2E0ITG and the Satellites

 

The title sounds like a rock band! I decided to take the plunge and sit the RSGB Intermediate examination on 10th November 2023. I passed and applied for my license and my new call sign is 2E0ITG. This will give me 50 Watts to play with so contacts should be much easier from now on. Also, I will be able to work extra bands including 5 MHz and some microwave frequencies, along with other privileges. I am currently looking into VHF / UHF communications for satellite work. 

 I have removed my QFH antenna from its current position in the garden and done a few minor repairs and maintenance tasks on it. It is now ready to be sited on the roof line. This antenna has been excellent for receiving and decoding weather satellites in the past. When I first constructed it, it was designed to be used as a transmitting antenna, so it should perform well. I tested it with my analyser and all looks good for the required frequencies. I will be using my UV-5R radio for this and will be limited to 5 Watts. This should be fine because you are not allowed to use high power for satellite work as it drains its power supply If you want to follow my progress you can pick it up at https://2E0ITG.blogspot.com

Introducing the SV1428 - 14 & 28 MHz Short Vertical Antenna.

 

 

Since I've been using my EFHW antenna, I haven't really felt the need for another one. Problem is that this antenna is horizontally polarised. I wonder sometimes if a decent vertical antenna might perform better on those days when contacts are hard to come by. The reason I think this is because of the disparity in signal reports I receive, when I know full well that the signal should be better. The reverse is also true - I might get a high signal report only to send a poor one back.

The main reason for not having a vertical antenna erected is because of its appearance. I try to be as inconspicuous as possible. As a compromise, I came up with this short 14 MHz vertical. After all, I was really surprised at the performance of my shortened dipole which uses the same principles. I did attempt this antenna before using a centre loading but the frequency response was way out. I must have miscalculated somewhere. It seemed to be resonating at about 9 MHz no matter what I changed - so no use for anything really!

The overall height of this antenna is 3.5m. Doesn't look too obvious if mounted a couple of metres below the apex of the roof. I didn't want to top load the antenna because it would make it top-heavy and unstable in high winds. I also wanted the loading to be above the centre mainly because, I'm led to believe by so called experts, that the first couple of metres of an antenna is where the work is done. I also needed it to be calculated properly if it was to have a chance of working on 28 MHz too. Finally, after checking, tweaking and double-checking my calculations, I came up with this design. 

To limit the number of turns required on the coil to a sensible size, I had to increase the diameter of the former to 42mm, allowing me to use only 16 turns, which also keeps the weight down. The wire I used is 2.5mm2 solid insulated household wiring cable. Hopefully this will minimise any resistive losses. All of the antenna is built using an old fishing pole for the main part. I stripped down an empty silicon sealer tube to make the reducers to match the coil tube down to the diameter of the pole, and glued in place. I also left about 1 foot of extra wire sticking out of the top to give me some trim capacity.

On to the testing. Any 1/4 wave vertical needs a good ground plane to perform. I found that two pieces of wire about 2m long stretched out in opposite directions at about 45 degrees and connected to an 8 foot aluminium ladder on top of the garage did the trick. I will add more radials later as I see fit. There may be some experimentation needed here because it can be quite finicky to get the right result into a small space. If there is enough room, you can fit full 1/4 wavelength radials which would probably be better. This antenna may also benefit from an additional ground connection. The antenna was fed by Mini RG8 coaxial lead. So first of all I connected the analyser and did a sweep from 13MHz to 15MHz to see where the sweet spot is. The excess wire at the top had to be removed as it happens.

As you can see there is a good dip of low SWR from about 13.5 to 14.8. Perfect! Any mismatch can be sorted with the ATU. A quick call on FT4 and 10 Watts got two instant responses from Germany and the Netherlands, both with positive signal reports. The SWR reading on the rig was even better than the analyser suggested. I put this down to the length of coax that was now being used. Moving on to check at 28Mhz I was pleased to see a good SWR here too, as can be seen below.

An operating range of 27.7 to about 33MHz - very useful! Once again, operational SWR was better with the rig. An even better ground plane would allow this antenna to perform to its full potential. I find it extremely difficult to compare one antenna with another. I still seem to get more contacts with the EFHW, but it does work extremely well. 

Here we can see the spot reports from Gridtracker.

More operational trials may be required under different conditions. I am going to name this antenna the SV1428. This will be my vertical option for the present time. Here it is just above the edge of the roof line.

