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.
Multi-Band Delta Loop Antenna View
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.
Multi-Band Delta Loop Antenna 30m 2D Far Field Plot
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.
Multi-Band Delta Loop Antenna 20m 2D Far Field Plot
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.
Multi-Band Delta Loop Antenna 17m 2D Far Field Plot
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.
Multi-Band Delta Loop Antenna 15m 2D Far Field Plot
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.
Multi-Band Delta Loop Antenna 12m 2D Far Field Plot
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).
Multi-Band Delta Loop Antenna 10m 2D Far Field Plot
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.
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.
M0AWS 13m (43FT) Multiband Vertical HF Antenna Info (Click to Enlarge)
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.
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.
M0AWS Inverted-L Antenna View
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.
M0AWS Inverted-L Antenna 160m 3D Far Field PlotM0AWS Inverted-L Antenna 160m 2D Far Field Plot
(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.
M0AWS Inverted-L Antenna 80m 3D Far Field PlotM0AWS Inverted-L Antenna 80m 2D Far Field Plot
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.
M0AWS Inverted-L Antenna 60m 3D Far Field PlotM0AWS Inverted-L Antenna 60m 2D Far Field Plot
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.
M0AWS Inverted-L Antenna 40m 3D Far Field PlotM0AWS Inverted-L Antenna 40m 2D Far Field Plot
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.
M0AWS Inverted-L Antenna 60m/40m Global Coverage
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.
M0AWS Inverted-L Antenna 30m 3D Far Field PlotM0AWS Inverted-L Antenna 30m 2D Far Field Plot
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.
M0AWS Inverted-L Antenna 20m 3D Far Field PlotM0AWS Inverted-L Antenna 20m 2D Far Field Plot
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.
M0AWS Inverted-L Antenna 17m 3D Far Field PlotM0AWS Inverted-L Antenna 17m 2D Far Field Plot
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.
M0AWS Inverted-L Antenna 15m 3D Far Field PlotM0AWS Inverted-L Antenna 15m 2D Far Field Plot
Once again the 15m band looks very similar to the 17m band, low angle radiation but, with a slightly more complex far field plot.
M0AWS Inverted-L Antenna 12m 3D Far Field PlotM0AWS Inverted-L Antenna 12m 2D 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.
M0AWS Inverted-L Antenna 10m 3D Far Field PlotM0AWS Inverted-L Antenna 10m 2D Far Field Plot
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!
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.
M0AWS 20m Band Delta Loop Antenna – Antenna View
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.
M0AWS 20m Band Delta Loop Antenna – 3D Far Field Plot
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.
M0AWS 20m Band Delta Loop Antenna – 2D Far Field Plot
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.
M0AWS 20m Band Delta Loop Antenna – SWR Curve
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.
M0AWS Homebrew Pi-Network ATU
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.
M0AWS 160m Inverted L Antenna SWR Curve
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.
M0AWS Map showing stations worked on 160m using Inverted L Antenna
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.
I’ve been active on QO-100 for a few days now and I have to admit that I’m really pleased with the way the ground station is performing. I’m getting a good strong, quality signal into the satellite along with excellent audio reports from my Icom IC-705 and the standard fist mic.
I’m very pleased with the performance of the NooElec v5 SDR receiver that I’m now using in place of the Funcube Dongle Pro+ SDR receiver. Being able to see the entire bandwidth of the satellite transponder on the waterfall in the GQRX SDR software is a huge plus too.
M0AWS QO-100 Satellite Log map showing contacts as of 23/06/23
As can be seen on the map of contacts above, I’ve worked some interesting stations on some of the small islands in the Atlantic and Indian Oceans. The signals from these stations are incredibly strong on the satellite and an easy armchair copy.
DX of note are ZD7GWM on St. Helena Island in the South Atlantic Ocean, PP2RON and PY2WDX in Brazil, 8Q7QC on Naifaru Island in the Maldives, VU2DPN in Chennai India, 5H3SE/P in Tanzania Africa and 3B8BBI/P in Mauritius.
