A new year, a new callsign

In 2013 I applied for M7P as a Special Contest Callsign, and have used it successfully in a large number of contests throughout the years. One of the reasons I chose that particular callsign was for the rarity value when working the WPX contests, my logic being that people are always chasing new multipliers and the M7 prefix was quite rare with only a potential 26 callsigns.

In October 2018, Ofcom started issuing M7xxx callsigns to new applicants for the Foundation licence and so my contest callsign suddenly lost the rarity value.

I decided that when it was due for renewal that I’d change. I’d never been entirely happy with M7P when using it on SSB as I’ve found that getting the final letter across can sometimes be difficult in crowded and noisy bands. Of course that’s not a problem on data or CW but that, combined with the reason above made me start looking around at alternatives.

I decided very quickly that I didn’t want an M prefix again, simply because what happened in October could quite easily happen again. I could have picked an unused M prefix but as and when M0s run out, I could have been caught out again.

I looked at G prefixes and immediate discounted 0, 1, 2, 3, 4, 5, 6, 7 and 8 simply for the fact that they’re still relatively common. That left me with the G9 prefix and once I started researching, I discovered that G9 callsigns have only been issued commercially for experimental purposes and never used on the amateur bands. This doesn’t include the G9+1 callsigns that are now issued as Special Contest Callsigns.

The RSGB post a list of which Special Contest callsigns have been issued and at the time I checked, there were just nine G9+1 callsigns. I looked through the list and decided to apply for G9D.

My application form was duly completed and emailed on the 1st January 2020. At 09:00 on the 2nd January I received confirmation that G9D has been issued to me.

I’ve got this callsign for at least five years and I’ve already registered it with LoTW so all QSOs made using it will be uploaded there. It’ll be a few years before solar cycle 25 kicks in properly but I’m looking forward to giving it a good airing.

If you hear G9D during a contest on SSB or CW or see it scrolling up your screen during a data contest, please give me a call!

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A personal, non radio related update.

It’s not often that I write an update here that’s completely unrelated to radio but it’s time for that now.

On the last day of November, I visited a friend of mine who lives about a mile away for a meal and a couple of drinks. Although it was a cold night, it was dry and I decided to wrap up warm and walk home. I’m no stranger to walking – I’ve been carrying a Fitbit tracker since 2011 and in that time I’ve walked nearly 15,000 miles so a fifteen minute walk was no problem. I had a torch with me to light my way.

On the way home, I tripped on a pothole and fell over, landing heavily on my upper right arm and shoulder.

As I laid on the floor, my smartwatch fall detection kicked in and it offered to call the emergency services for me. I remember struggling to reach to it with and hit the “I’m OK button”, even though I clearly wasn’t OK.

With hindsight, I should have let my watch contact the emergency services but being a typical bloke, I initially thought I’d just be able to get up, dust myself off and walk home.

I tried to get up but couldn’t. The pain wasn’t that bad but I just couldn’t move my right arm. I laid there, hoping that a passerby would stop and help me. Luckily, even though it was after 23:30, it didn’t take long for a car to stop and I was aware of people talking to me, checking to see how I was. One of them was an off-duty police officer and he and his partner were very caring, they produced a tea-towel from their car to mop up the blood coming from my mouth. After my arm hit the floor, my head must have bounced off the ground as well as I had a grazed nose, a cut on my chin and I’d badly bitten my tongue.

While they looked after me, a police car which happened to be passing also stopped and they took over. They were very professional, first asking if I’d had a drink and then checking to find out what had happened as they were concerned there may have been a fight. They gave me a once over and after determining that I lived almost literally around the corner, they offered to give me a lift home which I very happily accepted.

My wife got quite a shock, to have someone knock on the door at 23:45, only to discover a couple of police officers and her husband! They immediately quashed her fears as they said that I wasn’t in any trouble but had had a fall. They suggested that they thought I might have broken my arm.

Once inside, my wife and daughter quickly decided to take me to A&E in Colchester and despite my protests, within a couple of minutes, we were on our way.

Luckily, the A&E department wasn’t that busy and it didn’t take long before I’d seen someone and been taken off for an x-ray. By this time, the pain had started to build and I was given strong pain killers.

The results of the x-ray came back and it was determined that I’d broken my humerus in “at least” four places in what is called a proximal humerus fracture. Because of the location of the break, I was told that I wouldn’t be put in a cast but instead given a collar and cuff sling to immobilise the arm and be called back to the fracture clinic in a few days to see what should be done next.

