Saturday, January 15, 2022

Mobile whip versus end fed half wave vertical

Those who have read previous reports of my portable activities know that I usually put in quite a bit of effort to set up a DX worthy station in the field - when possible using my hexbeam and a bit of power.

On the other end of the scale I still have a mobile antenna laying around from when I re-started the hobby in 2010. The antenna is known as D-Original DX-UHV and had some glaring reviews at the time. I did work across the pond to W with up to 7500km in phone and to PY and LU on psk31 (11.000km).

Quite quickly however I moved on to using end fed half wave wires for my portable activities, trying to cover more distance. 

Noticing that there are a number of castle (WCA) and nature reserve (WWFF) activators that use a mobile antenna, I was wondering how effective that antenna actually is. I have no doubt the end fed wire is superior to the mobile antenna, but how much better is it? Should I consider going back to using the mobile antenna?

So time to bring out the two WSPRLite beacons (two identical 200mW WSPR beacons that I can use simultaneously) again and head out to my test location north of Arnhem. My reference antenna is a half wave end fed set up vertically - or almost vertically in the case of the 40m version as the pole I use is 18m high. 


I started out with the 20m configuration of both antennas. The mobile antenna is in this configuration 147cm long. I chose to bring the feed point of the end fed wire about 2m off the ground as I have used this set up as a reference in other tests as well - and it is a set up that would only require a 12m pole so probably more relevant to the average activator.

For the second test of the 40m configurations, I fully extend the 18m pole and then sloped the last couple of meters of the end fed wire so that the feed point was about a meter of the ground. This is how I usually set the 40m end fed up in the field. On the mobile antenna I changed the element for 20m to the 40m version (the antenna is then 195cm long). The DX-UHV antenna can hold two different elements at the same time but for this test I decided to use one at the time.

As expected there is a clear winner on both bands - not surprisingly this is the vertical wire. The question I had was how much the two would differ. Here is a breakdown of the data I managed to collect in the time I had (1 hour on 20m and 1 hour on 40m), 

Results on 20m

On 20m in 1 hour:

  • DX-UHV - 16 transmission - 56 spots - 11 spotters
  • End fed half wave wire - 16 transmissions - 118 spots - 24 spotters
DX-UHV did reach NAEnd fed wire copied by the same and more

Odx for the mobile antenna was 6000km to W2. Odx for the end fed wire was 8000km to W7. 
There were not a lot of stations that copied the signal from the mobile - less than half of the stations that copied the beacon on the end fed wire. There were 6 stations that copied both signals multiple times. Looking at the reports from these stations there is an average 9dB difference in the signal strength reported. 

Results on 40m

On 40m in 1 hour:

  • DX-UHV - 15 transmissions - 119 spots - 27 spotters
  • End fed half wave wire - 12 transmissions - 317 spots - 56 spotters

DX-UHVEnd fed wire

Odx for the mobile antenna was 2200km to SV8 (1 spot -29dB). Odx for the end fed wire was 3100km to EA8 (7 spots). Looking at the reports of stations that copied both signals multiple times, there is an average 10dB difference in the signal strength reported. 

On 40m the difference is more pronounced looking at the amount of spots. With less transmission cycles of the beacon the end fed wire reaches more than twice the amount of stations. The reach is considerably longer with TF, TA, 5B4 and EA8 only copying the end fed wire.

Conclusions

So what have I learned.. well the outcome really matches my expectations. 

Looking at it from the practical side, the mobile antenna is easier to set up and does not take any more space than the car itself does at the activation location - can be a huge plus in some places. It also requires a lot less room in the car so it might open up a few more possibilities for /P operations.
 
The consequences however are that I will reach less stations and especially less DX. I have also found that controlling a crowded frequency is more difficult if your own signal is relatively weak. On the other hand... it might not be so crowded if no one hears you (hihi) 

The difference is considerable but not overly dramatic though, when conditions are good and signals are around S9 on the end fed wire, you would still put in a good S7 with the mobile antenna. So I will give it a try in an activation when conditions are favourable and simplicity is important for whatever reason. tbc. 

