Posts Tagged ‘UKAC’
A simple approach to VHF contesting
October 15th, 2016 | 
Author: The UK Activity Contests (UKAC) are a series of VHF contests that happen every Tuesday night. There is a different band each week. The general set up is a signal report (genuine, not a 59 default), serial number and locator. The locator is used for multipliers. The calendar is as follows:
Every 1st Tuesday 2000-2230 (Local) 144MHz
Every 2nd Tuesday 2000-2230 (Local) 432MHz
Every 3rd Tuesday 2000-2230 (Local) 1.3GHz
Every 4th Tuesday 2000-2230 (Local) 50MHz & SHF
Every 5th Tuesday 2000-2230 (Local) 70MHz
So, its a pretty full calendar. I participate in the low power section, which is <10w but I actually run 5w from my FT817nd. Almost always portable and at most the 6m, 2m and 70cms sections. Antenna’s have been a mixture with some pretty substantial beam’s (for /p anyway) but my preference is for the now defunct Sotabeams SB270 for 2m and 70cm’s and a Nuxcom lightweight 6m yagi. I have moved away from heavy telescopic poles to a Harris 5m telescopic decorators pole.
The theme is to simplify some things but with a view to focus my spending on lightweight improvements. I find that this keeps my interest in building up as well as operating. Lets make this very clear, I’m not in it to win in, but to make use of the normally quiet VHF spectrum for some fun. DX is unusually no further than the south coast or the north of Scotland and the occasional trip a little bit further but conditions need to be exceptional.
So the latest addition is a more appropriate support for the pole. I was sick of using a drive on plate that was frankly destroying my £16 investment in a decorating pole. My car has a tow bar. I bought a ball attachment several years ago as it was right in front of me and very cheap. I now have a use for it.
The tow bar mount is made from a few off cuts of 47mm x 100mm (or 2″ by 4″ if you prefer) and a piece of rough sawn timber that was being used for shuttering for the summer house foundations. I used a 38mm hole saw so that the base is snug, but the upper support needs some kind of removable wedge.
It has been painted with Wilko’s timber paint left over from some other work (which is very good). I’ve yet to try it out but I’m impressed how quick it was to make. Let’s see how it performs, its certainly a lot simpler than buying an expensive drive on plate.
It remains to be seen if this is a worthwhile addition but it only has to deal with a little over a 1Kg in static mass so chances are even the most severe winds. In which case I won’t be out /p anyway. Next stop the antennas. To increase gain or not to increase gain, that is the question. I kind of know the answer really.
6m/70cm antenna updates at the QTH
The 70cm yagi was to replace the small 7-element one which I pressed into service as a hand held antenna for potentially finding my HAB payloads last year.
To be honest I wasn't really after a 6m antenna due to the size and visual impact. I have a 6m 'wooden' moxon I made back in 2014 but it is heavy, ugly and unstable so had been collecting cobwebs in the garage. I decided with the prospect of 'Sporadic E' season around the corner I would be foolish not to put it up.
The HB9CV wasn't in the best of conditions but seemed complete albeit it was purchased dismantled. The elements were a little weathered so I set about cleaning them up with a light rubbing down with some wire wool and a rag with a drop of WD40. On closer inspection the tube that made up the front element had some noticeable bending and on removing the plastic mounting to investigate I spotted a crack in the tube wall by the hole for the mounting bolt.
While it hadn't totally separated it would only be a matter of time before it did fail as it was flexing, the plastic mount was the only thing holding it together. I found a suitable piece of alloy tube from a scrap antenna which was a perfect fit inside the broken element. I cut a suitable length and pushed it up inside the element to the appropriate position and then simply drilled through and bolted either side of the central hole to stabilise and strengthen it (can be seen in image below)
The next issue I had to address was the feed point, it came with about six inches of RG58 coax projecting from it where it had simply been cut for removal by the previous owner. I prised off the cover cap to find it full of water, the reason being a hole in the back and it being stored outside I believe.
Thankfully the trimming capacitor seemed okay, while it was wet it wasn't corroded. It was all dried out and the hole plugged with silicon and I set about re-assembling the antenna which was a little fiddly to get the phasing line to sit properly but once done it was a simple matter of adjusting the capacitor to get the VSWR to a minimum in the SSB section of the 6m band. I mounted on the rotator pole just below the X50 collinear.
