Listening to the Camb-Hams from the Isle of Islay

The Camb-Hams are on their usual annual pilgrimage to Scotland and I’ve worked them on a few bands and modes.  I’ve also made a couple of recordings of them on 40m CW, showing how well the Kenwood TS-590SG can read Morse Code and on 40m and 80m SSB.

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Learning to code in Python – Hello Raspberry Pi!

After my posts about building an APRS RX iGate, I entered into email discussion with Alan, K2RHK who pointed me towards his website specifically to see his experiments in APRS.  While looking through his site, I noticed he’d recommended a book for those looking to learn how to program a Raspberry Pi.  I mentioned that this was something I’d just started doing and Alan contacted a friend of his, Marjan Bace at Manning Publications who very kindly posted me a copy of the book we were talking about called ‘Hello Raspberry Pi!‘.

I’ve only just started learning to program in Python but this looks like a fun and interesting book to get me going.  I’ve already sussed out some Python simply by examining existing code and tweaking it to do what I want but it’s good to get a proper guide to start me off with the basics.

Thanks Alan and Marjan!

Hello Raspberry Pi! by Ryan Heitz from Manning Publications

Hello Raspberry Pi! by Ryan Heitz from Manning Publications

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What can be achieved in twelve hours of 20m JT65/JT9?

WSPR is great, I enjoy running WSPR and seeing how far I can transmit using very low power but there are a couple of drawbacks.  I appreciate this will sound as though I’m knocking WSPR but trust me, I’m really not.

Firstly, it’s not a QSO mode.  I accept that many years ago, some QSOs were made using WSPR but that was in the very early stages of development and I don’t believe that the software is there to actually facilitate that any more.  I find it frustrating to hear people say “Oh, I had contacts all over the world yesterday on WSPR”. No, you didn’t.  You transmitted and someone received you, that doesn’t necessarily make a QSO.

Secondly, although WSPR is incredibly good at penetrating around the world, just because someone in (say) VK land heard your 200mW WSPR signal with a strength of -28dB, that doesn’t mean the band is properly open and that you can complete a QSO using SSB or CW.  You almost certainly can’t.

This is where the low signal data modes come in, specifically JT65 and the newer JT9.  I’ve written about JT65 a lot, I couldn’t have completed my original QSO365 without using JT65 and I discussed JT9 here.

Rather than run WSPR for a day, I thought I’d spend twelve hours yesterday just receiving JT65 and JT9 signals on 20m.  In theory, I should be able to work any station I can hear using these modes.  I fired up the latest version of WSJT-X which includes JT4, JT9, JT65, QRA64, ISCAT, MSK144, and WSPR at just after 09:00z, configured it for JT65 and JT9 reception, switched it to 20m and let it sit there receiving and uploading everything to pskreporter to produce the map below.

The results after twelve hours were quite astonishing.  I know these modes are popular but I don’t think I realised quite how popular they’ve become.  You can click the following two images for much larger versions.

Map of stations heard on 20m JT65 and JT9 over a twelve hour period

Map of stations heard on 20m JT65 and JT9 over a twelve hour period

Over a period of twelve hours I received 2,124 individual transmissions from 554 unique transmitters spread over 74 countries.  That’s quite incredible.

List of countries heard on 20m JT65 and JT9 over a twelve hour period

List of countries heard on 20m JT65 and JT9 over a twelve hour period

To test my theory that all of these should be workable, I made four QSOs in the evening.  I worked Venezuela, Japan, Puerto Rico and Brazil, all with JT65 and all using just five watts.  I still like to run bucketloads of power when it’s appropriate but for these low signal modes, you really don’t need to run a lot of power to make contacts.

The low power/low power data modes aren’t for everyone but they’re not difficult to use and are a great way of getting the most out of a small to medium sized station.  They drag every dB of performance out of inefficient aerial systems and it’s no surprise that my first ever QSO with VK back in 2011 was using JT65 and a short ‘long’ wire aerial.

