Friday, February 15, 2019

C-pole antenna for 40m - a dx profile at low heights

Yesterday I went out to test my newly built c-pole antenna. I have used one in the past but found out it had some construction errors - the effect of which was somehow hidden by the balun I added ( a couple of coax turns on an FT240 core). The balun did get extremely hot even with 100w - a sign something was wrong - and once I replaced it, the SWR went through the roof. 

I used an online calculator (http://svrc.org/cpole/) that turns out to give the wrong dimensions - at least for 40m. I did not notice it before but when using it again for my new version I found that adding all the various dimensions it gave resulted in significantly less wire than the calculator specified as "total wire needed for antenna". So considerable tweaking in the field was necessary to get the antenna resonant.

New c-pole antenna in action

Construction
This time I used two short cheap and light fiberglass fishing poles for the horizontal spreaders. I cut them to the right length and ran the antenna wire through them. I used the caps on both ends to position the wire - making a hole in each cap and a knot in the antenna wire at each cap. Apart from their low weight and high stiffness an extra advantage over the PVC pipe I used before is the fact that the fishing pole can be (partly) retracted - decreasing the size of the collapsed antenna.

To complete the antenna I constructed a W2DU style balun. It is light and simple and still provides more than 20dB common mode suppression at 7Mhz (if you use the right beads). 

The first time I brought it out I used all my time to get the dimensions right. In the end I got the antenna to dip around 7.1 Mhz with an impedance of something like 49 Ohm - perfect.

The next opportunity to go out was yesterday. I tried the antenna from a nature reserve, to see if I could get a decent amount of contacts on 40m. It was too early to get any serious DX but I did log 150 contacts up to 2500km. So it did seem to tx and rx.

Comparing C-pole to EFHW, Inverted V and Delta Loop
The c-pole is an addition to a range of antennas I have for /P operation on 40m. I mostly use either an (almost) vertical end fed half wave or an inverted V - depending on how much space I have to set up the antenna and what kind of radiation pattern I am looking for (more NVIS or more dx). The final option I have is a delta loop (more or less corner fed - so vertically polarised). The loop is more complex to set up than the others though.

All these antennas can be used when I have my 18m Spiderbeam pole with me. They are all omni-directional but have a different radiation pattern in the vertical plane - with the vertical, c-pole and delta loop in one category and the inverted V dipole in another. 
Using my 18m Spiderbeam pole the antenna patterns (over local ground conditions) look like this:


  • Pink is the inverted V. It has nice NVIS qualities with a lot of gain on high angles of radiation (5.4 dBi straight up) but at a takeoff angle of 15 degrees only -5dBi.
  • Blue is the delta loop. It is almost the opposite of the inverted V dipole. It has most gain at a takeoff angle of 20 degrees (3.3 dBi, 3.1 at 15 degrees)
  • Green is the (almost) vertical end fed half wave. A bit less pronounced than the delta loop. It has a max gain of 1.6 dBI at 15 degrees.
  • Red is the new C-pole. It has a max gain of 2.1 dBi at 15 degrees. 

Looking at the three antennas with a "dx profile", the delta loop is the clear winner. It has more gain on low angles but also significantly more gain than the other two at higher angles. It is a bit more work to set up though and needs space.

The reason I started looking at my c-pole again is that there are situations in which my 18m pole is not available (I could not take it, or - in a team expedition - it is in use with another antenna). The next option I have then is my 12m Spiderbeam pole.
Now things are a bit different. For one, the delta loop is not an option anymore. The half wave vertical is also out of the question. That one becomes a sloping end fed half wave with quite a different behaviour.

Using my 12m Spiderbeam pole the antenna patterns (over local ground conditions) look like this:


  • Blue is the inverted V. It is still radiating most of its energy up at high angles but the max gain is now down to 1.8 dBi. Gain at 15 degrees is down to -9dB.
  • Green is the end fed half wave sloping. It is now also radiating more at high angles with a max gain of 3.8 dBi straight up. Gain at 15 degrees is -1.4dBi
  • Red is the c-pole. Max gain is now 1.7 dBi at 20 degrees and 1.4 dBi at 15 degrees. 

