After initially finding that I couldn’t tune the 868Mhz ground plane antenna with the radials bent down at 45 degrees I decided to experiment to find out why.

Initially I had the radials connected to the 4 corners of the base of the chassis mount N Type socket. This works great if you have the radials completely horizontal and gives an SWR of 1.1:1 but, with the radials bent down at 45 degrees the best SWR is around 2:1.

Removing the radials from the base of the N Type chassis socket and soldering them to the outer of the N Type plug at the same level as the feed point for the radiating element I found that an almost perfect SWR can be achieved very easily.

It seemed weird to me that such a small change could have such a big effect on the obtainable SWR for the antenna but, as can be seen in the image below with the radials soldered to the N Type plug and bent downwards I immediately got an SWR of 1.07:1 and a much wider SWR curve.

By making my own antennas I’m learning a lot about antenna design for the 800-900Mhz frequency range. Minor changes seem to have a much bigger impact than they do at much lower frequencies.

More soon …

This is a question I get asked regularly via email and so I decided to post this article so that I can refer to it in future emails.

Callum of DXCommander fame has just published a great video explaining the difference between dBi and dBd that is well worth watching if you don’t understand the difference between the two.

More soon …

In my quest to improve my Meshtastic signal range using home-brew antennas I’ve finally put together a neat little ground plane vertical antenna for the 868Mhz ISM band.

The design follows the normal ground plane simplicity using 4 radials and a vertical radiating element albeit on a tiny scale. The radiating element is 82mm long and the radials are each 92mm long.

Initially I modelled the antenna at a height of 3m above the ground with the radials tilted downwards at 45 degrees. I took this approach as this is how I have built ground plane verticals for the 70cm band in the past and so I thought I’d try the same approach on the 868Mhz ISM band. (I later found this to be detrimental to tuning!)

The 3D far field plot for the antenna shows it has a very nice, relatively high gain lobe at just 2 degrees elevation with a number of lower gain lobes higher up.

Looking at the 2D far field plot you can get a better understanding of the radiation pattern and gain figures at various angles. At 2 degrees there is 6.7dBi gain with the next major lobe being at 8 degrees with 4.36dBi gain, far more than I imagined I’d see for such a simple antenna.

Putting the antenna together was easy enough with particular attention being paid to the measurements of both the radials and radiating element. I soldered some lugs to the ends of the 2.5mm diameter solid core wire radials to enable easy attachment to the N Type chassis socket that I decided to use as the base for the antenna. This worked out well and provided a good solid mechanical and electrical connection for the 4 radials.

For the radiating element I used an N Type plug with the vertical 2.5mm solid core wire element soldered to the inner centre pin of the male connector. I also slid a small piece of insulation down the wire to stop it from shorting against the metal outer of the plug and then pushed in a tight rubber plug to stop water ingress.

Connecting my VNA I found the antenna was mostly resonant at 790Mhz with an SWR of 2.5:1. I knew this would be the case and that the wires would need a little trimming.

Trimming the wires a couple of times in 1mm nibbles I got the point of resonance up to 868Mhz but, the antenna was still exhibiting a lot of reactance that was keeping the SWR above 2:1. Trimming the radials reduced this slightly but, I could not get an SWR much lower than 1.95:1.

Scratching my head I decided to try moving the radials back up so that they were horizontal rather than at 45 degrees downwards, this had the immediate effect of the SWR dropping to 1.1:1.

The SWR stays below 1.2:1 from 868Mhz to 871Mhz which is plenty wide enough for the Meshtastic devices. Why there is so much reactance when the radials are bent down at 45 degrees I am not sure, but it was easy enough to resolve.

The finished antenna is tiny but, seems to work well. Signals from my other nodes are up by 6-9dB according to the SNR reports in the Meshtastic app. I now need to make a couple more of these for my other nodes and then hope to hear some other nodes locally once they appear on air.

Remodelling the antenna in EzNEC with the radials as shown above the gain at 2 degrees is now 5.5dBi, down 1.2dBi but, the overall radiation pattern is identical to the original.

Total cost of the build is about £1 and an hour of my time tinkering with it, bargain!

More soon …

This antenna modelling session came about after a conversation with Michael, DK1MI on the Matrix. I believe the antenna design was originally done by Artur, M0PLK with reviews being on EHAM.