There are many EU stations on the satellite too and quite a few regular nets of German and French stations. I’ve not plucked up the courage to call into the nets yet, perhaps in the future.
There are a lot of very experienced satellite operators on QO-100 with a wealth of information to share. I’ve learnt a lot just from chatting with people with some conversations lasting well over 30mins, a rarity on the HAM bands today.
We also had our first Matrix QO-100 Net this week, an enjoyable hour of chat about all things radio and more. We have a growing community of Amateur Radio enthusiasts from around the world on the Matrix Chat Network with a broad spectrum of interests. If you fancy joining a dynamic community of radio enthusiasts then just click the link to download a chat client and join group.
The bi-directional slot fed HF antenna isn’t mentioned very often these days for some strange reason. It’s a real shame as it is an excellent antenna that gives high gain through the loop between the frequencies of 14Mhz and 29Mhz.
M0AWS 20m – 10m Slot Fed HF Antenna
Construction of the antenna is relatively simple, 3 x 3m long horizontal wires and 2 x 9.2m long vertical wires. I’ve modelled the antenna using 20mm diameter copper tubing for the horizontal conductors and 2.5mm wire for the two vertical conductors. Using the 20mm copper tubing provides a rigid platform for the mounting of the antenna on a non-conductive mast whilst reducing weight by using 2.5mm wire for the vertical conductors. You could of course use 20mm copper tubing for all the conductors if you have a non-conductive mast that can handle the weight.
An alternative option is to hang the antenna from a high tree and secure it in position with non-conductive nylon cord. This works very well and makes it extremely easy to manually rotate.
The antenna is fed at the centre of the middle horizontal tube (conductor 2 in the image above) using one of the following methods:
Method 1 – Use a 4:1 Balun and ATU either in the radio/Radio Shack or connected directly to the Balun. Connecting a remote auto ATU to the balun directly at the feed point is the best option as you will then have a perfect 50 Ohm impedance match to the coax cable going back to the radio. (I’ve used my AH-705 and a 4:1 Balun at the feed point in the past with excellent results).
Method 2 – Connect a remote auto ATU directly to the feed point of the antenna and then 50 Ohm coax back to the radio shack. This will provide a perfect SWR match on all bands and works extremely well. (I’ve used my AH-705 remote auto ATU in this configuration as well in the past, again with excellent results and no discernible difference to method 1).
Method 3 – Feed the antenna with 450 Ohm open ladder line and use a 4:1 Balun and ATU in the radio shack to match the antenna to 50 Ohm radios. It’s important to bring the 450 Ohm ladder line away from the feed point horizontally and not vertically downwards. This will then help to protect the radiation pattern.
Looking at the 2D Far Field Plots this antenna provides excellent gain at relatively low radiation angles on all bands 20m – 10m making it an ideal antenna for chasing DX.
20m Band 2D Far Field Plot 17m Band 2D Far Field Plot 15m Band 2D Far Field Plot 12m Band 2D Far Field Plot 10m Band 2D Far Field Plot
The gain on each band is as follows:
20m Band – 7.83dBi at 24 Degrees 17m Band – 9.07dBi at 20 Degrees 15m Band – 9.63dBi at 16 Degrees 12m Band – 10.36dBi at 14 Degrees 10m Band – 10.99dBi at 12 Degrees
10m Band 3D Far Field Plot
The 10m Band 3D Far Field Plot above shows the typical radiation pattern for the antenna. Maximum radiation is through the loop with very little high angle radiation making it ideal for chasing DX stations. Gain increases as frequency increases however, angle of maximum radiation decreases as frequency increases improving DX capability of the antenna on the higher bands. It’s worth ensuring that the antenna is rotatable as this will then enable you to point the antenna at the DX station to maximise signal strength at the DX end. Pointing this antenna North/South makes it great for working VK/ZL over the North Pole whilst at the same time being able to work South Africa from the UK.