The C-pole does not seem to suffer that much from the change in height. It actually performs a bit better on the higher angles without losing much on the lower angles. 

Comparing the C-pole at 2 meters off the ground and 7 meters off the ground shows that this antenna is better off on my 12m Spiderbeam pole:


Red is the C-Pole with the top at about 11.5m and Blue is the same antenna with the top at about 16.5m. At low angles almost no difference but at 45 degrees the lower C-pole has 7 dB more gain (at 60 degrees the difference adds up to 13 dB).

Looking at the radiation shape of the higher C-pole (in blue) you can see a central lobe that you can expect to grow when you put the antenna even higher - and it will. However height is not a variable I can influence that much. It will be somewhere between these two extremes.

Conclusion
The practical test showed that the antenna works - I logged a lot of contacts with good reports and the SWR is now perfect - and the model shows it is a decent addition to my set of antennas, especially when I am constrained in height.

Friday, December 14, 2018

Looking ahead at 2019

Discussing plans for next year with my YNOMY team brought me to ponder what radio-activities I would be going to undertake. I have rarely been in the vicinity of my radio this year and I think next year will be the same. Conditions are such that I can hardly make any interesting contacts with the setup I have at home. At the same time my work commitments limit the /P opportunities. I hope to be able to go out some more to activate some nature reserves or castles than I did this year. Perhaps I will re-use some of the special calls I used in 2017 (P*44FF). 

As I look ahead, I can see three highlights on the horizon: 

1. YNOMY expedition
LX and HB0 were so much fun that we have decided to spend another weekend in May together in some relatively remote place activating nature reserves. We have some ideas where to go to but more details will follow once we finalise our plans. 

2. COTA-PA special event
The world castle award program turns 10 years in June. The COTA-PA program - the local castle award program for PA - will participate in the festivities. I am currently organising a group of operators to use a number of special callsigns in June for the celebration.

3. Summer holiday
The summer holiday always gives me time and opportunity to go out /P. I will be in France this summer and expect to activate some nature reserves there.

No PACC
Not on this list is the PACC - our national contest. I have been participating with my YNOMY team for the last 5 years and we won the last 3 times. Looking ahead at 2019 we found that we lacked motivation to go for a fourth win. 
We did not make any changes to our field day setup - so there is nothing to test and learn. As it is a field day setup and as we enter the contest to win, it is a considerable effort. Repeating last year is just not enough fun for us to put that much effort in.
We might return to the contest in a couple of years if conditions improve - as that will change the contest dynamics and gives us an opportunity to improve on our own highscore (in points).

Perhaps the end of the year will give me an opportunity to go /P for a change. At the moment planning the May expedition is the major source of radio fun. 

Thursday, November 29, 2018

SWL-ing the DX cluster

Our radio hobby has many different sub cultures each with their own challenges and rewards. You can climb mountains carrying your radio equipment, collect lighthouses from your armchair, participate in contests until you lose your voice, provide emergency communication (or just endlessly prepare to provide it), design and build equipment, etc.

Some of these I find more interesting than others, but I can relate to the enthusiasm people have for all these activities.

There is however one activity that really puzzles me: SWL-ing the DX cluster
What could be the fun in that?

I think I have an extra hard time in relating to this activity because I consider an accomplishment something personal - something you do to please / prove something to yourself.
I mean, I can imagine it is great fun to use a remote super station in another country to chase DX. Nothing wrong with that. But when you use this setup to boost your own score inside the context of the DXCC program (or any other program for that matter), you lose me completely. Without a split personality I cannot phantom how you are going to fool yourself - I mean, you were there...

In this example - using a remote station while trying to fool yourself - you at least have the fun of making radio contacts. So, there is some fun in the doing. Now imagine you try to fool yourself but you choose an activity that is as boring as can be: SWL-ing the DX cluster.

