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  • The Great South African G90 2021 Tour

    I used to own a Yaesu FT-857D, three of them, in fact. With them I made all sorts of contacts: straight contacts, QRP digital contacts, mobile FM contacts, and they even pushed my FL2100Z amplifier to full output when I needed to. I loved them and trusted them. While the screen might have been a little small for my older eyes, the radios never ever let me down. I still miss them a lot.

    But times are moving on and instead of following the way of the FT-101 and other dinosaurs (don’t get me wrong: They were excellent radios) I wanted to get some first hand experience of the more current SDR radio trends. First I bought a mcHF portable 5 watt radio which was a great buy and I’ll talk about that more in another post, but then I wanted to but a really “complete” radio for the bush. Smaller than the FT-857 but bigger than the mcHF and an all-rounder. The dice was rolled and fell on the Xiegu G90 which arrived in my shack a few weeks ago. While we can discuss all the details at length in other posts, this post is to let it travel around the country and experience different operators and conditions and antennas.

    Thus, the idea of “The Great South African G90 2021 Tour” was born. I decided to let my baby go visit some new places. My ICOM 7100 will have to do backup duty in the shack while the baby is travelling.

    First stop of the tour was my bush camp. I took my Xiegu G90 on a week long tour to the bush in Dikhololo (north of Brits and Hartebeespoort Dam). I have to admit it was a lot of fun to operate, even though the noise levels were appalling and in many cases made operating impossible on a particular spot.

    In summary I was very happy with it. It is not a big radio but it can stand its own.

    • The cabling takes up a lot of space
    • Look at that noise!
    • My assistant helping me with the antenna
    • My little assistant providing comments
    • A standard 49:1 toroid from my shop hastily mounted in a small box
    • A hastily cut EFHW resonates perfectly
    • Quickly soldering the balun in place
    • Hiding in the corner is the G90
    • The support kit takes up most of the space

  • The Joy Of Building Kits

    The QCX+ from QRP-Labs

    I managed to get my hands on a few of the latest (2020) QCX Plus kits from QRP-Labs and as usual I had no difficulty finding homes for the extra kits, obviously keeping one for myself to build in the wee hours of the morning when it is quieter.

    It was – as always – an easy build and I finished in maybe 3.5 hours. The documentation is good and the components even better.

    I love building kits and maybe if I am lucky I will win the competition over at The SWLing Post for a MFJ-8100K shortwave receiver kit. That would be an awesome complementary radio!

  • LED Lamp Behaviour

    LEDlamp
    LEDlamp

    So I got my hands on some of these 12 volt LED lamps (chips / modules / lights / whatever) and since I had enough to burn one or two “by accident” I thought I should spend a few minutes to get to know them better.

    I’m not referring to your regular little round 1.2 volt LEDs that we use by the millions for indicators and things on our projects, but instead the square, yellow modules around 25mm per side that makes white light for floodlights and so on.

    So before you pull out your 12 volt battery and blow up some lights, here is an important message: LEDs are current devices, they do not like constant voltages and will promptly reward you with a puff of smoke if you persist, much like the inkfish did in the sea when it tried to escape. You have been warned. Use a constant current to feed them and everyone will be happy.

    The other thing I completely underestimated is the amount of heat dissipated. They come without any protection whatsoever and your first job is to stick them to a heat sink. The 10 watt units I have require a heat sink not unlike the ones found in old computers.

    Once I had my head wrapped around this weird change from incandescent lamps, I had a lot of fun playing with my packet of LEDs. They produce good white light at reasonable powers, so even if you drop the current through a small resistor from a 12v car battery they will still work.

    However, there is one worrysome feature that I noticed. Assuming that each little LED is dropping around 2.98 volt (a not unreasonable number according to https://www.ledsupply.com/blog/wiring-leds-correctly-series-parallel-circuits-explained/) then you will end up with a matrix like this:

    LEDmatrix
    LEDmatrix

    or like this:

    A B C
    D E F
    G H I

    This is not the end of the world, except that if the LEDs are not closely matched they will draw different currents, with the weakest link obviously blowing first. I expect this will manifest as one LED lighting up slightly more than another in the chain.

