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Yet another Antenna for 2 Metres

22/2/2014

3 Comments

 
Over the past year I've activated a few SOTA summits with nothing more than a handheld and the stock antenna supplied. I have also looked at a couple of options to improve performance and keep weight and bulk down to a minimum.

The first thing I tried was a pigtail wire. This is simply a ¼ wave length of wire with a lug at one end that simply screws down on the SMA connector between the antenna and the radio and acts as a counterpoise for improved performance. Playing around with one of these does make a marginal difference and might be enough to get the contact logged where you would otherwise fail.

One of the other things I've tried is to unscrew the ground independent dual band whip from the vehicle take it to the summit sticking out of the backpack. A 5 metre length of coax with a BNC and base socket for the antenna is the connecttion for the radio and are the main parts of this setup. At the transmitting site, a string can be tied to the tip of the antenna and thrown over a tree limb to hoist it up a few metres. The antenna can also be taped to a squid pole or other support. This setup is versatile and light and takes up the least amount of room and is ideal for HT only activations with the only disadvantage being the length of the whip sticking out of the backpack being a nuisance when traversing through thick bush. A setup like this will almost certainly allow you to qualify summits within striking range of urban areas quickly without the need to mess around setting up radios, batteries and bulky antennas for other bands.

I've also tried a 2 metre J-pole antenna made from 300 ohm TV ribbon which is wonderfully light and compact but the biggest problem has been reliability. The wire is so fine that it it quickly breaks usually at the most inconvenient time.

  Something that caught my eye recently was the SOTABEAMS 2 metre MFD ( Multi Function Dipole). I like the idea of a complete self supporting antenna such as the vertical HF antenna I frequently use on SOTA activations as it packs completely within the backpack without the need for an additional tuner or bulky squid pole. The MFD promises reasonable performance with the flexibility to mount the dipole section vertically for FM or horizontally for SSB operation. To buy the kit from SOTABEAMS in the UK would cost around $55 with the optional goody bag consisting of some nylon rope, 3 ground pegs and a couple of velcro straps. Another option is a ground spike at an additional cost. Fair enough but looking at pictures and a youtube video of the antenna, I decided that I would build one myself as I had all the other ingredients except the 20mm electrical conduit, T-connector and couplings.

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The MRG MFD with the pole sections and spike
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A quick trip down to Bunnings and a short time later I had a 4 metre length of conduit and the other bits for under $5.

The ingredients for MRG MFD antenna as constructed:
3.5 metres RG58/U
1 x BNC connector
1030mm insulated copper strand wire
1 x twin terminal block
1 x small cable tie
4 x 510mm lengths 20mm pvc conduit
1 x 110mm length 20mm pvc conduit
2 x 20mm conduit couplings
1 x 20mm T-connector with inspection cover

Optional parts to complete the antenna:
3 x 2.5m nylon rope
3 x tent pegs

A ground spike of some description is worthwhile. I happened to have an unused aluminium spike from a low voltage garden light which the conduit screwed into perfectly. The spike also has a cover made from an offcut of conduit to protect the spike from damaging anything in transit.


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Putting the antenna together is simple enough. Cut the conduit lengths as described. The wire I used for the dipole was striped out of an old extension cord. Cut the 1030mm wire into 2 x ¼ wavelengths for the dipole. These will be trimmed to SWR later. Strip the insulation on one end of the wires and screw into the terminal connector. Push the 110mm conduit firmly into the bottom of the T-connector and carefully drill a hole and feed the RG58/U into the connector. Strip back the coax and terminate the braid to one side of the terminal block and the centre lead to the other. Get your glue gun and melt a big blob of glue onto the back of the terminal block and quickly position it centrally inside the T-connector before it sets. Gently pulling the coax back through the drilled hole will help position the terminal block before the glue sets. Feed the dipole wires out each side of the T-connector and then tightly wrap 15 turns of the coax around the conduit to form a choke balun. Drill 2 small holes in the conduit adjacent to the last turn of coax and install the cable tie to hold the choke balun in place. Terminate the end of the coax with a BNC or other connector to suit your radio. The choke balun consumes almost one metre of the coax and the remaining 2.5 metres or so is ample for most portable setups.