How does it work?
Well, imagine you are an SWL and you like to get some credits for one award or the other. Instead of turning on the radio though, you open a DX cluster page on the internet. Now you either wait for the right station to be spotted (depending on the award you are looking for) or you search for it in the recent spot history. As soon as you find a candidate, you write a QSL card to that station claiming to have heard a QSO between him and the spotter.

Quite straightforward really.
If you keep up the good work you will end up with all sorts of awards.

That is really cool - knowing that you did not qualify for the award and that you spent your time copying text from the internet.

Eh?

PS:
How do I know this activity actually exists? I have an old account on a cluster node that I started when I had my novice license. The user name on this node still is my old call. 
Once in a while I use this cluster node in the field (it is listed in an app on my phone) when spotting for a special event. In case I am the operator, I get the QSL cards.

So.. if the cluster-copying SWL forgets to check QRZ carefully, I will get an SWL card claiming my previous (now inactive) call worked me, while I was operating a special event.... go figure. 
And yes, there is actually an SWL - DH5FA - that has managed to send me such a card. Even more peculiar than that, he has sent me more than one (for different special calls) - even though I warned him after the first one.

My fellow earth dwellers never cease to amaze me..


Tuesday, October 30, 2018

5b dxcc

This weekend I reached the "5 band DXCC" level. Quite a remarkable milestone considering the journey...

Where it started
When I came back to ham radio in 2010 I was eager to work as many DXCC as I could. I started with a shortened dipole in the attic - very far from ideal - but each and every country was a new one. Even with limited radio time my progress was smooth and I was happy for a while.

I upgraded my license in 2011 adding a load of new bands and with that the challenge increased: I would have to collect at least 100 DXCC on each (why?... I don't know, that is how addiction works).

My antenna changed into a wire behind the house running from 8m high to 2m high in a corner of the garden. An upgrade from my in-house dipole and an opportunity to add a few more DXCC.

Chasing /P
In the mean time I had developed a new addiction: activating WWFF nature reserves. Going /P inspired me to develop better antennas. Portable operations have their limitations (especially if you look at it from your multi tower station) but in my case I saw opportunities I did and do not have at my QTH.

From a mobile whip I quickly moved to vertical end fed antennas that already were more effective than the wire behind my house. And as time went by, adding more DXCC meant going out /P.

I took the opportunity of big contests - with lots of DXCC's active at the same time - to make my /P DX hunting as effective as possible. All the while trying to improve my /P station.

Beaming with delight
In 2012 I had one of my most pleasant chases when I went out with a 4 element beam for 10m (a band still open at the time) during CQ WW SSB . I added 24 atno's and 14 new bands, working a few hours on Saturday evening and a few hours the following morning. I don't think I have ever worked so many new ones in just two time slots.

Although the 10m beam was instrumental in the fun that time, it was also the first time I used the folding hexbeam that I just finished building in the week before the contest. This became and still is my favourite /P antenna. It has helped me work DX even now, at the bottom of the solar cycle.

With the hexbeam and a small mobile amplifier I added to my /P setup, I went DX fishing during a few other contests the next year. I scored 10 atno's and 22 new band dxcc during WPX in 2013 with the hexbeam, 4 atno's and 27 new band dxcc during EU HF contest  in 2013 and 6 atno's and 24 new band dxcc during CQWW SSB 2013.

3 band DXCC
By August 2013 I had logged more than 100 DXCC on three bands: 10, 15 and 20m. 17m was the candidate for the next 100 and I think I reached that somewhere in 2016 (time to play radio had been rather limited in the interim and I had not been out to actively chase DX /P).

By 2016 12m was no longer a feasible candidate to reach 100 DXCC as the sun spots had disappeared and I had failed to give that band enough attention in the preceding years. So my focus shifted to the lower bands. In 2016 I went out again during a CQWW SSB. This time focusing on 40m and 80m. I was only able to add 4 new DXCC to 40m, while adding 12 new ones to 80m and 28 new ones to 160m.

