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.
Going through some old photos today I found a few great memories from the past of my old valve radio stations that I’d restored over the years.
These old radios gave me some wonderful moments over the years and a fair few hours of restoration to get them into operational condition. They sounded great on air and I often got comments from other amateur stations about how warm the audio sounded. Some did also mention the drift of the transmitter with temperature changes but, you just have to accept that when using vintage radio equipment.
M0AWS FT101E Transceiver, FL101 Transmitter, FR101B Receiver and TS520S Transceiver.
Above is my old FT101 line up. It consisted of the great FT101E transceiver, a complete standalone solution that was extremely popular in its day. Below it is the FT101 line up made up of the FT101 transmitter, FR101B receiver and matching speaker.
Top right is the lovely Trio TS520S with the matching digital frequency display which is incredibly rare and very sought after today.
These radios gave me a lot of pleasure for many years and I wish I still had them today.
My second Yaesu valve line up took a lot more restoration than the 101 series and was quite challenging at times but, with a lot patience and time spent sourcing parts I got them back to as close to new operational condition as was possible.
M0AWS FLDX400 Transmitter, FRDX400 Receiver, FL2000B Amplifier and FTDX501 Transceiver.
The Yaesu 400 series line up consisted of the FLDX400 transmitter, FRDX400 receiver and was finished off with the FL2000B amplifier. These 3 pieces of radio equipment looked beautiful in the flesh and were wonderful to operate. Taking a good 15mins to warm up and become stable you couldn’t rush getting on air. This line up was my favourite by far even though they weren’t as good as the 101 line up.
Above the 400 series is the later FTDX501 transceiver with matching speaker. This was a great radio in its own right but, not as much fun to operate as the 400 line up. To the right of the FTDX501 is the matching Yaesu Microphone for the 400/500 series. This mic is incredibly rare and I had to visit many radio swap rallies to find it, worth the effort though.
Top right you can see my old SWL receiver, the great Drake SW4A. I never had a Drake line up as they are quite rare in the UK but, it certainly would had made a great addition to the station.
M0AWS FLDX400, FRDX400 & FL2000B Station being operated by M1ACB and G6ALB
Finally this is a photo of two friends of mine, Steve Thomas M1ACB (Current General Manager of the RSGB) on the right and Andy, G6ALB with whom I spent many hours sending and receiving morse with to get our Class A licences. We had a fun day together operating the old radios and taking it in turns to handle the pile ups!
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.
15m Band Delta Loop Antenna View
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.
15m 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.
15m Band Delta Loop Antenna 2D Far Field Plot
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.
15m Band Delta Loop Antenna SWR Curve
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
Since purchasing my Retevis RT85 2m/70cm handheld radio I’ve noticed that it seems rather deaf when using the antenna that came with the radio and isn’t as strong into the local repeaters as I imagined it would be.
Considering the local 2m and 70cm repeater isn’t that far from my QTH and there is pretty much a clear line of site view in the direction of the repeater I was somewhat surprised that on 70cm the repeater never breaks the squelch, even if it is set on it’s lowest setting of zero.
M0AWS Retevis RT85 dual band VHF/UHF Handheld Radio
Connecting my home made end fed dual band vertical dipole at 10m above ground the performance of the radio improves drastically as one would expect.
Having recently purchased a JNCRadio VNA 3G antenna analyser I decided to connect the Retevis supplied antenna to the analyser and see what the resonance was like on the two bands.
The antenna is labelled as 136-174Mhz and 400-470Mhz. This is an extremely wide frequency range for such a small antenna and clearly isn’t going to perform that well over such a wide bandwidth.
Connecting the antenna to the VNA and setting the stimulus frequency range to 144-148Mhz I found that the SWR curve of the antenna wasn’t particularly good.
M0AWS Retevis RT85 Antenna SWR Curve 2m
As shown above the SWR curve on the 2m Band is pretty poor. At 144.0Mhz it’s just over 3:1, at 145.496 (closest I could get to the 145.500 calling channel) the SWR is still 2.1:1. The antenna doesn’t really get close to resonance until 148Mhz where the SWR is 1.46:1.
With an SWR this high the radio will almost certainly be reducing the O/P power considerably to protect the PA stage from over heating due to so much power be reflected back into the transmitter. This explains the poor performance when using 2m repeaters locally and the somewhat limited range when using the OEM supplied antenna.
Looking at the SWR curve on the 70cm band, the antenna is much closer to resonance than it is on the 2m band but, it’s still not perfect.