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A spike from a low voltage garden light fits perfectly
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Feed one side of the dipole wire back through the centre for storage or transporting
  Next assemble the antenna. Erect the two lower pole sections using the couplings and either strap it to a vertical support or spike it like mine. There should be at least 10mm of conduit at the end of your choke balun to push into the vertical section. Feed the dipole wires through the other two conduit sections and push into the T-connector. Congratulations. You now have a horizontal dipole for 2 metres. The next thing to do is SWR the antenna. I tuned my antenna for the middle of the band at 146.000 Mhz. The easiest way to cut the dipole is to pull the dipole tubes out and cut the wires together side by side. Reassemble the supporting tubes and test the SWR again. Continue as many times as required to tune the antenna but take it easy. Cut no more than 2mm at a time when the SWR gets down around 1:5 to 1 or you may take too much off.

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Once tuned, a quck test with the multimeter just to detemine which leg of the dipole is connected to the centre of the coax. Mark an arrow in the T-connector so when the antenna is used vertically, this side of the dipole will be at the top. When disassembled the conduit in the “hot” side of the antenna is pulled apart and the wire is simply fed back through the T-connector for storage. Be sure to leave a little loop near the end so it can easily be pulled out when assembling the antenna.

To test the antenna in field conditions I went down to the local park. I first set it up vertically. It was a reasonably windy afternoon and the antenna waved around a fair bit so I guyed it out with three lengths of light nylon rope with a loop in each end. With the antenna steadied I checked the SWR once again which hadn't changed from the initial tuning at all. I set up the FT-817 and tested out the antenna on a number of repeaters and was easily able to hit all of them that I could normaly do with a handheld. Next I put out a call on 146.500 FM and straight away got a response from Tony VK3CAT at his QTH, a distance of around 17 km. Not too bad with 5 watts across the suburbs.


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The antenna guyed in vertical position
Picture
The antenna set up in horizontal position
  The next test was to set up the antenna horizontally and try SSB. It only took a minute to configure the antenna set up roughly broadside to Tony's position. This time I didn't really need to guy it despite the wind. Even though the antenna was little more than a metre parallel to the ground I received a good report once again from Tony and we also experimented moving the antenna end on where my signal remained perfectly readable despite dropping 2 or 3 S points. No real match for a 5 element yagi mounted a couple of metres higher but good enough for a SOTA peak without too much extra weight to lug around. It should prove to be a fairly reliable and robust antenna.

The packed down size is still a little bulky for a small backpack but manageable.

3 Comments

Summer VHF-UHF Field Day & 3 SOTA Summits

18/1/2014

3 Comments

 
 The weekend of the VHF/UHF Summer Field Day turned out to be a good one for visiting three summits to the West of Melbourne that I had not yet activated. It was also an excellent opportunity to use the higher bands that I seldom use on the FT-817 particularly in SSB mode as the chance of contacts were high. I lugged more gear than my usual QRP setup and decided to make myself comfortable for an overnight summit stay on VK3/VC-032.


PictureBulky but manageable 2 Metre setup.
VK3/VC-032

Activated 11 January 2014

I left Melbourne around midday Saturday and headed for VK3/VC-032 located in the Wombat State Forest. I stopped and visited a group of fellow EMDRC club members set up for the VHF UHF Field Day on nearby McLachlans Lookout before heading a few kilometres further West to my location where I planned to set up. VK3/VC-032 is an unnamed summit with gentle slopes and easy vehicle access. I found a clearing just off the road down a little from the highest point but still well within the activation zone. Knowing that there was a chance of other activators around, I parked the car in the clearing and set off with all my usual backpack radio gear plus a tripod. 5 element homebrew 2 metre beam and a broomstick as a mast for the beam. The quickest way to walk out of the activation zone and back was not along the road but due west into medium density forest and regrowth. This was rather awkward carrying all this extra gear and particularly the beam which had a propensity to catch the foliage. At one stage I slipped badly almost falling on the beam which would have most likely destroyed it but fortunately it survived.

Upon staggering back I selected my operating position and set up initially for 40 metres. I worked 9 stations in 15 minutes including S2S contacts with Brett VK2BNN and Greg VK2FGJW. When things quietened down on 40 metres I kept monitoring the band whilst setting up the beam for 2 metres SSB. I then had no problems at all working a steady stream of contest stations with good reports from most stations logged aware of my QRP status. Flicking back to 40 metres I logged another S2S with Nick VK3ANL.

