Thursday, September 30, 2021

IC-7300 - Strange SWR anomaly

 To measure an antenna concept like I have you need something different from an antenna analyzer. Since the ATU needs a signal of at least 10W to tune the antenna. With an analyzer it would mean I choose a frequency transmit a signal, disconnect antenna, connect analyzer and note or make a photo from the results, next frequency same thing. This would take at least a hour to measure all 5 bands. The IC-7300 (and my old IC-706 as well) has an option to make a SWR graphic. And the outcome from my antenna concept system is of course different from the pictures you see normally since the ATU is an integral part of the antenna system.

You see that I have excellent SWR all over the bands. Logically because the ATU is tuning to minimum SWR on all frequencies. A lot of fun and very fast to measure with this radio.

The strange thing however is this:

I tried this several times. And you can be shure the SWR is 1:1 at 28.500 MHz and above. But the IC-7300 keeps giving me 1:2 SWR when I use this SWR tool. I think this has something to the with the filter switch which I hear clicking when I tune over 28.500 MHz. Not shure why this is affecting the measurement. Can somebody give me a logical explanation?

Wednesday, September 29, 2021

Memmert Island post updated with photos

 Thanks to Markus DJ4EL who sent me some nice pictures from their activation.

For more photos see the previous post this month...

Tuesday, September 28, 2021

Concept antenna concept

  Another concept antenna or is it an antenna concept? Previously tried quarter wave wires direct on my antenna with less success. Couldn't get a good SWR on 12m and 10m with the ATU. I even tried to attach quarter wave wires as counterpoise instead of my tower. Then I did read some articles that multiband dipole antenna wires should at least be separate 10cm from each other to minimize the interaction. Another challenge is to make quarter wave radiators the right length. Measuring is no option since I always use an ATU at the feedpoint. So I calculated some wire lengths and made a practical experience wild guess. Counterpoise is again my tower. You can see this whole thing as a massive OCF vertical dipole with a ATU in the feedpoint. I also keep my wide band 1:1 balun between the antenna and tuner, not shure if this helps? A 1:4 balun could be a better choice?

Since I had to remove the duoband 6m/4m beam for the winter I decided that it was time for another antenna experiment.

Somewhere on the internet I saw a video from someone that had a nice idea to separate the quarter wave wires. So I lend the idea to implement on my own vertical as experiment. The secret to build this thing is "shockcord" to keep the wires straight under all circumstances. I ordered 20m from it on the internet. The only wire I could not attach shockcord was the 4,9m long wire for 20m since the antenna is basically too short, but I don't see that as a big problem. 

If you think this is a strange contraption....look at our sunflower...

Last time I counted it had 12 flowers in it. And it grows wildly.

You can see the results I have with this antenna and 100W RTTY in the previous post. Not that it is always the antenna that gives good results since we all depend on propagation. But I'm very satisfied with it so far. SWR is good on all 5 bands I designed it for. I measured it with the IC-7300 and took some pictures. I will publish that in a separate post since I found some strange behaviour on my IC-7300 measuring SWR on 10m above 28.500 MHz.

Monday, September 27, 2021



Due to the COVID-19 restrictions we were not able to get to our club evening. Exchanging QSL via bureau was on a hold. Last friday was the first time in a year we could get and send our QSL cards again. The local QSL manager had something to tow. Most of the QSL cards are for the PE75FREE activation from last year....!!!!

This is what my PE75FREE QRZ page has to tell about QSL:

It seems reading is more difficult as contacting me via radio ;-)

The question is.....why??? All bureau cards for PE75FREE have been sent, do not send me any QSL cards as reply. I don't want them and don't need them.