Here you can see the initial x-ray with the the four most obvious breaks highlighted.

I had a very uncomfortable few days – My pain killers were increased a couple of times until all I was suffering was a dull ache. I kept my arm immobilised and got very bored, very quickly.

My appointment at the fracture clinic came through quickly and the consultant started off by saying that I “probably” wouldn’t need surgery but he called for another x-ray and a CT scan of my shoulder to be sure.

The CT scan was done and I was called back a week later. This time, the consultant went into much more detail and after some discussion, he decided that I would need surgery to repair the damage. In particular, one piece of bone had moved from the back of the humerus and would stop movement. He said that as I’m relatively young and active, he really had no option but to operate. If I’d been a lot older then it would have been a different matter but without surgery, I’d probably end up with so little movement that my arm would be effectively unusable.

I asked how much damage there actually was and he started out pointing out the broken segments within my arm but stopped counting at eight and said “it’s just like a mush in there.”

The surgery was booked for the following week and went without any major hitch. I was on the operating table for about two hours which is a lot longer than originally intended because the bone fragments had already started to knit back together. The surgeon had to scrape those bits out before he could even start the repair process.

I had a metal plate fitted, along with three screws and eight pins to get all the fragments back in the correct places and held together. This metalwork will be in my arm forever because once the bone has grown back it fits the metalwork at microscopic level. You can’t apply enough torque to turn the screws without breaking the bone so they’re basically fused in.

It’s still very early days as I haven’t even had the thirty staples out yet which are holding the incision closed. My arm continually aches but I’m pleased to report that I’ve already started physio and have got more movement now than I had before the surgery.

This healing process isn’t going to be quick. I can’t drive and I can only use a keyboard one handed. I’ve been writing this article using voice recognition so I don’t have to do much typing.

One of the big issues I’m suffering from is lack of sleep. Since the fall, I’ve not slept continually for more than about forty minutes because I just can’t get comfortable. I find a position that’s relatively painless, nod off and then wake up again soon after. The medication I’m on for the pain causes a dry mouth and each time I wake up, my mouth is so dry that I can barely open it to pour some water in. I’m just catnapping whenever and wherever I can for a few minutes at a time.

I was told that when I’m all healed and this is all over, if I can raise my arm to shoulder level then it’ll be considered a success. I want more than that, I’m doing all the exercises I’ve been told in the hope that I can get better than what the surgeon predicts as ‘best case’.

As I progress through the healing process, I’ll post updates on Twitter.

I’m just bored though. At this stage, there’s not much I can do. I can play a bit of radio but my attention span isn’t very good and it soon frustrates me. I’m putting this down largely to the lack of sleep and am looking forward to the time when I’ll get a full night again, or even just a few hours uninterrupted sleep.

I suspect that going through security at airports will be challenging in the future as well.

Addendum (28/12/2019)

This arrived anonymously in the post today, I genuinely have no idea who sent it to me but if you’re reading this then thank you!
It gave me a much needed laugh.

Addendum 2 (31/12/2019)

The dressing and the staples were removed two weeks after surgery and now the long process of rehabilitation starts. My aim is to get as much mobility and strength back into my arm as possible.

Posted in Not amateur radio | Leave a comment

Rebuilding and raising my ADS-B receiver

Earlier this year I replaced my Hexbeam (with another Hexbeam) and I wrote about it on this site. There was a gap of a couple of weeks when I was between aerials and to take advantage of that, I temporarily moved my ADS-B receiver to a temporary stub mast, effectively raising it 7ft from the original height.

Although this was only a small increase in height, the difference in performance was very noticeable and it germinated a seed that I’d planted in my head some months earlier. I’d been trying to work out if I would benefit from mounting my ADS-B aerial on top of the Hexbeam and even whether it would be possible or not.

Clearly the answer to the first part this was a huge “yes” but the next part was whether I could attach the aerial to the Hexbeam. I contacted the aerial manufacturer who suggested I could fix the 40m centre support pole to the Hexbeam and mount the ADS-B aerial on that.

You’ll remember that when I replaced my Hexbeam, the one I put up included the 40m element so after changing the aerial, I could see what I’d need to do regarding the ADS-B receiver.

