OpenVPN for remote access

I love operating digital modes remotely. Whether away from home or sitting in my living room beside a cosy fire, I just need my laptop in front of me to see what’s happening on the bands and work a few stations.

Two key considerations when setting up remote access are:

  • Ensuring hackers can’t get into my network through ports exposed to the Internet (and they WILL try).
  • Ensuring that routers/firewalls in hotel/coffee shop/airport WiFi don’t block the ports I’m using for remote access.

Both of these objectives can be achieved by using a VPN. A well designed and configured VPN will keep attackers out, and as all the remote control traffic is routed through the VPN tunnel, it will be protected from interception and not be affected by any filtering present in the bearer network.

I use OpenVPN as it is a free and well respected solution, with a VPN Server configured on the laptop connected to the radio, and  a Client configuration on my main laptop.

Guidance on how to set up OpenVPN can be found here: so I won’t repeat it. As advised, use UDP as that gives better performance.

I change the port used by the VPN from the default to 443, as pretty much all networks allow this through. There is a small risk that traffic may be blocked by more sophisticated networks which spot that its not actually HTTPS: traffic, but I have not had a problem yet.

You should use the server option to disable compression, as that is a small security risk.

Also enable tls-auth as that provides some excellent extra protection, and put tls-version-min 1.2 in the server configuration.

As all software has reported vulnerabilities from time to time, you should always make sure you run the current version.

As you are connecting direct from the remote computer to the internal one, connection speed and latency should be as good as you can get.

To connect the laptop to the radio, I use the G4ZLP CAT interface and the Mini Pro SC souncard interface, which both work well.

Some radio control software has built in remote access functionality, but I would be cautious about exposing it directly to the Internet. This has been designed as radio software, not security software, so is more likely to have security weaknesses than OpenVPN.

Hotel fun

Being stuck in a hotel by yourself is never great, but being able to make a few  QSOs from the hotel restaurant livens things up.

I had a few nice contacts on 80m PSK31 this evening as the band was quite lively, including a station  celebrating 100 years of the Republic of Austria.

I’m using a simple setup at the moment, with TeamViewer giving me remote access to the shack laptop connected to the station. I’d prefer using Remote Desktop as that handles the different screen resolutions between remote and local PC better than TeamViewer, so will be setting up OpenVPN soon to give me a direct network connection.



QRP or QRO for portable ops?

When considering a first rig for portable ops, a QRP radio is a common choice.

Small size and weight coupled with low current (and therefore small battery requirements)  make it a very attractive prospect.  In some situations, where weight must be kept to a minimum, it is pretty much the only choice.

In other circumstances though, where more weight and bulk can be tolerated, it may not be the best choice, as low power will limit the contacts you can make. For many, the challenge of this is what makes it fun, but for newcomers it may be discouraging.

To get an idea of the difference power makes, I ran some predictions for the 20m Band using 5W, 10W and 100W SSB.

In the diagrams, Dark Blue is 10% likelihood of contact and Pinkish is 60%.


Based on these predictions, the QRP SSBer would have had a pretty disappointing time.

What Battery?


Sealed Lead Acid batteries have been the mainstay of portable power for a long time. While not inexpensive, they are not outrageously priced, and their voltage is a good match for Amateur Radio gear.

They do however have many disadvantages:

  • Lead is a dense element, good for Nuclear shielding, less so for humping about.
  • The voltage drops significantly during the discharge cycle.
  • Deep discharge can badly damage the battery, reducing its capacity.
  • In normal use you will get much less than the rated capacity out.

Amateurs have long looked for good alternatives, and currently the lithium iron phosphate (LiFePO4) battery fills the frame nicely, now that prices have become more reasonable.

These cells have a working voltage of 3 – 3.3 Volts, so 4 in series give 12-13.2 Volts, which is a great range for Amateur equipment. Best of all, the voltage  stays in useful range until it is nearly fully discharged.

This means that the useful energy you get out is much nearer to the Ah capacity of the battery than for Pb cells. Also your equipment doesn’t have to cope with a sagging input voltage.

The C rating shows maximum current draw, C x Capacity = Amps, so 30C x 4.2 = 126 Amps for the above battery.  This seems optimistic for such a small battery, but it gives me confidence that using it for a 100W rig peaking at 23 Amps will be fine.

4.2 Ah won’t run a 100W rig for very long, but I find having multiple 4.2 Ah batteries and swapping when needed is more flexible than just having a big one.

Battery charger choice

Battery chargers for LiPo & LiFe batteries are a popular topic for discussion.

The one I chose is shown above. At 50W its not the highest power available but it charges batteries fast enough for me, and it was reasonably priced.

It is a very flexible charger, able to charge a wide range of batteries:

  • LiPo
  • LiIo
  • LiFe
  • NiMH
  • NiCd
  • Pb

It has a balanced charging connection for Li batteries of varying voltages & can charge all the battery technologies you are likely to come across.

A feature I particularly like is the ability to charge from mains or a 12v source. Just unplug the mains lead and plug in the DC cable, shown loose in the picture.

This means that if I have small portable batteries to charge and access to a car or other source of 12V such as a large bank of lead acid cells, I can use the charger for that.

I’ve changed the DC input and output connectors to PowerPoles to match the rest of my equipment.

I can’t comment on long term reliability, but will report any issues which arise.