The antenna takes the form of a simple inverted triangular loop with a 5.8m flat top and two diagonals each 5.6m long coming down to a point. The antenna is fed in the centre of the flat top with 450 Ohm open ladder line and a 4:1 Balun. This antenna will require an ATU on all bands as the modelling shows a very wide range of impedances at the feed point.

The design seems to suggest using two fixed aluminium tubes with the wire fed up through them for the two diagonal elements of the antenna however, it would probably be easier to use a pair of collapsable fibre glass poles (Not Carbon fibre) with the wire attached via some clips or tape.

I decided to model the antenna with the top horizontal wire 10m above ground putting the point of the triangle 5.2m above ground. I felt this was an achievable height for most HAMs. Lowering the antenna will raise the resultant angle of maximum radiation on all bands.

Looking at the 2D Far Field Plots (2DFFP) the antenna radiates through the loop as expected with a higher radiation angle on the lowest band and the lowest radiation angle on the highest band. The antenna is of course bi-directional and so could be rotated just 180 degrees to obtain global coverage.

On the 30m band the antenna has a very high angle of maximum radiation making it ideal for short distances. There is a little gain to be had at 25 degrees however, this is nowhere near the maximum but, will possibly aid working longer distances. A maximum gain of 5.31dBi is obtained at 72 Degrees on the 30m band.

On the 20m band the 2DFFP is fairly similar to that of the 30m band but, with 5.57dBi gain at a lower angle of 34 Degrees. This will provide excellent results on medium distance contacts and reasonable results on the long haul.

Once above 14Mhz things start to get more interesting. From the 17m band upwards the radiation pattern changes quite drastically and starts to provide some excellent gain at relatively low angles. This will improve the antenna’s DX performance considerably on the higher bands.

Looking at the 17m band the angle of maximum radiation is now down to 26 degrees with a gain of 7.64dBi. At 12 degrees there is a gain of 4.59dBi. This radiation pattern will make this antenna ideal for the medium to long haul contact with very little interference from NVIS signals.

The 15m band follows the trend with the angle of max radiation now down to 22 degrees with a max gain of 8.54dBi. Even at 10 degrees there is a gain of 5.34dBi which will be very welcome for DXing. There is slightly more near vertical incident skywave (NVIS) radiation on the 15m band and so the antenna should provide short, medium and long haul contacts with the latter being favoured.

Moving up to the 12m band the angle of maximum radiation now comes down to 18 degrees with a gain of 8.61dBi. There is also 5dBi of gain to be had at 8 degrees which is ideal for DXing. Unfortunately there is slightly more NVIS radiation on the 12m band than there is on the 15m band. I’m sure with a little change in height this could be reduced such that the antenna provides only low angle radiation.

Finally we reach the 10m band, this is where the antenna has the lowest angle of maximum radiation. With 8.56dBi gain at 16 Degrees, 5.59dBi at 8 degrees and a much reduced NVIS radiation. This antenna should be excellent for the long haul on 28-29Mhz. (It would also make an excellent 11m/CB antenna).

It’s interesting to note the similarities between this multi-band delta loop design and my Bi-Directional Slot Fed Antenna design. They both exhibit very similar radiation patterns and gain figures with the Slot Fed Antenna providing slightly more gain and an even lower angle of maximum radiation on the supported bands.

Overall this easy to construct multi-band delta loop antenna would be ideal for the HAM that just wants a single antenna for 30m and upwards or is looking to go portable. The only disadvantage is that a good Remote Auto ATU is required to provide matching of the antenna to the 50 ohm coax at the feed point. Something like the LDG RT100 would be an ideal ATU choice for this application and would remove the losses caused by having a high SWR on the coax feed to the antenna.

Using an ATU in the radio in the shack isn’t going to provide the same results as the coax cable from the antenna to the shack will become part of the antenna and will be detrimental to the antenna performance. It will also create high losses on the coax feed to the antenna due to high SWR being present over the length of the coaxial feed.

I’ve been doing some antenna modelling and comparisons for John, W2VP comparing some phased and parasitic arrays. One of the phased arrays I modelled was an End-Fed-Half-Wave (EFHW) phased vertical array for the 40m band. It’s got such a nice radiation pattern that I thought I’d add it to my antenna pages here on the website for others to read too.