Quite comfortable in this spot I decided to stay the night and play radio for as long as there were people to talk to and switched between 40m, 20m, 2m and even a couple of contacts on 70cm with a couple of contest stations on the HT.


PictureMy cosy operating spot at night in the rain illuminated with an LED headlamp
A pleasant sunny day cooled in the evening considerably and by 9.00pm local time a hazy fog settled around me and a few spots of rain started falling. I was able to cover the gear and keep operating but it was becoming rather unpleasant so I stopped around 1130z and jumped into the swag which was quite cozy in the conditions.

It was fairly cool and foggy in the morning but with good weather forecast I decided to string up the doublet as an inverted V from my squid pole well as the vertical HF antenna I had been using and called for SOTA contacts on 40 metres with better results this time. Several stations this time said that they could not hear me the previous afternoon but could now log a contact. This time I logged 23 SOTA contacts in around 40 minutes including another S2S with Greg VK2FGJW on another summit.

As part of my contribution to the VHF UHF Field Day I logged a few contacts on 70cm FM with the HT, and 35 contacts on 2 metres SSB with the beam and the FT-817. This included a couple of S2S contacts with Andrew VK1DA on Mt Ginini, the second one where he also switched to his FT-817 and made the contact QRP both ways, a distance of 460 kilometeres. I also worked 2 meters into VK2, VK5 and VK7 with my flea power before packing up and heading of to Mt Warrenheip.



PictureRegrowth on the northern side of the summit after a recent fire
  Mt Warrenheip   VK3/VC-019

Activated 12 January 2014


Mt Warrenheip is easily accessed from Forbes Road behind the gaudy tourist attraction of Kryal Castle nestled at its base and visible from the Western Highway. There are three main towers on the summit and a sealed road to the top. I drove up here and parked, grabbing the backpack and going for a stroll in a north easterly direction following a powerline past the third tower and then down a fire trail outside the activation zone to the road I had driven up earlier. I returned back up the fire trail and there were several spots that I could have set up but within very close proximity to the powerline that may have been very noisy on HF. I continued past my car and back into the bush around the far side of the first tower and set up in the shade with the doublet thrown between two trees.

All contacts were on 40 metres and the first was with Peter VK3PF who spotted me and helped the activation off to a speedy start. I logged 15 contacts in under 20 minutes including an S2S with Bernard VK2IO/3 on The Horn which I activated both sides of the UTC New Year. Conditions on the band were pretty ordinary with lots of QSB both ways making the contacts difficult for chasers.

With the summit easily qualified I packed up and headed for Mt Bunninyong knowing that with a major cycling event on in the area that access would still be possible but I would be walking quite a but further than I would otherwise normally have to.



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Panoramic view from the Fire Tower at Mt Bunninyong
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  Mt Bunninyong   VK3/VC-018

Activated 12 January 2014

This summit is by far the prettiest of the three summits visited this weekend. I had studied the route of the road race which ran in a circuit to the west of Bunninyong township but did not impede my access by foot to the summit. I parked down from a policed road block amongst a large number of spectator vehicles on Yendon Number One Road, walked through the road block and left into Yankee Flat Road which joined with Mt Bunninyong Road to the summit. I major walking track crosses the road about half way up and I took this zigzag track to the summit which opens into a pleasant grassed picnic spot with a shelter and a couple of picnic tables shaded with mature gums.  To the left, a short walk takes you to the fire tower that allows access to a public viewing platform.

I climbed to the viewing platform and the fire tower was manned. I could overhear the firewatch radios in the room above me whilst I decided to attempt to qualify the summit on 2 metres with the HT. I was easily able to get several repeaters from this vantage point and tried to drum up some simplex contacts. Andrew VK3BQ was mobile on his way home from the VHF UHF Field Day club station VK3ER when he heard me via the Mt Macedon Repeater. We couldn't make a simplex contact but he was able to spot me and assist in a couple of contacts, Ernie VK3DET and Peter VK3TKK. Still needing a couple more contacts I left the tower and strolled over to a picnic table and set up the FT-817 with the vertical antenna and pulled in 16 contacts on 40 metres, including an S2S with Greg VK2FGJW/1 on VK1/AC-042.