Pelicase alternative

Pelicases are widely used for Go-Boxes and protecting equipment on the move, and they are excellent, but not inexpensive.

At a trade show I came a cross a display of the MAX IP67 cases, which are made in Italy, and seem to have many of the characteristics of  Pelicases, but are a lot less expensive.


With IP67 rating they are waterproof and dust proof, and have an air  pressure release valve for when taken on a flight. One of their markets is Military use, so that suggests they are pretty rugged too, as does their promo video.

The feature they don’t have is the option of a metal frame to screw into the top of the large compartment for mounting a panel on. It does however look as though there is space to drill and insert small self tapping screws directly into the plastic, to mount a panel directly. Also, if your panel is fairly thick, the lid will keep it in place when closed and on the move.

Pelicases are glass reinforced while these are polymer only, so if your box will have to take a real hammering when closed maybe you need a Pelicase, but most Amateur use cases are not that severe.

Find out more at


Securing your Battery

Securing a battery into a plastic case can be challenging.

The most secure way would be to bolt some brackets into the box which would hold the battery rigidly in place. This may however break the waterproof integrity of the case, so is not ideal.

A method which I have found to be quick, easy and good enough, is to use strips of adhesive Velcro.

In the example shown, the case has curved corners between the sides and the bottom, so I’ve used some plywood as a standoff to create a 90 degree angle, held in place by Velcro.

I’ve then covered the side of the battery in contact with the box bottom with adhesive Velcro and stuck it down. When the box is in use and horizontal, the weight of the battery pushes down on the Velcro, and when the box is standing upright, the weight is taken by the plywood packing so does not stress the Velcro.

In normal use, this seems to adequately hold the battery in place. Dropping the box from a height on its left hand end might dislodge it, but that’s not a risk I feel the need to mitigate, given the use case I have.

If the battery does become loose, it can be easily Velcro’d back in position.

I put the battery against the side to take advantage of the bracing it offered, but it does make the box a bit unbalanced when carrying, so if I did it again I’d put the battery in the middle, and probably use a LiFe battery to reduce the weight.

Particle Photon

The Particle Photon is a neat little micro-controller board with an STM32 ARM Cortex M3 micro-controller, a  Wi-Fi chip with on-board or external antenna, and  multiple digital and analoge inputs & outputs.

As you can see by comparison with the breadboard, its really small. I added an external Wi-Fi antenna for more range, but is not needed if your signal is strong.


To program you create a cloud account, link it to your device, and then program in the cloud IDE and deploy to your device. Dead simple!


Even simpler is the Particle smartphone app. Just link it to your device and you can read and set analogue and digital values for the IO pins.

The smartphone app reads from and controls the Photon via the Particle cloud. Therefore  when I’m standing by the board and pushing a button on my phone to make the light come on, traffic is going from my phone to the Particle cloud, then back to the Photon. Cool.

I’m hoping the traffic to and from the Particle cloud is authenticated and encrypted, but will be checking before I give it any serious use. I’ll do some packet sniffing with WireShark and also use an intercepting proxy with DNS spoofing to see how it fares against Man in the Middle attacks.

In the breadboard photo, the Green LED is connected to D0, which has been set to High using the App, and lo and behold, its lit up.

This makes it useful without any programming as by connecting TTL relays to digital pins, you can turn them off and on at the touch of a (virtual) button.

Interestingly, with suitable programming, you can link to the Amazon Echo, and control the outputs via voice.



VHF/UHF Frequency Counter

When setting up memory channels for example for Satellite or Repeater use, its handy to have a quick way of making sure the transmit frequency and other parameters such as CTCSS are correct.

Nothing worse than failing to make contact and then eventually (when its too late) finding that when setting the CTCSS tone, you were one knob click off the correct one.

I find the Surecom SF-401 Plus a convenient and fairly inexpensive device for this.

Its light weight but doesn’t feel too fragile, has a rechargeable battery with auto turn off feature, and while a colour display isn’t essential, having it makes the counter nicer to use.

Its not a tank, like my OptoElectronics Scout, but that doesn’t do CTCSS and might be finding its way onto e-bay soon.


Connecting Batteries

Having moved to using LiFe batteries for lightweight portable power, I needed to make them compatible with the PowerPole connectors most of my equipment uses.

The 4200 batteries come with 5.5mm bullet connectors, so the easy way was to buy a bullet to banana plug cable from the same supplier as the battery and replace the banana plugs with PowerPoles. These cables have very flexible insulation, so are great when in use.

I noticed that an insulation gap appeared where the 5.5mm bullet connectors joined together, so to keep things safe and stop the connectors coming apart inadvertently, I covered the join with heat shrink tube and  I’ll keep an eye on it.


An alternative is to connect the PowerPoles directly to the battery.


You need to be very careful not to short the battery cables while doing this, and do take off any metal rings on your hands, as if you short via a ring you may lose the finger.


I use 30A PowerPole inserts and you may find that the battery conductor is too big to fit. As I am not needing more than 30A, I just trim the cable strands off until they fit snugly, I also put a bit of thin heat shrink from the cable to the crimp part of the PowerPole.

You might be wondering where the fuses are, and they will be in the circuit which is connected to the battery. Putting them on each battery lead would have been clunky, and if reasonable care is taken, its unlikely that there will be a short across the PowerPoles on the battery.

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