The EFHW Vertical Phased Array is as simple as two vertical half wave wires both of which are fed via their own 49:1 Unun. Wire 1 (radiator) is exactly 20m tall and wire 2 (reflector) is 21m tall. The space between them is exactly 10.5m.

This simple antenna arrangement gives a surprisingly good radiation pattern with a reasonable forward gain and front-to-back (FB) ratio.

The antenna has quite a wide beam width which is to be expected from a pair of phased verticals. The nice thing about this array is that it has very little in the way of high angle radiation. This makes this antenna ideal for long distance communications. This isn’t an antenna for local chatter!

The 2D Far Field Plot shows that the antenna has a forward gain of 3.16dBi at 19 degrees. This is some 8 degrees lower than a typical 1/4 wave vertical phased array. The array also has a very respectable front-to-back (FB) ratio of 20.53dB.

Both elements in the array will need to be fed via individual 49:1 Ununs with the reflector requiring a feed phase angle of 100 degrees. A 100 degree phase angle gives better performance than the typical 90 degree phase angle that is typically used for 1/4 wave arrays.

For such a simple design this antenna should give great DX results as long as you have the necessary supports for the two vertical wires and the space for the guy lines. If only my garden was much bigger and I had some large trees to hand!

Summary:

Radiator (Element 1): 20m
Reflector (Element 2): 21m
Reflector Feed Phase Angle: 100 Deg
Wire Dia: 4mm
Feed Type: 49:1 Unun on each vertical element and a phasing harness
Impedance: 50 Ohm
SWR: <1.5:1 across whole band

Following on from the article I wrote about the performance of my multi band vertical antenna I’ve now put together a table showing it’s performance on each band as experienced over a period of 18 months.

It’s interesting to note the antenna wavelength measurements on each band as 13m (43FT) seems to be an almost perfect length for a simple multi band vertical HF antenna with excellent DX capabilities.

Looking at the information you can see that performance on the 160m band is poor. This is to be expected as the antenna is far too short for a band with such a long wavelength. I knew this would be the case from the outset and never planned to use this antenna on the 160m band. I’ve included the data here just for completeness. If you’re looking for a reasonable 160m band antenna that can fit into an average UK garden then take a look at my Inverted-L antenna article.

Performance on the 80m band is surprisingly good considering the antenna is only 1/6th of a wavelength long. With contacts into Indonesia achieved using relatively low power levels this antenna surprised me with its performance on the 80m band. A 1/4 wavelength antenna would of course perform better but, like all multi band vertical antennas for the HF bands there is always a compromise.

On the 60m band the antenna is pretty much a 1/4 wave vertical, it works great on this band and I’ve had a lot of fun chasing DX in the winter months. With the longest contact being into Brazil at 6144 miles this antenna performs extremely well for such a simple design.

On the 40m band performance is better still. With the antenna being just over a 1/4 wavelength long the point of max current is above ground level making this a very good DX antenna. With multiple contacts into Australia at distances over 10,000 miles this antenna is the ideal 40m band DX chaser for small gardens.

Moving up onto the 30m band this antenna now begins to really shine. Being a half wave long on 30m the point of max current is half way up the wire lowering the angle of radiation considerably. This results in excellent global coverage with contacts into Australia being a breeze. With the longest distance achieved being 11,776 miles into New Zealand this really is the goto antenna for fans of the 30m band with small gardens. This antenna easily out performs my 30m band Delta Loop design whilst giving better global coverage.

On the 20m band this antenna performs very well indeed. Considering it’s 3/5th of a wavelength long which is a strange length to have, it’s no slouch. Global coverage is excellent and working into Australia is relatively easy. I’ve yet to work into New Zealand on the 20m band using this antenna but, that’s mainly due to me not being on air at the right times. Best distance worked so far on this band is 10,656 miles.

On the 17m band the antenna is 3/4 wavelength long. This is a very useful length and easy to tune as it presents pretty much 50 ohm impedance at the feed point. Performance is simply stunning on 17m, if you can hear the DX you can work them. I am amazed at how well this antenna works on this band. It seems to have a low angle of max radiation making it excellent for chasing DX stations. Giving me my first contacts into Alaska and New Zealand this is my goto antenna for the 17m band.