    This is exactly what EDN found on their site at
    https://www.edn.com/design/led/4325905/Driving-high-power-LEDs-in-series-parallel-arrays



    I’ve made a short YouTube video to illustrate my concerns https://youtu.be/nf1654eiy1A

    Watch how the LED in position “C” lights up first and then goes on to illuminate brighter and brighter. It may be the one that burns out first, or overheats the most.

    What do you think, am I right or am I wrong?

  • Replacing the BS170 in an Ultimate3S Beacon

    The new BS170 in its socket
    The new BS170 in its socket

    After the weather zapped the output transistor (a BS150 FET) of my Ultimate3S beacon from QRP-Labs yet again, I was forced to replace the device, again. It is not a difficult job at all, just a little chore. This time I decided to make it easier on myself. Instead of replacing the transistor by soldering it in, I decided to use a plug-in base so that I can just whip it out and plug in a new one.

     

     

     

     

     

    The bad guy
    The bad guy

    The offending object is shown clearly out of focus, just to gain some perspective. I always solder mine in with at least 5mm long legs sticking out above the PC Board to allow for fitting a heat sink.

     

     

     

     

    Decapitated
    Decapitated

    Decapitate the weakling in one go! Don’t waste time, just stick in the cutter and cut out the weakling, but do it as far away from the PCB as possible, leaving the stumps for later removal. I placed a small piece of paper behind the legs to make it easier to see in the picture.

    Now you can just heat the legs one-by-one and tap the board so the legs will drop out. Easy.

     

     

     

     

     

    IC Sockets
    IC Sockets

    Next, consult your trusty junk box or buy some of these IC sockets. They can be any number of pins from 8 to 28, it doesn’t matter. I just happened to have 8-pin variants in stock. Avoid the cheap ones with the single flat blades that pushes to one side of the IC only.

     

     

     

     

     

     

     

     

    Cylindrical pins
    Cylindrical pins

    This is what you want. These cylindrical (or tubular) legs will make good contact with the FET’s legs and they are tapered and coated so your connection is guaranteed to be solid.

     

     

     

     

     

     

    Three Pins
    Three Pins

    Solder three pillars into the three required holes. I managed to keep the front two pillars together and the back pillar is separate due to space constraints. You might even put a drop of glue to hold everything together, but that isn’t necessary and I didn’t do it.

     

     

     

     

     

    In Place
    In Place

    Cut the FET legs a little bit shorter, but not too short, and plug it into the sockets. Make sure it goes down all the way and is oriented correctly.

     

     

     

     

     

    You can see a close-up view of FET in position at the start of this article.

    Completed
    Completed

    Admire your work upside-down and from the side, making sure everything fits correctly.

    Put back your heat sink, close the covers and away you go!

    Next time, replacing the BS170 will be a cinch.

  • Making (Big) Waves

    Yaesu FL-2100Z
    Yaesu FL-2100Z

    The Yaesu FL-2100Z is a classic HF amplifier. It sits near the end of a long life line of multiple variations and models of the basic 811A or 572B triode valve, all using exactly the same grounded-grid core design, and all of them making nice big waves in the ether when fired up.

    I was lucky enough to lay my hands on three of them over time. The first one came to me from an estate in Durban, KZN, in perfect working condition I might add, and I was stupid enough to sell it to a fellow ham that pleaded poverty. He still owes me money after selling it onwards immediately at a profit. The last two came my way in more fortuitous ways and have been a pleasure to own and I’ve made big waves with them while they were visiting my shack.

    The one was nearly in original (i.e. unmodified) condition, the other lacked the row of input filters in the back. The one had 572B lamps whereas the other was retro-fitted with 811A lamps. Both were sort-of working but not really, and over many evenings I painstakingly studied the details of what was working and what was failing. It was great to have two examples with two different faults, because I could compare faults and figure out their individual problems.

    Just remember, I have never worked with valves before. I don’t know them, I don’t like the seriously high voltages around them, nor the heat, and just to add injury to insult I once forgot to disable the HV interlock switch sending me running for cover as the whole thing exploded with loud noises and blown fuses. These things are like hot women: Pretty to look at but you will get burnt if you touch them.

