OCDX – of Contesting and Antenna’s

One of the Radio Activites I have really enjoyed over the last few years is the Oceania DX Contest –  where the world points their antenna’s to Oceania and we are the wanted stations.

I have chosen to enter a category of SingleOp All band (160-80-40-20-15-10) SSB QRP.

My first entry was in 2016, and it was basically on a bit of a whim, and I made a handful of contacts, submitted a log and to my surprise  actually came 1-3-3  (Country-Continent-World) with a score of 2660 Yes, First in VK, 3rd in Oceania and 3rd in the world.

This motivated me somewhat to actually put in more of an effort for 2017, and in 2017, my score was 30% higher than the winning score from 2016.  Fast forward a few month’s and my results were  1-2-2  with a score of 10,368.  Yes I had achieved 1 aim of improving my score and this time moved up to 2nd in the world.  The conditions in 2017 were nowhere near as good as the previous year either.

Fast forward to early August (2018) when the 2017 Results were published, and it prompted me again to see what I could do to again further improve my score.

It came down to the 1 thing that I could change – and that is to work really hard on Antenna’s – and that is what I did.

First off, I spent some to time to come to terms learning and understanding how to use 4nec2 to model antennas and started off with the basics – model a simple dipole (Inverted-V) antenna and use it as a baseline to validate  that the model was about what I was seeing in the real world – and yeah, close enough to not get too hung up about things.

Secondly, I modeled the Antenna’s I had used for the 2017 OCDX and this alone was a real eye-opener – and actually really surprised me as to how much of a disadvantage I had put myself at!

My Antenna choices for 2017 were.

  • Titan Challenger 80-10 Vertical
  • End-fed “random” wire of about 57M long and 8M high with a couple of counterpoise wires
  • inverted V on 40 (and also used on 15m)
  • 20m 1/4 WL vertical with elevated feedpoint and radials

The Titan vertical is an awesome RX antenna – but pretty useless for TX – so was hardly used for TX.  The Inverted V – yep NVIS only on 40M and the 20M Vertical was OK.

As I had  done my base learning and modelling of the 40M inverted V, I knew the pattern is all up – so not a DX antenna at all, so I went ahead and modeled my longwire across the 3 bands I used it on.

2017 OCDX Antenna
3D model of the end-fed wire and counterpoise wires

Once I had entered all the data, it was time to run some modelling across the 3 bands that I used this antenna on – and this is where things really sunk in!

160M H and V radiation pattern

At first glance for a simple Antenna on 160M this looked OK, not all the signal was straight up, but then the I noticed the gain – Ouch – -4.9dBi – I was literally taking my 5W of RF and throwing most of it away and effectively using on about 1.5W!

80M H and V Patterns

The 80M pattern was not really a lot better – Again, only 0.6dBi gain  – and the main lobe was pointing in totally the wrong direction for for me to actually use!  with the 90 being North, most of my power was being sent right into the Southern Ocean where there is literally Nobody!

40M H and V pattern

The 40M pattern again was not brilliant – whilst a slight gain of 5dBi when looking at the pattern, it was mostly in the wrong direction again!  where I needed it – there was a nice deep null  where I really needed a signal and probably why in hindsight that I relied on the 40M Inverted V for most of my 40M contacts.

The Challenge

Now, with an insight of how bad the antennas utilized actually were, I needed to look at modelling some better Antenna’s – and the beauty of modelling, is the try before build – which means fitting Antenna’s into the available space I had.  the second Challenge was to do all this and actually build all the required antenna’s within a fairly short period.

40M – (my favourite band)  – I wanted a decent Antenna on 40M as this is a band that I love operating on.  Whilst the dream is a 4-Square array  and yes, I’m fortunate enough to have (just) enough space for such an antenna, I didn’t have the time to build it – so off to the Internet and looking at what I might be able to do given all the restraints I had.

In the end I came up with a 2 Element Vertical Beam – that took me many iterations in 4nec2 to come up with something that met my objectives and was actually a reasonable match as well.

40m Vertical Beam

Now this does not look like a “conventional” beam, given the reflector is 3 segments and not the usual 2. and it is a very “odd” looking shape – but hey, this will become clearer as I explain a bit more.

40M OCDX 2018 H and V pattern

Notice anything nice about this radiation pattern – again 90deg on the circle is North.

Not only have I got a nice wide (about 200 degrees) beamwith, pointing in the desired direction (mostly)but there is nothing wasted out the back, and look at  the vertical pattern is – an awesome DX Antenna.  and with 7.6dBi gain, yet still enough for the up for the close NVIS/single hop contacts.

visualized gain of 40M beam

Not only did I get the desired pattern, it is a pretty darn good match!