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One of my last contacts was Allen VK3HRA who was pleased to hear me operating close to his QTH. He invited me to drop by on my way through and steered me with directions via the radio to his home. We discussed many things radio and also sat around the computer for awhile with a couple of cold Coronas planning some winter activations before I headed home.



I'll certainly be out if plans permit for another VHF UHF Field Day and preferably on a SOTA summit where it is possible to stay the night – several that I'm now familiar with come to mind with relatively straightforward access to make the lugging of all the extra gear manageable. I was a little surprised that I did not hear more SOTA activity over the weekend. One of these VHF UHF Field Day events is well worth going out on when you will be guaranteed of much better success working the higher bands and getting many more contacts than would normally be the case. It is a great opportunity to see what your equipment is really capable of. Unlike some of the contest weekends on HF bands where QRP stations often get swamped by deaf operators running maximum power, the higher bands are different. Not everyone that you may hear will be able to hear you but you may be surprised. Give it a shot on a SOTA summit on the next VHF UHF Field Day.


3 Comments

A little QRP can go along way.

22/9/2013

6 Comments

 
The local weather forecast was looking rather uncertain for the past week but it seemed to have turned out better than expected. With the close of winter and the days getting warmer, it has been a good time to get out and make the most of the bonus points on some of the higher peaks. This seems to have fuelled a fair amount of SOTA activity including a string of midweek activations from Mitch VK3FMDV and Rik VK3KAN. I was fortunate enough to be handy to the radio at home during the week and bagged some worthwhile chaser points.

The weekend was busy with a few multi summit activations from Tony VK3CAT, Andrew VK2ONZ and Kevin VK3KAB all appearing a number of times in my log. Some of these contacts I made from home and I was fortunate enough to pack the gear out on both Saturday and Sunday aftternoons for some portable operating.

On Saturday I went to Warrandyte State Park and set myself up in an elevated spot near Pound Bend. I managed to get the doublet strung between a couple of trees just the way I wanted and had some good contacts on 40 metres as well as a few more summits when they appeared on the band.

I've heard reports that we are on the downside of the current sunspot cycle and that it is not going to last as long as some previous ones, but propogation conditions seem most favourable to me lately. When things quietened off a little on 40 metres mid afternoon, I decided to have a tune around the bands. There was no joy on 15 metres but from mid afternoon 20 metres was jumping with DX.

My first DX contact for the afternoon was Andy RG4F who came back to me with a 55 report. Shortly later things really started to pick up and I had a very comfortable QSO with Andy SP8BRQ in Poland who surprised me with a 58 report. Next was Angelo IS0FDW with a 57 report followed by Victor RX1A in St Petersburg who gave me a 54 report. These were all contacts where I had to jump in and battle with much larger stations in the pileup but still managed to get through. Before packing up for the day, I found a quiet spot on 14.208 Mhz and put out a single CQ call. Ralf DL3EA came straight back to me with a 56 report.

This was the best DX session I have had operating DX with nothing more than 5 watts. I amazed myself as well as most of the stations I worked.

Sunday was similar. I was in need of a decent walk and took off towards the city and ended up at the Studley Park Boathouse. The area was packed with people so I left the car there and went for a nice hike along some of the river tracks and found a nice elevated spot away from the RF and people noise and set up the HF vertical antenna and had a short play on 40 meters. I had one SOTA contact with Kevin VK3KAB on VK3/VN-002 before packing up and walking around Dights Falls and eventually back acrossthe foot bridge near the boathouse aroud the park land past the Yarra Bend Golf Club.

Following the road across the Eastern Freeway, I found another elevated spot high up overlooking the Merri Creek and errected the vertical antenna once again. Signal reports on 40 metres this time were better and again I tried 20 metres.

Most of my portable DX contacts have been on the doublet in the past and I have really only worked a couple of ZL stations before with the vertical. Today was different. I wasn't expecting to do quite as well but I bagged the following: Janez S51DX in Slovenia with 59 both ways, Peter DL5SAM who dropped his power to 5 watts with 56 report sent and 57 report received, Oleg RY3D with a 55 report, Rene DD2VO giving a 54 report and Ivan OE3DIA in Vienna with a 57 report.

