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Making Waves – A DIY HF Antenna for the smallest spaces

Is your garden the size of a postage stamp? Or maybe you live in a flat/apartment with just a balcony, then this could be the antenna for you to get on the air using HF frequencies. We all know that an HF dipole for 40m (7MHz) is going to be 20m (66ft) in length and not everyone has the available space to fit one in (hell, a 1/4 wave vertical is going to be 10m (33ft) long and may require planning from your local authority. So how about a vertical antenna that is only 1.7m in length and covers all HF amateur radio frequencies from 7MHz to 28MHz via your ATU? Impossible I hear you say, not at all – read on to see how it is done….

What will you need? Not much really, you will need a length of plastic pipe, 1.70m long, 41mm in diameter – this is sold in the local hardware stores as 40mm waste pipe but be careful, 40mm is the inside diameter and it is available in either 41mm or 43mm outside diameter – 13.6m of 1.5mm insulated copper wire, some 20mm long cable ties (200 * 3.6) and a 4:1 UNUN (see later for instructions).

Effectively, take One end of your wire and secure it to one end of the 1.7m pipe using one of the cable ties. Wind on 67 turns of the wire over a length of 220mm and secure with a cable tie (insulating tape can also be used). Now drop the wire vertically for a length of 360mm and secure again. Wind on 22 turns (in the same direction as previously) over a length of 70mm and secure again. Then wind three turns, wide spaced over 820mm (and secure again leaving the end free. This end then needs attaching to your 4:1 UNUN.

For the 4:1 UNUN you can either build your own by following the image below:

Or buy one ready made (Magituner A) from www.m0cvoantennas.com .

Leave a short amount of space at the bottom of the pipe to fix either a bracket (if you are going to pole mount it) or use cable ties to fix it to railings on your balcony, etc. You will need to attach an earth wire to the second peg/machine screw. This only needs to be short – maybe 4 or five foot but does help with the matching. Attach coax to the SO239 socket using a PL259 plug and run back to your radio via an ATU (the internal one (if fitted) may be able to cope with this) tune up and away you go.

Making Waves – Reducing Power

From time to time we all need to reduce the output from our transmitter – maybe it’s in order to use sensitive equipment such as a Spectrum Analyser or oscilloscope to test the output from a transmitter we are building or from an existing transmitter that has an issue. For whatever reason it is good to have something to hand to prevent damage to expensive test gear.

Therefore, this blog is designed to give instructions for you to build your own dummy load and attenuator. Maximum input power will be 10W so this is really for the QRP guys (why would anyone wish to use high power for test purposes?). It does, however cover a wide frequency range from 1Mhz – 500Mhz so is good for both the HF guys and the VHF guys.

Components:

R1 – R2 100R, 5W, 500V Metal Film

R3 – R6 620R, 600mW, 250V Metal Film

R7 – R8 100R, 0.5W, 350V Metal Film

PL1 – PL2 BNC sockets (or socket of your choice)

Looking at the diagram above it can be seen that this is a relatively easy project to construct. R1 and R2 are connected in parallel from the centre pin of the input connector directly to earth. This provides a 50 ohm load to the transmitter and a 1:1 SWR which will protect the finals. It will handle up to 10W but may get warm if this is for too long. R3 – R6 are connected in series between the two BNC connectors on the live side (centre pin – centre pin). The total resistance is 2.48k which presents a 40dB attenuation to the signal. R7 and R8 are again connected in parallel from the centre pin of the output BNC to earth to provide a 50 ohm load and protect both the transmitter and the test equipment.

Using the diagram as a guide build it how you wish but to prevent stray RF it is advisable to enclose it in a metal case.

Making Waves -Break downs and silver linings

It all began when something went wrong with my trusty Yaesu FTdx1200.  This being my main HF/6m radio what was I to do?  The screen had gone from displaying all the necessary information to enable QSOs to be made to simply being the white screen of death.