Now the reason for the “odd configuration”  Simple, the 12M squid pole supporting the reflector and the top of the driven element is mounted at 7 Metres high on top of a shed,  and I needed to have the reflector split to go each side of the shed.   Nothing more than adapting a design and working it into the environmental’s and space you have available.

The installed 40M beam

Make no mistakes, this is a BIG antenna – the top of the 12M Spiderbeam pole that is supporting the antenna is up at about 19M high and dwarfs the 2M antenna on the adjacent pole.  the photo is taken lookup up along 1 of the reflector elements.

So this antenna was erected a couple of month’s ago and wow –  does it perform!  Very impressed with the results before the OCDX – and the real-world usage indicated that the modelling was in fact very close to the results.

The Low Bands

I spent a lot of time researching as to what sort of antenna’s I could use on the low bands that were going to be achievable in the 4 weeks I had left and eventually settled on a 160M Horizontal loop for a few reasons – mainly because after reading and modelling a lot of different options, this was the antenna I could use and it met (most of) my design objectives.  It is also one of the few antenna’s that the relative performance is much better than a Dipole at low heights – as a 160M and 80M dipole at the 9M height i could achieve with this loop was no better than the random wire I used in 2017.

I did model a few that I would love to build that are in fact much better than a horizontal loop, but ran out of real estate to install it.  Co-incidentally, it was also a very good option for being so close to the ground on the low bands.

The loop was modeled, then the model was re-worked once it was installed to reflect what was actually installed.  I ended up feeding the loop with 300 ohm Ribbon cable, with a short Coax from Radio to a 1:4 balun.   Whilst it is not a perfect match, the Tuner was easily able to achieve a decent match on both 160 and 80, and the analyzer gave me a good indication that It is in fact resonant where I needed it on these 2 bands.

160M H and V pattern

Now while this pattern might not seem like it is a big improvement over the 2017 one – it actually is  a massive improvement.  Yes, it is a lot of straight up, but it is 1.4dBi gain – or a 6db improvement over the previous year – and where every watt counts…

80M H and V pattern

Again, at first glance, 80M doesn’t look to be brilliant, but then again – a big step up from the previous year with around a 3db improvement.  The nothing straight up was not really a hindrance to how it performed and it was remarkably good.

The Higher Bands

For 20M this year, I opted for a Full wavelength dipole  with the 3/4 w/l leg pointed at around 120 Degrees.  this antenna provides a broad “beam” with around 5db forward gain along the longer segment at reasonably low radiation angle and a bit of F/B. – Again, not the “perfect” antenna, but proved to be better than the previous year.

Given that 20M is literally  the POWER band I was simply hoping to grab a handful of multipliers here and If I worked 10 I would be happy.  I did miss out on a Short Path EU opening because I had the antenna fixed in a single direction and if I had anther antenna or been able to quickly re-orient this one may have picked up a few more contacts.

I used the 40M antenna on 15 as well – and yeah, some more effort needs to go into the modelling of the antenna to see if the 15M could be improved without degrading the primary band, or of course build a better 15M antenna – something for next year.

15M pattern from the 40M beam


This year, the gap vertical was again used  but mainly for RX, with exactly 2 contacts on it – 1 on 40M to VK7 where I am at a slight disadvantage on the Beam and 1 on 10M.

Honestly, I did not put much effort into the high bands (15 and 10) given the band conditions and unlikely chance of a decent opening on these bands.

The Results

Well the proof of the modelling and antenna effort was well and truly rewarded.

This year, the conditions were nothing short of horrid yet I was able to nearly triple my score and my submitted score  this year is 29,068

2017 Log Summary
2018 log summary

The bottom line  is and, what I hope is the take-away after reading this post is Antenna’s matter – and if you take the time, model what you have you can (generally) work out how to do something better than what you may already have in place.

Final word – I enter QRP not because it is easy, but because it is hard!

VK5 is of course also at an added disadvantage – given that we are 1 hop further away than the other states – and over land and not water, further compounding the need to maximize our Antenna efforts.

I missed out on a heck of a lot of potential contacts because in am 20+ dB down with my power, but I had a blast actually doing what I did.

Update 12/10

I forgot to mention and now adding it in here.

One of the issues I had last year was my callsign – VK5FO – Whilst it has a certain charm and schoolyard smut factor, it was actually a problem during contests.  I spent a fair bit of time, listening to the bands, listening to callsigns and then went and looked at available callsigns.

I applied for and was Granted VK5HC (Hotel Charlie,  Henry Charlie, Honolulu California, or my favourite – welcome to the Hotel California) and yes, the callsign makes a difference when you are (I am) on the RX stations noise-floor). The callsign choice probably helped me actually complete 5 to 10% of the very difficult contacts.

A “contest callsign” that is phonetically easy is a worthwhile addition

WX Sonde

A short sharp and shiny post !