If you’ve never tried these modes, I encourage you to give them a try.  You’ll be happily surprised at what you can work.

Posted in Amateur radio, Data, HF, JT65, JT9, QSO365, WSPR | Tagged , , , | Leave a comment

More new test gear for the shack

Back in 2012 I wrote about some new test gear that I’d bought for the shack.  Well time doesn’t stand still and it’s always nice to have new toys in the shack, especially if they’re useful.

My miniVNA Pro always did me well but recently I’ve started doing things on higher frequencies, such as building aerials for ADS-B reception and it’s frustrated me that I’ve not been able to fully test them.  With that in mind, earlier this year I bought myself an AAI RF Vector Impedance Analyser N1201SA from Banggood.

AAI RF Vector Impedance Analyser N1201SA

AAI RF Vector Impedance Analyser N1201SA

This is a cracking little piece of kit which covers from 137 MHz up to 2.7 GHz in 1 kHz steps.  It can measure SWR, resistance, reactance and S11. It’s not stupidly expensive either at around £130.  Being battery operated and fairly simple to use, it’s a very good piece of equipment.

The only downside to it is that there’s no way to save the measurements it displays apart from taking a photograph of the screen.  There’s no denying that it looks good though, here’s a plot of my Diamond X510 from earlier today.  It’s also not a full blown VNA so it can’t be used for such things as measuring the performance of filters.

AAI N1201SA scan of my Diamond X510N on 2m

AAI N1201SA scan of my Diamond X510N on 2m

Despite these downsides, if there was an HF version of this analyser, I’d be all over it.

The next logical step for me was an upgrade to my old miniVNA Pro.  It’s a fantastic piece of kit that’s served me very well over the years but I wanted something to cover higher frequencies.  I looked into a number of items and decided that the best thing for me was to change to the newer miniVNA Tiny.  Despite the name sounding as though it’s a downgrade (Pro to Tiny), it’s actually a decent upgrade as it covers from 1 MHz up to 3 GHz which is far higher than I can ever think I’ll need.  It looks quite similar to my old VNA, it’s just a little smaller and has a different connector.

miniVNA Tiny from mini RADIO SOLUTIONS

miniVNA Tiny from mini Radio Solutions

One of the first things I did with this was to test my new Diamond X510N vertical which I put up a couple of weeks ago and here are the results on 2m and 70cms.  It’s encouraging to see that the 2m measurement matches up with the N1201SA image above.

Both these images are clickable for much larger versions.

Diamond X510N 2m SWR measured with miniVNA Tiny

Diamond X510N 2m SWR measured with miniVNA Tiny

Diamond X510N 70cms SWR measured with miniVNA Tiny

Diamond X510N 70cms SWR measured with miniVNA Tiny

Finally I’ve been able to get my hands on something I’ve wanted for quite a long time and it serves multiple purposes.  I’ve wanted an accurate power meter for measuring the output of my WSPR/QRSS transmitters. It’s all very well having a super-duper QRO meter but when trying to measure down to a couple of hundred milliwatts, that’s not exactly suitable.

I bought myself a Yaege FC1-Plus Portable Frequency Counter which covers a massive 10 Hz to 2.6 GHz from 409shop.  Not only is this a frequency counter (which is useful by itself) but it’s also a power meter which is good up to two or three watts.  I wouldn’t want to put any more power into it.

Yaege FC1-Plus Portable Frequency Counter

Yaege FC1-Plus Portable Frequency Counter

If you’re looking to buy one of these, be aware that there are two models.  The FC1 and the FC1-Plus.  If you want the power meter version then you must buy the FC1-Plus.  It’s a little more expensive at around £50 but if you want it as a power meter then it’s worth it.

Here’s the display in frequency counter mode, monitoring my WSPR transmitter.

