A venture into the world of Meshtastic

Meshtastic is a relatively new thing in the internet of things (IOT) world and is gaining traction in the U.K. at the moment.

So what is Meshtastic?

Meshtastic is an open source, off-grid, decentralised mesh network built to run on affordable, low-power devices on the 868Mhz industrial, scientific, and medical (ISM) band. (Some devices can also run on the 433Mhz 70cm HAM band.)

The ISM band is licence free but, has limits on the RF power levels that can be used. The one plus over the HAM bands is that you can legally transfer encrypted messages over the ISM band making it secure.

The best way to think of Meshtastic is a radio version of the online decentralised Matrix chat system but, without the large server requirements and ever growing database!

Heltec ESP32 v3 Wifi, Bluetooth and 868Mhz device for Meshtastic
Heltec ESP32 v3 Wifi, Bluetooth and 868Mhz device for Meshtastic

There are quite a few Meshtastic compatible devices on the market today with many costing around the £20 mark whilst others like the LillyGo T-Echo costing over £100 in the U.K. even though they are less than half the price in the USA.

Since I’m just starting out on my Meshtastic adventure I thought I’d start with a pair of Heltec ESP32 v3 devices that are normally readily available on Amazon but, due to the current push to build a U.K. wide mesh, they are currently out of stock pretty much everywhere.

Loading the Meshtastic firmware onto the devices is fairly straight forward and can be done using the web installer via either the Edge or Chromium web browsers.
(Note: If using Windows O/S you will need to install some drivers from the Meshtastic website to be able to communicate with the devices)

Having neither of the two browsers and being a Linux command line junkie I decided to use the Python programme to load the firmware onto the two devices. It’s worth noting that you don’t need any drivers to be able to communicate with the devices if you’re using either Debian or one of the many Ubuntu flavours of Linux O/S.

Using the Python command line program sounds like a more complicated approach but, in reality it’s super simple, extremely reliable, quick and if like me you use a Linux PC in the radio shack then you most likely already have most of what you need to get the job done. Just follow the simple steps as laid out on the Meshtastic web site and you’ll have the firmware loaded in no time at all.

Installing the Meshtastic firmware onto my Heltec ESP32 v3 using the Python command line tool
Installing the Meshtastic firmware onto my Heltec ESP32 v3 using the Python command line tool

The firmware takes less than a minute to copy across to the Heltec device and is automatically rebooted ready for configuration once the transfer has completed.

It is possible to configure the device via the command line tool however, since there is a nice GUI app for both Apple iOS and Android devices I decided to install the Meshtastic app on my iPad and connect to the device via Bluetooth to configure it.

Once you’ve got the Meshtastic app installed on your device and have connected via Bluetooth you’ll be ready to start configuring the device to join the mesh. The first thing you want to do is set the region. This is different in each country but, in the UK we use the EU_868 region settings. This will set the device to use the 868Mhz ISM band which is the band being used to build the U.K. wide mesh.

View of the Meshtastic app on iOS showing the configuration options for the Heltec ESP32 v3
View of the Meshtastic app on iOS showing the configuration options for the Heltec ESP32 v3

There is a multitude of configuration options within the app which I will go into in greater detail in a series of articles at a later date.

Heltec ESP32 v3 running Meshtastic Firmware
Heltec ESP32 v3 running Meshtastic Firmware

For those of you that, like me aren’t near any other nodes you can connect the devices to the internet and use the Meshtastic MQTT server to communicate with other nodes. This of course isn’t off-grid but, it will get you started until the mesh grows into your local area at which point your device will automatically start communicating with the other nodes over radio.

Meshtastic MQTT connectivity
Meshtastic MQTT connectivity

Once you are connected to either the MQTT server or other nodes via radio you will see the other node details appear in the Meshtastic app. It’s interesting to look at the information and see signal strengths and traffic levels etc for each node.

View of the Meshtastic app on iOS showing Nodes in the Mesh and Device Metrics for the M0AWS-1 Node
View of the Meshtastic app on iOS showing Nodes in the Mesh and Device Metrics for the M0AWS-1 Node

There are a multitude of cases available for the Heltec v3 devices, especially if you have access to a 3D printer. One of the nicest cases I have seen is the Bender from IKB3D (I know, it’s a strange name!) but, it really is a super little case for the Heltec series of devices.