M0AWS Retevis RT85 Antenna SWR Curve 70cm
At 430Mhz the SWR is 1.56:1, at 435Mhz 1.63:1 and 440Mhz 1.72:1. Since the antenna is much closer to resonance on the 70cm band I would expect it to perform better than it does.
Looking at the SWR curves over the entire supported frequency range of 136-174Mhz and 400-470Mhz, there is only one point of resonance on VHF around 148Mhz and on UHF around 400Mhz.
With such disappointing performance on both VHF and UHF I’ve decided to investigate making my own 2m/70cm antenna for the handheld to see if I can improve both the SWR on each band and the overall performance of the radio.
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.
MFJ-259B Antenna Analyser
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.
M0AWS – JNCRadio VNA 3G PackagingM0AWS – JNCRadio VNA 3G in box with connectors and cables
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.
JNCRadio VNA3G showing 20m Band EFHW Resonance
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.
JNCRadio VNA3G showing 20m Band EFHW Resonance 14Mhz to 14.35Mhz Sweep
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).
We’ve not had rain for over 6 weeks here in Eyke, Suffolk. The ground is incredibly dry and dusty. The farmers have been pulling vast quantities of water from their bore holes for weeks to keep the crops alive and we’ve been putting extra water out for the birds and animals that visit our garden daily.
Then one night we had about 30mins of light rain, not much at all and it was consumed by the dry earth is seconds. By morning you’d never of known it had rained however, strangely the next day when I fired up my QO-100 ground station I noticed that my signal into the satellite was way down from it’s normal S9+10dB level. Checking drive into the up-converter and SWR at the IC-705 everything looked fine. I then decided to check the SWR from the 2.4Ghz amplifier output only to find that it was off the scale.
I checked inside the enclosure for water ingress but, all was bone dry as normal. I disconnected the coax cable from the output of the amplifier and the IceCone Helix uplink antenna, tested with a multimeter and found everything was fine, no short and perfect continuity.
After scratching my head for a few minutes I decided to take both the N Type and SMA connectors apart to look for water ingress. Since the inside of the enclosure was dry I wasn’t expecting to find anything.
The N connector at the Helix antenna end on the dish LNB mount was perfectly dry, no water ingress at all. The layers of self amalgamating tape I’d put over the connector had done its job perfectly. Shame I had cut the tape off to remove the plug!
Upon removing the SMA connector at the amplifier end of the coax I noticed a tiny drop of water in the bottom of the housing where the pin goes through the white plastic insulator, not a good sign.
Sure enough upon further inspection I found that the white plastic disc that is situated above the pin on the centre conductor was wet and the coax braid felt damp. I knew immediately this wasn’t good.
At first I didn’t understand how there could possibly be water in the SMA connector when the rest of the enclosure was dry. Where the coax goes into the top of the enclosure there is a water tight junction that tightly grips the coax cable and seals it, supposedly stopping water ingress.
Since there was water in the SMA connector I feared that perhaps the water had gone further and entered into the amplifier so, I decided to remove the amp from the enclosure and remove the top cover to check.
2.4Ghz amplifier with top cover removed
After some close inspection I found the amp to be perfectly dry and free from water ingress, a relief for sure.
Before putting it all back together I decided solder on a pair of wires to the SWR and FWD-PWR pins on the amplifier and run them down into the radio room. This would then allow me to check the SWR and power output without having to get up to the enclosure with a multimeter.
Once this was done I then set about cutting 5cm of LMR-400-UF off at the SMA connector end so that I had a fully dry piece of coax cable to refit the SMA connector to. Having to do this outside and up a ladder wasn’t the easiest but, with a little perseverance and cooperation from the breeze I managed to get the pin soldered back onto the end of the coax and the connector back together.
I reconnected the amp to the 28v feed so that I could check the SWR and power output at full rating instead of the lower 12v setting that I had been using. Checking the voltage on the SWR pin I found that it fluctuated between 0.2v and 0.44v. This wasn’t what I was expecting as the PDF manual for the amplifier states that with a 1:1 SWR you should see 1.5v on the SWR pin.
DXPatrol 2.4Ghz Amplifier Manual Page for SWR/FWD-PWR voltages
After checking all the connections and retesting and getting the same voltage reading I emailed Antonio at DXPatrol detailing my findings and asking if he could advise on the voltages I was seeing. Sure enough in no time at all he came back to me saying that the manual was incorrect and that I should see between 0.2 and 0.5v on the SWR pin for a good SWR match. Being happy that the readings I was getting were fine I emailed back thanking him for his swift reply and then moved on to check the power output safely in the knowledge that the SWR reading was within tolerances.