Yaege FC1-Plus in frequency counter mode

Yaege FC1-Plus in frequency counter mode

This ties up within a few Hz of the frequency I’ve got my GPS based transmitter so I’m happy with the accuracy.

What I was really interested though was power.  I fired up my WSPR transmitter into the meter in power mode.

Yaege FC1-Plus in power mode

Yaege FC1-Plus in power mode

This reads fractionally higher than I was expecting although I am running a higher voltage to the output stage of the U3S transmitter.  I have no reason to disbelieve the accuracy as I’ve been assured from a couple of sources that these meters are pretty much spot on.  Even if it’s only within 10%, I’m still happy but it does mean that I’m probably running a little more power on the lower bands than I thought.

I think that good test equipment in the shack really is essential now – Long gone are the days when we only used an SWR meter to check and align aerials and although a lot of amateurs only use commercial products, it’s still useful to be able to test performance to make sure everything is working properly.  I play around with low power experimental transmitters so this sort of kit is essential really.

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A new record – G to ZL on 60m QRSS

Toward the end of March I ran WSPR and QRSS on the 60m band for a couple of weeks.  I did some experiments on 60m nearly three years ago which gave good results and I was keen to improve that.

I posted on the new Knights QRSS list to announce that I would be active on 60m in the hope that some of the grabbers around the world would switch to 5MHz to listen for my signal and I was very pleased that a number of people happily switched over for a while.  It’s an unusual band because there aren’t that many countries that have a 60m allocation and they don’t always match up around the world.  Of course, anyone is free to receive on the band so that helps.

I was very pleased to receive the following reports.

G6NHU to ON4CDJ on 60m - 208km

G6NHU to ON4CDJ on 60m – 208 km

G6NHU to G3VYZ on 60m - 400km

G6NHU to G3VYZ on 60m – 400 km

G6NHU to VE1VDM on 60m - 4,637km

G6NHU to VE1VDM on 60m – 4,637 km

G6NHU to W4HBK on 60m - 7,293km

G6NHU to W4HBK on 60m – 7,293 km

All very good but no improvement over the tests we did before.  There’s one more though.

G6NHU to ZL2IK on 60m - 18,130km

G6NHU to ZL2IK on 60m – 18,130 km

This is a stacked image and is still quite weak so let’s zoom in a bit.

G6NHU as seen on ZK2IK's 60m QRSS grabber

G6NHU as seen on ZK2IK’s 60m QRSS grabber

Here’s a capture from Pete’s eight hour grabber showing my received signal repeating itself around twelve times between 06:00z and 08:00z on 23rd March 2017.

Eight hour ZL2IK grabber showing G6NHU on 60m QRSS

Eight hour ZL2IK grabber showing G6NHU on 60m QRSS

As far as I’m aware, this is the first time that QRSS signals have been successfully transmitted from G to ZL. I’m using my Hans Summers U3S transmitter with around 250mW output into a random length doublet, just 30ft AGL at the east end, sloping down to 20ft AGL at the west end.  Pete, ZL2IK is using an Icom IC-R75 communications receiver locked to a GPSDO frequency standard (no drift) and a combined 80/40m dipole fed through an ATU to match it to 60m.

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Returning to data modes after an enforced break

My shack computer is an Apple iMac.  For a few years, I’ve operated a lot of data modes and been very successful in data contests.  I’ve always enjoyed data modes and in 2012 I operated GO6NHU to celebrate the London 2012 Olympics exclusively using data.

Back in 2015, Apple released a new operating system called El Capitan and as soon as I upgraded to it, I noticed some problems with fldigi (my favourite data software).  I would switch to transmit, and roughly 60% of the time, the transmitted audio would come out of my iMac internal speakers instead of being sent to the radio.  It was the same with WSPR and any other software I tried which sent audio to the wireless via the USB cable.

My Kenwood TS-590 is connected to the iMac by a single USB cable.  The radio has a built in sound card and fldigi simple recognises that for everything it needs.  Data (CAT control) and audio pass down the same cable and PTT control is via data VOX.