On the 15m band this antenna is 7/8th of a wavelength long. Performance doesn’t feel as good as it does on 17m but, with the longest distance achieved being 8023 miles there’s really no reason to doubt it. With only 87 contacts being made on this band due to the fact that I always get trapped chasing DX on the 17m band and never make it any further up the bands, I’m sure this antenna will perform extremely well long term on 21Mhz. I just need to make more effort to get on this band.

The 12m band is one of the bands I didn’t expect this antenna to perform well on.
Being 1 and 1/8th wavelengths long it’s not a length that you would normally consider using for an antenna however, performance is excellent. This is most likely due to the point of max current being a fair way up the wire resulting in a low angle of maximum radiation. DXing is great fun with this antenna on the 12m band and it’s surprised me time and time again at how easily I’ve been able to work DX stations. With the best distance worked so far being into the Falkland Islands at 7973 miles, this antenna has huge potential on this band. Like the 15m band, I need to make an effort to spend more time on the 12m band and see how far I can push this antenna.

Finally we reach the dizzy heights of 28Mhz on the 10m band where the antenna is 1 and 1/4 wavelengths long. Again this is a useful length as it presents almost 50 ohm impedance at the feed point. DX performance on the 10m band is good. It’s probably very good however, like the 15m and 12m bands, I rarely make it up onto the 10m band and so I’ve not really given the antenna the time to prove itself at 28Mhz. My best distance worked so far on this band is 4872 Miles into the USA but, I’m sure I could easily do better if I committed more time to it.

I’ve pretty much covered all the good points of this simple multi band antenna so, now let’s look at the not so good points.

If you’re in the UK and are looking to work other UK stations then this antenna isn’t for you. Like all vertical antennas there isn’t much in the way of NVIS radiation and so you’ll find UK stations just won’t hear you. You’ll also often find you won’t hear UK stations at all due to the null at the top of the antenna that attenuates signals arriving from high/very high angles. For me this is fine as I wanted an antenna that was focused on DXing as much as possible.

From 10Mhz upwards the antenna also isn’t that good for working stations in nearby Europe. Most of the time you will only hear European stations that are more than 1000 – 1500 miles away, anything closer just doesn’t appear in the receiver. On the 15m and 12m bands often you will never hear European stations at all, only DX stations. This does of course reduce the QRM from UK/EU stations considerably making it easier to work those weak/QRP DX stations.

So as you can see, 13m (43FT) of vertical wire is probably one of the best lengths you can possibly use for a multi band vertical HF antenna especially if like me, you have a small garden to squeeze your antennas into. I don’t like to say it but, this could be the magical length we’re all looking for when making a multi band HF vertical antenna.

Tuning of the 13m (43FT) vertical antenna is achieved using my CG3000 remote auto ATU. I initially started off using my home-brew Pi-Network ATU but, changed over to the CG3000 so that in the winter months I don’t have to run out into the rain and wind to change bands. It’s important to note that the ATU must be at the base of the wire and not in the radio shack. It’s also important to note that I have 4 x 20m long radials connected to the CG3000 along with an earth spike at the base of the wire. This combination of ground and tuner works incredibly well with the ATU tuning on each band with ease in less than 3 seconds. I’ve also not had any issues with the CG3000 attempting to retune whilst in the middle of a QSO, once it’s initially tuned it doesn’t retune again until I either change band or make a large change in frequency.

The achieved SWR on all bands is <1.5:1 except for 160m where it is 1.8:1.

More soon …

Since I put together my Inverted-L antenna and Pi-Network ATU I’ve been having a lot of fun on the low bands.

Getting back onto 160m has been most enjoyable and I’ve now had over 100 ‘Top Band’ contacts with distances covered as far as 3453 Miles into Sosnovoborsk Asiatic Russia.

I must admit I am amazed at the distances achieved on the 160m band as the antenna isn’t very high above ground level when compared to a single wave length on 160m.

The Inverted-L antenna at the M0AWS QTH was designed purely around the size of the back garden. Using a couple of 10m Spiderpoles the vertical section of the antenna is 10m tall and the horizontal section is 28m long. Naturally the antenna resonates around 2.53Mhz but, can be tuned to resonate anywhere on any band using the Pi-Network ATU I built that is situated at the base of the vertical section of the antenna.

