Thursday, August 06, 2020

Logging noise floor with hamlib

From time to time I see terrible interference right across HF and even up to VHF here. Sometimes it comes on for under ten minutes and while I make a note in the log when I see it, automatically logging the noise level seems like a good way to find out if there is a regular pattern.

At this point I haven't satisfactorily visualised the problem but I wanted to leave a note about progress so far.

Here's a graph of one minute samples of the S meter reading on 40m for the past few days. Times are local.

The values are read via a USB CAT interface to a Yaesu radio tuned to 40m. The values seem to be roughly S4 = 400.

I use the hamlib command line utility rigctl to do the real work.

To log these values I have a cron job that executes every minute and runs this script:

The resulting log file looks like this:

There's a tab between the date/time and the value.

To draw the graph, I use Gnuplot running this little script.

So far this isn't clearly showing when the interference is "on". Possibly the logarithmic Y scale doesn't help. I think it's interesting to see the noise floor measurements but they vary widely and I think the next step might be to take multiple measurements each minute and perhaps log the average or minimum.

Here's the graph of an additional day but with five quick readings taken and averaged each minute. Still not a clear result.


Monday, August 03, 2020

Graph of SNR now in WSPR Watch app

I've just updated the iOS and macOS app WSPR Watch to include a new graph of signal to noise ratios. So far I'm not seeing any useful information on this graph at my location. It's been suggested that to be valuable it would need to work with the callsign search feature so you can plot SNR over time between just two stations.

This version, 3.11.1, also fixes a surprising (to me) bug that affected users in the UK. As dates and times are in UTC and so is the UK for some reason my date parsing was failing for those users. I'm astonished that I hadn't heard about this before now.

My thanks to Paul, G0DIH, for the bug report and for working with me to test builds until the issue was sorted out.

Here's how the SNR, and other, graphs look now.


HF horizontal loop antenna in a small back yard

The back yard in our new house is very small and there is an intermittent interference source that has plagued me since setting up here. Phil, VK7JJ, is a great advocate for horizontal loop antennas which he uses to attain world-beating WSPR reception. Phil encouraged me to fill the available space with a horizontal loop.

The area between the back of the house and the front of the garage is about 5m x 3.6m and at the right you might be able to make out a loop made with thin black hookup wire. This antenna was fed from coax from the operating position via a common mode choke.

There's a small verandah with a wooden pole which is convenient for mounting baluns etc out of the rain. Here's the first attempt.


Later I did a better job and used an electrical junction box. 


The base nails to the wood and then the top is screwed on to that. Not waterproof but fine for my use. 


The loop works well on 20m but wouldn't do 40m. I'm not sure why at this point, but the loop's signal to noise seems indistinguishable from that of the 20m dipole along the fence line.

I've been improving the dipole by attaching one end to the tripod on the garage roof and I think the height advantage evens things up. One idea is that I might put more poles on the garage to hold up one end of a loop and as well as increased area I'll get some more height.

Saturday, July 18, 2020

Operating on 20m with good initial results

I was pretty depressed about the terrible interference on 40m here during the week. Happily on Saturday it stopped. My hope is that either it was some equipment, perhaps a welder, that is only in use from time to time, or perhaps it's something from a business that won't be running on the weekends.

The back yard isn't big enough for a 40m dipole so I measured out some speaker wire for 20m and have strung it between the window on the first floor at the back of the house, to a painter's pole on the fence (which holds the balun), and the corner of the garage.

Quickly I had received stations in New Zealand and Perth. My first transmission, with 10W is shown here on the right and I'm clearly getting out well. I've reduced power to 5W now.

This is great news and I think the dipole can be improved by suspending one leg from the tripod on the garage roof that holds the 2m/70cm vertical. You can see the dipole here, not great, but working.


If the interference comes back I will go for a walk again and try to find it. Even if it's back it will have less effect at 14Mhz than it did at 7Mhz so the move to a higher band will help there. Amazing that a small wire antenna in a tiny back yard get connect me with the world.


It's now Monday night and the terrible interference hasn't returned so far. I'm happy with 20m WSPR results except that I can't get to Sydney so far. Lots of contacts to North America.


3pm local time is best for 20m DX by the looks of it.


Thursday, July 16, 2020

On ABC RN's Download This Show talking "Stalkerware"

This weekend I'm a guest again on ABC RN's Download this Show which is largely created by fabulous Marc Fennell.

Due to the pandemic both Ariel and I are at our respective homes. Each of us records video locally at 4k and send in the video. It's amazing how this is now possible when it seems like only a few years ago that postage stamp sized video was the state of the art.

Download This Show goes to air a few times on ABC RN over the weekend or you can listen here or subscribe to the podcast.

One of the stories, this time about "stalker ware" is played on ABC News24 on Saturday morning and you can see it here:


Marc kindly let me plug GovHack which is coming up on August 14-16 and will be totally online this year.

Terrible interference on HF at new home

I've got a good antenna for VHF and UHF so it's time to get something going for HF. Unfortunately, a dipole in the back yard is picking up amazingly terrible interference. Let me know if you recognise the sound or look of this noise.

A walk around with a portable shortwave radio seems to indicate it gets stronger the further towards the back of the block I get.

It's not sunny today so I doubt it is any type of solar inverter. To me it sounds like something that is sparking, perhaps a motor?

Here's a short video where you can hear the sound it makes.


This is going to be a real challenge to overcome. 

This morning I noticed that the interference had changed to broadband noise but then it switched back to the pulse style. I went for a walk along the lane behind our house.


It seems to be maximum strength behind the neighbour's back shed. I'm wondering if it's a solar charge controller or similar.