This had worked perfectly for a number of years but broke when I upgraded to El Capitan.  I tried many things to attempt to resolve the problem, software reinstallation, replacement cable, reset the radio and other fixes but nothing worked.  One of the later patches to El Capitan did include a fix for external USB audio devices but that didn’t help either.  I found this article which went some way to explaining what the problem was although there was no recognised fix apart from reverting back to OS X Yosemite.

I simply stopped operating data modes and when Mac OS Sierra was released, I tried again but had no further success.  It was just the same.

Recently I did some more testing, I set up clean installations of both OS X El Capitan and Mac OS Sierra on an external drive to see if I had the same problem – I did.  I then built a clean version of OS X Yosemite on an external drive and it worked perfectly.  My hardware is OK, it’s just the changes to how Apple handle external USB sound cards that is the problem.  Searching the internet found a lot of people with exactly the same problem although frustratingly, it’s not universal.  I know of people with the same model iMac who don’t have any issues.

It was time to finally find a fix.  I decided to bin the USB cable and go the old fashioned way, using an RS-232 interface lead and an audio interface.

The first thing to find was a USB to RS-232 adapter.  I went with a UGreen USB Serial Interface cable based on the PL2303 chipset because it claims to be fully compatible with Mac OS.  I also needed a null modem cable to connect to the back of my Kenwood TS-590 which was simple enough to get hold of.

That completed the CAT side of things and it worked perfectly well.  I had full control over the radio from the computer and the next thing to deal with was the audio.

It’s well documented that to avoid earth loops, hums, audio feedback etc, one should use an audio isolation transformer.  I would need two of these, one each for transmitted and received audio.  There are many of these available for a few pennies on eBay or Amazon but most of them are shipped from overseas with a lead time of weeks.  This wasn’t good enough for me so I drove to the Rapid Online trade counter and bought two Vigortronix VTX-131-001 line matching transformers.  These were mounted on a piece of veroboard and fitted into a small box along with screened cable for the audio in and out.

Home brew interface for data modes using two audio isolation transformers

Home brew interface for data modes using two audio isolation transformers

I considered using a metal box but decided that as all the audio cables were screened and as I’d put decent ferrites at each end, a metal case wasn’t absolutely necessary.  If I get any problems, I can always change the box afterwards.

With this all built and working, I connected one side of the interface to the accessory socket of my radio and the other side to the audio input and output of iMac to test.  It worked perfectly and I was back on the data modes.  However, this wasn’t ideal as it meant that I’d effectively lost all normal sound on the computer and I had to be careful to avoid inadvertently transmitting computer audio!

I did some research to try and find a USB audio device that would work properly with the latest version of the Mac OS and found reports that a fairly cheap card, the Creative Labs Play! 2 was compatible.  I bought one from Amazon because their returns policy is superb and I knew that if this didn’t work, I’d be able to return it. It arrived the next day and as once I’d loaded the drivers, it worked like a dream.

Finally after around two years, I’m fully back and able to work data modes using my iMac.

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Building a Raspberry Pi internet watchdog

I wasn’t sure whether to post this or not as it’s not specifically amateur radio – But there’s a small amount of electronics involved so I figured it might be of interest.

A few days ago while Susan and I were out, I received a text from my son saying “I thought you’d like to know that the wifi isn’t working”.  What this actually meant was that our home internet connection had gone down. I recently changed my ISP and had been warned that for the first couple of weeks, there might be an occasional interruption to the service.  I know the router should automatically connect but sometimes that doesn’t happen.

I spoke to David and quickly determined that this is what had happened but that the router hadn’t automatically reconnected.  All he had to do was switch it off and back on again and it sprung back into life. This got me thinking that perhaps this could be a good use for a Raspberry Pi as a watchdog.