Looking at the far field plots for the antenna on each band we see that as we move higher in frequency the radiation pattern becomes more complex and the radiation angle gets lower, exactly what we would expect from such an antenna. The antenna runs pretty much North/South in the garden ( X axis on the diagram above) and so we would expect the antenna to radiate East/West (Y axis on the diagram above) however, this isn’t always the case.

(Click Far Field Plots for full screen view)

On 160m the antenna favours the South (-X Axis) and presents some usable high angle gain although, from using the antenna you would never know this to be the case as it seems to have pretty good all round coverage. With the best distance of 3453 Miles being covered to the East into Asiatic Russia the antenna performs well even though the far field plot is slightly biased to the South.

On the 80m band the Inverted-L antenna becomes a cloud warmer and exhibits very high angle radiation. On 80m the antenna is ideal for NVIS Inter-G propagation and is great for rag chewing with other UK/Near EU stations.

Looking at the far field plots for the 60m band once again the antenna provides lots of high angle gain however, there is also some very useable lower angle gain that has proven to be excellent for working long hauls into North America and east into Central Asia. On the 60m band during the day the antenna is excellent for Inter-G chatting, using just 20w-40w I can very easily chat with other UK HAMs even when the band is noisy.

Moving on up to the 40m band we find the far field plot starts to get a little more complex. Looking at the 3D plot you’d think that the antenna favoured the South (-X Axis) however, in reality it favours the NorthWest with both some high and low angle gain. This antenna has proven to be excellent for DXing into North America on 40m but, has also been great for DXing into South America getting great signal reports from stations in Panama at a distance of 5415 Miles. During the day NVIS propagation is excellent and I find I can chat with other UK and near EU stations with ease using just 25w.

Above is a screen shot from PSKReporter showing stations that have heard me on the 40m and 60m bands. As you can see, global coverage is excellent with stations as far as Australia and New Zealand hearing me on the 40m band and stations on the West Coast USA hearing me on the 60m band. I was also pleased to see I was heard in Africa on both bands, a region of the world I would like to get more contacts from.

On the 30m band the Inverted-L antenna starts to exhibit two lobes with gain to the NorthEast and NorthWest. This makes the antenna ideal for working into the USA and Australia/New Zealand over the North Pole. Working US stations is a breeze with relatively low power and I almost got a contact with New Zealand during the evening greyline but, unfortunately the DX station dropped out before I managed to get my signal report back to him. As time goes on I’m sure the antenna will more than prove itself on the 30m band.

So far I’ve not ventured above the 30m band with the Inverted-L antenna as I’ve really been enjoying access to Inter-G chats on 80m, 40m and 60m and chasing DX on 160m, 60m, 40m and 30m. I need to venture up onto the higher bands before the long winter nights settle in and the higher HF bands close for the winter season.

Looking at the far field plots on the higher HF bands the antenna has huge potential as it provides some nice low angle radiation in useful directions.

On the 20m band the far field plot starts to get much more complex with lobes at many different angles. The main gain lobe is to the NorthEast towards the USA and is at a fairly low angle and so this antenna should be great for working stateside on the 20m band. There are also lobes to the NorthEast and so hopefully working VK/ZL over the pole should also be possible. As I said above I’ve not yet used the antenna above the 30m band and so at this time cannot confirm performance but, it looks promising.

The 17m band also looks promising with a similar far field plot as the 20m band but, with lower angle of maximum radiation and more gain. It will be very interesting to test this antenna on 17m especially since the noise level is below S0 and I can very easily hear the weakest of stations on this band.

Once again the 15m band looks very similar to the 17m band, low angle radiation but, with a slightly more complex far field plot.

The 12m band far field plots continue the theme with the angle of maximum radiation slightly lower than on the 15m band and slightly more gain. This antenna should be great for chasing the DX on the very quiet 12m band.

Finally the 10m band is very similar to the 12m band in that the far field plots show low angle gain albeit with an even more complex radiation pattern.