    But we made peace and progress more or less at the same time and eventually both are working. My feeling is that the circuits are relatively simple and the resulting box robust. Once you have twiddled all the knobs and read all the meters, they actually produce some nice power and can make nice big HF waves. For example, with an input of 25 watts the 572B valves (after tweaking for optimum output) spat out a good 500 watts key-down on 40m where I like to operate. The 811A valves were also willing but maybe a tad less capable at 450 watts. I must add that the 572B’s were eager to give a little more with a little more drive, whereas the 811A’s needed a slightly bigger push to give out more. Both worked very well though.

    I uploaded a short video of the testing of the first one to go live at YouTube Video Link showing how easily it puts out 500W key-down even in a somewhat mis-matched feed with high SWR. It is shaking that wire mercilessly by the tail!

    Sadly I have to let them both go. I started another project to build a solid-state amplifier in the same output range, the so-called DN-600, and there isn’t enough rack space in the shack for all of them. The Yaesu FC-902 tuner stays, though, as it has proven to be both accurate and useful. I compared the power it measures on its built-in meter with an expensive scope-voltmeter into a dummy load and I’m satisfied that it tells the truth. Plus my only antenna that can handle that sort of power is my (unmodified) G5RV which, as you know, needs a little impedance matching. Having said that, when I use the G5RV for WSPR (QRP 200mW) I consistently get very good spots, so please don’t come tell me it is rubbish and you lose power when you use a tuner – my experience is exactly the opposite.

    I will be remiss if I don’t mention the three gentlemen who assisted me in this project. Firstly Jacques Scholtz ZS6JPS who introduced me to the AWA (Antique Wireless Association) and was always willing to give advice. Secondly Renato Bordin ZS6REN who kindly donated a secondhand 811A which came in very handy, thank you. Finally Adi Loupo ZS6CNC for setting up the valve tester and helping me test all my motley collection of good and bad lamps, and helping me to get two pairs or lamps that worked together. Thank you guys, you were demonstrating the true amateur radio spirit.

    I’ll publish some more details and photos of the work I did in the next few days, I just wanted the word to get out so long. Here is one last photo of the pair of 811A’s to close off with:

    811A's Working Full Steam
    811A’s Working Full Steam

  • The QCX – a Nifty Little Gadget

    QCX
    QCX
    So yesterday (it was a Sunday) I had a lot to do, but nothing more important than to cut open the wrappings of the 20m QCX kit that I purchased from QRP-Labs a few months ago. Yes, it was still lying in its protective wrappings after all this time. Work is seriously interfering with my hobbies.

    At first when I shook out all the packets with all the little parts into a tray (standard practise), it was a little intimidating. It wasn’t just a small Ultimate3S kit which I can build with my eyes closed in less than an hour. Instead of taking shortcuts (which the documentation warns against) I decided to follow the manual. That in itself was the best advice ever – the 138 page manual is clear and laid out in logical order.

    I did take a few shortcuts, purely because I have one of those cute assembly rigs where you can insert the components, hold then in place with a foam block, then flip it over to solder all the leads at once. I did all the caps in the first round, and all the resistors second round. I have a habit of checking each solder joint when I snip the wire and in this case the unit worked first time.

    The slowest part of the construction was the toroids. Not because it is difficult, but because my eyes are not so good any more and I have to work under the magnifying light which restricts movement a little. Each one of the 8 wires must be inserted in the correct hole with a tweezer or small longnose.

    My PCB is a version 1 so I did the two recommended modifications.

    All-in-all a very viable kit and very enjoyable to build and use. I particularly liked the idea of the little microswitch “hand-pump” which gave me no end of giggles.

  • Argentine balloon to fly to South Africa and beyond

    Argentine balloon to fly to South Africa and beyond

  • Sizing of a Solar Charging System for a QRP Beacon

    When you run a small low power beacon like the
    Ultimate3S from QRP-Labs it is attractive to consider
    powering it from batteries with a solar panel.
    But how long will it last?