This left a challenge with still quite a few to go on 40m. The most feasible new ones required different operating hours than I could use from home (with the whole family asleep). So it looked like I needed another contest and /P operation. However I did not find the time. 

The final push
Then came last weekend with yet another CQ WW contest. I had not planned to be particularly active. There was no time to go /P but I did have some free slots to switch on the radio at home. Somehow I had brought my total to 96 DXCC worked on 40m in the meantime. With no expectations at all I started chasing some new ones I could hear. With the simple setup at home I could not reach all of them but with some persistence I was at 99 DXCC on Saturday evening. Of course this was not going to be the end result of the weekend. I continued my chase on Sunday in between other obligations and by the end of the day I was at 102 DXCC with an amazing JT and KL7 in the catch (thanks to their antennas).

Next up: 80m.. only 50 DXCC to go.


Tuesday, October 23, 2018

Testing my VDA on 20m

Last Monday I found some time - at last - to go out and do a proper test of the VDA I built many months ago. It is a 20m version and I only built it to test the effectiveness before deciding to build one for 40m - for which I don't have a directional antenna yet.


My 20m VDA
The only way - imo - to assess the performance of an antenna is to compare it to one or more (default) antennas at the same time. Conditions vary strongly by the minute, so you need an A/B type of setup. 

What I did was the following:

1. I set up the VDA on my 18m SpiderBeam pole with the feedpoint (at the bottom - as my VDA is end fed) at about 3m high.
2. I set up an end fed vertical for 20m with the feedpoint also approx 3m high.
Vertical at the picknick table
VDA with vertical in the background

I then performed three types of tests:

1. I ran 2 identical WSPRLite beacons for 90 minutes (0.2w output)  
2. I generated spots on FT8 with my FT857 (50w output) using an antenna switch and comparable feedlines 
3. I did some live SSB RX tests using the s-meter and one TX test (100w output) with the help of Timo OH7JHA.



One of the two WSPRLite beacons
I collected the WSPR data from the WSPR database and the FT8 reports from hamspots.net


Data collection (and some first impressions on the go)

Overall impression

Looking at all the data there is not an easy path to a final conclusion. So bear with me.
Especially the FT8 data seems to present a complex picture - where sometimes the vertical is the only one heard and then the VDA while they both have decent reports with that particular spotting station. My assumption is that the FT8 data is less reliable as the band was crowded at the time. I saw that I was often competing with other stations on the same frequency. For me that could explain why some of the patterns in the data seem to contradict / give inconclusive outcomes. 

In general I find that with 50w (@FT8) output the simple vertical generates more spots (is received more often). This makes sense as it is omnidirectional and the spotters can be found in all directions. With 0.2W (@WSPR) this is no longer the case as the omnidirectional signal becomes too weak to be picked up in many cases. In fact at one point the conditions had gone down and I received no spots at all with the vertical while still being spotted with the VDA (btw I swapped the beacons to be sure there was no influence there).


Looking at both the WSPR and FT8 data I can also see that the VDA almost always "wins" when the station is in the direction the VDA is pointing in (assuming a 60 degrees beam width).


WSPR results

Using only the WSPR data the VDA is a clear winner. The vertical only wins once and only marginally while the VDA was pointing in the other direction. There are a number of ties but when the station is in the direction the VDA is pointing in, the VDA wins 100%.
The VDA makes it across to PY (9000km), while the vertical only reaches EA8 (3000km). 

FT8 results

The FT8 data paints a less clear picture:
  • The VDA is the only antenna that reaches VK (multiple spots from VK2 and one from VK8 up to -13). 
  • When pointed towards JA the VDA creates a lot more spots than the vertical (from more spotters) but the overall SNR is only about 1dB better on average.
  • When pointed towards W the VDA is comparable to the vertical with only about 0.5dB better reports on average.
  • When pointed toward 4X the VDA clearly wins (5dB, 2 spotters) while it mostly loses when pointing the other way (as you would expect with a directional antenna).
  • In EU the VDA mostly wins when directed towards the spotter with the exception of EA (several spotters - maybe there was some obstacle in that direction?). However the VDA also loses sometimes or wins when it is pointing in another direction - which does not make sense if it is directional. It seems that in 1 skip distance the directivity is not as noticeable or other factors play a more important role (FT8 qrm, type of antenna used by the spotter, etc.).