#CQWW RTTY 2021 - running into issues

Event: CQWW RTTY contest 2021

Section: Low SOAB
Logger: N1MM+ 
Station: Icom IC-7300
Antenna 1: Homemade vertical with ATU @16m
Antenna 2: 10m LFA @14m
Antenna 4: 2x20m inverted-V doublet apex @12m

 The RTTY contest, you really have to love it or hate it. The mode is ancient, the technology in use these days to work RTTY mode in a contest is quite sophisticated. If you don't contest often, like me, you probabely run into some issues once and a while. And I did this time. This is what happened already at the first QSO:

What? Can't log the contact, am I missing something.... So I wrote avid neighbour contester PA4O Peter for help but at first he couldn't think of a thing that helped. I tried to start the computer again, the software again, made a new log, made a new database....really I tried an older N1MM+ version. Nothing helped. It was late saturday evening and I decided to stop after a few QSO because it wasn't fun, I couldn't log any american stations. I also decided to call for help in the N1MM+ io groups. And got a lot of suggestions from people. Till John K3CT wrote something about an UDC file, that triggered something and Peter PA4O wrote me if I still used the country and UDC file from the last PACC. And yes I did....

If you ever run into the same issue. Try to install the latest country file. It solved my problem...

My own stupid fault? No, I don't think that way...N1MM+ is packed with too many options. I'm shure we need everything but it doesn't make things easy...the support, however, is fantastic!

Because of antenna work Saturday I actually made most QSOs on Sunday. Testing a new concept antenna was my priority. The only QSO on 10m was made with ZX2B by the way..
Most time was spend on 15m which was in excellent shape.

Notice: flag colour: yellow=10m, light blue=15m, dark blue=20m, green=40m, red=80m
Click on this map to view a more detailed one.

Thursday, September 23, 2021

Magnetic Loop Antenna - my practical mods so far

 As written before building and experimenting a MLA is very addictive. You can always improve things and learn a lot from it. First of all I have to tell that my MLA is designed for indoor use, I consider it too weak for the outside and tuner box is not watertight. Although I can always put the box into a plastic bag or something.

First of all I had issues with the coupling loop. It was soldered directly to the PL259 chassis (or is it a SO239 chassis?). The soldering broke many times when experimenting so I decided to copy kind of OM0ET's idea, although I'm not that gifted. Practically it works well... I also decided to keep the length of the coupling loop 72cm, smaller as I had before. 

Another thing I would like is a possebility to mount the MLA on a tripod. My tuning box was designed to put it on a table of some sort. But if not available I had to put it on the ground which causes too much losses. How to solve this challenge since the thread on the tripod is 1/4" UNC. Something not really common in the Netherlands and hard to find a tap for it. But since I have a job in repairs we have some UNC/UNF bolts and nuts in stock. I found a suitable nut. The thing I did is drilling a hole in an iron strip big enough to fit the nut in and weld it to the strip. The strip is mounted on the bottom of the box. Challenge (or problem) solved. If you wonder why I didn't mount it at the center, the bolts would touch the variable capacitor on the inside.

Yes, I would like to have a bigger cap. This one is only usable for QRP powers. For now it does fine.

Mounted on tripod now.

80m configuration

Just to give you all an impression. Things might change in the future. So far I only tested range on 30m. But will try and test other bands soon. I want to test it outside as well although the loop is designed for inside.

Sunday, September 19, 2021

6m FT8 on an ordinary day in September


Don't have much time to play with the radio hobby these days. But find a free hour today. Decided to give CQ on FT8 with about 70W in all directions on 6m. Antenna is the YU7EF 5 el. 6m/ 5 el. 4m duoband beam on 15mh. Didn't receive any signal. Although others did receive me...

I decided to do the same on 10m later on. Received quite stable signals from V51MA (Namibia). And he received me as well.

On 10m I used 100W into the 4 elem. LFA on 13mh

Just to show there is always some sort of propagation even on a deserted band...

As a matter of fact, just a few moments later I made a QSO with ZS6AF (RSA)... His signal boosted by the greyline was -4dB at the moment we were in QSO.

Tuesday, September 14, 2021

Magnetic Loop Antenna - The wrong path, questionable. But it ends well...

Tuning box outside
In my last post about experimenting with the MLA I commented to John AE5X that I had to figure out how to get my MLA resonating on 28MHz. I thought a smaller cap (switchable) would be a solution. John gave as answer a link to a calculator to see what value I would need.