This post is one of a series of antenna comparisons I have done. The index to the other tests is here,

Monday, December 27, 2021

Enjoying better conditions as PG44FF

With Christmas approaching I had a bit of time available and I had already arranged a special call for the holiday season. Looking at the slowly awakening sun I was motivated to go out portable again on Dec 24. Normally I would go out somewhere in the afternoon and into the evening to get both some DX on the higher bands and lively conditions on the lower bands but Christmas Eve meant I had to be back home at 16h local time.

PAFF-0167

Trying to find a PAFF nature reserve that I had not activated before and that looked like it would allow me to set up my hexbeam (so not in the middle of a forest) I found one at 1.5h driving distance. Even though this would mean I would spend more time travelling than on the air I settled for it.

Setting up in the mudHexbeam looking towards OC

The weather forecast showed overcast but dry conditions. This turned out to be a but too optimistic. It was raining when I arrived at the nature reserve. The area I had selected to set up my station had turned into a big muddy pool. Still I managed to set up the hexbeam without getting everything covered in mud.

It was around 10.30 UTC so contacting the far east and perhaps even OC was theoretically still possible. So I started out on 20m with the hex pointing northeast. Skip within EU was a bit unstable but strong most of the time. After about 20 QSOs ZL3LF came through the pileup with a signal peaking at S8. A very nice surprise indeed. I called for more DX but got no reply however 6 minutes later VK2ON made it through the EU chasers with an S9. It shows that the band was wide open in that direction. I called OC a couple of times but it seemed everyone else was enjoying Christmas Eve away from the radio.

222 QSOs spanning the globe

It was busy all the time. In 2h20m I logged 222 QSOs in phone with chasers from a whopping 43 DXCC, 8 different W states and 3 VE provinces. 

I tried the higher bands but 10 and 12 were dead and even 15m did not result in more than a handful of QSOs. It would probably have served me better later in the afternoon. However the skip in EU was quite wide running all the way from 150km (still within PA) up till the edges of EU. So there was no real need to go down to 40m - which would have required changing antennas.

Nice wide skip in EU on 20m (orange = 20m, turquoise = 15m)

All in all again a pleasant activity and worth the 4h travel and setup time. HNY to all!

Sunday, June 13, 2021

Time flies: 10 years as WWFF activator

It is hard to believe but it is 10 years ago that I did my first WWFF PAFF activity on June 27, 2011. I had just upgraded my license after getting back into the hobby in 2010.

Actually sharing the experience of it is only the third post I wrote on this blog.

As I was just back on the radio after 15 years of inactivity, I took equipment with me whenever I could, working /P and /M regularly. That day in June I was in the north of the country for work, staying in a hotel. At the end of the afternoon I was able to get out of the office and head over to national park Lauwersmeer (PAFF-0014). It was only the second day that I was using my new PH0NO callsign. 

I had read about PAFF, probably on the blog of Hans PA3FYG or some other radio amateur website and was curious to see what it would bring to my /P operation.

In that period my FT897d was back to the dealer for repairs. So I only had an FT817nd that I bought as backup radio. With my whopping 5 watts, my end fed wire antennas and a rather thin Spieth 10m fiberglass pole (with extension rods to get the 20m wire off the ground) I was not expecting too much.

I was in for a surprise. It was the first time I had to deal with a pile-up. I logged more than 150 chasers and even one JA7 (mind you, SSB with 5W).

After this first experience I was sold. This started a hobby in a hobby doing many WWFF activities in various countries in Europe and VE, including memorable YNOMY team expeditions to LX, HB0 and GJ. 

Being enthusiastic about the program I was keen to help grow it both in PA and worldwide. I ended up coordinating PAFF and working as part of the WWFF team a couple of months later and up till the present day.

Impressions from 10 years WWFF

In all these years I met a lot of people. There are thousands of WWFF chasers but there is a hardcore group in the hundreds that have become familiar voices. I was also lucky to meet a couple of WWFF-ers in real life both in PA and abroad.

As a sort of commemoration I will be returning to PAFF-0014 on June 27. This year that is on a Sunday which is rather convenient. I will be using the last - so far unused - of the series of P*44FF calls that I have used before: PH44FF.