"Live" results
The live data also gave some different outcomes. Testing with Timo - pointing the VDA to OH - gave no conclusive advantage (Timo reported an s9 on both antennas) while turning the VDA away only decreased the signal by 1 to 2 S-points. 
Listening around the band and switching between the two antennas increased my understanding of the difference in practice. When the signal was loud the difference was hard to notice.  However, when the other station was DX and weaker (FH, W) the VDA was up to 2 S-points stronger. I have made a short video of W1ZY/M station working with a mobile antenna, where - even though there is QSB - you can see the difference in RX quite well.




Conclusions

Getting more hard facts - so as to be able to make any claims about gain figures - would require setting up both antennas for a couple of days with the two beacons. Sadly I do not have the space to do that. 

So for now, we will have to work with what I have learned on Monday and by going through the data:

The VDA is not a miracle antenna. The theory (as I discussed here) shows that it should have around 3dB gain over the vertical I used as reference. Practice shows it has gain over the vertical that is noticeable (relevant) on multi-hop DX (eg with VK) and weaker signals but on shorter distances the effect is less clear. The data also shows that the VDA has directivity but I have not been able to assess how much that is.

All in all this to me is not enough to warrant a 40m version of this antenna. I will be taking this 20m version along on my future /P adventures as it does not take up that much extra space. If I learn more, I will share it.


If you have other experiences with this antenna or comments on the way I constructed or tested this one, let me know. I am always eager to learn more.


Tnx to Timo for his help and the many spotters (that were unaware of their support to this test).

Tuesday, August 7, 2018

To CW or not to CW

A long time ago, when I decided to get my ham radio license, it was still mandatory to acquire CW skills before you could get an HF license. At the time I did not picture myself learning CW off of cassette tapes. In my early twenties I had much better things to do. So I went for a novice license that allowed me access to a part of the 2m band in FM with a whooping 10 watts. This was fun for a couple of months and then the radio went in a box in a closet for a long time.

HF without CW

In 2010 I returned to the hobby when I found out I could go on HF with my old license and that for a full license CW was no longer mandatory. I upgraded to full half a year later.

So all these years CW was never more than an obstacle to me. I have made a few CW contacts using my computer but then CW becomes just another digital mode. A bit boring.


As I am quite capable of using my voice - and have been for many years and hopefully for many years to come - I perceived this whole CW-thing as a needlessly difficult and indirect way of communication.

Also I found that CW carries with it a certain amount of snobbery (only by some, but still noticeable): you have the nobles that use CW to communicate and the plebs that uses phone. Hardly inviting.

The need to change

Things changed this year. We have a small radio group (M, YY and myself) that amongst other things participates in the PACC contest. We have done so for the last 5 years, winning the last 3. CW is crucial in this contest and only one of us - M - masters CW. 
This year M could only join us a couple of hours into the contest. That would make it impossible to achieve a competing score. Luckily we found a local OM that was able to jump in on last notice but we clearly saw our weakness as a team. Until now it had only been a practical nuisance with M taking a 24h shift with only short periods to doze off, while YY and myself could work in several shifts.

This is when YY and myself decided we had to learn CW. At least to the level that we could take CW shifts during the slow early morning hours.


Learning curve

Reading up on all the tips regarding learning CW I started using the Koch method via a website, but found it waaayyy too boring. There was no way that I could slow myself down to that level with normal life happening. 
YY in the meantime informed me he was using morserunner and that it was nice to learn to copy calls better and quicker. Rather frustrating as I had just made it to Koch lesson 2 and still confused the K and R.