I calculated my antenna as follows:

Antenna length 2.70 meter (notice don't use a comma but a point!), conductor 0.9 cm diameter, 28MHz, 10W.

I would be needing a 23pF capacitor. However in practice I needed a 9pF capacitor to match as good as possible, still a 2:1 SWR. Well, you see the comments: 2.7 m is not ideal. I thought that's why I probabely don't get a good match. The antenna is self resonating since it is a quarter wave long, I should avoid that. The only way is to make a smaller loop. A antennalenght of 2.55 m will do fine. Unfortunately it will cost me some efficiency. But with these kind of antennas it is always a trade off.
So I redesigned it and calculated it as follows:

Notice that I now actually measured the diameter of the coax braid which is 7mm. Tuning capacitance would be approx 29pF but unfortunately even using my minimum of 15pF gives me a max. usable frequency of 22MHz.

So, I was thinking now. I would be pleased with a small MLA that would cover 80m-10m. Normally that is impossible. But why not using an extra loop in series? A so called multiturn loop. Yes, it is not efficient, but always better as a dummyload. So, I found another calculator on the web. This one seems to be more accurate and you can calculate multiturn loops as well.

Calculating with the same values as before I found that the capacitor needed would be 12pF which is much lower, actually it is half the value I got with the first calculator. Strange this calculator didn't warn that the loop would be too long, but on the other hand, that's the theory you should know as MLA builder. I constructed another 2,5m long loop and connected it in series with the existing one. The 80m is available this way without any problems tuning it.

But now I was thinking, when visiting the website from OM0ET who heavily influenced me in designing my own loop. Why is he using a too long loop (3m) and still be able to tune it between 40-10m. Someone pointed me to a possible answer. OM0ET only uses the core from the H1000 coax he uses. This is what is written on his website:

The Main Loop is made of an excellent quality coaxial cable BELDEN H1000 (made in Holland) which is 10,3mm thick in outer diameter. Inner conductor is made of solid Bare Copper 2,62mm thick core which allows to hold the perfect circular shape of the loop without deformation of gravity. In all my Magloops is connected only the inner core. Outer shield is disconnected for improve the SWR results and less sensitivity of nearby objects.

Theoretically this can't work very well since the core has only a diameter of 2,7mm. And we all know as experienced loop builders that the larger the diameter the more efficient your loop will be. But you never know, I could be some coupling between inner/outer conductor takes place. At least I found it valuable to experiment with it and I only connected the inner core to my tuning box. Unfortunately tuning the antenna was almost impossible now, and it looked like it was even more sensitive when I came close with my hand to tune the whole antenna. Besides that best SWR was 1:1,7 (R85 X=15) at most peaks and highest good SWR available was at 20MHz. Not really a success. So, I connected the shield again to continue my quest for tuning the MLA to 28MHz.

I measured the capacity of my variable capacitor again. It is 15-525pF approx. The minimum capacity is too large to tune the loop above 22 MHz, that is something for shure. I needed a system to lower this capacity. So I thought of a simple switch, switching a capacitor in series with the existing one or short this capacitor out to disconnect it. As a simple capacitor I used 9cm of RG58 instead of a mica cap used before, it has a value of about 9pF in theory (in practice as well after measuring). The nice works! I'm able to tune 24,8-28,8 MHz now. 12m and 10m with a flip of a simple switch. 

However, with this experiment I'm now convinced that the capacitor is the most important thing in the whole MLA installation. Most valuable would be a variable capacitor with a range of 0-1000pF or so. The problem is that such a device probabely does not exist and if needed you have to construct it yourself. Keep in mind that you need some kind of reduction device otherwise tuning would be impossible.

Experimenting with Magnetic Loop Antennas is very addictive. It is simple to build such an antenna and there are a lot of "simple" challenges, practical and theoretical, to explore. To not make this blog post too long I decided to write another post about the practical modifications I made to my loop, including some photos from the experiments so far. I might do some on-air tests in the mean time, because that's were an antenna is made for.