Monday, May 24, 2021

PAFF-0079 on the high bands

Acceptable weather for a change motivated me to go out to activate PAFF-0079. This reference had had some attention in the past (>500 QSOs) but most of it years ago. Expecting some Es conditions I brought my hexbeam and my 2-4-6m yagi.

Hexbeam and 2-4-6m yagi

It was rather busy in the area with people happy to be able to go out for a walk. It was difficult unfolding the hexbeam without getting in people's way. Ofcourse I got a lot of questions about this rotary clothesline..

The rotary clothesline

I started out on 6m but that band was not really alive. I only worked one EI station. So much for the effort to bring and setup the yagi.

I went over to the hexbeam starting on 15m as that band sounded quite active.. and it was. I logged more than 70 contacts on that band. Most of those were in the UK - there seemed to be a nice cloud over the North Sea. I was also greeted by Len VE9MY and Linda VE9GLF (P2P) and 5 US stations including the usual suspects Tom KG8P and Robert KD1CT.

After about 1.5h I went down to 17m again logging mostly UK stations and VE5. 17m was not too busy so after 30 minutes I went down one more time to 20m. 20m was in an okay state. It was never very busy but I did log almost 150 contacts in 2h. At the start I had the beam pointing towards NA - logging KA8H and W1OW - but I noticed spots to the east so I turned the beam. That probably helped me log 3 JA stations.

A cloudy but dry day out in PAFF-0079

I had skipped the 10m band earlier thinking the Es was not strong enough but I still saw spots on that band (past 20h local time) so I decided to go back up hoping for an opening to SA. With the beam in that direction I logged PU and some 20 more contacts in EU - mostly from south DL to I. 

It was getting late but there was one band to my immediate disposal I had not visited yet: 12m. The first response came from Max IK1GPG, who I just spoke to on 10m. In these last few minutes I logged a few more EU stations and FY to my surprise. 


It was so much fun on the higher bands that I never came around to breaking down the hex and going for the low bands. Normally I make most of my QSOs on those bands. However with a bit more time spent than usual (5h) I still managed to log 286 QSOs from 45 DXCC with 12 P2P.

Monday, September 28, 2020

Building a new lithium battery

For years I have been using lithium batteries to power my radio equipment when portable, both LiPo and LiFePO4.
If you want to know more about these different types read this post I wrote a few years ago.

I started out buying batteries from HobbyKing in China. Then I decided to build a few myself with pouch cells I bought from AliExpress. 

Recently I lost two LiPo pouch cells when I abused a battery - forgetting to attach the under voltage alarm. Another LiPo cell of a different pack turned out dead without a clear cause. I ordered a new cell but they are quite expensive. Losing three of those cells in a short period of time I suspect I might have to replace more in the future. So I started looking for other solutions with cheaper building blocks: smaller cells.

LiPo cell after abuse

Looking at smaller cells I first stumbled upon the 18650. A popular Li-Ion battery and quite small but you need a lot of them to get a useful capacity as they are around 2Ah a piece. However I found more practical LiFePO4 cells with a 7Ah capacity: 32700. I bought a set of those with strips of nickel attached to the ends for soldering as I do not have a spot welder (yet).

The voltage of four of these LiFePO4 cells is too low for my amp - that is why I opted for LiPo up till now - but as the amp is designed to handle up to 18V a battery of 5 cells would do the job. So I decided to go for a 5s3p design (5 cells in series and 3 in parallel).

Building a 5s3p battery

I bought a BMS as well with the idea that it will protect the battery from under voltage. And it allows me to charge the battery even with a simple (non balancing) charger. I was hoping that a BMS is more effective in balancing than the chargers I have - that take quite some time to balance an unbalanced pack.

Completed battery with BMS

Testing the battery my first lesson was that you cannot charge a battery that has a BMS with a smart charger. The BMS starts kicking in when the first cell approaches its maximum. The charger notices the increasing resistance and shuts down with an error ("connection break"). 

Charging through the BMS with a smart charger 

Time for Plan B I used a 12V source and a step up converter to 18V to act as a "dumb" charger. Meanwhile I checked the charging current and the voltage of the individual cells to see what was happening. 