For the last few years, I’ve been using a FlightAware 26″ 1090 MHz aerial and I’ve been very satisfied with it. I wanted to buy a new one and started looking around. Unfortunately there were none available in Europe whatsoever and all the suppliers I contacted in the USA either weren’t prepared to ship to the UK or wanted ridiculously high carriage. I contacted FlightAware direct and explained my situation. They were happy to ship me an aerial which sadly got lost by the courier and so they arranged for their European partner, Jetvision to send me an aerial. That arrived in early October while I was on holiday in the Channel Islands.

I also ordered 10m of Messi & Paoloni coax. After poring through the specifications, I decided to go with Hyperflex 10 as I figured it would give me an acceptable level of loss and be suitably flexible to go around the rotator. Incredibly, this was also lost by the courier (a different one) and a second shipment was arranged which arrived within a day of the aerial, while I was on holiday.

I’d also decided to rebuild the entire receiver system in the box as well. I was going from a Raspberry Pi 3B+ to the newer Pi4 and wanted to replace the slightly bodged power arrangements I’d used previously with an official Raspberry Pi PoE HAT.

With everything ready to go, all I had to do was wait for the weather to be decent enough. I needed a combination of a few days without rain and then not too cold with no wind. This took longer than expected and it wasn’t until the 24th November that I was able to lower the mast and do all the work.

I fitted the new aerial to the top of my Hexbeam and routed the coax down to the receiver box. I then stripped everything out of the box and rebuilt the receiver with the Pi4 and new PoE system. I cut the coax to length, installed the N-Type connector and fitted everything back together before raising the mast back up. The whole process took around three hours.

Because my new Hexbeam is taller than the old one, my ADS-B aerial is even higher than I’d hoped for. It’s now 11ft higher than it was and so is 44ft (13.4 metres) above the ground which is quite a substantial increase. However I’ve introduced some loss into the system which didn’t exist before due to the coax run. I’ve calculated this to be around 0.7dB which I consider to be acceptable.

A few days after I did this work, I went out for my morning walk and it was a typical autumn morning. Very chilly and bright, with a beautiful, cloudless, clear blue sky so I just had to take a picture. You can clearly see the Jetvision aerial on top of the Hexbeam and the box the equipment is all mounted in on the side of the mast. If you look closely, you can also see an aircraft in the background, although you might need to click the picture to zoom in.

Hexbeam with ADS-B aerial

In practical terms, it’s relatively easy to work out how much difference this upgrade has made. Taking into account the raised aerial and the change from the Pi3 to the Pi4, I’m seeing approximately 50% more messages per day, an increase of around 20% in the number of aircraft per day and I can see from the coverage graph on the FlightAware statistics page that I’m now receiving signals from aircraft out to 250+ miles in all directions. At time of writing, my message rate/second peaked at just over 2,900 on the 11th December.

I’ve done extensive testing while transmitting on all bands with high power through the Hexbeam and the RF doesn’t affect my ADS-B receiver at all.

You can see the live feed from this receiver and the two others I am responsible for on this page which also contains other links such as graphs, statistics and daily heatmaps.

I feed my data to a number of providers and also to Essex Radar which is my own consolidated Virtual Radar Server.

For completeness, here’s a list of every piece of equipment used in my installation from top to bottom:

Jetvision aerial
5.5m of Messi & Paoloni Hyperflex 10 coaxial cable
N-type female to SMA pigtail
RTL-SDR-LNA
Bias-Tee injector
SMA to SMA pigtail
Airspy Mini
Raspberry Pi 4 Model B (2Gb RAM)
Raspberry Pi PoE HAT
30m CAT 6 cable
TP-Link TL-PoE150S PoE injector

Posted in ADS-B, Amateur radio, Construction, Raspberry Pi | Tagged , | Leave a comment

Building an MMDVM hotspot on a budget

I bought myself a new handheld at the Newark rally earlier this year, an Anytone AT-D878UV to use on DMR. When I went on holiday in October, I took a couple of copies of RadCom with me and in one of them there was a review of my handheld. The author mentioned that he’d used it through a hotspot and this got me thinking because although there’s a DMR repeater near me, I’d never played around or experimented with hotspots. In fact, I’d never even seen one!

I like learning about new things so I contacted the author of the review asking for recommendations about hotspots and he suggested the Zumspot as being a decent pre-built hotspot that’s easy to get going. I dutifully ordered one while I was away and it was waiting for me by the time I got home.

Setting it up was very straightforward and within a few minutes, I had it all up and running and working perfectly with my handheld. I quickly learned all about the different modes it can be used with and spent some time upgrading it to the latest version of the software and fine tuning it.