Free Ham Radio Software for Signal Decoding

 

 Introduction

Another branch of the hobby I have enjoyed for many years now has been detecting and decoding digital data and messages that are all over the airwaves. I thought it would be a good idea to list some of the excellent free software available on the internet, and share a few hints and tips. (I have included a list at the end of this article with links) It can be very satisfying knowing that you have tuned into a signal and decoded it when you were never meant to! 

RTL-SDR

 By far the cheapest, easiest and most convenient way for anyone to enter into the world of radio frequency scanning is to use a USB dongle plugged into your computer. Usually referred to as RTL-SDR dongles. These cheap devices were first manufactured to receive free-to-air TV broadcasts for a computer. Some bright spark realised that by employing software to 'hack' the tuner inside, they could be repurposed as a handy radio receiver. Since then, manufacturers have cottoned-on to the idea and now they are modified and sold as RTL-SDR instead of DVB-T sticks. This means that the prices went up, but they can still be found for a modest sum. In my experiences the best ones have the RTL2832U chip. On the down side, these radios cannot compare with a dedicated scanner for sensitivity and reception, but they are less expensive. 

Uniden make a good range of dedicated scanners both home-base and portable.

Antennas

The frequencies that you wish to tune into will determine the type of antenna you will need. Alternatively, you could go with a broadband scanning antenna which will cover many frequencies, but these tend to be more expensive to purchase. like the one pictured here. However, for more specific decoding the antenna will have to be more specialised.  You can always 'home brew' an antenna, and it's surprisingly easy, the simplest being a wire dipole. There are many articles on making your own antenna on line, so I won't go into that here. The main requirement is that, if possible, get the antenna erected outside and as high as possible for best reception. Antennas do work quite well in an attic space, but it will fare much better outside.

AIRBAND & VHF

Where to start, well the list is virtually endless. Let's start with the VHF (Very High Frequency) band that everyone should be familiar with. We are all used to listening to radio stations on FM (Frequency Modulation) between the frequencies of 88 and 108 MHz. But if your radio can tune in just above this range, you will find all kinds of radio traffic. For a start, you can hear the Air Band chatter between aircraft and air traffic control on AM. Search around on this band and you will also hear some brief screeching sounds at 131.525, 131.625,131.725 and 131.825 MHz AM (Amplitude Modulation) These are the sounds of ACARS (Aircraft Communication Addressing and Reporting System) messages sent from aircraft transponders. With the correct decoder you can position aircraft on a map to do some plane spotting, if that's your thing. There are also lots of Amateur Radio operators chatting on this 2m band on FM. Also on the 2m band you will find pager communications, weather satellite transmissions, taxis and a whole lot of other stuff. Moving down to the lower limits of the rtl-sdr dongle, CB transmissions can be received between 27 and 28 MHz. This is the 10m band so a longer antenna will be required. At around 137 to 138 MHz you can hear APT (Automatic Picture Transmission) satellite transmissions from weather satellites at certain times during the day. These can be decoded into pictures that are really impressive using WXtoIMG. Your receiver must be set to receive FM at a bandwidth of about 40KHz though. Your SDR, when set up, will be able to manage this easily. This program also lets you know when they are flying over.

HF

If you have a radio receiver capable of getting the HF (High Frequency) bands, this is where the fun really starts. An SDR dongle is not capable of tuning down to lower frequencies below about 24MHz, unless it is modified in some way with a converter. On these bands you will find radio hams exchanging digital and voice communications between each other 24/7.  Morse code, FT4, FT8, RTTY and many others. HFDL (High Frequency Data Link) from aircraft can be decoded giving positions of aircraft all over the world and not just within your own country. Using HF bands increases your range for scanning. It is possible to find Stanag 4285 transmissions from NATO stations, however this is usually encrypted, except for when a test transmission is sent. The French Navy are favourites for this.

This is a decoded test signal using Sorcerer.

 WEFAX (Weather Facsimile Picture Transmission) signals can be found on several frequencies. 7.878 MHz USB finds the Deutscher Wetter Dienst WEFAX transmission. I used FLDIGI to decode it into picture format.

 

 

 

 

 

 

 

 

 

 

 

There really is too much to mention here because each mode is worthy of an article on its own. But its all there to be listened to with the right decoders. Some of the decoders listed here are capable of many modes. A lot of research is required to find information on how to do it, but it all depends on what you want.