This time the charger patiently waited for the BMS to allow for a current to run. The BMS would drain the cells for a bit and then allow a charge current until one of the cells hit around 3.5V and then the cycle repeated. However it did not seem to be able to bring the cells closer together. After an hour there was still a spread of 0.2V between the cells. 

After letting the pack sit for a while I found out that the BMS aims to keep the cells at around 3.4V (on my V-meter). So during charging - aiming for 3.6V - a cell might go higher but the BMS will continue to discharge it until it is back at 3.4V again.

I will have to see if this noticeably impacts the capacity of this battery pack. When I have some more time on my hands I will run some tests and see how it behaves under the stress of powering a 400w amp.

Update May 2021:
After using the battery pack for a while I decided to remove the BMS. In my situation - having balancing chargers - the BMS only adds complexity.

The second thing I noticed is that the pack was struggling delivering the high amperage the ALS-500m pulls. Testing the pack at home with a dummy load I saw the nickel tabs I used to solder the main + and - wires to became hot, red hot even. 


So I decided to solder wires to the first and last set of (three) parallel batteries to spread the current. Testing that thoroughly I found it to work perfectly. All cells now discharge evenly, even under high load.

Shrink wrapped end result (with built-in Voltmeter)





Friday, August 7, 2020

40m wire antennas compared

Before going on holiday I managed to get some life into my old C-Pole using a new home made choke. I re-tuned the antenna (with some challenges) but did not get a chance to use it. 

In the past I did use it quite a bit and was pleased with the results but as always - this does not tell you a lot. HF conditions vary too quickly and dramatically to base any evaluation on single antenna experiences. You really need simultaneous A/B testing.

A gap in my schedule allowed me to go out and do some testing of different wire antennas for 40m. I ended up testing a C-Pole versus an end fed halve wave more or less vertical and the same C-Pole versus an inverted V dipole.


Test setup

I used two identical WSPRLite beacons that transmit with 200mW on the WSPR frequency. 

  • The C-Pole was set up so that the feedpoint was at approx 2m above ground (that would be your typical setup with a 12m pole, like the Spiderbeam I have - with the top of the antenna at 11m). 
  • The EFHW was attached to my 18m pole and therefore almost vertical. The last 3-4m I set up sloping so that the feedpoint was at approx 1.5m above ground.
  • The Inverted V was set up so that the feedpoint/apex was about 13m high. 

The test period was the end of the afternoon. Not the best time for 40m and certainly not the best time to test DX performance. However it was the time I had available. 


C-Pole meets EFHW vertical

The first run was the C Pole vs the EFHW vertical. I let the beacons run for about an hour. After that time I had:

AntennaTransmissionsSpottersSpots
C-Pole1560328
EFHW1560392

On first glance the EFHW vertical seems to fare better. It has been heard more often. However both antennas reached the same amount of spotters. So nothing too dramatic here. There is not a lot of difference in the stations that received the signals - so most of the spotters returned data for both antennas.

Now looking at the SNR reported by the spotters there is more to say about the difference. I averaged the reports per spotter to decrease the amount of data points. The graph below shows the signal strength reported (SNR in dB on the Y axis) at the spotters' distance. It looks like the EFHW (in orange) performs better.

I then calculated the average difference in signal strength per spotter of the EFHW over the C-Pole - so only for spotters that returned reports for both antennas. The graph shows the difference the EFHW scored in dB - above the line means the EFHW beat the C-Pole. 

This clearly shows the EFHW beats the C-Pole on almost all distances and sometimes by a fair margin. The outlier is S51RS at 950km. That is the only spotter favoring the C-Pole significantly.

So if you have enough height available the EFHW is the one to choose out of the two at least for the ranges tested today. This is what I expected from the theoretical analysis I did some time ago.

An interesting followup would be to see how the EFHW would perform with the same top height (sloping from the 12m pole or tree branch). With a slingshot one can easily get a vertical wire up 20m, so I would normally aim for that height with this antenna.

C Pole meets inverted V dipole

Now how about the inverted V? This one adds another element to the game as it is horizontally polarised (as opposed to the vertical EFHW and the C-Pole).

I chose a height around 13m (not fully extending the 18m pole). In retrospect I might as well have gone 2 meters lower to compare the antenna if set up on the same 12m pole as I used for the C Pole antenna. Here we have a slight advantage for the inverted V.