Summary:
Horizontal Wire Lengths: 3m @ 20mm Diameter Vertical Wire Lengths: 9.2m @ 2.5mm Diameter Modelled Height above ground at Centre (Conductor 2): 10.6m Feed Type: 4:1 Balun + ATU / Remote Auto ATU / 450 Ohm Ladder line with 4:1 Balun & ATU
Over the years I’ve built many multi band vertical HF antennas including multi-element quarter wave verticals like the DXCommander configuration, multiple end fed vertical dipoles all on the same pole and a host of other configurations. As with all multi band antennas there’s always a compromise, on some bands it performs well and on others it doesn’t, it’s the nature of the beast.
For some time now I’ve been using a multi band vertical antenna that has over the last year performed incredibly well on all bands from 80m to 10m. Don’t get me wrong, it’s not perfect however, it has out performed every other multi band HF vertical I’ve tried to date even though it’s by far the simplest antenna design and according to the antenna modelling software I have it shouldn’t be as good as it is.
So what is this magical multi band HF vertical I speak of? Well it’s nothing more than a piece of wire 13.4m long taped up a 12.4m vertical Spiderpole with 1m of wire tucked down into the top of the Spiderpole.
Obviously this is not going to be resonant on any band without some sort of impedance matching circuit at the bottom of the wire. Originally this antenna was my end fed half wave vertical antenna for the 30m band that was fed via a 49:1 Unun. This antenna worked incredibly well on the 30m band allowing me to work DX globally with ease but, it was a single band antenna and I wanted a multi band solution.
I decided to remove the 49:1 Unun and replace it with a home brew LC circuit made up of a coil made from 5mm copper tubing and a large air spaced variable capacitor I had laying around from an old ATU project I built many moons ago.
This simple LC arrangement at the bottom of the wire worked incredibly well and tuned the wire from 80m to 10m with a perfect SWR on each band using nothing more than a ground rod and 4 x 12m radials. Performance was surprisingly good on all bands 80-10m giving me the ability to get some DX stations that I’ve never been able to hit before. The only drawback to this solution was the fact that I had to go out and manually tune the antenna every time I wanted to change band. Not so much of a problem in the summer but, in the winter in the pouring rain and howling wind it’s no fun at all. (I resolve this issue further down in the article!)
Multi Band Vertical HF Antenna using a 12.4m Heavy duty Spiderpole at the end of the garden
Performance on the HF bands is incredibly impressive with this antenna. Modelling it on EzNEC software it shouldn’t be that great on bands above 20m however, it seems to defy the modelling software as it performs amazingly well on 17m, 15m and 12m, better than any other vertical antenna I’ve made for those bands. How this can be I do not know, normally my antenna builds match closely what the modelling software shows but, in this instance it doesn’t and I’ve really no idea why.
Multi Band Vertical HF Antenna showing loop at top and wire tucked down into pole
Always wanting to put things into perspective here’s some details of the contacts I’ve made on each band showing how well this antenna has performed over the last year or so.
Firstly the 80m band, I’ve not used this band much over the winter months as I’ve got into the higher bands however, the map below shows all the stations worked on 80m using this antenna.
Stations worked on the 80m band from the M0AWS QTH
There are 51 contacts in total, not a big number by any means however, there are some good distances made with contacts into North America, South America and Indonesia. I’m sure I could had done better if I’d spent more time on this band, something to aim for next winter perhaps.
Next is the 60m band, a band I really like and have enjoyed over the winter months. The antenna performs incredibly well on this band even though we have very limited access to 60m here in the UK. With 288 contacts in the log with a good spread of distances I’m really pleased with how this antenna performs on this band.
Stations worked on the 60m band from the M0AWS QTH
Moving up in frequency the 40m band is the next one on the list, this is a great band and one that I’ve loved for many years. I’ve spent countless hours on CW on this band in the past and worked some great DX. The performance of this antenna on the 40m band is excellent, if I can hear the DX normally I can work them regardless of where in the world they are located. With 226 contacts in the log spread globally over the winter here in the northern hemisphere I have no complaints about performance of this antenna on the 40m band.