It didn’t take much investigation to find some basic Python code to check for the presence of an internet connection so I grabbed that and then looked into the hardware. I’ve not played with the GPIO before but it all looked pretty straightforward.  I didn’t have a suitable relay so decided to test this with just an LED playing the part of the relay so I could see if it worked.

First version of the Raspberry Pi internet watchdog

First version of the Raspberry Pi internet watchdog

The idea is that if the Raspberry Pi Zero W detects the internet has failed, it will trigger a relay and drop power to the router for a few seconds.  This first version worked perfectly and I tested it by pulling the internet connection from the back of the router.  After a couple of minutes, the LED flashed.  I was very happy with the way this worked and so I ordered a relay.

I wanted things to be a little more sophisticated though and started delving into the code.  I’ve only just started learning Python so this was a nice educational exercise for me.  It wasn’t long before I got things as I wanted.  At regular intervals the Raspberry Pi checks to make sure there’s a good internet connection and if not, it drops power to the router for ten seconds, brings it back up again and then pauses to allow the router to reboot and reconnect before checking again.

The relay I’d ordered turned up and I was able to set it up and prove everything working – Once again, it’s on breadboard and you can see the green ‘OK’ LED along with the red ‘fault’ LED, although that’s disconnected and the relay is in circuit showing that power is passing through.

Raspberry Pi internet watchdog being tested

Raspberry Pi internet watchdog being tested

I made sure to use the normally closed contact on the relay so by default it isn’t energised, it will only activate if there’s a failure so this means I can reboot the Raspberry Pi without killing my internet connection.  However there was a problem – Each time I restarted the Pi, it would click the relay and it took me a while to work out what was happening.  It turned out that my Python script was starting before the WiFi had initialised and connected to my network.  The script was seeing that as an internet error, going into a fail state and triggering the relay.  I resolved that by adding a delay to the cron command which started the script.

I decided to use an official Pi Zero case which has a hole in the top for the camera and to repurpose the hole for the green LED.  Sadly the hole was far too large for a 5mm LED so I picked up some 8mm LEDs.  Of course, the 8mm LED was too large for the hole!

Raspberry Pi Zero W case and 8mm LED

Raspberry Pi Zero W case and 8mm LED

It didn’t take much to enlarge the hole slightly so the LED would fit and before long it was glued in place.

8mm green LED in the Raspberry Pi Zero W case

8mm green LED in the Raspberry Pi Zero W case

While the glue was drying, I built the rest of the watchdog.  I actually used a different Raspberry Pi Zero W to the original one I had been testing with as I didn’t need the entire GPIO header, just needed to solder a few wires straight onto the board.  Here you can see the Pi mounted in the case with the wires for the relay feeding in through the bottom and soldered onto the board.

Raspberry Pi Zero W in the case along with the relay

Raspberry Pi Zero W in the case along with the relay

When the glue had gone off, I wired the LED to the GPIO pins and fitted it all together for final testing.

Finished Raspberry Pi Zero W internet watchdog

Finished Raspberry Pi Zero W internet watchdog

After this it was a simple job to integrate it into my setup.  My router has a standard DC power connector on the back so rather than destroy the manufacturer supplied power brick, I grabbed one of my many power cables, cut the positive wire, fed it through the relay, connected it all up and switched it on.

Raspberry Pi watchdog timer all set up and working

Raspberry Pi watchdog timer all set up and working

You can see I managed to catch it as it flashed the ‘OK’ signal.
The first time I started everything up with the router connected was a good test as it proved everything.  The Pi started before the internet had initialised so it saw a fault condition and rebooted the router, then paused itself for four minutes to allow the router to restart and the internet to connect.  Everything worked perfectly.

I consider this the perfect use for a Raspberry Pi – Think of something for it to do, find a way to do it, tweak as required and then get it working.

This entire project took just three days to complete.  It was conceived on Wednesday afternoon and by Saturday afternoon it was fully implemented and working!

Posted in Construction, Not amateur radio, Raspberry Pi | Tagged , | Leave a comment