26 February 2013

DVB-T Dongle. Cheap and Easy SDR?

Having been inspired by the article in QST January 2013 page 30 titled 'Cheap and Easy SDR' by W9RAN I went ahead and ordered one of these dongles from Amazon.com. This dongle can be used to receive radio signals from 64MHz - 1700MHz (except 1100 Mhz- 1250Mhz). It uses the chipset RTL2832U and the Elonics E4000 tuner chip. The SDRSHARP software will decode almost any mode.

I probably paid over the dollar for this kit but I have a good chance of being able to make it work since this dongle is listed on the Osmocon website.

I like the fact that the implementation does not require the use of sound cards. This is a full digital interface with a 2MHz view of the spectrum! Fantastic. Maybe I can progress towards making a homebrew panadaptor down the road?

I watched a UTube video showing a decoding of Amsat signals. This looked really interesting.

My level of ambition is to simply be able to decode the local FM broadcast stations using the supplied whip antenna. Thereafter better antennas will be required.

I tried to search the web for a local source for these dongles here in South Africa but with no luck. I was surprised since I know that DVB-T is coming to South Africa in the next few years.

Go here to the Osmocon website if you are interested: http://sdr.osmocom.org/trac/wiki/rtl-sdr

Herewith is a copy of my order from Amazon.

"SDR Starter Bundle: EzTV668 DVB-T USB Receiver & Low-Cost Software Defined Radio (SDR) with Free PAL to BNC Adapter - Realtek RTL2832U + Elonics E4000"
Electronics; $59.95

25 February 2013

Walkhaven Dog Park
On Sunday morning  Feb 24th Berry (my wife), and I, took a drive out to this dog park called Walkhaven  http://www.walkhaven.co.za. This park is just a short 20 minute drive from our Fourways QTH in the Cradle area north of Joburg. This is a really nice place where the dogs roam free in a very large area. There are also 2 lakes for the dogs to swim in. We enjoyed a nice breakfast there while being highly entertained by the antics of the many and different dogs! It was a bit disconcerting when our dog Chaiya decided to join a pack of dogs. We had a hard time getting her back!

I took my radio gear with me but in the end did not do any operating. It is certainly a possible place to operate. There are skyhooks but one would have to get there early in order to be able to set up under the trees. There are trees near the restaurant, however this area is too populated to make a good radio spot. I decided that the best place would be in the upper areas of the car park. However some form of shade, such as a portable umbrella, would definitely be needed. The ground slopes gently upwards towards the north. The optimum location would put you about halfway up this slope. There would be a nice take off towards the west and east and of course south for working 40 meters and South Africa. To operate from the car park would require setting up a mast since there are few trees in that area.

View looking west. A gentle slope towards the horizon from the park

22 February 2013

The ZS6TJS Mast. My learning experiences

This last weekend I took my new ZS6TJS mast to the field for the first time. OM Thomas Scott ZS6TJS had been extremely helpful in building me one of these masts before the ARRL Int. CW Contest. I picked up the mast from Thomas the day before. Thomas gave me a few tips on how to deploy the mast in the field. I was rearing to go.

ZS6TJS MAST in it's carrying case
 As you can see from the included pics, the mast is a
beautifully put together product. The kit consists of a very rugged carrying case, the aluminum mast sections (7*1 meter sections), two sets of guys, a hoist rope to allow hoisting of wire antennas, 3 tent pegs and an instruction sheet. The kit is professionally made. It is obvious that Thomas has access to the professional tools required to work in aluminium.

I had to get this mast in the air as soon as possible!

ZS6TJS MAST components

On Saturday I drove to the Krugersdorp game reserve picnic area. Here I found wide open spaces and a perfect area to set up the mast. See my previous blog for more details of this site. I first laid out the pieces on the ground, established where I wanted the mast to stand and measured out approximately 3 meters from the mast base to locate the first tent peg spot. I hammered the peg in very easily since the soil was quite soft. In fact I did wonder if the peg was going to hold. I then estimated an arc of 120 degrees from the base and hammered in the second peg, also 3 meters from the intended base. The same with the 3rd peg at an estimated angle of 270 degrees. I then slotted the first three mast sections together and inserted the first guy set onto the third section 'tongue'. Proceeding to slot the sections together, I then inserted the second guy set onto tongue number six before slotting the last and 7th section into place.

I then hooked two of the top guy ropes onto the appropriate pegs while leaving the third rope off it's peg. I simply left the lower set of guys off the pegs at this point.

Having done this I sat back for a few minutes and surveyed the scene, drank some water, took a deep breath, recalled what Thomas had instructed me and proceeded to 'push/lever' the mast into position by leveraging it upward in a line between the two pegged guys (easier done than said in this case). The mast went up without incident. Once in the vertical position, I then grabbed the third guy and walked it carefully out towards it's peg. Ha! The thing was in the air! I then walked around adjusting the guy ropes until all was square and the guys were reasonably taunt. I then hooked and adjusted the lower set of guys. I guess the whole job took me about 20 minutes.

