A simple approach to VHF contesting

The UK Activity Contests (UKAC) are a series of VHF contests that happen every Tuesday night. There is a different band each week. The general set up is a signal report (genuine, not a 59 default), serial number and locator. The locator is used for multipliers. The calendar is as follows:

Every 1st Tuesday 2000-2230 (Local) 144MHz
Every 2nd Tuesday 2000-2230 (Local) 432MHz
Every 3rd Tuesday 2000-2230 (Local) 1.3GHz
Every 4th Tuesday 2000-2230 (Local) 50MHz & SHF
Every 5th Tuesday 2000-2230 (Local) 70MHz

So, its a pretty full calendar. I participate in the low power section, which is <10w but I actually run 5w from my FT817nd. Almost always portable and at most the 6m, 2m and 70cms sections. Antenna’s have been a mixture with some pretty substantial beam’s (for /p anyway) but my preference is for the now defunct Sotabeams SB270 for 2m and 70cm’s and a Nuxcom lightweight 6m yagi. I have moved away from heavy telescopic poles to a Harris 5m telescopic decorators pole.

The theme is to simplify some things but with a view to focus my spending on lightweight improvements. I find that this keeps my interest in building up as well as operating. Lets make this very clear, I’m not in it to win in, but to make use of the normally quiet VHF spectrum for some fun. DX is unusually no further than the south coast or the north of Scotland and the occasional trip a little bit further but conditions need to be exceptional.

So the latest addition is a more appropriate support for the pole. I was sick of using a drive on plate that was frankly destroying my £16 investment in a decorating pole. My car has a tow bar. I bought a ball attachment several years ago as it was right in front of me and very cheap. I now have a use for it.

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The tow bar mount is made from a few off cuts of 47mm x 100mm (or 2″ by 4″ if you prefer) and a piece of rough sawn timber that was being used for shuttering for the summer house foundations. I used a 38mm hole saw so that the base is snug, but the upper support needs some kind of removable wedge.













It has been painted with Wilko’s timber paint left over from some other work (which is very good). I’ve yet to try it out but I’m impressed how quick it was to make. Let’s see how it performs, its certainly a lot simpler than buying an expensive drive on plate.

It remains to be seen if this is a worthwhile addition but it only has to deal with a little over a 1Kg in static mass so chances are even the most severe winds. In which case I won’t be out /p anyway. Next stop the antennas. To increase gain or not to increase gain, that is the question. I kind of know the answer really.

Sotabeams Laserbeam DSP Filter

I’ve bought a few odds and sods from Richard, G3CWI at Sotabeams in the past. Stuff like a super cheap End Fed Half Wave tuner for my MT5B that took about 30 minutes to make, a SB270 dual band 2m and 70cm yagi which is my favoured UKAC antenna and things like antenna winders. But, I ventured into DSP and bought a Laserbeam CW DSP filter on a whim at the NARSA Norbreck rally and to my shame haven’t really used it too much. The complaint was that I didn’t get round to boxing it up. Now all that has changed. There’s a kit! not just a box but an amplifier as well.


Richard now sells plenty of different types of filter from single SSB and CW types as well as a variable version and even one for the ft817 (next stop I think). He also sells a neat little box and audio amplifier kit. Something that was clearly missing from the original line up. I paid my money and a few days later mine arrived. Some downloaded instructions from the website were used and within 30 minutes the very good quality PCB was populated and they enclosure being prepared. Here is a small niggle, the case is an aluminium extruded type that follows the Hammond 1455 style but is an alternative that is no doubt cheaper. The end pieces are laser cut and engraved acrylic that don’t quite fit flush with the holes and the self tapping screws are driving int thick aluminium and as such are prone to slipping and potentially able to fowl the front panel. There is a very minor issue with fit and in my case the audio jacks sit ever so slightly too far out and as such force the thin acrylic to bow. Lesson learnt is that fit those parts more conservatively to avoid the bowing. That being said its a small gripe.


Powering up is straightforward. Anything from 5-15v works and so my standard 12v ‘checking stuff’ battery powered it up first time and I soon noticed that the audio was quite loud with my headphones. The front panel has a volume control and a handy LED reminder if you drive it too much. The sweet spot is just below the level LED ‘light up’. A second LED shows the incoming signal and a wide / narrow switch chooses between wide and narrow settings of course. The website shows lots of graphs and technical guff but using it is clearly what I’m after and it certainly doesn’t disappoint. The ability to remove unwanted signals is just brilliant. For such a cheap unit I can’t think why I didn’t get my backside in gear earlier.