I used it last month in the 6m UKAC and while my operating not exactly earth shattering I was happy with its performance using just 10W in the low power section just "search and pouncing" for a little over an hour.
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The 70cm Yagi was straight forward as was already assembled, I just had to make a slight tweak to the gamma-matching bar as the VSWR was unexpectedly high around 2:1 in the SSB segment of the band, it seemed to have been tuned for the FM portion of the band. I managed just an hour "search and pouncing" in Aprils 70cm UKAC, I started late and while signal reports both ways were a marked improvement I found the extra directionality and off beam rejection something I will have to get used not helped by a temperamental rotator.
6m/70cm antenna updates at the QTH
The 70cm yagi was to replace the small 7-element one which I pressed into service as a hand held antenna for potentially finding my HAB payloads last year.
To be honest I wasn't really after a 6m antenna due to the size and visual impact. I have a 6m 'wooden' moxon I made back in 2014 but it is heavy, ugly and unstable so had been collecting cobwebs in the garage. I decided with the prospect of 'Sporadic E' season around the corner I would be foolish not to put it up.
The HB9CV wasn't in the best of conditions but seemed complete albeit it was purchased dismantled. The elements were a little weathered so I set about cleaning them up with a light rubbing down with some wire wool and a rag with a drop of WD40. On closer inspection the tube that made up the front element had some noticeable bending and on removing the plastic mounting to investigate I spotted a crack in the tube wall by the hole for the mounting bolt.
While it hadn't totally separated it would only be a matter of time before it did fail as it was flexing, the plastic mount was the only thing holding it together. I found a suitable piece of alloy tube from a scrap antenna which was a perfect fit inside the broken element. I cut a suitable length and pushed it up inside the element to the appropriate position and then simply drilled through and bolted either side of the central hole to stabilise and strengthen it (can be seen in image below)
The next issue I had to address was the feed point, it came with about six inches of RG58 coax projecting from it where it had simply been cut for removal by the previous owner. I prised off the cover cap to find it full of water, the reason being a hole in the back and it being stored outside I believe.
Thankfully the trimming capacitor seemed okay, while it was wet it wasn't corroded. It was all dried out and the hole plugged with silicon and I set about re-assembling the antenna which was a little fiddly to get the phasing line to sit properly but once done it was a simple matter of adjusting the capacitor to get the VSWR to a minimum in the SSB section of the 6m band. I mounted on the rotator pole just below the X50 collinear.
I used it last month in the 6m UKAC and while my operating not exactly earth shattering I was happy with its performance using just 10W in the low power section just "search and pouncing" for a little over an hour.
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The 70cm Yagi was straight forward as was already assembled, I just had to make a slight tweak to the gamma-matching bar as the VSWR was unexpectedly high around 2:1 in the SSB segment of the band, it seemed to have been tuned for the FM portion of the band. I managed just an hour "search and pouncing" in Aprils 70cm UKAC, I started late and while signal reports both ways were a marked improvement I found the extra directionality and off beam rejection something I will have to get used not helped by a temperamental rotator.
70cm contest using a 2m big wheel
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| Stations worked on 70cm tonight with 5W and a 2m big-wheel omni |
This evening was the September 70cm leg of the RSGB’s UKAC contest, so I decided to give it a go with my 2m big-wheel and 5W SSB. The match on 70cms was very good, but I had no idea how it would actually work. Well, the answer is “very well” as you can see by the stations worked. Best DX was 182km. To say I was pleased is an under-statement! I shall be able to use this antenna again in 70cm contests. I was also able to copy the new beacon NW of Leicester GB3LEU which was pretty good copy on 432.490MHz.
A dark cold evening in a layby
Several hours sitting in the car on the side of a deserted road in the dark and cold was worth it. Despite some initial trepidation I really enjoyed the experience until I got spooked at the end.
Like the last time I operated from this location I put the small yagi approximately 3-4 metres up on the top of my 'painters' telescopic pole stuck in to a parasol stand. I sat in the car and reached out the open window to rotate the pole as required. I wrapped up well and had a blanket over my legs and a woolly hat on and kept surprising warm despite it being just 1°C, turning the courtesy light on only when I needed to write in the log.