Pic1Fig 1. The Yaesu FTdx1200 white screen of death

Well, I tried doing a full reset but no change, I opened it up and reinserted all the ribbon cables relating to both the screen and the FFT-1 unit but still no change.  So it was time to first contact the dealer I had bought the radio from originally (5 years ago).  They told me that it was probably a screen fault and that the screen would need replacing at a cost of £167 plus labour at £60/hour. So I then phoned Yaesu UK who told me pretty much the same. OUCH!

I ordered a USB to RS232 (9 pin) cable from eBay to see if a software update would cure it. I also found an ICOM IC-746 on auction currently at £299, I put in a maximum bid just in case and, in the meantime, set up my stand by radio for HF – the FT-817ND.  I turned it on and tried to copy some CW but after the lovely DSP features and narrow filters available on the FTdx1200, it sounded like someone had left the barn door open and there were a hundred stations all working on top of each other. Not good at all.

In the meantime, the USB to RS232 lead arrived but, to my chagrin, was the wrong gender – I needed a female RS232 head and this was a male one.  So I ordered another, the other way around.  Whilst waiting for the new cable to arrive I watched the price of the IC-746 rising as others put bids in over the days.  None of them came to the level that I put in originally though and suddenly I am the winner of an eBay auction  for what was one of the radios I could only have dreamed of owning when they were available (very expensive back then).  The price – £344 plus £30 shipping, £374 altogether. So, I scrabbled around in my piggy bank for loose coins and paid for it.

The new (to me) IC-746 arrived five days later complete with a pair of headphones.

Pic2Fig. 2 The IC-746 

I now had to find somewhere in the shack to set it up..

It is a little smaller than the FTdx1200 but still weighs in at 11Kg so |I looked to set it up on the second bench in the shack.  Now this radio would give me something that the Ftdx1200 didn’t have – 100W output on 145mhz as well as HF/50MHz.  I do enjoy operating on 2m SSB and CW but I had another problem following the storms that struck the UK during February my rotator on my VHF mast has broken – it won’t turn so is fixed beaming south west. This will be a job when the weather improves as it means going 8m up a ladder in a tight spot. However, I did manage to find room for the IC-746 and get it set up for 2m using the beam.

Pic3Fig.3 The IC-746 running 144mhz USB and a FRG-9600 RX receiving local airport traffic.

Then the new USB-RS232 cable arrived, so I plugged it into both my laptop and the CAT port on the rear of the Yaesu and logged onto the yaesu.com website.  Following the instructions on the software update page I turned on the radio whilst pressing both the up and down arrow keys and presto – it came back to life.  Wow, that could have been an expensive repair for the sake of a software/firmware glitch! So now I have two HF sets and one good QRO VHF set.  The ICOM does seem more sensitive than the Yaesu at picking out weak signals on SSB and CW but misses out on some of the nice features of the Yaesu which is more a SDR than a traditional radio.  The ICOM does have a scratch in the centre of the screen but I can live with that.  How will they be used? Well, I will use the Yaesu for CW and contests on HF as I have it plugged into the linear amp whereas the ICOM will be used mainly for VHF and, once I get a second antenna up for HF, can be used for dual band monitoring.  I am currently using an antenna switch to switch between them so I can compare them both but this is never the best way.

73 until next time, M0CVO

Making Waves – Building the KANGA Products OXO Transmitter Kit (Part 2)

December 21, 2019 Leave a comment

2

Following on from yesterday when I started building this excellent kit from Kanga Products, I have today managed to build the rest of it, all that it needs now is a power source and a Low Pass Filter before it can be plugged into an antenna.  Neither of these are included of course but the power supply can be a simple 9V battery (or 12V PSU) and the LPF a simple 5 or 7 pole LC filter.

7The completed board

Overall the PCB was easily populated with the components and personally I shall add a polyvaricon to the terminal beside the XTAL labelled Cvar.  The option was to either bridge this and have the frequency rock set to the XTAL value or add a variable capacitor to enable a swing on the frequency.  Therefore I am going for the latter option.  If I have any criticism of the kit it is that the XTAL(s) supplied are in a large can – I would probably replace them with the smaller low profile ones – and they are supplied at 14.050 and 7.028MHz, not the QRP frequencies of 7.030 and 14.060MHz.  I am planning on designing/building a switched XTAL bank to allow operation on all the QRP frequencies from 80m – 20m (possibly 15m) using XTALs I have here.