Software

Here you can find links to download your free software. All the decoders here can use your sound card as a modem for decoding. If you are serious about decoding, there are many excellent non-free packages for sale that you may want to consider.

 

You will need to install a different driver for your dongle, otherwise your computer will still think that it is a DVB-T stick. Use Zadig to install the correct driver.

 

You'll be needing a software defined radio. HDSDR  is the simplest and quickest way to get going.

For HDSDR to work with your dongle you will need an ExtIO.dll file. It can be difficult to find this file and you may have to install a different package just to extract the dll. After you have installed HDSDR, find the HDSDR program folder on your computer and copy the ExtIO.dll file there or it will not work. There is a good set-up guide on this page with links HDSDR Set-Up

Another free SDR to consider is Sigmira which has a selection of decoders built-in.

If your sound card doesn't support Stereo Mix or similar, no need to worry. Just install this virtual sound card software and it will pipe the sound from HDSDR to your decoder when selected VB-Audio

 

When you finally get up and running and are ready for some decoding, it helps greatly knowing what a particular signal actually sounds like. Signal ID Wiki can help you here.

 

wxtoimg is the best software for decoding satellite images 

 

FLDIGI has a wealth of decoders built into it including WEFAX, Morse and RTTY.

If you want to decode ADS-B 1090 MHz signals for aircraft tracking try this RTL1090 . This is a stand-alone program which connects directly to the RTL-SDR dongle, so no sound card set-up required. 

You can then feed the output of RTL1090 straight into your very own Aircraft Radar with VRS

 

If you do want to work HF signals, Sorcerer is a good decoder for HFDL, Stanag and many others.

Other software you may be interested in:

WSJT-X for ham band decoding of FT4, FT8 etc.

MSHV same as above.

PDW for ACARS and pager decoding.

 

Reflecting on The Story So Far....

 

Since acquiring my Amateur Licence in June this year, I have accumulated a few bits and bobs, and lost a few quid! It makes me wonder what it will be like a few years down the line! My (untidy) set-up can be seen above. Simple but effective. The Icom IC-7300 has many features built-in which reduces the number of accessories I need. The computer takes care of the rest. I bought a SWR / Power meter because I wanted a second opinion on the power output, but it turns out I could have saved myself some money. The readings always correlate. It will come in useful though for doing remote power readings with the dummy load. The Nano-VNA has been a good investment. It has proved very useful for testing antennas, baluns, ununs and transformers. The power supply upgrades are a triumph, giving me important feedback on power supply parameters.

I have made several antennas, but as the hobby dictates, you are never satisfied with what you have. I like to make my own gear where possible because of the learning experience. The EFHW antenna has been marvellous. I am making contacts as far away as Africa, South America, USA, Australia and New Caledonia. You soon learn that the simplest solutions are usually the best. The search for constant improvement goes on. I am enjoying the hobby so far, but the dream would be to have plenty of space to erect a tower and have an array of antennas high up. Perhaps a move to the countryside?

I think the power allowance for Foundation Licence holders at 10 Watts is too low. I mean, even users of the Free Band on 27MHz are allowed 12 Watts SSB with no licence required! It is a struggle to get a voice QSO at all! I understand that the need for reducing interference is critical, but if you cause interference, no matter how much power you are using, you are obliged to put it right. Most foundation licence holders have usually had a good grounding with CB etc. so its not like they are coming in totally green. Modern TV's and other equipment is far less prone to RFI these days anyway. It seems I am consigned to using digital for weak signals for the time being. I may look into upgrading my licence to Intermediate next year, just so I can operate with a better power level.

End Fed Half Wave (EFHW) Antenna

 

 Ever since I saw a video of someone with this antenna operating portable on 20 Watts I have been compelled to build one. He was making contacts all over the place with it just slung over a couple of trees. This is a 1/2 wave resonant antenna for 40m, but should also be good at the harmonic frequencies too, making it somewhat multiband. There are lots of resources on line about these antennas and I recommend some research is done before attempting the build. The 49:1 unun in particular needs to be studied because it isn't straight forward. The 9:1 and 16:1 ununs and transformer types I have employed before will not suffice for this project. They will be too lossy and inefficient at this ratio with a resonant antenna.  Capacitors need to be employed to improve SWR and performance on the higher bands. (counter-acting the inductance at higher frequencies)

(Diagram of 49:1 unun)