The noise has stopped. The noise floor is still pretty bad but the terrible pulsing interference stopped some time on Saturday afternoon.


As we say in programming: bugs that go away by themselves come back by themselves. I will continue to monitor the situation and improve my antenna. 

Wednesday, July 15, 2020

Google Pixel Buds vs AirPods Pro for an iPhone user - review

Rather than reading the instructions and using an Android phone - which I’m sure is the optimum experience - I’m reviewing the new Google Pixel Buds earphones with an iPhone running iOS 13 and just normal assumptions about how Bluetooth headphones work. My daily headphones are Apple AirPods Pro which work pretty well as you’d expect.

The plastic case is a matt white finish that looks great. The lid is held with a magnet and flips open easily. Two LEDs light up white. The bottom of the case has a USB-C charging port. (I am a big fan of the future world where everything is USB-C). The case is a similar size and shape to the AirPods case and would be as comfortable in a pocket.

With the case open, but the buds still in there, the phone’s Bluetooth screen showed them and they quickly paired. (Contrary to the instructions, I didn’t need to hold the pairing button, maybe that’s needed for additional pairing).

Inside the box are alternative silicon tips, larger and smaller. I found the medium size tips fine in my ears. Also supplied is a high quality USB-A to USB-C charging cable and a little booklet.

The shape seems a little weird and they distinguish themselves from iPods by having an upward projection compared to Apple’s downward stork. They are very comfortable in my ears.

Compared to AirPods pro, the Pixel Buds seem to have a little more bass and a little less top end. They sound fine.

Latency, the delay in sound, is much longer than with AirPods. Typing on the keyboard on the phone shows this clearly. Latency is not a problem when listening to music and it’s certainly well under half a second so won’t be a problem on calls but my guess is that Apple is doing some of their technology stack magic to win the latency war.

Tapping either side sends a play/pause signal. Swiping adjusts volume - something which AirPods lack. I found the swipe gesture a little difficult to get right but this turned out to be because I had assumed that it was swipe up for louder and down for softer - turns out you swipe forwards to increase volume. Other touch controls are double-tap for next track, triple-tap for previous track. All of these controls work with iOS.

Removing an AirPod from your ear pauses playback, the Pixel Buds don’t do this - a feature I miss.

AirPods Pro have noise cancelling, which Pixel Buds do not but the ear seal seems ok except in busy streets. I do like the noise cancelling and transparency modes that AirPods Pro have but you do pay in both price and battery life for these features.

The microphones I tested by recording in the Voice Memo app. They sound clear and, I think, better than the mic system in AirPods Pro for a straight recording.

On a phone call I found the Pixel Buds blocked my ears so my own voice sounded muffled to me. The AirPods seem to feed a bit of voice back into the ears so speaking on the phone felt better. The person on the other end of the call preferred my audio with the AirPods compared to the Pixel Buds. It may well be that they work better on an Android phone.

In summary, The Google Pixel Buds are a quality in-ear headphone with good sound. The volume control gesture is welcome but the lack of noise cancelling and fold-back made them not quite as good in phone calls on an iPhone.

Pixel Buds are AU$279 from Google compared to AirPods Pro at AU$400 so I think they are an excellent headphone for the price.

My thanks to Google for supplying a review unit.

Monday, July 13, 2020

New antenna for 144/432Mhz now up on the garage

I'm very happy to report that my antenna drought is over. Today, Khan, The Antenna King mounted my 2m/70cm vertical on a pole on the roof of the garage.

Previously I had tried to get someone to put it on the roof of the house but it's a two level roof with very steep sides and, apart from being dangerous for the installer, it would have been impossible for me to get up there to do any maintenance.

Mounting the antenna on the flat roof of the garage means it's easy to work on. The drawback is a longer coax run. Tests so far show excellent signals from repeaters around Melbourne.

Currently I'm running WSPR and only hearing VK3DXE. I'm transmitting 10W and so far no one has spotted me.

The focus for now is 2m but I've also run two pieces of RG58U out to the back yard with the intention of adding a 20m dipole and whatever else I can come up with in very limited space.

I should add that I did not do the roof climbing but merely supervised. Here's a picture Phillipa took showing the limit of my management.


The 2m antenna is working well and tonight I had simplex contacts with Ralph, VK3ZZC and Chris, VK3AML.

Great book: "Radio Girl: The story of the extraordinary Mrs Mac"

I'm currently enjoying "Radio Girl: The story of the extraordinary Mrs Mac, pioneering engineer and wartime legend" by David Duffy. It's a terrific story of early radio in Australia and the remarkable career of Mrs Mac, the first, and at the time, only female electrical engineer in the country.

Mine is the Kindle edition but it's also available in Paperback.

Peter, VK3RV, (fellow FreeDV enthusiast) mentioned the book when we spoke recently. Thanks for the tip!

Saturday, July 11, 2020

macOS Big Sur is going to need larger screens

Apple has released an early version of the next macOS known as Big Sur. When I ran it on a Mac mini with my normal 4k screen my first thought was that I had the screen resolution wrong. Here's the current macOS "Catalina":


Here's the new "Big Sur":


As you can see, the dock is the same but the user interface elements in everything else is more spacious. I tried setting the screen resolution to the next sharp option and it was too small.

I like the new look. It is more consistent with iOS. I do like using small laptops though and I hope there's a way to scale back the size of elements a bit.

Both iOS 14 and macOS 11 betas seem much more stable than the versions released at this stage last year. Happily my apps work fine and even build for Apple Silicon without any obvious issues.

Update: my mistake, Catalina was scaled.



I didn't realise that I had my Catalina OS set for scaling to show more. When I tried scaled options under Big Sur they all look more blurry than what I see with Catalina. (You'll need to click on these to enlarge them).