I originally put this antenna up so that I could work Inter-G on the low bands but, it has proven to be a much more worthy antenna than I originally thought it would be. I need to spend more time with this antenna on the bands above 30m to really see how it performs on the higher HF bands but, so far I’m really pleased with it’s overall performance on all the bands tested to date.

I can highly recommend using FT8 to test new antennas. With PSKReporter and my own NodeRed World Map WSJT-X interface I can see realtime the antenna performance on each band. FT8 is an extremely useful tool when it comes to testing antennas to see if they perform as per the modelling and can often provide some performance surprises!

More soon …

I recently put up a 38m Inverted-L antenna (10m vertical/28m horizontal) and tuned it on the 160m band using a home-brew Pi-Network ATU. It’s working great on top band and I’m really pleased with performance so far.

I decided today that it would be good to try the inverted-L out on some of the other low bands too. Since my other HF antenna is a large vertical that’s great for DXing but, terrible for Inter-G I thought perhaps the Inverted-L would fill the inter-G gap.

Having recently purchased a JNCRadio VNA from Martin Lynch and Sons it made tuning the ATU for each band really easy. When it comes to antenna resonance I like my antennas to have an SWR of less than 1.2:1. With the VNA connected it is really easy to tune the antenna for a 1:1 SWR on a particular frequency, make a note of the tune information and then move to the next frequency and start again.

I marked up each turn on the large copper inductor so I could record the position of the input wire onto the inductor. I then added some markings on the two capacitors of the Pi-Network ATU for the resonance points on each band/frequency I wanted to resonate the antenna on.

After about 40mins I had all the settings recorded on a pad ready for testing from the shack end of the coax run. Connecting my Yaesu FTDX10 to the coax I ran through each band setting checking the SWR as I went. All bands tuned up perfectly 160m through 30m and receiving of Inter-G on the bands that were active was excellent.

Wanting to test the antenna on 40m for the first time I found Nick, M7NHC calling CQ and gave him a call using just 5w output. He came straight back to me and we had a quick chat.

Nick was using an Icom IC-7300 using just 10w into an end-fed long wire from Eastbourne down on the south coast so, we were both QRP. Nick was a 5/7 with QSB and he gave me a 5/8 with QSB, not bad at all consider how much power we were using.

I’m hoping to have a chat with some of the guys from the Matrix this evening on 60m SSB so, it will be interesting to see how the antenna performs on 5Mhz.

More soon …

I’ve had this antenna model for ages now but, never got round to putting it onto the website until Alex, GM5ALX was talking about making one the other day whilst chatting on the QO-100 satellite.

The 20m band delta loop follows exactly the same design principles as all the other delta loop designs I’ve already put on the website. They are designed such that they present a 50 ohm impedance at the feed point and thus have no requirement for complex impedance matching circuits/transformers.

The dimensions for the antenna are as follows:

Wire 1 – Horizontal exactly 1m above the ground for its entire 10.2m length.
Wires 2 & 3 are exactly 6.18m long each with the top being 4.5m above the ground.

The 3D far field plot shows a typical delta loop radiation pattern with the maximum radiation through the loop and a deep null in the centre.

The 2D elevation plot shows that the antenna will give a maximum gain of -0.79dBi at 30 degrees when used over average/poor soil types. If like me you use your Delta Loop antennas on the beach then the antenna will present considerably more gain as it will benefit from the salt water reflection.

If you want to lower the angle of maximum radiation and increase the gain over average ground just raise the antenna up so that the top is around 7m above ground. This will give a much lower angle of radiation and improve the gain figure by 2-3dBi. Don’t forget that if you raise the antenna the point of resonance will also rise in frequency and so you may need to shorten the wires a little to get the point of resonance back to where you want it.

The SWR plot shows that the antenna will have a fairly wide bandwidth and match to 50 ohm coax extremely well. The antenna is designed to be fed in one of the lower corners via a 1:1 balun for best results.

Summary:

Total Wire Length: 16.38m
Horizontal Wire Length: 10.2m @ 1m above ground
Diagonal Wire Lengths: 6.18m
Wire Dia: 2.5mm
Height at Centre: 4.5m
Feed Type: 1:1 Balun in bottom corner (Can use coax if necessary)
Impedance: 50 Ohm
SWR: <1.5:1 at resonance

Since setting up the new HAM station here in the UK the one band I’ve not yet got back onto is 160m, one of my most favourite bands in the HF spectrum and one that I was addicted to when I live in France (F5VKM).

