason why it's working so well for me.

In my case the noise level on the sense antenna is very high and I have to set the gain control almost at the bottom of the range. I might try installing a smaller sense antenna on the fence specifically to pick up the neighbour's interference. The two phase controls are quite sharp and together can be used to null the noise very well. Signal strength is reduced but can be boosted with a pre-amp, the main thing is that the signal to noise ratio is greatly improved.

I was tempted to buy the MFJ-1026 for US$239.95 + shipping, but Terry's kit works well and if you can do a little soldering I recommend it.

Note that antenna noise cancellers do not work in all conditions. The best scenario is where there is a single source of noise that can be picked up close to the source. I understand that broadband noise may not be able to be cancelled but in my case the broadband noise I see between the switching supply bands are cancelled nicely.

Update: I'm having doubts

I've been playing with noise antennas and I'm starting to doubt that this is working properly. I think I get some noise cancellation but it's only when the main antenna gain is fully reduced. Bear with me while I experiment further.

Update 2: All good

It's all about the noise sense antenna. Originally I used a 20m dipole but the noise level was extremely high. Next I tried a short vertical connected via a balun - that's when things got weird. Finally I've simply clipped a meter or so of wire to the centre of the coax and the controls on the noise canceller work as expected.

Noise is reduced by playing with gain and the two phase controls.

Tuesday, November 03, 2020

Soldering mat using silicon baking mat

In the new shack I've been soldering on a cutting mat but it turns out this is not a good surface as it quickly melts if a hot component is rested on it. I've now purchased a low cost silicon baking mat and this works well. It's a strangely sticky material and is quite thin but it does not complain about melted solder being placed directly on the surface.

This one was purchased from Amazon Australia and cost AU$8.95 (but I notice that the price seems to vary). There are purpose made soldering mats around but they cost at least double this.

Having used it a bit now, it works well but the slightly sticky surface makes it a bit hard to pick up small components and snipped wires.