 

I have yet to do a smoke test and check the stability of the RF generated yet but this will be in the next stage as I have other things to be doing now.  I shall be checking both with and without a LPF straight into a dummy load before I plug it into an antenna of any sort though.  I also need to find a suitable enclosure for it.

Making Waves – Building the KANGA Products OXO Transmitter Kit (Part 1)

December 20, 2019 Leave a comment

2

As it’s nearing Christmas 2019, I decided to treat myself to an OXO TX kit from Kanga Products UK.  This is an updated version of the OXO transceiver made famous by the late GM3OXX now providing a multi-band version.  So I ordered it from KANGA and it turned up here yesterday in a jiffy bag/envelope.  Taking it out it was nicely packaged in a sealed plastic sleeve.

1

Making sure I had all necessary test equipment ready (including the Sandford Wattmeter also from Kanga Products) I set to work to start assembling it on the CVO towers workbench.

Opening up the outer sleeve and removing the contents I was pleased to see that all the components were sorted in separate bags of resistors, capacitors, transistors, etc.  tis makes individual components much easier to find as opposed to just having everything dumped into a single bag.

3 everything sorted into individual bags

The instructions needed to be downloaded from the website and consisted of a three page .PDF file.  To quote one paragraph from them:

“Though the fitting of the parts is straight forward, it is highly recommended that all components are soldered in the order they are listed in the component list”

Although this may seem a no brainer it is good advice as you can then mark off each component as it is fitted and it runs in order of resistors, capacitors, transistors, crystals and then connectors.  This also follows the order of the bags.  My only criticism here is that the coil isn’t mentioned in the list but is mentioned in a separate paragraph.  It needs winding by hand and is 17 turns of 24SWG ECW wound on a very small ferrite toroidal core.  This is surface mount and laid flat on the PCB and should be mounted first ideally.

4The PCB is nicely printed and fairly easy to follow

5

So, contrary to my earlier advice I first fitted the resistors to the board.  Fairly easy through hole devices and Dennis, from Kanga UK, has kindly listed the colour coding of each resistor beside its value in the list.  Not really necessary for those of us in the know but for those not familiar with resistor colour codes a handy help.

6

Next I wound the coil.  The former is very small and this can be fiddly.  Note, if you are going to build one yourself do leave the ends long as if you cut them too short….  Anyway once wound I fitted the coil to the board using the plastic screw, washer and nut supplied before soldering the tails to the pads on the board.  Contrary to popular belief the enamel coating on the copper wire doesn’t melt away to reveal bare copper when you apply a soldering iron.  I use a Dremel Multi-tool to remove some of the enamel coating before applying solder.  Once this was secure I then applied the capacitors in order, with the large electrolytic one being fitted last of all, ensuring the polarity was correct.  that was it for today as work got in the way but I will continue when I next get round and will hopefully have it complete and ready to test next time.

C# WPF programming / my other side

October 21, 2019 Leave a comment

As well as antennas and radio I am also quite keen on coding/programming in C# for mainly Windows applications.  I started writing programs in the 1980’s using Commodore BASIC and moved on from there.  A few years ago (about 10) I picked up where I left off and started using Visual C# in Visual Studio.  Funnily, although I started out with BASIC, I just couldn’t get on with Visual Basic – a feeling I hear echoed amongst many of my friends and contacts – so I gave C# a go.

I started like most with the standard “Hello World” program:-

  • static void Main(string[] args)
  • {
    • Console.Writeline(“Hello World”);
  •  {

and then moved on to Windows Forms programming which was quite easy and self explanatory. Using Windows XP and Windows 7 (never touched Vista) Windows Forms were great and I created many small but useful programs, some of which I published through the Microsoft app store.  Then with the advent of Windows 8 Windows Store apps were more for the Windows Phone which, unfortunately was too late to the already flooded smartphone market and was later withdrawn.  Also around this time, I moved from using Windows Forms to using WPF in Visual Studio 2012.  What a difference! Gone were the square regimental blocks used in WinForms and suddenly transition between pages and windows was much more fluid and reasonable animation was possible.  However, it did mean also having to learn XAML.

