Amateur Radio Hardware

Mobile Radio Upgrade

I’ve had great service from my trusty Yaesu FT-7800E transceiver for around 15 years. It’s lived in a few different vehicles, performed really well and been easy to operate on the go. That is until a few months ago, when I started to get reports from other stations that my transmitted audio was weak intermittently…

Mobile radios can sometimes suffer, given the harsh conditions of mobile radios in terms of vibration and extremes of temperature. Cleaning all of the plugs and sockets on the connecting cables would usually fix things, but sadly not this time. Even swapping the microphone didn’t help.

Studying the circuit diagram, I found there are a few semiconductors in the transmitted audio signal path which control gain and it seems one of these might have become faulty. Due to lack of time and the small surface mount nature of these parts, I decided the easiest fix was to upgrade the radio to a newer model. I’ll repair the FT-7800E in due course, as I need a dedicated radio in my shack to park on the local FM repeater channels.

I chose another Yaesu transceiver for the replacement, and went with the FTM-300DE. This offered more features than the radio it replaced:

  • True dual band allowing simultaneous reception and transmission
  • C4FM Digital Voice capability, and access to internet gateways
  • APRS (Automatic Packet Reporting System)
  • Bluetooth
  • MicroSD card for easy programming of channels
  • And finally, a fancy colour screen!

The only drawback compared to my current radio was that the microphone attaches to the radio body, rather than the display head so I had to reroute some cables in my vehicle:

A mess of wires behind a dashboard

I also had to change the antenna on the vehicle roof. My previous antenna was designed only for UHF use on 70cm. The new radio would need to transmit regularly on 2m VHF as well as UHF, so I swapped to a dual band antenna, which was also slightly shorter. I’ve lost some of the range I had on 70cm, but I’ve gained 2m TX capability and of course APRS.

After an afternoon of fiddling around, the new radio body is hidden away with the control unit neatly on the dashboard and an extension speaker providing crisp audio directly into the cab:

Final install with dashboard refitted

I didn’t really think I needed APRS, but it has been interesting so far. I’ve had text messages from stations in neighbouring countries who have received my position beacons, which has allowed me to assess how far my signals are travelling. I can see local amateurs driving around near me, so I know to give them a call. One day, I started receiving position reports from lots of stations I don’t normally hear. So the radio is automatically giving me a ‘heads up’ on enhanced propagation events without me having to pay too much attention. Finally, the location of my vehicle is recorded by the APRS internet system, and so I can be tracked live on websites such as Google Maps APRS and this has resulted in a fresh cuppa being ready as I pull up outside home!

I’m usually monitoring the local repeaters GB3GD and GB3IM as well as the FM and Digital Voice calling frequencies when I’m driving around. Feel free to give me a call!

Amateur Radio Hardware

SDR Trouble

One of my colleagues asked me to have a look at receiver that wasn’t behaving well. It was one of the many USB receivers that are around based on the RTL 2832U and Rafael Micro R820T tuner chips. The device was very intermittent, but he wasn’t sure if it was a problem with the hardware, or with the software (and drivers) on his Windows PC. I don’t run Windows myself, so would be able to easily rule that out as a potential problem.

On connecting the device up to my Linux machine, it appeared to be behaving itself and showed up listed as a DVB-T device when I typed ‘lsusb’ into my terminal. However, when trying to actually use the device, it returned lots of errors before disappearing from the USB bus. Re-plugging it would make it come back to life again.

In my experience, complex microprocessor based things generally either work or they don’t. So to see a device that would speak happily over USB but fall over when used was a bit odd. What might cause something to misbehave in this way?

Thankfully my first hunch was correct. I swapped the rather long and thin USB cable for a short fat one. Hey presto – the device behaved perfectly and I left it running for a few hours without any issues. The resistance in the original cable, combined with the high current draw by the receiver was causing the voltages to drop, interfering with the normal operation of the device.

So, it’s always worth trying different cables when troubleshooting something, even if (as in this case) the original cable appears to be doing its job.

Amateur Radio Hardware

SharkRF OpenSpot

I’ve been having a lot of success using my MD380 DMR transceiver together with the Isle of Man’s DMR repeater network. Sadly though, my house isn’t in coverage of the repeaters. This means I can’t use my handheld at home.

The solution to this problem has come in the form of a Radio/IP gateway called the OpenSpot, and manufactured by SharkRF.

This allows my DMR radio to send packets to global DMR networks (Brandmeister, DMR+ etc.) and for incoming packets to be sent to my radio over RF.  Essentially it’s like having my own DMR ‘repeater’ at home so that I can use my handheld radio on all of the global networks as if I was in coverage of a DMR repeater.

Configuration was easy, via an HTTP web interface. Once set up, all the control can be done from the radio. Linking and unlinking can be done by sending group calls to specific talkgroups which means there’s no need to keep using a computer to use the device. All you need is your handheld radio.

I’ve been impressed with the build quality, the support forums, and the constant releases of new firmware with new features. I haven’t tried it yet, but it should be possible to use my OpenSpot to also communicate on the non-DMR D-STAR and System Fusion networks too, even though I only have a DMR radio. You can’t even do that with a full on DMR repeater!

Amateur Radio

Losing yourself…

About once every year, I like to log in to Ofcom’s website and re-validate my amateur radio licence. I do this so that it becomes a sort of habit, and so that I’ve no risk of going beyond the statutory five year limit.

This year, my login details didn’t work. It turns out that Ofcom have upgraded their online systems and I need to re-register. Provided that I use the same email address, they’ll match up all of my details.

Or so the theory goes. Sure enough, the system found my name and my address without issue, but sadly not my amateur radio licence. Instead, I’m now the holder of an old club callsign which I used to use when running a radio club at a school in England about 16 years ago. My actual licence and callsign is nowhere to be seen.

This matters, and not just for the legal reasons of needing to have a licence to transmit. To radio amateurs, your callsign is your name. It’s your identity. It’s how people recognise you. It matters when it’s gone. That’s why the right to personal identity is recognised in international law through a range of declarations and conventions.

Anyway, I’ve spoken to Ofcom on the phone today. Twice. They’re very polite and helpful people, but they can’t fix it for me. I’m waiting for a call back at some point today.

I don’t like being an unnamed, stateless individual. I want my identity back!

Amateur Radio Hardware Isle of Man

The Things are coming…

Recently, I attended #offcamp – a barcamp style discussion around open data which was organised by @bcs_isleofman and free to attend.

The morning sessions were OK and it was good to see that some thought is being given to making data open and available, especially data that has been collected by governments and already paid for by the public.

However, what really caught my attention was the crowd sourcing of data using sensors and the Internet of Things. I hadn’t realised that the problem of expensive telecoms links for remote IoT devices is beginning to be solved by new RF chipsets based on spread spectrum techniques similar to those used in QRP amateur radio experiments.

Sadly most of these RF technologies are proprietary, but that doesn’t mean that the infrastructure built with them has to be. A group of people from Amsterdam have built The Things Network which is an open movement with the aim of providing free and open communications for IoT devices around the world.

Given my interest in radio and electronics, together with the open philosophy of building something free for community use, I knew that I wanted to get involved with this. So, I’ve established an Isle of Man community with the aim of getting our very own Things Network established here.