    A number of things are conspiring to make our lives as amateur radio experimenters difficult. On the one hand the cheap Chinese imports make it very easy to add small but useful gadgets to your shack. On the other hand technology itself is rapidly moving towards smaller and less power-hungry devices causing your stuff to e outdated two days after you buy it!
    At the confluence of these two streams sits low power beacons: Small devices that can send out a radio signal and only sniffs at the fuel tank. The latest amateur party balloon experiments are a case in point: With a total payload measured in grammes they circumnavigate the world several times over.
    But what about the more common homebuilt beacons? Let us take for example the Ultimate3S beacon kit that was constructed by several South African amateurs: Can this beacon be powered from a solar panel? Let us investigate further.

    How deep is your pocket?
    The first and most important factor to take into account is that almost nothing is impossible if you spend enough money. You can buy incredibly efficient systems with enormous battery capacities at a price that will bring tears to your bank manager’s eyes.
    I don’t operate at those altitudes, my oxygen supply will be cut off very quickly by my Minister of Home Affairs. I’m going to limit my spending to items that the average hobbyist can afford.
    Thus, it is spoken, that we will be limiting the most expensive part of the discussion – the batteries – to standard 12 volt 7 amp-hour (gelcel) batteries. I want to do this because my experience is that the batteries are the items that require the most money and the most maintenance. This might not produce the most optimized technical design, but it will certainly optimise my chances of survival when I get home.

    However, for the technically inclined I have a challenge near the end of this article – please participate!

    How much is enough?
    In order for you to size your solar system for your beacon correctly, you need to note the power rating of the beacon and all its support components that will be drawing power from the system.
    For example, let us take the popular QRP-Labs Ultimate3S beacon to see how one might calculate the correct size of the solar system. This example system is configured with:
    • no receiver slots and no 3G or network connection
    • a standard GPS for timekeeping
    • no relays for band-hopping
    • a standard Si3531A frequency synthesizer
    Measuring the beacon together with the GPS it draws around 150mA from the 5v supply in receive mode (standby as some would call it). During transmit it jumps to 350mA or more. However we are only transmitting for small periods at a time and let’s say we are running WSPR with one transmission every 20 minutes, i.e. 2 minutes out of every 20 minutes or around 10% of the time.
    This is easily calculated to be:
    • In Standby mode about 2 Watt for about 90% of the time; and
    • In Transmit mode about 4.7 Watt for about 10% of the time.
    Without being too scientific we can estimate an average consumption of about 200mA .
    Now a very basic assumption is that I want to operate around the clock 24×7 and thus:
    TOTAL WATTS = 12 VOLTS X 0.2 AMPS = 2.4 WATTS, X 24 HOURS = 57.6 WATT-HOURS PER DAY.
    Before you kill me for using the wrong numbers, remember I am drawing current from a 12v battery through a linear regulator (LM7805), thus 12v x .2A = 2.4W. We can easily round this up to 60 watt-hours per day.

    If you fitted the OCXO (Oven-Controlled-Crystal-Oscillator) to gain better frequency stability you must add at least 200mA to that number, which doubles your demand. Quite frankly I would not recommend that for a solar powered system.

    Sizing of the Inverter / Converter / Regulator
    Reducing the 12 volt battery line to the 5 volt line required by the beacon, we often take the easy way out with a small 3-pin linear regulator a la LM7805.
    The more modern solution might be to use a switching inverter or regulator (12V → 5V or 3.7V → 5V), but that comes accompanied by its own set of negative attributes such as noise which cannot simply be ignored.
    Assuming your peak power drawn is only 350mA during transmit, your inverter / converter / regulator needs to be able to deliver this power without overheating. This translates loosely to heat in the quantum of:
    7V X .35A = 2.45 WATT!
    Yes, a heatsink is recommended.
    Note: The inverter/converter must always be bigger than the maximum peak power demand.