I am only using low power so just one toroid core should suffice. It seems that the higher the power, the more cores you will need, and the transformers can get hot. I have seen people opt for the FT240-31 core, but after researching the differences between type 31 and type 43, I decided to go with the recommended type 43 core. The capacitor required is a 100pF high voltage type which I found to be expensive compared to the 220pF of similar spec. I acquired some 220pF 15kV ones. If I connect two in series the capacitance will be halved and the working voltage will be doubled resulting in a 110pF at 30kV rating (belt and braces). Also, if your wallet allows, the theory is that using two toroids makes the transformer more efficient, especially at lower frequencies. Your choice. Theory also dictates that a good ground is required, however, with the right length of coax, the coax screen can act as a counterpoise because the current flow will be minimal at resonance. Some experimentation is required here. It might be that a counterpoise wire will be required on the ground connection, anything from 1m to 10m long. A good ground plane system can also be used if available. My finished project can be seen below.

I am assuming it will be good up to 50 Watts, but if the SWR drifts at higher power, this could be a sign of over-heating.

The box will have to be at least 100mm square. Mine is about 115mm square. There is a terminal post on the left for the antenna radiator. A link was made to a terminal post on the right to accomodate a ground / counterpoise connection.The two capacitors can be seen connected at the SO-239 socket, with some hot glue as a make-shift insulator on the joint.  I have left two large holes at the bottom for cooling / ventilation. I need to cover these with some kind of gauze to keep nasties out. I initially intend to house the box indoors. Just needs the 20m radiator wire erecting and we should be good to go. I want to construct a pulley and weight arrangement at the far end of the wire to maintain tension and prevent breakage in high winds.

Results and Testing

I can just fit a 20m wire from near the top of the roof to the diagonal corner of the garden. There is about 3m of radiating wire in the loft making connection to the box and counterpoise. A post was erected in the corner with the pulley attached at the top.

A piece of nylon rope was threaded through the pulley and connected to the wire.

The weight, a plastic bottle with just enough water to hold the wire tight, was tied to the rope and tension was achieved.

The theory is that any extra tension on the rope from high winds, temperature expansion / contraction or perching birds will allow the weight to rise and fall accordingly, relieving the strain on the wire. I think the antenna would perform much better if higher from the ground. At the moment it stands at about 12 feet at its lowest, rising to about 25 feet. 

Results

After experimenting with various counterpoises, 2m, 3m and longer lengths, I settled on a 1m length of wire. I really didn't know where to check the SWR for adjusting, so I decided to check at 14MHz, which is a full wavelength. The reading was about 1.5 after snipping about 6 inches off the radiating wire. Further cutting of about 2 inches caused the SWR to rise a small amount, so I decided not to trim the wire any more. I also experimented with varying the capacitance value from 220pF to 110pF, 73pF and no capcaitor at all. Some interesting and weird results were obtained. Using 220pF flattened the SWR peaks, but raised the overall SWR over the bands. 73pF raised all the readings. So I settled with the design spec of 110pF. At one point I was also getting gradually rising and falling SWR values at the higher frequencies which I couldn't explain. I guess it was something to do with changing the capacitor values, or a dodgy solder connection. The analyser results pretty much reflect the results from the radio SWR readings. Obviously, looking at the graphs, the SWR will be lowest where the impedance is 50 ohms.

(Analyser results - 1.8MHz to 30MHz sweep)

Final SWR Readings

1.8MHz = 2.9

3.5MHz = >10 (useless)

  7MHz  = 1.9

10MHz  = 1.6

14MHz  = 2.1

18MHz  = >10 (useless)

21MHz  = 2.2

24MHz  = 3

28MHz  = 1.7

Conclusions

The final results I obtained are far from perfect with respect to SWR, but the antenna is very effective when used with the internal ATU. It was immediately apparent that the received signals sounded much better and clearer compared to my other antennas. It would also seem that the antenna works better at long distances rather than closer to home, judging by the signal reports. Contacts with USA for example, are much easier to get now, but I can still make contacts across the UK. I will have to do without the 3.5 and 18MHz bands for now until I come up with a solution. The problems must lie with the transformer build. I might try a different approach in the future. Generally very impressed with this antenna, once again proving that the simplest methods are usually the best. 