WinFormsSample Windows Forms layout in VS2017

WPFSample.JPG WPF layout in VS2017, note the XAML beneath the design screen.

Then Windows 10 happened.  With Windows 10 the Windows Store became more difficult -apps had to be written in UWP(Universal Windows Protocol) format.  An absolute nightmare for most developers.  This was a much stricter protocol with limitations on what was allowed and , due to the many different form factors including PC Desktop, tablet, Phone, etc, it need to be able to resize without truncation.  So what now for all of us who had been happily writing software in WinForms or WPF?  Did this mean that we would have to learn UWP coding?

UWPSample UWP Layout in VS2017

Not at all it turns out.  Thankfully, if you upgrade to Visual Studio 2019 (even the Community Version) you can write your desktop apps using WPF in order to tweak them and perfect them ready for uploading to the Windows Store.  However, before you can you must first right click on the solution and add new project.  This should be a UWP blank app. There is no need to write any code for this project, just right click on the project and associate it with the app you have created in WPF.  Once you have done this right click on the UWP project that you have added and scroll down to publish and then create Windows Store App Package.  This will create a package that can be uploaded to the Windows Store (.appxupload, appxbundle, etc).

Of course, in all samples above, the result is the same, the message “Hello World” is displayed in the screen. However, in the first, console project the command to do so is

“Console.Writeline(“Hello World”);

in the Windows Form and WPF the command is

“MessageBox.Show(“Hello World”);

and in the UWP app the command is

“MessageDialog msg = new MessageDialog(“Hello World”);
msg.ShowAsync();”

Showing how each of the different packages differ in their command format.

Making Waves, New Opportunities, KW and beyond…..

September 28, 2019 Leave a comment

It has been a while since I have written anything on my blog but this is mainly because I have been rather busy.  The antenna business ( www.m0cvoantennas.com ) went from being busy to very busy at the beginning of the year and has remained so since.  In March of this year I was given the opportunity to take over as Director of K.W.Electronics Limited (Company #08587607).  progress was slow at first but in July 2019 I received certificates transferring over the title of Director to myself.

KW_Logo

KW Electronics was first founded in the 1950s by G8KW.  They produced many receivers, transmitters and accessories for the amateur radio market, the most famous being the KW Vanguard Transmitter that featured in Dr. No, the 1962 James Bond film as can be seen HERE.
Now under new ownership, KW Electronics Limited is all set to bring you new products aimed at the amateur radio and commercial radio market suitable for the 21st Century.
The first products introduced to the new KW Electronics company profile are a Morse Code Practice Oscillator, either completed and boxed or the same in kit form (not including the box.
DSC00716
The K.W.Electronics Morse Code Practice Oscillator available HERE
DSC00727
The K.W.Electronics Morse Code Practice Oscillator Kit available HERE
There are other things currently being worked on such as a VHF preamp and an all band active antenna (both for RX only).  We also currently have an all band HF antenna – the KW-V – which is the CHAD (Compact Helical Asymmetric Dipole) developed by Ken Ginn, G8NDL.  However, as we are awaiting some parts this is not currently available.
Full details of K.W.Electronics Limited can be found HERE.

Building Block kits

As radio amateurs we all love to build kits – maybe a test meter, maybe a small receiver or whatever but, if it is home built it is something we can be proud of.  With this in mind, M0CVO Antennas designed the VXO Oscillator kits way back in 2017.  I their simplicity these are based around a Colpitt’s Oscillator and provide a sine wave output that can be followed by a mixer by other modules to create a small transmitter, a receiver (Direct Conversion) or many other things where a stable known signal source is required.These became popular in the UK for Foundation Licence radio amateurs who wished to advance to the Intermediate Licence, part of the course for which entails building a kit that would/could be useful in the radio shack later.  They are currently available for either 40m (7.030MHz) or 20m (14.060MHz).  Both of these are available from HERE. This kit, whichever frequency you choose, is the BB1 kit or Building Block #1.

untitled The VXO Oscillator.