You can either buy the 3D print files for £8.99 and print it yourself or just order a pre-printed and assembled case directly from the website although, due to demand there is a long lead time currently.

More soon …

Taking the Hiss out of QO-100

I’ve been on the QO-100 satellite for about 7 months now and I have to admit I love it!

Having a “Repeater In The Sky” that covers a third of the world really is a wonderful facility to have access to however, there is one thing that I find tiring and that is the high level of background noise that is always present.

Even though the signals are mostly 59-59+15dB the background “hiss” is very pronounced and gets very tiring after a while, especially if like me you have tinnitus.

Currently I’m using a NooElec Smart SDR for the receiver and GQRX SDR software on my Kubuntu Linux PC. This works great but, there is one short fall, there is no DSP Noise Reduction (NR) in the software or hardware.

To fix this I recently invested in a BHI Dual In-Line Noise Eliminating Module. The unit itself is nicely put together and has a good combination of inputs and outputs making it easy to connect up to my MacBook Pro to record QSOs and connect my headphones at the same time.

M0AWS BHI Dual In-Line Noise Eliminating Module
M0AWS BHI Dual In-Line Noise Eliminating Module

At £189.95 plus postage from BHI direct it’s not cheap but, it is nicely put together and comes complete with a power lead and a couple of cheap audio cables. The quality of the knobs and mechanisms is good apart from the little grey DSP Filter Level knob that feels cheap and is very wobbly on the switch below. I’m not sure how long this is going to last with prolonged use and will most likely need replacing with something a little sturdier at some point in the future.

Overall noise reduction is good but, the audio amplifiers on the Audio Input Level and Line Out Level distort very early on in their range and you cannot get them much above level 5 before distortion starts to appear on the received signal. This is disappointing as my headphones are of reasonable quality and are let down by the distortion creeping in from the audio amplifier in the BHI unit.

I’ve tried altering the levels on the input from the IC-705 and no matter what I cannot get a good audio signal in my headphones without some distortion on the higher frequency ranges.

Overall the device does do what I want, it reduces the background “hash” considerably reducing the fatigue whilst chatting on the satellite. Below is a recording from a conversation on the satellite showing the noise reduction performance of the BHI module.

M0AWS Example BHI DSP NR Recording

The recording starts with the BHI DSP NR off, at 00:07 the DSP NR is switched on, you can clearly hear the difference. At 00:23 the DSP NR is turned off again and at 00:36 the DSP NR is turned on again. The BHI DSP NR Module is set with the DSP Filter Level set at 3 out of 8 which appears to be the best level to use. Switching to level 4 starts to introduce digital artefacts to the audio which only gets worse the higher the DSP Filter Level goes.

With a setting above level 3 there really isn’t much improvement in noise reduction and the audio becomes progressively more affected by the digital artefacts than it does from the background noise.

M0AWS BHI Dual In-Line Noise Eliminating Module with Icom IC-705 QO-100 Ground Station
M0AWS BHI Dual In-Line Noise Eliminating Module with Icom IC-705 QO-100 Ground Station

The only other problem I have with the BHI Dual In-Line Noise Eliminating Module is that is comes in a plastic case. The case itself is solid and of good quality however, it offers no RF shielding whatsoever and the unit is extremely susceptible to RF getting into the audio chain and then being heard during transmit in the headphones and via the line out connections. For the money I would had expected the unit to come in a metal case that provides proper RF shielding. This is a real shame as it lets the unit down considerably.

As setup in the photo above I am using 300mW O/P on 144Mhz from the IC-705 into a perfect 1:1 SWR presented by the DX Patrol 2.4Ghz Upconverter via some very high quality LMR-400 Coaxial cable from Barenco but, I get terrible RF interference via the BHI unit during the transmit cycle. Considering I am only using 300mW I dread to think what it may be like if I was using a 100w HF radio. This is something I need to investigate further as it really is very annoying.

Moving the unit to a different location in the radio room does help a bit but, doesn’t solve the problem completely. At 300mW RF O/P I really didn’t expect there to be a problem with RF getting into the BHI unit.

Having a proper line-out facility on the BHI unit really is nice as it makes it very easy to connect to my MacBook Pro to obtain good quality recordings of signals on the QO-100 satellite as can be listened to above.