There’s been a clear increase in interest in tracking and chasing the Bureau of Meteorology radiosonde launches here in VK5. Many have been tracking these on tracker.habhub.org and aprs.fi, and there have been quite a few new faces sighted near sonde landing locations!

to this end, I have set up a mailing list where items such as RX ground stations, chasing, and chasing co-ordination can be discussed.  This will also help avoid situations that have been encountered recently, where people have travelled quite long distances to find a sonde has already been recovered.

If you are an active RX station or a chaser we would encourage you to subscribe to the VK5 WX Sonde list.  All new members need to be approved before posting, and that will usually be done within a day or so.

For those new to this activity, the following resources will help:

Launches out of Adelaide occur twice a day, at 8:45 AM and 8:45 PM. The automatic sonde receiver stations usually detect the sonde shortly after launch, and upload telemetry to the HabHub Tracker ( https://tracker.habhub.org/#!mt=roadmap&mz=7&qm=6_hour&mc=-34.13946,138.42875 ).
Mt Gambier launches occur on Mondays and Thursdays at 8:45AM. Launches are also performed from Woomera and Ceduna, though we don’t currently know the schedules for these sites.

The Mailing list was established so that the Various RX station operators can discuss any issues and or set-up hints and tips.  For the Chaser, the list can be used to co-ordinate and notify when you intend to chase and to notify  when you actually find a Sonde.

2017 Summer FD

This year,  for something a bit different the FD was never about building a full-on 4 band station and going all out for a big score – it was all about doing more with less.

We (Me, Bob VK5FO and Ray VK5RR) teamed up with Andy, VK5AKH and went QRP portable and went for a “nice” hike up to Black Hill Summit – a summit that is a hike in – and at 460M above sea level in PF95ic

We met down the bottom of the hill about an hour before the start and packed up the gear and antennas and away we went

We were taking gear to get us on the air on 4 bands for field day – 6m, 2m, 70cm and 23cm.

After nearly an hour, we finally made it to the summit at around 01:10 UTC just after the start time and proceeded to set up Antennas and Radio’s

Here you can see the Antenna’s – 1/2 Wave Vertical for 6m on the blue pole, and on the Camera Tripod, you can see the 11 Ele on 23cm, the 6 Ele on 70cm and the Slim Jim for 2m.

Andy making a contact on 6m with the KX3.

The summit, while it doesn’t offer great views has shade! which makes for a pleasant place to operate from.

Did I say minimal station set-up.  Here I am with the KX3 and you can see the 70cm XVTR and batteries in the foreground.

We were set up pretty much at the old trig point – I say old, because someone has ripped it all out of the ground at some point and built a pile of rocks adjacent to it on the walking trail.

The aim of the day was to enjoy the hike up to the top of the hill and play a bit of radio and within an hour or so we had contacts on all 4 bands.  It was all about getting out for a few hours, and getting a few contacts and handing out contacts to the other stations who were also out and about.

As far as FD goes, it is a decent location for a minimal set-up basic antenna’s that we carried in, and very modest power  on all bands – we had 5w on 6m, 2m and 70cm and 3w on 23cm.  It truly is a case of “height is might” when it comes to VHF/UHF and above.

Mid-afternoon we packed up and headed back down the trail.

It doesn’t look it, but it was a decent hike – with about 2km each way and 250+M elevation change.  Coming back down was a bit quicker it was only about 40 minutes. Here we were about 5 minutes from the bottom.


We had APRS running on the Handheld while hiking in and out.

At the end of the day, I logged 16 contacts for FD, and Andy logged 21, in the 3 hours or so we were at the Summit.

As we were operating from Black Hill, this also qualified as both a SANPCPA and VKFF Activation.


VKFF-1683 Anstey Hill Recreation Park

Managed to find a bit of time and got out to activate one of the new parks as a first activator this afternoon.

With good early spring WX I packed up and headed out.  After having a lot of reports of the bands being well and truly on the decline, I packed the amp as well.

We headed around to the park and set up near the top of the range off Range Rd,  While it offers elevation, it also has a very nice 415Kv transmission lines running right across the top of the park and I was hoping it would not be too noisy.

Planned on a PSK and SSB activation and set up initially on 20m.  Had a few issues but finally managed to get everything working and started calling CQ on PSK31 on 20m,   at around 06:45UTC

The Shack for the activation

No luck at all – called for about 15-20 minutes and not a single response, so dropped that and went to SSB.  Knowing things were probably not too good, I had the HR-50 amp on and was running around 40w

Posted a spot and called and first call was replied by F1BLL. over the next 20 minutes worked VK4, ON4 and VK6 before moving down to 40m

It was a fairly constant response on 40m and worked callers from VK1, 2, 3, 4, 5, 6 and 7!