It was nice to be noise free and I made 29 contacts, nothing earth shattering but with a modest set up and operating in the AL section (10W max) I was more than happy and got my first contact in the Isle of Man.
From the reports posted on line it seems conditions were flat and activity was low. Frustratingly several times I found a distant station only for it to be drowned out by splatter. I know some of this is down to my radio and the antenna but the source is nearby and so strong that even turning the beam makes little difference. Ironically being higher up meant the signal was even stronger than I experience at home.
The annoyance is compounded by the operator's habit of regularly changing calling frequency seemingly with little regard of who is currently operating there. This SDR screen capture shows an example of the same contesters signal during a recent 2m UKAC. Captured using a vertical collinear several strong clean(er) signals are clearly visible even with the mismatched polarisation. Sadly it is not a one-off and I have observed similar splatter from this source during both 70cms and 6m contests.
It was very dark and eerie on the quiet road and I'm afraid I got spooked with 20 minutes of the contest left, a 4x4 drove past slowly and appeared to shine a spotlight at my car. I was midway through a QSO writing in the logbook so I only caught it out of the corner of my eye so wasn't sure if they did. But a while later I saw what looked like torch beams moving in the nearby field that seemed to be getting closer. In retrospect it was nothing untoward when I checked the map later there are farm buildings in that direction but I've seen one too many horror films so decided not to hang about so threw everything in the car and headed home with out looking back..
.... you'll see him if you look
Operating /P for the 432MHz UKAC tonight
I have a small Moonraker 7-element ZL-Special on the main antenna mast, purchased originally for monitoring satellites and was pressed into service for SSB when I got licensed. It has never wowed me performance wise and I have been intending to replace it for quite a while but since I only use it one day a month it hasn't been a priority. So the mast came down last night and I removed it so I can take it out with me to operate portable from some higher ground tonight.
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| Using the 2m delta beam in June 2014 |
Last year I had a go at operating portable from the car and posted a write-up. It is my intention to repeat this exercise but with the 70cm antenna on top of my 'painters pole' mast. I have serviced the antenna and fitted a new short run of quality coax and spent a far amount of time with the AW07A analyser adjusting the antenna's tuning capacitor and have got the VSWR right down to 1.1:1 on 432.200MHz so things should be optimal.
I am looking forward to this evening, hoping it pays some dividends.
As I mentioned the 24 hour March 144/432MHz VHF Championship contest took place last weekend. I took part to give away some points just grabbing a few short sessions with the radio. I concentrated on the 2m band due to my issues on 70cm.
In my AW07A analyser review I mentioned some issues with my 2m LFA YAGI, thankfully these have been resolved. The use of some wire wool to remove some corrosion and a hacksaw to take 10mm from the long elements of the loop allowed the end elements to 'trombone' in sufficiently to get the antenna resonant and the VSWR is down to 1.2:1 on 144.300Mhz.
I only made 18 contacts, but was happy with the distances achieved with 30W, getting a lot further south than I normally do, given I am 18m ASL. There was also some local wideband noise (I captured a screenshot on the SDR) and the conditions gave some interesting fading.
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| M0NRD QSO map March 144 VHF |
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| Noise across the band |
UK Activity Contests
Every Tuesday evening the RSGB organises a VHF/UHF activity contest. I have just in time submitted my entry for the low power section of last Tuesday evenings 50MHz contest. With just 3 QSOs logged there is no way on this earth that I’ll be anywhere but near the bottom! Having a V2000 omni vertical antenna, 5W, and a stroke damaged voice is no way to enter a 50MHz, UK based, contest! The V2000 and even 2.5W is great in the Es season (I work most that is around), but it is far from ideal working inter-G on 6m SSB.
Tonight is the 144MHz (2m) March leg of the UKAC. My small 3el beam should turn again now (manually) so I’ll see how long my voice holds out. 45 minutes to 60 minutes is usually my limit. Last week I was on very little time. My best DX seems to be around 200km with 5W on 2m in “normal” conditions.
At this time of the year there are fewer portable stations active but activity (SSB and CW) is usually very high so this is a good opportunity to work some new squares. People have been very friendly. If in the UK or nearby join the fun 2000-2230z on 2m. I usually go QRT by 2100z because of the strain on my voice.
Just checked where I sit in the Jan 2015 AL section of the 50MHz UKAC. You guessed? Bottom! Well someone has to be!
