RaDAR – Compass basics

Browsing the Net, I found this awesome blog at http://lensaticcompass.blogspot.co.za/ and a summary is worth repeating here! Compass work can become an essential part of the RaDAR operators toolbox.

I used Google Earth to produce this satellite image of my trail running and RaDAR training ground close to home. The grid lines are included for easy alignment to north. A similar “map” can be made of any area on earth using Google Earth!

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An extract from the blog. ” …….  take your map and lay it down on a flat surface (i.e. the ground). Take your lensatic compass and open it up all the way so it is one flat line. Lay the compass down on the map so its long side is parallel with the north/south axis of the map. I generally line it up with a north/south gridline.

Next, rotate the entire thing (map and compass) until your compass is telling you that it’s pointing north. Now your map’s true north is lined up to your local magnetic north, and you’ve just completely circumvented the whole problem of declination (also removing a potential source of error since declination changes with time).

From here it’s simple. All you do is take your compass and line it up from your current point to your desired destination and look at the compass reading. That’s the heading that you need to move along to reach your desired end (or way) point. Pick up your map and head out!”

Resection

Resection with a lensatic compass is a process whereby you can determine your own location from that of two known points in the distance. Typically these features are prominent, such as a hilltop, a man-made structure, or an intersection, but they can be more nebulous if you’re in a tight spot.

The key to the whole operation is having a map and being able to locate these features on that map. Then, from where you are, shoot an azimuth to the feature as accurately as possible, and calculate the back azimuth from that reading. The back azimuth is nothing more than the opposite direction of the reading you’re taking. That is, take the azimuth you recorded and subtract 180 degrees from it, or 1600 mills if using a military lensatic compass.

Next, do the same for the second point.

Now, take your map and draw lines (at the back azimuth angle you calculated) on the map through the features that you’re using as reference points. Those lines will intersect at some point if you’re done your resection properly. The point where those lines cross is your location, and the accuracy of that location is only as high as the readings and calculations that you’ve made”

A really excellent method!

73 de Eddie ZS6BNE

RaDAR – An addition to the family

I sold off some unused equipment to pay for a second hand Yaesu FP-30 220 v.a.c. to 13.8 v.d.c. power supply for the QRO kit, namely the FT-897d. The tiny unit easily weighs in at 1.5 kg, just about the weight of a 7 A/Hr SLAB!

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This unit simply slips into an unused battery compartment at the base of the 897, the height of the 897 increasing by a cm or so.

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An internal battery is a limitation as the QRO setup is limited to 20W output so really, an external battery is better in the case of going higher power (up to 100W) other than QRP for RaDAR on some occasions.

This setup opens other doors. One never knows, even on foot, where you may get access to the grid and use it while it’s still there saving on batteries. RaDAR encourages the use of whatever is available at the time of need. Adapt and improvise!

Looking forward to testing this configuration within the context of RaDAR.

73 de Eddie ZS6BNE

 

RaDAR

 

RaDAR – The Prodigal Son

For quite a few years now I have left the standard dipole in search of a truly rapidly deployable, multiband, effective, antenna for use with RaDAR.

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I have tried open wire fed, random length dipoles, various configurations of the W3EDP, delta loops (good), open wire fed delta loops, manually tuned end feds (good), The FUCHS multiband end fed, wire J-Poles (they work) the ZS6U minishack special and also the ZS6BKW multiband open wire fed dipole (similar to the G5RV) not to mention the 9:1 UNUN fed long wire (multiband but shocking!).

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The closest to my goal, for specifically RaDAR, were the resonant length end feds, especially the single band manually fine-tuned ones (they work WELL and the earth / counterpoise is not that much of an issue).

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I guess what brought me back to reality was seeing the SWR as the AT-897 ATU tuned the 9:1 UNUN fed long wire during the recent African DX contest. SHOCKINGLY HIGH SWR. OK I have worked DX running QRP with this antenna but things don’t look quite as right as they could be!

My thoughts returned to the link dipole (I had tried one once too) and I drew up a chart of calculated resonant lengths for an inverted vee. Being RaDAR, it’s quite unlikely that the antenna ever be deployed as a dipole, that’s just not going to happen, so the lengths were calculated as if the antenna would always be an inverted vee.

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I built the antenna this weekend. It took me a while. Although not quite the best for RF, I used crimp on bullet connectors. I might add that the crimp on idea works great for RaDAR if you want to put something together quickly in the field!

I did a few SWR tests last night and found one or two places where I had measured incorrectly and after trimming, I had perfect SWR on my FT817ND’s meter. The antenna is rapidly deployable and will fit together pretty nicely with my painters pole RaDAR mast.

Rolling up the antenna when packing up was always an issue but I included a facility using chopping board where the coax meets the antenna. I guess I could have made it more compact but the general idea seems to work OK. The next one I will build will include all the improvements I may see fit while doing actual deployments.

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All ready for next weekend’s summer QRP contest!