Overall I am happy with the BHI Dual In-Line Noise Eliminating Module but, do wish that more care had been taken over using a metal case instead of a plastic case to protect the unit from RF ingress and better audio amplifiers within the unit that don’t distort/clip so early on in their O/P levels.

Is this the perfect noise reduction unit?

No but, overall it is better than nothing and does help to reduce the background noise to a more acceptable level reducing the overall fatigue during prolonged conversations on the QO-100 satellite.

UPDATE: I tried the BHI unit with my FTDX10 on the HF bands and the RF interference is horrendous, even when using QRP power levels! This device clearly hasn’t been designed to work in an RF environment and the total lack of shielding or isolation lets it down terribly. If you are an SWL then this unit is fine but, if like me you like to monitor your transmitted audio whilst on air through headphones then this isn’t the unit for you. To prove the problem isn’t in the radio shack I put the BHI unit in the house some 30m away powered by 12v battery with nothing connected but a pair of headphones and still the unit suffered from RF interference even at QRP levels.

More soon …

Home-Brew 12v DC Distribution Box

I’ve been wanting to tidy up the cabling to the 12v DC PSU for some time in the radio shack as like many HAMs I have a number of radios/devices that all need a 12v feed but, only two connectors on the front of the PSU. The net result was a birds nest of wires all connected to the PSU making it impossible to disconnect one device without others getting disconnected at the same time.

Looking online I found that many of the HAM outlets stores sell nice little 12v DC distribution boxes that would be ideal however, they’re all priced somewhat high for what they are so, I decided to purchase the parts and make one myself.

Searching on Amazon I found all the necessary parts for less than a quarter of the cost of commercially made units. A couple of days later the parts arrived and sat on my desk in the shack for a few weeks. Yesterday I finally found the time to make a start on the project.

M0AWS home-brew 12v DC Distribution Box
M0AWS home-brew 12v DC Distribution Box

After much drilling and filing I had the necessary holes/slots cut in the plastic box for the 4mm connectors and fuse holders and started wiring them up. Part way through my 30 year old soldering iron decided to die and so I had to stop and wait for a replacement to arrive.

M0AWS completed 12v DC Distribution Box
M0AWS completed 12v DC Distribution Box

With the new soldering iron in hand it only took 30mins or so to complete all the joints and I soon had the box together ready to test with my multimeter to ensure I didn’t have any shorts or crossed wires.

With testing complete and fuses in place I connected it up to the PSU and then connected all the devices one by one checking for voltage drops as I went.

M0AWS 12v DC Distribution Box
M0AWS 12v DC Distribution Box

I now have my CG3000 remote auto ATU, GPSDO, QO-100 ground station and IC-705 all nicely connected in a much tidier fashion than before, all for considerably less than the commercially available alternatives.

More soon …

Multi-Band Delta Loop Antenna

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
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
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
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
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
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
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
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.

40m EFHW Vertical Phased Array

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.

M0AWS 40m Band EFHW Phased Vertical Array Antenna View
M0AWS 40m Band EFHW Phased Vertical Array Antenna View

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.

M0AWS 40m Band EFHW Phased Vertical Array 3D Far Field Plot
M0AWS 40m Band EFHW Phased Vertical Array 3D Far Field Plot

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!

M0AWS 40m Band EFHW Phased Vertical Array 2D Far Field Plot
M0AWS 40m Band EFHW Phased Vertical Array 2D Far Field Plot

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!


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

13m Multiband Vertical Antenna – 18 Month Summary

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
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.

More soon …

A quick chat with Callum – DXCommander on 80m

Using just 20w I had a quick chat with Callum of DXCommander fame on the 80m band using my Inverted-L antenna.

Very happy with the signal report and being able to hear myself after the event was very interesting. I’ve not used my Yaesu FTDX10 much on SSB and so I was very happy to hear that the audio sounded nice and clear.

More soon …

Modelling my Inverted-L Antenna

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
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.

(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.

M0AWS Inverted-L Antenna 60m/40m Global Coverage
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.

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 …

Making my 160m Inverted-L into a Multi band Antenna

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.

M0AWS Pi-Network ATU using my JNCRadio VNA to find the ATU setting for each band
M0AWS Pi-Network ATU using my JNCRadio VNA to find the ATU setting for each band

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.

M0AWS Pi-Network ATU settings noted for each band
M0AWS Pi-Network ATU settings noted for each band

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 …