I decided that I’d like another hotspot to use with D-STAR as there are many reflectors not available through the local D-STAR repeater and I thought it might be interesting to listen to some of them.

Rather than buy another Zumspot I thought I’d try and buy all the parts needed to assemble one myself and see how cheaply I could do it.

There are lots of MMDVM modems available on eBay so I just picked this one at random and ordered it. It wasn’t quite the cheapest but it was within a few pennies of the absolute cheapest. I paid £14.07 but I see that the same module from the same supplier has now dropped to £13.39.

It arrived quicker than expected as well – I ordered on the 1st November and it was delivered on the 13th November which I thought was pretty good considering it came from China. Unusually, the online tracking worked as well.

This is what I got:

MMDVM Hotspot Support P25 DMR YSF 32 bit ARM Processor for Raspberry Pi XY from eBay
MMDVM Hotspot Support P25 DMR YSF 32 bit ARM Processor for Raspberry Pi XY from eBay

The two sets of pins are for the GPIO header on a Raspberry Pi and the SMA aerial socket needs soldering to the board. The size is perfect for mounting on a Raspberry Pi Zero W and I had one spare so it only took a few minutes to solder the header and the socket in place and I quickly had a unit ready to go.

MMDVM Hotspot attached to a Raspberry Pi Zero
MMDVM Hotspot attached to the Raspberry Pi Zero

I wrote the SD card with a Pi-Star image, put it in the Pi and booted it. I’m not going to go into the details of how to write a card or configure Pi-Star as there are many places on the internet showing how to do this. The site by Toshen, KE0FHS is the best I’ve found for Pi-Star resources and you can visit it here. It took me about ten minutes to set everything up and reboot it.

A lot of hotspots come with little screens on them. In the limited time I’ve had the Zumspot, I really don’t look at the screen at all so I didn’t include one as part of my build.

This homebrew hotspot is working as well as the Zumspot. It doesn’t come in a fancy case, it doesn’t come with a screen but neither of those are important to me as I just want functionality.

Here’s a full breakdown of the cost:
MMDVM modem from eBay – £14.07
Raspberry Pi Zero W – £9.60
Raspberry Pi PSU – £8.00
16Gb SD card – £5.99

Total cost – £37.66

I could have built four of these for less than the cost of the Zumspot.

I’m not saying that people shouldn’t buy commercial hotspots but just wanted to demonstrate that it’s very easy to get the parts separately and assemble a fully working hotspot.

Posted in Amateur radio, Construction, D-STAR, DMR | 5 Comments

My new Hexbeam is broken … and fixed

Nearly two weeks ago the UK suffered from ‘Severe storms’ with high winds across most of the country. I went outside in the rain on the Saturday morning, looked up at my aerial and was disappointed to see this.

Broken Hexbeam blowing in the wind

You can see the 40m element in the top is very loose and blowing freely in the wind.

Broken 40m element
Broken 40m element

It wasn’t immediately clear what had happened because although I could see that the 40m element was flapping around, it wasn’t obvious exactly what and where it had broken. I checked and the VSWR had gone very high so something bad had occurred.

Today was the first combination of a calm and dry day we’ve had since so I took the opportunity to lower the mast and check. Once it was lowered, it was very clear what’s actually happened. The loop at the end of the element has simply slipped off the centre pole and the element has threaded itself back through the first spreader.

The loop at the end of the element
The loop at the end of the element

All I had to do was hook it back over the top of the centre support above the balun.

The loop hooked back over the top
The loop hooked back over the top

To stop this happening again, I used a couple of cable ties, one through each loop and securely fixed in place.

Two cable ties holding the loops in place
Two cable ties holding the loops in place

This also gave me the opportunity to make sure I can reach the top of the aerial without any difficulty by using my new ladder. I’m going to install an ADS-B aerial right on the top and now I’m confident that I can get to it safely. Note that when I climbed the ladder to work on this that I had people supporting the base and it’s also well pushed into the garden.

Working position for the top of the Hexbeam
Working position for the top of the Hexbeam

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Installing a dipole for 30m

I’ve never had a decent aerial for the 30m (10 MHz) band and have struggled to work much on the band either with my old doublet or the inverted L that I’ve had up for the last couple of years.

About a month ago, I realised that I could hang a single band 30m dipole in the space that I was previously using for an off centre fed dipole. I’ve tried an OCFD a couple of times now but they don’t seem to work well for me.