In the mix today, there were a couple – well 3 P2P contacts – the first with Phil, VK6ADF operating from VKFF-1446 on 20m then the next was with Gerard VK2IO from VKFF-0048 on 40m and then just as I called for final contacts, Phil, VK6ADF again from VKFF-1446 this time on 40m.

By the time we finished chatting with Phil, the sun was down and the light was rapidly dropping, it was a mad dash to pack up and walk back to the car in the last light.

Last light while Working Phil, VK5ADF
Last light while Working Phil, VK5ADF

At the end of the day, there were 48 contacts in the logs making the very first activation of this park a big success.  Those HT lines – well, not such an issue – sure, there was a little bit of noise, but hardly anything to cause issues.

This activation was the first time I used the VK-Port-a-Log for all logging.  Wow, what a difference it makes vs paper logging – much easier, especially considering that when I got home it was trivial to send off the logs to Paul for upload to WWFF and also import into my other logging program for upload to E-QSL, Clublog LOTW etc.

Seriously, if you have not tried it- give it a go on your next activation!

It was a great day to be out playing radio in a park!

Loops, Verticals and Inverted V’s

Over the last few days I had the opportunity to borrow a 40m Transmitting Magnetic Loop Antenna with a big thanks from Steve – VK5SFA for the loan of his 40m loop so I could conduct some comparisons.

We were at the shack in PF95wu where I have the GAP Challenger Vertical and where I could put up my portable 40m Inverted V antenna.

VK5SFA 40M loop
VK5SFA 40M loop

The loop is physically quite small  at only about 1.6m in diameter – and as you can see it was mounted on a tripod with the bottom only 1.8m off the ground, and as far away as my coax would allow from the shack – which was about 10 or 12 Metres.

Gap Challenger Vertical 80-2m
Gap Challenger Vertical 80-2m

The Gap Challenger, which has been put to use as the primary RX antenna for the KiwiSDR – was one of the comparison antenna’s used over the few days.

For the TX experiments I used the KX3 and HR-50 Amp and was transmitting at between 40 and 55 Watts of power.

Observations – the Loop

The bandwidth of the loop was quite pronounced – tune the loop, tune the RX across the band and it was pretty obvious – about 40khz wide.

TX – well, it was nowhere near 40Khz wide – more like about 12 or 13khz 1.5:1 VSWR bandwidth.

The first night, we had a bit of rain earlier and the ground was a little damp.  We found it impossible to actually tune the loop – best we could get was about 4:1 VSWR on TX.    The next night it was much better!

Tuning – well touchy is an understatement!  The tuning is manually done via an insulated rod – and 1/4 of a turn was like 40khz!  It was a case of tuning for maximum RX noise, then some careful fine-tweaking to get it there.

RX Bandwidth

The Loop was tuned to 7.140 and plugged into the SDR

40M loop on SDR
40M loop on SDR

Without changing any settings on the SDR, the Vertical was plugged back in.


IT is pretty obvious as to the RX bandwidth and how sharp it drops off away from the centre frequency.

Click on both Images to see full sized.


I made use of the Loop to talk during the day – local, single-hop contacts (VK2, VK3, VK4) – and when 40m is open, it is open – 59 contacts – no real difference between any antenna.  DX – I did have a couple of contacts to the West-Coast US using the Loop – and got respectable reports back based on my 50W!

The Loop has  2 large lobes, and quite a deep, but fairly narrow null on each side.  The null is about 50-60 degrees and 2 S-points – or probably around the 12db  mark (give or take).  We did have a little bit of local noise, and rotating the loop we observed the noise drop right off to S1-2 when nulling the noise.

Side by side, with the Vertical – RX was on par, and TX was much better – just because there is a slight directivity associated with the loop .

Side by side with the Inverted V – well this was much more interesting – The Inverted V was only 8m high with each end about 2m off the ground.

The Inverted V was 2-3 S-points noisier than the Loop, but also 1 S-point stronger on the signals.  With an  S6 noise and  S9 Signal for the VK contacts, versus’s the loop, with an S3-4 noise and an S8 signal.

It clearly had at least 10db better signal to noise versus’s the Inverted V – and well, hands down beat the Vertical on TX!

The far stations reported slightly stronger signals on the Inverted V, but I don’t hold much faith in that as there was heavy QSB – I would call it a tie.


I would conclude that it is about on par with a dipole in typical performance – but has a considerably smaller footprint!  I was actually not expecting that the performance to be as close to the Dipole/Inverted V as it actually was – remarkable considering that you only need a very small space to have the equivalent of a rotatable dipole!

For the Amateur who is space-challenged or has a lot of noise, then yes, a loop is certainly worth considering for the low bands.

As we have the Loop for a couple more days, we will set it up in a typical urban lot – where we simply cannot use 40m as it is always S9+ noise  and make some observations as to how effective it is in a much noisier environment.