I did notice that the guys were not quite evenly spaced at the requisite 120 degrees and that they also were not exactly an even 3 meters from the mast base.

Since I have a compass app on my blackberry, the thought occurred to me that I could orient one guy, let's call it the 'main guy' to face true north. I could then use the compass to more accurately locate the other two peg positions at 120 degrees and 270 degrees. Maybe I will cut a 3 meter piece of cord to ensure correct distance also. This is not so critical if the mast were to be used for simple wired antennas, however when using it for something heavier, such as a moxon, it is more important to set the guy locations correctly. Another lesson learnt. Ensure that all other humans, your radio gear and your car are out of range of a possible falling mast!

Next the fun started. Having erected the mast and now feeling full of confidence, I then assembled my ugly moxon. This is an ungainly antenna at the best of times. It is very easy to trip over wires and generally get things in a mess. Having done this, I then secured a piece of 1.5 meter doweling to the top of the mast using two hose clips. The moxon was then set atop the dowel and allowed to turn freely (hard to explain  but easy to do). The moxon at this point is resting on the extension piece which is designed to hold the feeder cable (I will get more pics on this). I then tried to hoist the mast up as before. However I found this extremely difficult. I would get the mast to a certain point but then the base of the mast would rise in the air and the assembly would fall to the ground in spite of me applying full muscle power. After expending much energy and now red in the face, I dug a small hole in which to set the base of the pole. Much the same as a pole vaulter would do. Now with the base somewhat secured in the hole I was able to apply force to the mast and walk it into the vertical position. This time the mast went up without incident. Once past the 45degree point it was very easy to push it to the vertical point. I noticed that there was certain bending in the mast as I was hoisting it through 45 degrees, however I did not feel that it was being over stressed. The lesson learnt by this exercise was that even a light weight structure such as my moxon was in fact very 'heavy' when attached to the end of a 7 meter pole. Physics lessons came back to mind. What was the formula? FORCE = MASS X MAST LENGTH.....hi hi.

Interestingly, at one point I was able to raise the mast quite easily using just 6 sections as opposed to the full 7 sections. I was amazed at the difference. But then of course I had to find a way to get the full height out of the system. I can say that once the system was QRV that all the effort is well worth it. What a great antenna!

When the time came to tear down I went through the same procedure in the reverse direction. Unfortunately at the point when the mast was at about 45degrees the base of the mast 'flicked' out of it's hole and the whole assemble came crashing to the ground. Luckily nothing was broken. In fact I realized that although the moxon looked ugly, it is quite robust. The 20mm pvc spreaders simply bending a bit when they hit the ground.

Another challenge I have found in the field is the rolling of ropes and wire in such a way that they do not end up in a tangle when the time comes to deploy. I like the velcro strips supplied with the mast, but they still don't quite solve the issue. I know all readers will identify with this problem. For another blog subject...

So what is the next step and what are the lesson's learnt? I will likely get a chance to try it all again this next weekend on Sunday afternoon.

  1. Use my blackberry compass and a piece of 3m cord to accurately locate the peg positions.
  2. Dig a mast base hole somewhat deeper. Say about 12cm deep. Keep the hole small in diameter (say about 4cms. Use my claw hammer and leatherman to dig the hole. If this procedure does not work then I will have to think about designing some kind of base plate. This I want to avoid if at all possible. My experience of field operations being to reduce the number of components required to an absolute minimum. Here the trade off is going to be between digging a small hole (manual labor) and installing a baseplate (manual labor plus another piece of hardware). Lets try the hole first.
  3. Take more pics of the proceeding. Maybe get the XYL, who is now back from europe, to take a video.

I will add to this report as I learn more.

Here below some pics taken so far.

Ugly experimental moxon on the end of a dowel. The dowel is fixed by hose clamps to the ZS6TJS mast

The mast is vertical, the pic is not! Note the cord  beam  rotator.
My operating position on Sunday. About 8 meters from the mast.

21 February 2013

ARLR Inter. DX Contest CW

Date Feb 16-17 March 2013. From 0000UTC Saturday - 2359 Sunday.

I participated in this interesting contest. The contest aim is to contact as many W/VE stations as possible. It is aimed at encouraging an understanding of DX propagation on the part of W/VE operators. 

I set up my field station at the Krugersdorp game reserve day picnic area. This is an excellent spot for radio. and there was no local noise on the band. There are many sky hooks in the form of very large eucalyptus trees and a lot of wide open spaces. The day entrance fee is R30 (I think per person?). The gate is open from 7am - 6pm local during summer, however I was told that you can depart the area anytime up to 10pm. I am not sure that the security is adequate after dark, but I did notice a number of security guards around the gate area. There are many braai areas and plenty of shade. The ground slopes up slightly towards the west which probably reduces the signals in that direction? The ground is soft and with few rocks, making it easy to hammer in pegs for guying masts etc. On the slight down side there are 4 lapa's there. On saturday there was a big and noisy party going on in one of the lapa's. On sunday there was more loud music coming from a group of picnickers. The area is also near the main road and thus there is a constant sound of traffic in the distance. All in all, I feel this is an excellent site. There is easily enough room to set up multiple antennas for experimental and comparative purposes.