I make no secret that I still consider baluns a magic art and I’ve not taken the time to get my mind around balun construction yet. In theory, I should be able to do this as I’ve wound so many wires around ferrite cores when I’ve been making filters and QRSS/WSPR transmitters that it’s become second nature. I’m just not comfortable with the idea of building baluns.

The largest rally in the UK is the Newark Hamfest which takes place in September every year and I was hoping to pick either a commercial 30m dipole or a suitable balun when I went but sadly I didn’t see any of either of them. Shortly after returning from the rally, I ordered a pre built dipole which as delivered a couple of weeks ago.

Although it’s not been particularly cold here recently, we’ve had a fair amount of wind and rain and this weekend was the first chance I’ve had to do anything.

The first thing I had to do was clear the bushes from the support pole at the end of the garden. I generally lower and raise my wire aerial a few times throughout the year but it’s been two years since the last time I did that and there was about three yards of undergrowth to clear (note to self: a hedge trimmer really isn’t suitable for this kind of job, a chainsaw would be far more useful). This took a good hour to clear and has made it obvious to me that I need to make the effort over the winter and clear the end of the garden properly.

Cleared space to the support pole
Cleared space to the support pole

With that clear, I was able to lower the paracord I use to hold the end of my wire aerials and then get the centre support pole down. I don’t like leaving the centre of my wire aerials just dangling so I have a 25ft pole in the garden which is strapped to a washing line end post.

It was straightforward enough to fix the new dipole to the centre support pole and lift it back up again.

Here you can see the centre pole, the dipole and the far support pole. Note that it’s well clear of the overhead power cables which are behind the pole.

30m dipole
30m dipole – If you can’t see it clearly, click the image for a larger picture.

I didn’t get a chance to properly test it straight away but I did make a couple of quick QSOs using FT8 and although the internal SWR meter on my TS-590SG showed below 1.7:1, I had to use the built in ATU to persuade it to transmit full power.

This morning I put my Mini VNA Tiny on the dipole and was surprised to see that the SWR was a lot worse than the rig had showed me at around 2.4:1 in the centre of the band (2). It was most resonant at 9.9 MHz (1) but wasn’t particularly good there at nearly 2:1.

30m dipole swr after installation
30m dipole SWR after installation

To feed the dipole, I used the length of RG-213 I previously had connected to my inverted L and added a run of Westflex 103 up the pole. To save me having to run backwards and forwards to the shack to check after each adjustment, I took my laptop outside, disconnected the Westflex 103 from the RG-213 and made my measurements there.

I had to lower the ends and chop three lengths off before I got the aerial tuned correctly. In total, I took just over six inches off from each side which brought it bang into the middle of the band.

You can see the results of my trimming below – The SWR is flat over the entire band (it’s only 50 kHz wide) at a fraction over 1.6:1.

30m dipole SWR after trimming
30m dipole SWR after trimming

The two markers are the band limits.

When I connected the aerial back to the wireless, everything was much better than before. The rig transmits full power without needing the ATU and the internal SWR meter reads unity.

I had a quick session this evening and have already worked a couple of new countries on 30m so it’s having the desired effect straight away.

The downside is that I now don’t have any aerial up for 160m, 80m and 60m but my SG-237 smartuner is now free and I’m wondering if I can string a loop around the garden somehow.

Here’s the dipole from the other side – Note again that it’s well clear of the cables you can see running across the picture.

Dipole at sunset
Dipole at sunset

Posted in Amateur radio, Construction, FT8, HF | Tagged | Leave a comment

Anderson Powerpoles

Some time ago back in 2012 I first heard about the Anderson Powerpole in episode 53.5 of the Practical Amateur Radio Podcast and I immediately bought a load of them to use in the shack. I have a number of tails hanging off my PSU, all terminated in Powerpoles.

I’ve always soldered the metal contact to the wires but last year at the Newark radio rally, I bought a Powerpole crimp tool from Richard at SOTAbeams and finally had a reason to use it as I needed to make a new tail.

Powerpole tail all ready for my PSU
Powerpole tail all ready for my PSU

When I’ve fitted Powerpoles before, I’ve always found them a bit fiddly to work on but the crimping tool made a big difference. If you don’t use Powerpoles in your shack then you’re really missing out on the convenience. I thoroughly recommend them.

Powerpole crimping tool
Powerpole crimping tool

Posted in Amateur radio, Construction | Leave a comment