Moving on a couple of years, M0CVO Antennas has now developed and released the second building block kit – the BB2.  This is a class A follow on/buffer amplifier.  Similarly to the BB1 kit is is rather simple in construction, the idea being for self learning in electronics so it can be built by anyone, whatever their level of electronics experience.  They are supplied with PCB and all components needed to build the unit but the constructor must supply their own enclosure if they require one.  All inputs and outputs are via MOLEX connectors.

20190509_135308  Completed BB2 Kit

If a crystal oscillator or VFO is used as the input (eg the VXO Oscillator Kit) this will increase the output signal power to ~1W depending on input voltage (9 – 12V DC).  A couple of these have been constructed and tested as can be seen in the following images:

20190511_091550 20190511_091539 20190511_091534 Under test

The fourth MOLEX connector at the top of the board is for either a switch or a CW Key.  It can be used in its complete state, with a suitable signal source, as a QRP(P) transmitter.  However, suitable filters (band pass or low pass) must be used and a suitable antenna must be connected.  Also a relevant amateur radio licence must be held in order to use it thus. These are available from HERE.

Build Yourself a 40/80m Antenna For Small Gardens Part 2.

January 14, 2019 3 comments

After writing the previous article on the small antenna for 40 and 80m HF Bands I was asked by several people for photographs of the antenna in question.  Therefore I have done this article as a follow on with pictures.

20190114_132908

Firstly you need the coil to be wound.  This one is 78 turns for 1mm ECW on a 41mm diameter former (plastic pipe) at 140mm long.  The screws hold the wire in place as described in previous blog post.

20190114_140408

Then you take two lengths of wire – one at 10.14m and one at 2m (or longer – I cut this one at 2.5m) and attach them either side of the coil.  Tape the longer section to a fibre glass fishing pole using insulation tape and allow the other end to lay loose beside it.  raise the pole and tie the hanging end off to somewhere convenient – I used the fence.

20190114_140424

A better picture of the coil on final position.

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Use of choc block to attach coax cable – second wire is a 10m long earth wire.

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The earth wire is just run around the garden.

20190114_144623.jpg

Final test using an AA30 antenna analyser shows the SWR at 3550kHz – just in the right place for a spot of CW DXing. Obviously , if you wanted the sweet spot higher, use a shorter length of wire at the end.

Build yourself a 40/80m antenna for small gardens

So, you’ve just got yourself a licence or a nice new HF transceiver and are hoping to be active on the lower frequency bands of 80m (3.5MHz) and 40m (7MHz) but are a bit concerned about how much space you will need for an antenna.  After all, an 80m dipole is going to be around 40m (132Ft) long and modern postage stamp sized gardens just can’t accommodate this.  So I am going to describe a single antenna for both bands that should fit into most gardens.

What will you need?  Well, firstly, you will need approximately 40m of insulated copper wire – the sort used for lighting circuits (single core, stranded), usually available from your local DIY or hardware store.  Also you will need a reel of 1mm enamel coated wire (ECW)this is available from RS Electronics – part number 357-788 – some choc blox (cable connectors) or powerpole connectors (available from www.sotabeams.co.uk), a fibre glass telescopic fishing pole – 10m would be ideal but anything from 7m up should suffice, a piece of 40mm drainage pipe (this will be either 41mm or 43mm outside diameter), some 4mm * 20mm machine screws and nuts, some 4mm ring crimps, a length of fishing line (fairly strong stuff 20kg strain or more), cable ties and a length of angled aluminium, or brass – also available from you local DIY or hardware store.