Having such a small garden here in the UK there is no way I can get any type of guyed vertical for 160m erected and so I needed to come up with some sort of compromise antenna for the band.

Only being interested in the FT4/8 and CW sections of the 160m band I calculated that I could get an inverted-L antenna up that would be reasonably close to resonant. It would require some additional inductance to get the electrical length required and some impedance matching to provide a 50 Ohm impedance to the transceiver.

Measuring the garden I found I could get a 28m horizontal section in place and a 10m vertical section using one of my 10m spiderpoles. This would give me a total of 38m of wire that would get me fairly close to the quarter wave length.

For impedance matching I decided to make a Pi-Network ATU. I’ve made these in the past and found them to be excellent at matching a very wide range of impedances to 50 Ohm.

Since I still had the components of the Pi-Network ATU that I built when I lived in France I decided to reuse them as it saved a lot of work. The inductor was made from some copper tubing I had left over after doing all the plumbing in the house in France and so it got repurposed and formed into a very large inductor. The 2 x capacitors I also built many years ago and fortunately I’d kept locked away as they are very expensive to purchase today and a lot of work to make.

Getting the Inverted-L antenna up was easy enough and I soon had it connected to the Pi-Network ATU. I ran a few radials out around the garden to give it something to tune against and wound a 1:1 choke balun at the end of the coax run to stop any common mode currents that may have appeared on the coax braid.

Connecting my JNCRadio VNA I found that the Inverted-L was naturally resonant at 2.53Mhz, not too far off the 1.84Mhz that I needed. Adding a little extra inductance and capacitance via the ATU I soon had the antenna resonant where I wanted it at the bottom of the 160m band.

With the SWR being <1.5:1 across the CW and FT8 section of the band I was ready to get on 160m for the first time in a long.

Since it’s still summer in the UK I wasn’t expecting to find the band in very good shape but, was pleasantly surprised. Switching the radio on before full sunset I was hearing stations all around Europe with ease. In no time at all I was working stations and getting good reports using just 22w of FT8. FT8 is such a good mode for testing new antennas.

As the sky got darker the distance achieved got greater and over time I was able to work into Russia with the longest distance recorded being 2445 Miles, R9LE in Tyumen Asiatic Russia.

In no time at all I’d worked 32 stations taking my total 160m QSOs from 16 to 48. I can’t wait for the long, dark winter nights to see how well this antenna really performs.

The map above shows the locations of the stations worked on the first evening using the 160m Inverted-L antenna. As the year moves on and we slowly progress into winter it will be fun to start chasing the DX again on the 160m band..

UPDATE 6th October 2023.
Been using the antenna for some time now with over 100 contacts on 160m. Best 160m DX so far is RV0AR in Sosnovoborsk Asiatic Russia, 3453 Miles using just 22w. Pretty impressive for such a low antenna on Top Band.

More soon …

This is a 15m band delta loop design that I’ve put together as requested by Wim, PE1PME.

The 15m band delta loop follows exactly the same design principles as all the other delta loop designs I’ve already put on the website. They are designed such that they present a 50 ohm impedance at the feed point and thus have no requirement for complex impedance matching circuits/transformers.

The dimensions for the antenna are as follows:

Wire 1 – Horizontal exactly 1m above the ground for its entire 7m length.
Wires 2 & 3 are exactly 4.12m long each with the top being 3.18m above the ground.

The 3D far field plot shows a typical delta loop radiation pattern with the maximum radiation through the loop and a deep null in the centre.

The 2D elevation plot shows that the antenna will give a maximum gain of 1.5dBi at 26 degrees with useful gain at lower angles.

The SWR plot shows that the antenna will have a fairly wide bandwidth and match to 50 ohm coax extremely well. The antenna is designed to be fed in one of the lower corners via a 1:1 balun for best results.