The minor mechanical niggle aside, I would recommend this as a simple and effective filter. It is cheap, simple, razor sharp and a really useful add on. Long may it carry on filtering!

Saved by something or other

Today I almost bought a new rig. I say almost because it has been the closest time I have ever got to buying a new rig. I had a week with a KX3 and found it wasn’t to my taste, not because it didn’t perform well but for some reason or another it just didn’t do it for me. So I looked at the new Icom IC7300 and was really taken aback by it. It looks like a great rig and I’m sure it’ll do a lot for those that buy it, one day I might get one. Today I almost did. My finger was hovering over the buy now….I put one in the basket and got the credit card out. My XYL pointed out I could afford it (This made me very suspicious). Then I realised I was sure I didn’t actually want it. Am I losing the fun of radio?

I don’t think so.

I bought a LNR Precision Mountain Topper last April and have used it a handful of times and enjoyed the portability of it all. The simplicity and the lack of domestic real estate needed to make it work for me. I put together a neat little pack for taking away with me and I think I’ll refine that a little. Some things might look familiar, others look like they’re missing, notably a ‘flight deck’ or ‘thing to put your radio on whilst you’re operating out and about’. I’m going to laser cut a bespoke one that will fit into the case (which by the way is an old Dremel carry case). More on that later

Portable pack


So I decided to save my money and think about a shack in the box that I really miss, a Yaesu FT817ND. I sold my 817 a couple of years ago and regretted it from the minute I sold it. I think I will get myself a decent second hand one of those with a few of the bells and whistles I didn’t have the first time around. At least that’s what I think I’ll do today.

Tomorrow I’m sure I’ll change my mind again.

Raspberry Pi APRS iGate

Further to my previous post(s) on APRS and Specifically Direwolf, here’s something with a bit more meat.

APRS has always been a bit of a thing for me. I like to go for a ride or a walk on the Lakeland fells and whilst I don’t get to go on as many SOTA trips as I’d like I do nearly always carry a hand held when I’m on the mountain bike. I know that there are a few local hams who like a bit of APRS and you never know when you’ll need a way of communicating when you’ve gone over the handbars and smashed your phone….

So what?

Well I also have an early Raspberry Pi model B and an RTL-SDR dongle. I live quite close to a digipeater and also have a terrible QTH for an iGate. So, I thought I’d combine the two with my liking f APRS. I’m glad to say the process was really easy and very robust. Want to have a go yourself? Ok…

So lets start

  1. Get you SD card and load it with the OS (I used the Raspian image from the Raspberry Pi site)
  2. Get a copy of the Direwolf software from WB2OSZ (and simply excellent documentation) from GitHub
  3. Have a look in the Direwolf docs folder. Follow the Raspberry-Pi-SDR-IGate instuctions and the Raspberry-Pi-APRS. I’m definitely not going to try and replicate of better these docs as they are perfect
  4. Get an APRS passcode from Magicbug
  5. Off you go, simple as that. Any issues then the Direwolf Yahoo Group should sort you out


That’s it really. There are a few little odds and sods like beaconing your iGate. This can be achieved by adding a line into the sdr.conf file so it looks a little like this:

# # Sample configuration for SDR read-only IGate.
# We might not have an audio output device so set to null.
# We will override the input half on the command line.

ADEVICE null null

# First you need to specify the name of a Tier 2 server.
# The current preferred way is to use one of these
# regional rotate addresses:
# noam.aprs2.net - for North America
# soam.aprs2.net - for South America
# euro.aprs2.net - for Europe and Africa
# asia.aprs2.net - for Asia
# aunz.aprs2.net - for Oceania

IGSERVER euro.aprs2.net

You also need to specify your login name and passcode.
# Contact the author if you can't figure out how to generate # the passcode.

IGLOGIN MX0WRC 12345 (your passcode)
PBEACON sendto=IG delay=0:30 every=10:00 symbol="igate" overlay=R lat=54^38.5611N long=3^3$

# That's all you need for a receive only IGate which relays
# messages from the local radio channel to the global servers.