Stations worked on the 40m band from the M0AWS QTH
Moving up onto the 30m band I have to admit this is probably my favourite band of all. I’ve spent so many hours on CW working some of the best fists I have ever heard on the air I’ve grown to love this band not just for the DX available but, for the quality of operator found on this narrow piece of the RF spectrum. Needless to say since the antenna is a half wave on the 30m band performance is stunning, out performing any other 30m band antenna I have ever made. It’s even better than the 30m Delta Loop antenna that I built and used when I lived in France.
With 467 contacts in the log on the 30m band you can tell this is my goto band and one that offers access to some of the best DX in the world.
Stations worked on the 30m band from the M0AWS QTH
The 20m band is a band that I never really used until I moved back to the UK from France. Living in France I had acres of land and so I was very much into the low bands, 160m to 30m and never ventured above this part of the spectrum. Now living back in the U.K. with a typical U.K. sized garden the low bands are much more difficult to get onto and so my interests have moved up in frequency somewhat.
Getting onto the 20m band I was amazed at how easy it is to work DX stations compared to the low bands, it’s simply a case of if you can hear them you can work them, there’s no real challenge to be honest. Because of this the band is always super busy with people shouting over the top of each other to get the DX. Not to be put off, I’ve made a surprising 412 contacts on 20m covering the globe. This antenna works incredibly well on this band and you really don’t need anything else to work DX on 20m.
Stations worked on the 20m band from the M0AWS QTH
Next is the 17m band, one of the WARC bands that I’ve never really ventured onto until now. I have to admit I really like this band, when it’s open it’s normally open to the world all at the same time. With an almost undetectable background noise level you can hear the faintest of signal on this band. This is one of the bands that according to the EzNEC modelling software this antenna shouldn’t be any good on but, I have to say that it’s performance is beyond anything I ever imagined. I’ve worked my longest distance yet on this band and with this antenna, ZL4AS at 11776 miles, a distance I haven’t achieved yet on any other band. The 17m band really is a great band, I’d actually say it’s better than the 20m band even though there is considerably less spectrum available. With 220 contacts in the log it’s been a fun band to use.
Stations worked on the 17m band from the M0AWS QTH
Continuing the theme of the WARC bands, the 15m band is another one that I’ve only discovered in the last 12 months. It’s only now that I realise what I’ve missed out on due to my addiction to the low bands for so many years.
I’ve only made 76 contacts on the 15m band, not a lot at all really. This is mainly due to the fact that I get easily side tracked by the 17m and 30m bands most of the time and the radio VFO never gets as far as 21Mhz. Performance of the antenna is good on 15m, I would say not as good as on the 17m band but, it’s no slouch by any means.
As you can see on the map below, I may of only made 76 contacts on the 15m band but, they are spread right across the world proving that this antenna’s DX-ability on 21Mhz really is rather good.
Stations worked on the 15m band from the M0AWS QTH
Finally we arrive at the top of the WARC bands, the little 12m band. Once again this band is very much like the 17m band, super low background noise level, when it’s open you can work huge distances with very little power but, often there is quite deep QSB that can make getting that elusive DX a bit more challenging.
With only 66 contacts in the log once again I’ve not spent a huge amount of time on this band but, it hasn’t disappointed. With global coverage from this antenna on 12m once again I am astounded at how well it works. With software modelling saying it should be terrible on 24.9Mhz with nothing but super high angle radiation, it really shouldn’t be a good antenna for DXing on this upper WARC band but, it is and I have no idea as to why!
Stations worked on the 12m band from the M0AWS QTH
Finally we arrive at the 10m band, another band that I have never got into even though many refer to it as the magic band. This is the band that I’ve made the fewest contacts on, not because the antenna doesn’t work at the dizzy heights of 28Mhz but, because I hardly ever get the VFO dial past the lower bands due to the level of DX available. I really should make more effort to get the best out of the 10m band, especially now the summer is coming.
With a measly 19 contacts in the log I should be ashamed of myself for not doing more on this band as it is very often open and busy with traffic. Since I’ve not really used the antenna that much on the 10m band it’s hard to say how well it performs however, I have had contacts into North and South America and so it shows potential.