Summary:

Total Wire Length: 15.24m
Horizontal Wire Length: 7m @ 1m above ground
Diagonal Wire Lengths: 4.12m
Wire Dia: 2.5mm
Height at Centre: 3.18m
Feed Type: 1:1 Balun in bottom corner (Can use coax if necessary)
Impedance: 50 Ohm
SWR: <1.5:1 at resonance

Many years ago I had an MFJ-259B antenna analyser that I used for all my HF antenna projects. It was a simple device with a couple of knobs, an LCD display and a meter but, it provided a great insight into the resonance of an antenna.

Today things have progressed somewhat and we now live in a world of Vector Network Analysers that not only display SWR but, can display a whole host of other information too.

Being an avid antenna builder I’ve wanted to buy an antenna analyser for some time but, now that I’m into the world of QO-100 satellite operations using frequencies at the dizzy heights of 2.4GHz I needed something more modern.

If you search online there are a multitude of Vector Network Analysers (VNAs) available from around the £50.00 mark right up to £1500 or more. Many of the VNAs you see on the likes of Amazon and Ebay come out of China and reading the reviews they aren’t particularly reliable or accurate.

After much research I settled on the JNCRadio VNA 3G, it gets really good reviews and is very sensibly priced. Putting a call into Gary at Martin Lynch and Sons (MLANDS) we had a long chat about various VNAs, the pros and cons of each model and the pricing structure. It was tempting to spend much more on a far more capable device however, my sensible head kicked in and decided many of the additional features on the more expensive models would never get used and so I went back to my original choice.

Gary and I also had a long chat about building a QO-100 ground station, using NodeRed to control it and how to align the dish antenna. The guys at MLANDS will soon have a satellite ground station on air and I look forward to talking to them on the QO-100 transponder.

Getting back to antenna analysers, I purchased the JNCRadio VNA 3G from MLANDS at £199.96 + postage and have been trying it out on a couple of antennas here at the M0AWS QTH.

Initially I wanted to check the SWR of my QO-100 2.4GHz IceCone Helix antenna on my satellite ground station to ensure it was resonant at the right frequency. Hooking the VNA up to the antenna feed was simple enough using one of the cables provided with the unit and I set about configuring the start and stop stimulus frequencies (2.4GHz to 2.450GHz) for the sweep to plot the curve.

The resulting SWR curve showed that the antenna was indeed resonant at 2.4GHz with an SWR of 1.16:1. The only issue I had was that in the bright sunshine it was hard to see the display and impossible to get a photo. Setting the screen on the brightest setting didn’t improve things much either so this is something to keep in mind if you plan on using the device outside in sunny climates.

(My understanding is that the Rig Expert AA-3000 Zoom is much easier to see outside on a sunny day however, it will cost you almost £1200 for the privilege.)

A couple of days later I decided to check the SWR of my 20m band EFHW vertical antenna. I’ve known for some time that this antenna has a point of resonance below 14MHz but, the SWR was still low enough at the bottom of the 20m band to make it useable.

Hooking up the VNA I could see immediately that the point of resonance was at 13.650Mhz, well low of the 20m band and so I set about shortening the wire until the point of resonance moved up into the band.

With a little folding back of wire I soon had the point of resonance nicely into the 20m band with a 1.35:1 SWR at 14.208Mhz. This provides a very useable SWR across the whole band but, I decided I’d prefer the point of resonance to be slightly lower as I tend to use the antenna mainly on the CW & FT4/8 part of the band with my Icom IC-705 QRP rig.

Popping out into the garden once more I lengthened the wire easily enough by reducing the fold back and brought the point of resonance down to 14.095Mhz.

The VNA automatically updated the display realtime to show the new point of resonance on the 4.3in colour screen. I also altered the granularity of the SWR reading on the Y axis to show a more detailed view of the curve and reduced the frequency range on the X axis so that it showed a 14Mhz to 14.35Mhz sweep. With an SWR of 1.34:1 at 14.095Mhz and a 50 Ohm impedance, the antenna is perfectly resonant where I want it.

It’s interesting to note that the antenna is actually useable between 13.5Mhz and 14.5Mhz with a reasonable SWR across the entire frequency spread. Setting 3 markers on the SWR curve I could see at a glance the SWR reading at 14Mhz (Marker 2) , 14.350Mhz (Marker 3) and the minimum SWR reading at 14.095Mhz (Marker 1).

I’ve yet to delve into the other functionality of the VNA but, I’m very happy with my initial experience with the device.

More soon …