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.


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).