    Sizing of the solar PV array (solar panels)
    For the beacon alone, excluding other losses, we will use approximately 57.6 Watt-hours per day. We need to generate more energy than we use to stay ahead of a flat battery, so …
    The charging hours effectively available per day can vary between 4.5 hours (Cape Town) and 6 hours (Polokwane) per day and let us therefore use 5 hours as a good estimating number.
    If we increase the 57.6 Watt-hours per day to say 100 Watt-hours (to allow for some extra charging when really-really needed), the amount of panels we will need is:
    100 WATT-HOURS / 5 HOURS = 20 WATT
    So the minimum panel size we need is a 20 Watter at 12 volts. More thoughts about the voltage later.

    Rating of the Batteries
    Normally it is preferable to design a solar system for higher voltages because that reduces the cable and system losses which could be as much as 15% more in a 12V system. However in this case a 12 V configuration should be fine.

    Also remember that we also do not want to cycle our batteries more than 50% deep, or even less if we can. To be honest, these cheap 12V/7Ah batteries shouldn’t be discharged to less than 80% of their rated capacity otherwise their lifetime is drastically reduced.
    If we agree to 50%, the batteries that we need must be in excess of 100 Watt-hour x 2. (times 2, to reduce the battery cycle to 50%). For 80% we need five times the rated capacity!
    So we need at least a 200 Watt-hour battery bank. This is the smallest bank of batteries you can go for in this application. You also know the average use is about 100 Watt-hour per day, so if you want additional capacity – say for a rainy day – you need an additional 100 Watt-hour of battery bank.
    But let us not digress. Let us get back to 1 day capacity. For our 12V system we need
    100 WATT-HOUR / 12V = 8.33 AMP-HOUR

    That is much more that the capacity of one battery. If we use standard 7 Amp-hour batteries, that would mean two batteries. Anything less could leave you powerless on a cloudy day.
    In fact, we could digress here into a discussion of two batteries in parallel, or two in series (24V) but sufficient to say that the 24V option is likely to be a more efficient approach.
    Also remember that if you change anything in the configuration, for example add additional bands, you must reconsider the above calculations.

    Rating of the Regulator (MPPT)
    A MPPT, or maximum power point tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank(s). They have become very popular lately, due largely to their ability to protect and extend battery life while transferring maximum energy.
    The MPPT solar regulator is designed according to the output current rating to the battery, in other words it is aligned to the battery characteristics. Don’t buy a lighter version thinking you are going to use less.

    We know we have 20W of panels (independent of the configuration). If we choose a 24V battery bank then 200W/24V = 8.3A MPPT. If we choose a 12V system, this would regulate 200W/12 = 16.6A MPPT. This may yet be another reason why you would want to consider a 24V (two batteries in series) system.

    The Complete Solar Power System
    From the previous assumptions and subsequent calculations, this is an example of a practical system:
    • 1 x 12 V to 5 V step-down regulator at 1 A
    • 1 x 20 W Solar Panels at 12 V
    • 2 x 12 V / 7 Amp-hour batteries
    • 1 x 16A MMPT Regulator
    Be aware that this is only a guideline and your mileage may vary. For example if you are not too concerned with battery life, you could quite happily operate with one battery.

    Gotcha’s
    The above discussion is very generic and there are many things that can go wrong or can go right, depending.
    The battery should be protected from discharging too deeply, but at the same time the beacon must be protected from the power cycling up-and-down too often. It could freeze upon startup.
    Any switching power supply will influence the quality of the signal and may even prevent the beacon from being spotted completely if not sufficiently dampened.
    The LCD display can be switched off completely to save a few milliamps and thereby reducing power demands.
    Adding bandhopping, more bands or more frequent transmissions may severely reduce battery life as calculated above.

    The Real Challenge
    I mentioned earlier that I have a challenge for the more technically inclined amateurs.
    It is my considered opinion that the system we discussed above doesn’t make very good use of all the resources we have at our disposal. I’m convinced that some optimisation isn’t only possible, but also easy to achieve.

    For example, I’m wondering if the latest lithium batteries running 3.6 V or 7.2 V or even 11.2 V (as used in model aeroplanes) isn’t going to be a much better reservoir.
    I’m also wondering if the up-and-down of voltages, from the solar panel to the battery to the beacon, cannot be done in fewer steps, or even eliminated completely?
    So here’s the challenge: Please send me your ideas (including eBay links if possible) for a better and more efficient system. The best design will be featured in the next issue of RadioZS.