Stations worked on the 10m band from the M0AWS QTH
As you can see, the performance of this antenna is self evident from the log entries, it works superbly even though the modelling software says it shouldn’t above 14Mhz. This is now my main antenna here in the U.K. and I’ve only made one change to the initial setup and that is to add a CG3000 remote auto ATU to replace the home-brew LC tuning circuit.
CG3000 Remote Auto ATU housed in a plastic box
With the CG3000 auto ATU in place I no longer have to venture out into the cold, wet garden in the winter months to change band, it’s just a case of sending a continuous 10w signal into it and leaving it to tune in less than 2 seconds. The CG3000 is a Pi Network ATU so it handles both high and low impedance loads with ease. A Pi Network ATU is one of the best you can have, I’ve made my own in the past and had excellent results.
So in summary, 13.4m of wire vertically up a 12.4m pole with 4 x 12m radials, a ground rod and a CG3000 Auto ATU will give any HAM station the ability to work DX on all bands from 80m to 10m without ever having to leave the shack to tune it.
Since I got the CG3000 off of Ebay for a bargain £170 and the 12m heavy duty Spiderpole for under £100 the total cost of the antenna is considerably less than many commercial offerings available and yet performs as well if not better.
If you want to get this antenna onto the 160m band then you just need to add a small coil into the mix at the bottom of the wire to increase the inductance in circuit. The CG3000 will then happily tune the entire 160m band. It’s best to remove this coil though for all the other bands otherwise performance is reduced.
Please be aware that the performance of this antenna will not be anywhere near as good if you use the ATU in your radio at the end of a coax run. This is because the coax becomes part of the antenna and the radiation pattern is all but destroyed. You will be extremely disappointed if you use the antenna in this fashion. The ATU must be at the end of the wire and connected directly to ground and the radials to get the performance that I have experienced.
Finally, if you have an Icom IC-705 and AH-705 remote auto ATU you can use the AH-705 ATU in place of the CG3000, you will get the same results as I have with the CG3000.
I have used my AH-705/IC-705 combo quite a few times with this antenna with excellent results although, the big antenna can sometimes result in the receiver of the IC-705 getting overloaded especially on the lower bands. This is easily resolved by reducing the RF Gain on the radio.
Following on from my previous article on Enhancing Digital modes with Node Red I’ve now got to a point where I have realtime decode information from the WSJT-X digital application being plotted on a Node Redworld map not just for CQ calls but, for stations in conversation too.
The flow has become somewhat more complex than it was originally as more and more functionality has been added. I have deliberately split out the flow process into more nodes than are really necessary so that the flow is easier to understand. Anyone from a programming background like myself will soon realise that a lot of the nodes could actually be combined into one big node however, the overall flow process wouldn’t be so easy to understand for the Node Red newcomer and would possibly put people off from trying it out.
Current WSJT-X Node Red flow
Above is a screenshot of the flow as it currently stands. It’s pretty easy to understand what is happening in the flow due to the fact that the processes are broken out into small, easy to digest blocks.
From the top down we connect to WSJT-X via UDP port 2237 and listen for the data stream. As the data is received it’s passed directly into the WSJT-X-Decode node that converts the information into a Node Red compatible format. The data is then filtered with only the information required being passed onto the next node. There are two outputs from the filter node as we require two different streams of information, namely “CQ” and “TX1” data. All the rest of the data from WSJT-X is ignored as it’s not required at this time.
The “Get freq & SNR + Others” node builds a decode message payload with all the correct data, in the right format ready to be passed on along the flow. This node also sets a number of parameters required by the map node to be able to control the display of the data.
The next node along is “Set msg.payload”, this brings together all the necessary data into a single message payload that is then worked on by all the nodes further along the flow.
The next 3 nodes perform the simple task of moving some of the data into the objects defined by the world map node, if the data isn’t moved into these specific objects the map will not plot anything.
Now we get onto the slightly more difficult bit that might put off those who aren’t from a programming background. The next 7 nodes are all javascript functions which I have created to perform tasks that cannot be done via the standard Node Red pallet.