Running the beacons for just under an hour I had:

AntennaTransmissionsSpottersSpots
C-Pole1045202
Inverted V1146219

The inverted V got one extra shot so it is hard to tell from this first glance which one performed better. 

Looking at the average report per spotter shows that the Inverted V (in green) seems to beat the C-Pole on most occasions. 

Moving one step further the indication is confirmed. The Inverted V wins (above the line) almost everywhere. The biggest outlier again is S51RS.

Conclusions

I did not test the inverted V against the EFHW vertical directly. However looking at the differences per test, using the C-Pole as "a reference antenna", there does not seem to be a lot of performance difference within EU. I would have expected the inverted V to do slightly better than the vertical on the shorter distances (with its higher radiation angle) but that might be only noticeable on even shorter distances.

So, this time I learned that within EU the C-Pole loses against an inverted V at more or less the some top height and loses against a vertical EFHW with the feedpoint at more or less the same height. 

One question remains - as the antenna's have different radiation patterns - would any of these clearly beat the others on multi hop DX? The simulations I did previously would suggest that the C-Pole would have an advantage over the inverted V because of more low angle radiation.

If it turns out the C-Pole does not "deliver on promise" there, then I cannot see a lot of situations where I would choose it over one of the other designs. Only if the footprint needs to be minimal and height is restricted (*).

This last question requires a new test around gray line time - when I can't use my favourite test ground as it is only accessible in daylight. Something to put on the "to do list".

*) Another one: would the C-Pole beat a shortened 40m EFHW of equal height - so approx. 12m? I have such a wire with spool that I used in the past for my 10-20-40m EFHW.

Wednesday, June 3, 2020

FREE month

Last month I spent more time on the radio than the preceding twelve months combined. I was on the air as one of ten stations with a special call in the P*75FREE(DOM) range to commemorate the end of WW2 in The Netherlands in May 1945.


Planning the event at the end of last year we had ideas to be active as a group or subgroup during the month with a large event from a war museum. They were happy to accommodate us a whole weekend. However COVID-19 changed all that. 

Initially I went out /P alone to a couple of PAFF nature reserves but as the month progressed we decided to do a smaller group activity with three operators from a nature reserve (PAFF-0168). We were able to set up two stations - one 40m and one 10 to 20m using the portable hexbeam. We changed the latter into a 60-80m station in the evening.


Hexbeam set up in a nature reserve with PD75FREE, PG75FREE and PH75FREE running two stations

Through email and Telegram chat the FREE stations kept in touch on the progress, the conditions and notable experiences. It is nice to see how working as a team motivates one to be more involved and spend more time behind the radio. Each participant made different choices based on preferences (like more or less digi) and set-up.

Another motivating factor were the most active chasers that tried to find us on each band and mode and even contacted us by email or Facebook to share their enthusiasm and look for opportunities to work us with OH2YV as the most striking example. His dedication was extraordinary. He finished first by a stretch only using phone and CW (so missing all possible digi points most other chasers did collect). 


All in all we made 25.000 QSOs with 13.000 stations. I was not the most active by a long stretch but still made a nice amount of contacts spread over the bands and modes (giving serious chasers a chance to accumulate points). There was a nice bit of sporadic E in the second half of the month, allowing for short skip on 20 and 40 but also openings on higher bands up to 2m.


In three pictures an idea of my activities (star = digi, dot = phone/cw):
VHF and high HF: 2/4/6/10/12/15m - sporadic E fun within EU

17/20m gave both Es and some F2 DX

Low band (30/40/60/80/160m) throughout EU and one DX on 40m to PY
To be able to work the chasers on low bands and further than the first hop (DX was challenging), I went out one last time in the last weekend of our activity to a piece of wasteland where I could set up an antenna for 160m. PD7YY joined me to see if we could work DX on 40m as well - and we did with PP7DX making it all the way.  

18m pole with low band wire antenna's and our YNOMY flag

After finishing collecting all data and producing 400+ awards the following challenge is QSL-ing all our chasers. For now the radio will enjoy some rest - probably until I go on holiday. I hope to be able to go camping in France - like previous years. We'll see how things progress in this peculiar period.