Checking the FWD-PWR pin I found that on SSB the voltage was fluctuating between 2v and 3v, this equates to 6w and 9w output, about right for SSB. Switching to CW mode I found the full 4v was present on the FWD-PWR pin confirming I had the full 12w output from the amp. Of course this set off “Leila” on the satellite immediately as I was a huge signal on the bird with such high power output and was a reminder to reconnect the amp to the 12v supply instead to ensure I didn’t exceed 5w output and thus keeping to a considerate level on the transponder input.
After further investigation I came to the conclusion that the water ingress could only of come from the cable inlet on the top of the enclosure, it had then run down the coax cable into the SMA connector. Somewhat annoying as the inlet is supposed to be a water tight fixing. Once I had everything back in the enclosure and securely fitted, I covered the cable inlet and coax in self amalgamating tape in the hope that this would stop any further water ingress. I also re-taped the N connector at the antenna end as well to ensure it was also protected from water ingress in the future.
2.4Ghz ground station enclosure ready for testing
I’m hoping this will be the end of my water ingress issues and that I have a dry 2.4ghz future ahead of me.
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 male to male SMA connector that Neil, G7UFO kindly posted to me arrived late this afternoon and I wasted no time getting it connected between the 2.4Ghz up-converter and the 12w amplifier.
Male to Male SMA connector for QO-100 Ground Station
Initially when I powered up the 12v to 28v converter board the output voltage was only showing 22v and so I had to adjust the onboard variable resistor to get the voltage closer to the recommended 28v for the amplifier. I decided to run the amplifier at 27v so that it wasn’t being pushed to it’s full and so readjusted the voltage converter back down to 27v. This seems to work very well with the amplifier not getting very warm at all during use.
M0AWS QO-100 2.4Ghz Uplink Hardware.
Getting on air I was really impressed at how strong my signal was on the 10Ghz downlink. With my own signal peaking 5/9+10dB I was very happy with the performance of the ground station.
I made a few contacts very quickly with the first being OH5LK, Jussi from Helsinki Finland. Jussi was actually the first station I worked on CW too when I was running just 200mW, it was great to have him for both of my first contacts on QO-100.
I then went on to work a few stations from Wales, Germany, Poland and Belgium but, the one that I was totally shocked to get on my first real day of QO-100 operations was ZD7GWM, Garry (HuggyBear) on St. Helena Island, South Atlantic Ocean. This is an Island that I have never had a contact with before on any band and so I was extremely happy to get a new first especially on my first QO-100 day.
Garry and I chatted for some 25 minutes covering many topics, it was great to have an armchair copy over such a distance, something that would be impossible on the HF bands. What a great way to start my QO-100 satellite career!
One of the things I really like about the operators on QO-100 is that they have time to stop and chat, this is so refreshing and a rarity today. I’m really going to enjoy this satellite.
I’ve been waiting for over a week so far for a male to male SMA connector to arrive from Amazon so that I can connect the 2.4Ghz up-converter to the 2.4Ghz amplifier. Since it still hasn’t arrived I decided to connect the up-converter directly to the IceCone Helix antenna to see if I could get a signal into the QO-100 satellite.
To my surprise I could easily hear my CW signal on QO-100 even though the total output from the up-converter is only 200mW.
I didn’t expect to be able to hear my signal since it’s a tiny amount of power that has to travel some 22500 miles to the satellite but, I could hear it and was amazed that it was peaking S8 on my SDR receiver.
2.4Ghz Up-Converter connected directly to the antenna bypassing the 2.4Ghz Amplifier
Being excited I put out a CQ call that was soon answered by OH5LK, Jussi in Finland. Jussi gave me a 579 report which I was extremely pleased with. He was of course much stronger at a 599+ at my end. We had a quick QSO and exchanged details without any problems at all. Its really nice to get a QRPp contact without any QSB or QRM.
M0AWS QO-100 1.1m off-set Dish and IceCone Helix antenna ground station
Neil, G7UFO who I chat with regularly in the Matrix Amateur Radio Satellites room has posted a connector out to me so I’m hoping it will arrive on Monday and then I’ll be able to connect the amplifier and hopefully get a few SSB contacts.
UPDATE: I’ve since had 2 SSB contacts via QO-100 using just the 200mW O/P from the up-converter. Both times I got a 3/3 report not brilliant but, perfectly acceptable for the amount of power I’m putting out.
More soon …
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