Directions:

Firstly cut two lengths of the insulated wire – one at 10.14m and the other at 2m. Strip a few mm of insulation from each end of the longest piece and from one end of the shorter piece.  Fit crimps where you have stripped insulation on one end of the longer wire, leaving the other end bare (you may wish to tin the bare end with solder) and on the stripped end of the short wire and solder them on for a stronger fitting.  These are going to make up your radiating element.  Put them to one side and we shall come back to them later.

Now saw a 140mm length of the 40mm pipe.  This is going to act as a coil former.  Measure in 1cm (10mm) from each end and drill a 4mm hole. Now rotate the tube by 90 degrees and drill another hole 10mm in from each end.  Scrape the enamel off the end of the 1mm ECW and thread it through the 1st hole on the left hand side of the piece of pipe.  Fit a crimp connector to this end and solder it for a stronger (and electrically better) connection.  Locate the ring beneath the second hole on the left side and push one 4*20mm screw through both and fix with a nut.  This now securely anchors the wire at one end.  Now wind 78 turns of wire onto the coil, you may wish to use insulating tape to hold the wire whilst you are winding it and once you have wound the 78 turns on.  At the other end, cut the ire long so there is plenty spare and thread it through the 1st hole at the right hand side.  On the inside of the pipe measure the wire to the second hole and make a notch/fold here.  Pull the wire out straight, cut it and scrape the enamel off.  Fit a crimp and again line the ring up with the hole and push a screw through, fixing with a nut.  This coil will act as an inductive load for 80m and a trap for 40m.  You may wish to wrap the whole coil in insulating tape to protect it from the elements.

Now take the 10.14m length of insulated copper wire and cable tie it along the length of the fishing pole with the bare end at the bottom.  Make sure the pole is fibre glass and not carbon fibre or graphite as these will affect the tuning of the antenna.  Start about 1Ft (300mm) up from the bottom of the pole.  The other end of the wire will be beyond the top of the pole, don’t worry about this, it needs to be.  Now at the far end of the wire, fit the crimp over the top of the screw you anchored the first end of the ECW to when you started winding the coil.  Fit another nut to secure it (you may fit an extra locking nut if you wish).   Now fit the shorter length of wire to the other end of the coil in the same manner.  Loop the end of the wire back on itself (about an inch) and secure with cable ties. Thread one end of the fishing line through this and tie off well.

1040_sch

Schematic of wire antenna.

 Dig a small hole in the ground (the depth should be half the length of the piece of angled aluminium/brass that you have) and stand the piece of angled aluminium/brass in it.  Fill the hole back in and check that it is secure.  Raise the fibre glass pole to vertical and secure it at the bottom using cable ties (or whatever) to the portion of aluminium/brass that is protruding from the ground.  Using the fishing line that you fitted to the top end of the wire, pull it out to an angle between 30 and 40 degrees and tie the other end off to a fence or something secure.  You now have the basis of your antenna and I shall now describe how to feed the antenna with RF and get on the air.

Fit a choc block (or powerpole connectors) to the end of your coax – it will need to be a double connector for both the inner and earth/braid.  Then connect the inner side to the wire of the antenna and add one or two 10m counterpoise wires to the other side of the outer.  If you have space lay these out at right angles to the vertical antenna, if not, don’t worry, they can be laid in spirals or bent to fit in, it is the electrical length that is important.  You could also connect a short wire to a copper ground spike and lay shorter radial wires out from this.  Take the other end of your coax back to the shack and fit a PL259 plug.  This will attach to your ATU or radio.  Check tuning on low power (5W or less) – it should be resonant on 40m and 15m (3rd harmonic) and a small portion of 80m (remember it is loaded for 80m so possibly won’t cover the whole band.  You can adjust the length of the end wire to match it where required, or use your ATU.  Make sure you insulate the choc block/powerpole connectors to protect from water ingress.

You now have a 40m vertical antenna (as far as the inductor) and an 80m inverted L.  This will give you a near omnidirectional (all round) radiation pattern with a low angle take off so will be good for both nearby QSOs (depending on propogation and atmospherics) and low angle DX. Have fun.

73 DE M0CVO