73 de Eddie, ZS6BNE

 

RaDAR – 2nd All Africa DX Contest

I wanted to take part from home and had strung up my ZS6BKW open wire fed multiband antenna but the QRM I was getting and me switching the household TV on and off with each transmission wasn’t going to work. My XYL suggested we go away for the weekend and then I can take part in the contest from our little house down by the dry, burning, river. So that became the plan, much like a RaDAR ops but this time it would be “fixed station” (in another building) RaDAR. I packed the car with all I needed and maybe a little more. Elrika sorted out the logistics side of things like food and milk for coffee, can’t be without coffee🙂

I went through a few hours before the contest to set up station. I put up simple wire antennas, one was the adjustable “clothes line” antenna and my trusty (QRP!) 40m end fed. I used my telescopic fiberglass “Eskom pole” for the mast guyed with nylon line and strong tent pegs. Didn’t want it to come down and damage the roof!

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It was difficult to set up the antenna for lowest SWR, a guess at best, a matter of correct length working blind really relying on previous markers. Eventually I used it for 20m getting a reasonably good SWR and used the QRP end fed for 40m NVIS.

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I’d never really used computer logging before but had played with the N1MM+ Logger software a day or two prior. I must say it was a pleasure. I’m used to writing hand written logs working in the field mostly. I was spoilt – no doubt!

I set up a nice comfortable station inside, the RG58cu coax coming through the window and a 220v a.c. supply from the wall socket just behind the table. This was “fixed station” RaDAR!

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The Heil headset wasn’t doing too well. One or two reports on the audio forced me to use a standard mic and headphone. It could have been settings, I’m not sure.

Making contacts was reasonably easy with a surprising number of local participants. DX a little more difficult. At least I was heard by the RBN but heard from a friend in Germany that there were extremely strong signals from Europe that made it difficult for a two way QSO.

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I had an easy SSB QSO with India though but seems my 100W signal was easily heard there on 20m. Certainly the clothes line antenna was doing it’s work!

After sunsent, things quietened down somewhat and I did my admin for the day uploading ADIFs to the “cloud”. My contacts were as follows :

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Well it was fun but now looking forward to the RaDAR challenge in November. That’s my focus for now. The 897 needs to go through a few on foot tests beforehand …. The 817 will be an alternative QRP solution.

73 de Eddie ZS6BNE

 

RaDAR – 817 vs 897

Well yesterday I had time to wire female sockets to my DC supply and a 7 A/Hr SLAB and a male plug onto the 897’s DC power cable. This allows me to quickly switch between a mains powered 13.8 v D.C power supply or the battery.

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It was time to take the 897 for it’s first introduction to RaDAR. I had a 20m inverted vee wire antenna hanging in the air barely four meters above ground.

I set the rig initially for a maximum output power of 5W and gradually increased power………… right up to 100W. The battery took the punch with a smile!

The proof of the pudding is in the eating and I had a great CW QSO with the Ukraine on 20m while sitting on the grass in the back yard!

In the picture a comparison in size between the 817 and 897. For twenty times the power of the 817, the 897 certainly stood its ground consumption wise, size wise AND weight wise!

I have already tried packing it in a waterproof container within the pack. It fits perfectly and well protected from the elements.

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Let the games begin!!!

73 de Eddie ZS6BNE

RaDAR – QRO vs QRP

Let’s face it, QRP is fun, reasonably lightweight, easy on the power supply and easy to carry for longer distances to your destination. It has many advantages but sometimes you need to bring in the artillery to win the battle.

I’ve had many successes with RaDAR while running QRP and a few failures too where I could just not get the message through. Somehow 20W compared to 5W does sometimes make a difference and then with 100W capability you’re almost sure it will make a difference when conditions are not quite that good.

Since acquiring the second hand FT-897d, I have made a DX contact each day. Actually not just the “rubber stamp” kind, real QSO’s! That is on CW and SSB. Much like a RaDAR deployment I had a wire antenna just outside the “shack” around four meters off the ground. This was almost impossible to do with the 817 the way conditions are at the moment. I guess the guy on the other side makes a difference too with a good radio and good directional antennas.

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Well, last night I reconfigured the rig to be able to fit everything into my larger pack. This setup weighs in at 4.5 kg. Not much really for 100W capability, an ATU that will tune just about anything, decent digital modes interfacing and an overall good number of facilities like Collins filters and DSP.

I must still fit the chopping board which will further protect the rig and permanent cabling at the back while in transit. The 897 can be fitted with it’s own internal batteries thus saving on space but for now I’ll start with a 7 A /Hr SLAB or two.

The whole lot can be changed to a “bare bones” system by simply removing the “mobile bracket” that clamps everything together thus removing the ATU and Signalink. The two units are protected by stick on “rubber feet”. It’s almost as if the system was designed this way, everything fits perfectly.

My friend Dennis, ZS4BS says now that the ATU lies on it’s side, it can only tune horizontal antennas🙂

73 de Eddie ZS6BNE

RaDAR – Manual tuners

A good friend gave me a MFJ tuner a few months back and today I took the time to delve a little deeper into the details of the tuner. The circuit diagram may look complex but really just a simple high pass tuner design. The complex part is simply just for the metering. I was using it as a SWR meter only, till now.

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Then I went looking on the Net for similar circuits and comments and found a few interesting ones. These are just variations of what we see above. A pretty versatile way of interfacing the 50 ohm rig connection to anything else!

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So I have this awesome tuner, maybe it’s time I started using it!

73 de Eddie ZS6BNE