I ran my Elecraft K2 at 5 watts QRP and operated on 15m and 10m of which I succeeded only in making  QSO's on 10m.  My key is a mini Palm which is designed for field operations. I used the internal battery in my K2 for the entire operation. My Antenna system was an inverted V center fed doublet on 15m. The apex was up in a tree about 10 meters and the wire length was about 40 meters long. This was center fed with a 300 ohm ladder line which did not quite reach the operating position. So I lengthened it with a piece of 450 ohm ladder line. This was tuned by an ancient ZW1 balanced tuner. On 10 meters I used a prototype moxon beam which I had fashioned out of some pieces of 20 mm pvc pipe, 0.5mm bare wire and a piece of plywood which I used as the hub. I attached a 1.5 meter piece of doweling to the top of my new ZS6TJS mast with two hose clips. The moxon can then be rotated using the armstrong method (see pics). See my separate write up for more details of this. 

On Saturday I was QRV at 12:30UTC. Setup time was about  50 minutes due to my unfamiliarity with the new mast set up procedure. I operated until 15:45UTC when it started to get dark and I had to leave the site. A total of 3.25 hours. I found that the 15m band was opened and that there was a huge amount of QRM from Europe. There was no way that the W/VE stations were going to hear my QRP signal. I moved to 10m which had much less QRM than 15m. On 10m I was able to get the attention of the big gun stations. I really appreciated their patience in pulling my signal out of the noise. Most of the stations asked for a repeat. I think this was due to a combination of weak signal and my difficult call sign. I noted that they generally copied ZS6R.. but had trouble figuring out the S and H hi hi. I did find that by QRS'ing down to about 19wpm that I scored a better non-repeat rate. I felt that many of the stations had multiple 10m antennas pointing in different directions since I did not notice any of them rotating their beams in my direction. Well put it this way, I did not notice their signal levels increase. These operators are very patient. I feel bad for them many times when they have to spend precious minutes digging out my weak QRP signal. But never once did an operator abandon the attempt and there was satisfaction expressed in the form of vy fb once they had copied and I sent QSL! I also noticed that a small tweek of my antenna to beam more accurately in their direction often resulted in them copying me. Next time I will take better azimuth bearing information to the field. The following stations were in my log for Saturday. K3OO (PA), K1LZ (MA), K3LR (PA), NY4A (NC), K1RX (NH), W3EP (CT), KE9I (IN), N4OX (FL), VE9AA (NB), K5RX (TX), N8AA (OH) gave me an honest 579, WB9Z (IL), W2FU (NY). When I went QRT the band was still opened and the signals were coming up as the sun set.

On Sunday I was QRV from the same site at 14:00UTC. This time I was a bit further up the slope and I only set up the moxon for 10m. I did not check out any of the other bands. I felt that the signals were stronger. However I noted that I had already worked many of the stronger signals. This time I stayed later and was QRT by 16:30UTC having operated for 2.5hours. I really noticed the signal strengths coming up as it got darker. There was much more QRM from Europe. Not sure if this was because they had exhausted 15m or if the band condx were better? The following stations were in my log for Sunday. K1ZZ (CT), N1UR (VT), K1WHS (ME), K8GL (MI), K4RO (TN), VE3JM (ON), VE3UTJ (ON), K3AJ (MD). 

In total I worked 21 stations over a period of 5.75 hours on 10 meters. The moxon performed excellently. However I wonder if a vertical might be more suitable for field DX purposes on the 10m band? It certainly would be easier to set up. The moxon has excellent F/B ratio but not much forward gain. However the problem for QRP is not so much eliminating QRM (since it is easy to copy the big guns) but more an issue of forward gain (IMHO). In a low noise field environment a vertical may perform better. It would be interesting to do some comparisons.

19 February 2013

It's a start!

I have started this blog with the aim of recording my adventures and comments related to my amateur radio adventures in South Africa.

My wife and I live in an area called Fourways in the Northern suburbs of Johannesburg in the province of Gauteng. We live in a very nice 'gated community' called Cedar Lakes. Our garden apartment is quite small and has a flat roof. For the past few months I have been experimenting with different stealth antennas. These have worked to some extent but the QRM levels are very high. Two weekends ago I travelled to the Manyane Camp ground in the Pilanesbery National park. There I set up a 1D operation (single op QRP) and participated in the SARL Field Day. I was absolutely amazed at how quiet the band was and it was an absolute pleasure to operate there.

I returned back to Fourways and resolved to focus on my QRP-to-the-field operations and to enjoy the wonderful outdoors that South Africa has to offer at the same time. 

During the field day operations I was lucky enough to make a QSO with ZS6A OM Pierre. I was delighted to learn that Pierre is also a QRP enthusiast. I have subsequently received some great tips from Pierre and suggestions of possible parks and picnic spots within reach of the Joburg area. I am very grateful to ZS6A for all his help.