It was a fitting end to my afternoon of radio with the last contact being another portable station, Lucy M6ECG/p about 90km northeast of London who was operating from the beach at low tide near her home, QRP with a vertical antenna. It's a constant surprise to me how well 5 watts can work and what is possible when the bands are open.

6 Comments

Bicycle Portable in North Balwyn

26/5/2013

2 Comments

 
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This morning I decided to stay close to home, jumping on the bike and heading down to some of the parkland alongside the Eastern Freeway in North Balwyn.  I was successful in avoiding most of the RF noise I suffer from at home and traded it for vehicle noise from the freeway instead.  I spiked the HF vertical antenna in the ground and got on 40 metres about 15 minutes after the UTC rollover. I was hoping to get a contact with Allen VK3HRA/p on Mt Bride but by the time I'd set up, he was nowhere to be heard and probably on the way to his next summit.  Eventually Allen appeared again on Britannia Range and the pileup started again. This time I also struggled to hear him however others were not having any problems copying and were giving him good reports.  I had a couple of contacts on 40m myself but no SOTA contacts.

On this outing I did more listening than transmitting and spent most of the time monitoring 40 metres.   I also had the HT monitoring 146.500 Mhz.   Whilst listening I thought I'd do a little antenna experimenting just with the gear I had on hand.   The main purpose of this was to improve my chances of reliable 2m contacts when opreating portable or SOTA summits but without having to carry a pole or a bulky beam.

On a few occasions when operating portable, I have used a dual-band ground independent mobile whip hung by it's tip from an overhead tree with a short run of coax to the radio.  This has worked quite well and is a big improvement on using a standard rubber ducky antenna screwed directly into a HT or the FT-817ND.  The main disadvantage can be the length of the whip. It can be a nuisance or even a hazard to carry through dense bush tracks.   This is also the reason I don't carry a squid pole.


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I also want to make more use of the vhf/uhf capabilities of the FT-817ND instead of relying on a HT and being limited to the FM mode only.  What I wound up with was a surprisingly effective vertical antenna but with the advantage of weighing almost nothing and all fitting neatly within my backpack when on the move.

The ingredients of this antenna are simple and I had all on hand without any pre-planning:
  • Four lengths of wire, roughly ¼ wavelength

  • A lightweight mobile base and lead assembly, 5 metres long terminated with a BNC

  • BNC to PL259 adaptor

  • 2 wooden sticks

  • a roll of electrical tape

  • string

  • OEM FT-817 Rubber Ducky antenna

Putting these items together was crude but effective. Firstly strip the insulation from one end of the four pieces of wire. Strip a good 3cm back and twist the wires together and then wrap around the theaded antenna base, using the lock ring and nut to secure.  Next get the two sticks and tape them together to form a cross.  Then tape the ends of the wire ground plane you have just made to the sticks and adjust so they hang at about a 45 degree angle from the base.  Connect the BNC/PL259 adaptor to the whip and then to the base.  Connect the BNC at the end of the feed to the radio, tape the string to the top of the whip and throw the other end over a nearby overhead tree limb and adjust for maximum allowable height.

Hey Presto! Instant emergency antenna for VHF and UHF.  This works so much more efficiently than mounting the whip directly to the radio which is cumbersome at the best of times.   Indicated SWR was very acceptable across the 2 metre band and I could key up a number of repeaters easily that the HT was struggling to reach. Next time I do this, I will experiment a little more with the length of the ground plane wires as well as the 70cm band.   I will also screw the longer stub on the OEM FT-817 whip and give the 6 metre band a try.


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This is the assembled antenna prior to hoisting as high as the 5 metre feed would allow.  I make the best use of any skyhooks that Nature provides when erecting antennas.  Where this is not possible or convenient, my antennas are self supporting when erected and easily transportable within my backpack.  This allows maximum mobility by bicycle or foot and allows me to traverse almost any terrain without getting snagged in foliage and damaging or losing anything en route.

2 Comments

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    Marshall  VK3MRG.
    Someone who likes to mix outdoor activities with radios at every opportunity.

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