Sunday, September 12, 2021

30m MLA test


Busy to write a blogpost about my new experiments with the homemade Magnetic Loop Antenna. But what would it be worth without testing the thing. Testsite for now is my garage, the antenna is surrounded by stone and iron.

Transmitter is the W5OLF WSPR VCXO-AXE. It transmits 1W on 30m.

All monitored by the excellent WSPR Watch app on my Iphone. 44 unique spots during the night. The transmitter was battery powered and functioned till it was empty.

Friday, September 3, 2021

QSOs with Memmert Isl. (video)

 Decided to make a video from both QSOs since signals were very strong. Did expect about S7 from both portable stations from Memmert Isl. but in reality they were S9.

Of course most of the "path" was a few km of water. I kept listening for a while and found that they received a lot more stations compared to me. I guess that it was the extreme low noise and surrounding by water. Markus told me he took some pictures so I hope I can update this post later...

Update 29-Sept-2021:

Thanks to Markus DJ4EL who send me some photos from their activation, photos are published with permission. Thanks guys for this nice first time activation of Memmert Island.

Wednesday, September 1, 2021

Working extreme rare places - Memmert Island EU-047

 Personally one of the highlights of this hobby is to contact people at far away places. We most times call it working DX. In our hobby working is the same as contacting, just to be clear about that! Working Mexico for instance is real DX and rare for a HAM in Europe but it is more common if you're in the USA. However working with rare countries (DXCC in HAM language) is one thing. You can also concentrate on working islands. There are actually HAMs trying to work as many islands as possible and there is a complete IOTA (Islands On The Air) program which has every island or group of islands divided in references. Of course the rarest islands are those that are normally not accessible to people, if you can contact people on such an island it is just like a little gem and most unique.

Source: Infografik der Welt

So it happens last week there was an item on the DX-world website about the activation of a rare island by two German HAMs. It is the first time activation from this bird sanctuary in the waddensea which can only be visited by a limited number of people each year. And Memmert island (EU-047) happens to be near to my QTH. Although......I never heard about this island before. Strange isn't it, because with good weather we are able to see this island if standing on the dyke just 6 km from my QTH.

I think these guys deserve some extra publication since this will be a short (probabely 1 hour) activation from a extremely rare island. Just to get there is not easy since there is no harbour. The only ship getting there is coming from the island of Juist which is a car free island, so traveling will walking or by bicycle. So imagine, those guys will bring both a IC-7300, Heil headsets, some batteries and antennas in for just 1 hour of activating this island! I know what it is since my last island activation in 2012 with just a FT-817 which is much lighter as an IC-7300. And what about the uncertain weather, I can tell you it is not really fun if it is raining and the wind blows on such an island. What can I tell you, this is real HAM spirit!!

If you're interested you can find a german article here:

To read it just translate with google translate in your own language, it worked for me!

On the other side of Borkum we have a similair kind of island which is of course Dutch. It is called Rottum and actually it exists from 3 islands, Rottummeroog, Rottumerplaat and Zuiderduintjes. A family lived on Rottumeroog till 1965. I really don't know if this island has been activated by amateurradio operators in the past. I can't find any info about it. Rottumeroog is also a bird sanctuary and you're unable to visit the island without a guide. 

Some information about the island:

(translate with google translate)

You can find some youtube videos from Rottum to see what it is like to be there:

I always dream of activating Rottumeroog. Although I haven't got the time and the experience to do such a thing. I know others have much better portable equipment and good skills, hopefully they will pick it up. It would be a great reward to work someone from a uninhabited island especially close to my QTH.

Above you can see Rottumerplaat and Memmert Island in relation to my QTH Roodeschool.

Look out for DJ4EL Markus and DJ5TM Thorsten on 20m and 40m SSB. They will be around this Friday 3rd of September at approx 11:30 GMT.  QTH locator JO33kp. From what I understood is that they will both work with their own calls using both a IC-7300, 100W, Heil headsets and vertical antennas. So there will be 2 stations on air at the same time. But be quick as the activation time will be about one hour only.

Good luck!

Update 1-Sept. 16:00GMT: Markus wrote me there is good news. They will be active for 2 hours now!