At this point it’s worth noting that I’m not a javascript programmer, I’ve used Python, Rust, Go, C and many other languages during my 40 plus year career but, javascript has never been one of them. I’m sure any seasoned javascript programmer will most likely raise an eyebrow at my attempt at javascript programming but, you need to remember that I’m doing this in my retirement and my enthusiasm for learning yet another programming language has wained somewhat!
So, getting back to the flow, each javascript function does just one task each of which is as follows:
Set rx_time – Sets the time the data was received/processed
Remove RR73 in tx1 – Remove decodes where RR73 is in TX1 instead of a valid callsign
Set Dynamic Icon Colour – Sets the icon colour depending on what type of call is decoded
Maidenhead to LON/LAT – Converts Maidenhead locator codes into LAT/LON Coordinates
Calc Distance – Calculates the distance between “My QTH” and the DX station
Calc Bearing – Calculates the bearing/beam heading to the DX Station from “My QTH”
Generate Search URLs – Generates the URLs for QRZ and my own online log lookups
Editing the Calc Distance function with debug info in the far right panel
Once all the functions have run the resultant data set is forwarded on to the WSJT-X Stations Map node where it is plotted real time on a world map.
To view the map point your web browser at your PC running Node Red as follows:
http://radiopc.your.domain:1880/worldmap/
Or if you haven’t got a DNS setup at home then just use the IP Address of the PC instead:
http://192.168.100.10:1880/worldmap/
Don’t forget that for all of this to work you must configure WSJT-X to send data via UDP on port 2237 otherwise the flow won’t be able to connect and listen for the decode data.
You may have noticed that there are 3 other nodes that I haven’t mentioned yet. The two green greyed out nodes are Debug nodes that can be enabled when required to help see what is going on in the flow. These debug nodes will display data in the debug panel on the right of the flow editor screen when they are enabled, they are extremely useful for debugging!
The third is the blue My QTH node, this contains data pertaining to my QTH that is plotted on the map using an orange icon. You can easily edit this node to point to your QTH instead.
WSJT-X Node Red map showing orange icon denoting my QTH
Once the flow is deployed you’ll be surprised how quickly the data starts to be plotted on the map. Stations calling “CQ” are shown by Green icons and stations that are in a QSO with another station are denoted by the Red icons.
Each icon is clickable and will present all the information collected by WSJT-X for each station viewed.
WSJT-X Node Red World Map showing FT8 stations realtime on the 12m Band
The popup also has two clickable entries, one will take you to the qrz.com page for the station being viewed and the other will search my logs to see if I have worked that station already and if so it will open a new tab showing the information.
Node Red Function Editor showing the Generate Search URLs function
You can edit the “Generate Search URLs” node so that it points to your online logs search engine so that you can view your own log data instead of mine.
Below is a close up of the popups that are displayed when each icon on the map is clicked. The popups show the information collected from WSJT-X for each station plotted on the map.
Left – Green “CQ” Popup and Right – Red “TX1” in QSO popup
If you fancy trying this out for yourself but, don’t fancy creating all the nodes in the flow manually then I have made an export of the flow available for download. All you have to do is download the file, unzip it and then import it to Node Red and you’ll have everything built ready to play with.
The 2023 new year has got off to a great start here at the M0AWS radio shack with my first QSO with New Zealand since setting up the new radio room.
It’s been almost a year now since I started putting the radio room together and throughout all this time I’d not been able to secure a complete QSO with New Zealand.
Well today was the day that I finally achieved what seemed like the impossible.
M0AWS WSJT-X QSO Map as of 3rd January 2023
ZL4AS was the first New Zealand station that I’d managed to complete a full QSO with, up until now I’d made a few ZL contacts but, never managed to complete the QSO due to conditions on various bands.
The band of choice today was 17m, a great WARC band that has provided me with much of the DX over the last year. This band really does give full global comms when it’s open.
With a new longest distance of 11776 Miles to ZL4AS in Balclutha New Zealand, I’m looking forward to see what new countries 2023 brings to the M0AWs radio room.
More soon …
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