Some time passed until I came across a nice Android app called "Mors.". It shows you an English word and then gives you a certain time to send all the letters by tapping the screen (dah - dit). The time you get to complete a word decreases, making it harder and harder. It is up to you to beat your high score. This gamification works for me. I quickly learned all the letters.


However... this way you learn the letters as dashes and dots and in a rather slow pace. It might give you some foundation but I was still unable to copy anything sent at a regular speed. 


So back to boring Koch.. and big time procrastination.


Four months had passed with little progress apart from the ability to translate letters in morse code v.v. on paper. Then came the summer holiday. The summer was extraordinarily hot and HF conditions were poor, so during my stay in OZ I decided to sacrifice some of my /P radio plans to just relax in the shadow and force myself to complete at least a number of Koch levels. M and YY advised me to start with a larger number of letters in stead of learning them two at the time. It helped making the learning less boring. Also the fact that there was nothing else going on then the kids enjoying the sea, helped to keep me focused.


I used (and still use) two Android apps to help me learn - see below for links: CW Trainer (using the Koch method) to send a random set of letters at a 24wpm with Farnsworth timing (slowing down the sequence but not the letter itself) and Morse Camp to send English words of a given length.


Some progress
By the end of the holiday I was able to copy all letters at 24wpm, making only a few mistakes along the way. Copying words is still a challenge as I really need the Farnsworth delay to mentally process what I heard.

So now the challenge is to keep on repeating what I learned, add numbers as new signs still to learn and start bringing down the Farnsworth delay (speeding up the sequence).


All that.. while normal life has returned. 

So far I have not touched any of the morse code apps yet but given the investment I have made so far, I am confident that by the time the PACC contest starts next year, I will be able to take my CW shifts.

And perhaps I will be able to make real life CW QSOs before that.





Links to the apps I use (on Android):
Mors. allows you to practice sending morse code. The nice thing is that it works as a game where you have to improve on your last high score. The down side is that it does not actually learn you to copy (rx) CW. 
CW Trainer is a nice trainer that allows you to use various training modes, including Koch. I liked the interface and versatility of the app so I decided to buy this one.
Morse Camp is a website and Android app (for which I cannot find the link anymore) that sends English words of a predefined length.

Tuesday, July 24, 2018

OZFF-ing meeting Jakob and Finn

So last Sunday I went out /P while on holiday in OZ. I started out in OZFF-0100 where I found that the best option I had was to climb a hill covered in trees. So I threw a fishing line into a tree and pulled my wire antennas up that way.

Set-up at OZFF-0100 - wire up in a tree


I started on an instable 20m with a lot of short skip. QSB was strong but a steady stream of chasers kept me on this band for more than an hour. I then set up a sloping wire for 40m. The set-up was not ideal and the band in a poor shape. 
In total I logged 107 different OMs from 22 DXCCs with most activity from I, DL, G, PA and SP.

I quickly dismantled my station and left for OZFF-0098 to meet up with Jakob OZ7AEI and Finn OZ3FI of the OZFF team. I know Jakob already from the start of the WWFF program but so far we had only had contact via e-mail and SSB. 

I arrived at the designated location to find Jakob and Finn already there. We had a quick chat but decided we could not let the chasers wait for too long. 

We spread out a bit to make the station to station QRM bearable. Finn went for 17m and 30m CW and Jakob and I used 20m and 40m. Finn had issues with his battery, which meant he had to stop operations early. We took a break and had some time for coffee and chat.

OZ/PH0NO, OZ3FI and OZ7AEI

Finn then left us and Jakob and I continued on 20m and 40m. 

In about 1,5 hours radio time (we spent about the same time chatting) I logged 105 different chasers from 28 DXCC evenly spread over 20m and 40m. Jakob also logged 100+ QSOs on the same bands.

On 40m I used a delta loop and on 20m an end fed vertical on an 18m pole. Most chasers I logged were OMs from DL, I, SP and PA.

It was great fun meeting fellow WWFF enthusiasts in person and of course all the usual suspects over the radio.