 

 

Update - September 2023

Just for the hell of it I decided to take apart the 49:1 unun and add another ferrite core to see if there would be any difference. Apart from a possible increase in power handling ability, its hard to see any real improvement with performance. No improvement with the higher SWR readings on the lower frequencies. However, I can now tune the 18Mhz band. I found a small improvement by disconnecting the counterpoise. I also noticed that after moving things around in the loft, there was a change in readings. This reinforces the fact that you shouldn't have any objects close to your antenna. My situation isn't ideal because part of my antenna is in the loft! On the positive side, all the frequency bands above 3.5MHz fall below the 3:1 threshold. This is still my best performing antenna. So my advice would be that if you are only running up to about 50 Watts, then I think you would be OK with just one ferrite. Above this, you probably need two. Below is the full band sweep from the antenna analyser.

Dummy Load 50 Ohm 50 Watts

I thought it would be useful to have a dummy load to take power measurements. Rather than buy one I decided to make my own (as usual!) I purchased 10 x 470 Ohm 5 Watt Metal Oxide Film resistors. They are low inductance which is very important at RF. My power is limited but I decided to make it rated for 50 Watts. 10 x 470 Ohm in parallel gives 47 Ohms nominally. Parallel connection means that the power rating becomes 10 x 5 = 50 Watts nominally. (I read one article online which stated 4 x 100 Watt resistors in series gave him 400 Watts. This is incorrect! A common mistake.) The main problem I find with most projects is the hardware, in particular, cases and enclosures. Mooching around, I found this sewing tin with a hinged lid. Using a metal enclosure ensures good screening and prevents any transmissions radiating from the unit. A quick inspection found that the SO-239 socket would just fit on the side, provided I cut the lid away to allow it to close. The metal is very thin, so care is needed when drilling the holes. Sharp drill bits and proper support whilst drilling is the key. When assembled I measured the DC resistance with a multimeter at 47 Ohms. I'm not sure how accurate my multimeter is.

                                        

I assembled the project in about 2 hours. The tin made for a neat compact unit. everything just fit inside really snug. Total cost was about £6.00. A lot cheaper than the commercial ones and it is rated at 50 Watts.

The resistors were all soldered onto 2 pieces of solid copper wire and covered with heat shrink sleeving. A bit of hot glue secured everything in place. The hot glue you can see on top is covering the centre feed wire to the SO-239 to prevent any accidental short circuits. The ground wire was attached via a small crimp-lug and bolted to the holding screw. On reflection, I could have put some sleeving over the wires. I've tested it up to 20 Watts on all HF frequencies and the SWR reading does not change from 1:1. If operating at higher powers, the tin could be filled with dry sifted sand to dissipate heat, and then sealed up.

Update:

I did fill it with sand and seal it up because I noticed that it got quite warm when testing up to 25 Watts. Hopefully, problem solved.

14MHz Coil Shortened Dipole

 After a multitude of antenna builds using other people's designs, I thought it was time I designed my own from scratch. I decided a single frequency would be best to start with so I chose 14MHz because of the amount of traffic on this band. I think it's so popular because the antenna size is not too large to construct especially in a confined area. I looked at trap dipoles and the like and the art of shortening using coils. My final design would be a 6 metre long dipole so that it could be formed into an Inverted V to join my nest of dipoles in the loft. The coils were calculated for a 20mm former and came out at 6.68uH - 25 turns of 1.13mm diameter insulated solid copper wire, at 14.15MHz centre frequency. I decided to centre load the elements.

Testing

14MHz = 1.1:1

Bonus: 50MHz = 1.7:1(ATU) 

I had to add about 100mm to each end to get the SWR down. This means the calculations, or the interpretation of them, was in error. The measurements were made to the centre of the coils which is probably incorrect. When tested at 50Mhz, it was found that the SWR was a useable 1.7:1. I suppose the antenna has a tuneable harmonic.

Contacts made:

Croatia -6dB    Poland -15dB    Germany -11dB    Belarus -12dB    France -12dB

Hungary -17dB    Croatia(2) -13dB    Hungary(2) -11dB  (All on FT8)

Spot Reports for 14.074MHz FT8:

Conclusions

The SWR readings achieved were to be expected. This is a single frequency antenna with a comparatively narrow bandwidth. The Inverted V angle was very large, probably greater than 120 degrees. If this antenna was erected outdoors, the performance would be much better. Loft antennas tend to perform a lot worse. It seems to be working very well though and I will keep this antenna on-line for using on a regular basis.