I’ve not managed to get it to start up automatically if it falls over with the dw_start.sh script but that is a work in progress. Here we are on APRS.fi


Ok, thats all very well but mine is remote. There are a few suggestions from the RPi people but I plumped for Weaved and tightVNC as a solution. Here are the instructions I followed for Weaved, and for TightVNC . If you don’t fancy a link then try this:

Install Weaved and run the installer

sudo apt-get install weavedconnectd
sudo weavedinstaller

Then TightVNC

sudo apt-get install tightvncserver

Run it once to do the password thing, then to run at boot

sudo su
sudo nano vncboot.sh

Enter this into nano

#! /bin/sh
# /etc/init.d/vncboot

# Provides: vncboot
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start VNC Server at boot time
# Description: Start VNC Server at boot time.


export USER HOME

case "$1" in
  echo "Starting VNC Server"
  #Insert your favoured settings for a VNC session
  su - $USER -c "/usr/bin/vncserver :1 -geometry 1280x800 -depth 16 -pixelformat rgb565"

  echo "Stopping VNC Server"
  /usr/bin/vncserver -kill :1

  echo "Usage: /etc/init.d/vncboot {start|stop}"
  exit 1

exit 0

Then chmod

chmod 755 vncboot


update-rc.d -f lightdm remove
update-rc.d vncboot defaults

I can’t tell you how useful to follow the steps enough. I found that one RTL dongle isn’t quite the same as another so there can be issues. So much so that I wiped the SD card a few times so as to get right and simple. If you didn’t want to run Jessie, Jessie lite will do but you’ll need to find an alternative way to remotely access the RPi, with something like SSH as VNC doesn’t work (easily) without the X server.

As always, comments, suggestions and alternative approaches are always welcome, after all this is a hobby and none of this hard work belongs to me, I just follow the instructions 😉

FreeCAD 3D design software

Our club has been (slowly) constructing a SatNOGS 3D printed satellite ground station. It uses a bunch of parts that have been designed on a platform called 3D CAD. This is a free (as the name suggests) 3D CAD solids modelling tool. For those not familiar with mechanical design here’s a very quick and simple run through.

The good old days gave you 2 dimensional CAD packages. One of the most famous was AutoCAD. There have been many releases and it still has a place today (you can even get a free version called Draft Sight).

Perfect for producing 2D drawings in the traditional was. Also ideal for those .dxf files for laser cutting front panels for example. These are simple tools to get your head round but ultimately very powerful. This technology has been used to deliver some pretty complex engineering so don’t underestimate its usefulness

3D CAD design can look like a complex business but as tools develop the proliferation of simple to use applications exist and as expected they use their own language. 2D drawings are no longer the standard and so 3D parametric CAD systems are available from a number of big players like AutoCAD and SolidWorks. They range from very expensive professional packages that have features that only the very keen would need (like finite element analysis, animation and computational fluid dynamics) through to offshoots that are particularly aimed at home users. In amongst these packages are offerings such as FreeCAD and SketchUp which are completely free and very well supported. There is only one preferred standard and that is for the .stl file type although there are key differences between types.

Solids modelling and Surface modelling. As the names suggest one type produces solid shapes which are determined through sketching a part in 2D then turning that into a 3D part by stretching or revolving it around and axis for instance. These are generally referred to parametric modelling tools and they produce solid shapes. Examples of these types are FreeCAD, AutoCAD inventor and Solidworks. SketchUp on the other hand produces hollow surfaces. An easy analogy is between a dice and a cardboard box. Both are cubes, one is hollow and the other is solid. 3D printers for example need to think in terms of solids. This doesn’t mean you can’t use a surface modelling tool to produce a part, it means there are some additional bits of computer based thinking that needs to be done.

FreeCAD falls squarely into the 3D parametric solids modelling camp (for the purists, yes it does do sheet and mesh work but stay with me on this). It is also nice and simple once you get your head round the basic premise. Sketch something in 2D then pad it to make a solid and perhaps put in a pocket for a bolt hole for example. I have been working my way through a few tutorials on YouTube and can recommend theses…..

Once you get into the workbench idea and the language used it is relatively straightforward producing designs. I think the issues are that the assembly workbench isn’t quite there yet and it isn’t as polished as commercial alternatives, but hey it doesn’t cost thousands.

There are also a number of developing online packages like 123D CAD and Onshape but I haven’t had a look at those in any detail. The premise is still the same. draw a 2D sketch, constrain it with dimensions, symmetry, equality etc and extrude, revolve, pocket to your hearts content. It is a really great step to see such powerful tools available for free.

It wouldn’t be fair to mention the extremely accessible surface modelling package that is SketchUp. A Once Google product that instead of producing solids models faces and uses clever tricks to make you thinks they are solids. This is a great tool and is good enough for 3D printing parts. Just beware of its limitations and well aware of the huge amount of models available in its warehouse.

Well worth considering for anything from shack layout to 3D parts design.

Hopefully I will get re-antiquated with this new tools as its been a while sine I behaved like a clanky (that is a mechanical engineer to you lot). There are some truly staggeringly clever products available that you only need invest a bit of time in learning.