    Until next time,

    73s de ZR6LU Leon Uys from Johannesburg 0825735580

  • Beaconing Five Modes in Twenty Minutes

    Beaconing Five Modes in Twenty Minutes

    While WSPR’ing across multiple bands (“band hopping”) has been done before, I thought it might be interesting to do five different modes on the same band. It was easier done than said!

    Argo SlowHell callsign
    Argo SlowHell callsign

    I was sitting with a customer’s QRP-Labs Ultimate3S beacon on my bench, all built up and ready to test. It was a single band version with the LPF for 40m installed. Nicely constructed and in perfect working order.

    After sweeping the filter and adjusting the LCD brightness and setting the output bias (all of 5 minutes – these are very easy beacons to build) I wondered what I could do as a “torture test” because WSPR’ing on 40 meters is so … common?

    It occurred to me that if I can’t jump to five or six different bands, why don’t I jump to five different modes?

    And that, as they say, is how the fight started.

    Setting your Frames
    Before using the Ultimate3S beacon, you have to enter your callsign and a few other basic details. The little Ultimate3S beacon has two pushbuttons on the front with which you can set and select your choices, by running through a menu system. I see it as two separate tasks (I’ll explain below) and a little bit of preparation will help you along nicely.

    The first decision you should make is how often you want to repeat your message(s). There is an informal arrangement to repeat a WSPR message not more frequently than 10 minutes, with 20 minutes probably a better choice.

    To start with, let us hypothetically hop to 5 bands:

    Each WSPR frame takes about two minutes and must start exactly on an even minute boundary. I have arbitrarily decided to start on top of the hour at 00:00:00, and each consecutive transmission will start on the next two-minute boundary e.g.
    00:00:00 First transmission frame – 40m WSPR
    00:02:00 Next transmission frame – 30m WSPR
    00:04:00 Next transmission frame – 20m WSPR
    00:06:00 Next transmission frame – 15m WSPR
    00:08:00 Next transmission frame – 10m WSPR
    00:10:00 Beacon calibrates after each transmission cycle
    This is how we used to do it for “WSPR-2” but it is very important to note that each mode has its own peculiarities and for example JT9/JT65 may use 1 minute frames and WSPR-15 uses 15 minute frames. I’m using WSPR-2 to make things simpler.

    Task One: Choose your Cycle
    In the above example you will notice that the last transmission starts exactly on the eighth minute and lasts for almost two minutes. There is barely 5 seconds left before the tenth minute begins. This is a BIG problem because the beacon needs time to calibrate the synthesizer, an activity which can take 30 seconds or 60 seconds or whatever you have chosen in your setup. Clearly, if the beacon starts exactly on the tenth minute, it will still be busy with calibration when the wake-up horn blows for the next cycle. Bad news!

    Thus, in the above example I could choose a 12-minute cycle, which is fine (six cycles per hour), but it might just be better to give it a small break and start your next cycle on 20 minutes into the hour, leaving a few minutes for breathing space.

    On the other hand, nothing prevents you from running a hard 24 x 7 x 365 schedule with no breaks. It is not a technical issue, it is just good manners to leave a break.

    Task Two: Choose the contents of your Frames
    Now that we have an idea of how long we want to make our cycle, we can decide the payloads for each frame. As I said before, if we want to only do WSPR we would end up with five frames like we did in Figure 1.

    However, if we only have one band with only one LPF (Low Pass Filter) fitted, we can choose to hop between modes. The little Ultimate3S can do 18 modes standard out of the box, and some of those modes even have sub-modes.

    A simple choice would be to target the more popular modes that are easily spotted. Let us put WSPR in the first frame, followed by a QRSS frame, then some SlowHell which is a gorgeous mode, then a CW-ID because it might be good manners and finally a JT65B because I have never heard what it sounds like.
    Here is a concept:
    Starting on the top of the hour again:
    00:00:00 First transmission frame – 40m WSPR
    00:??:00 Next transmission frame – 40m QRSS
    00:??:00 Next transmission frame – 40m SlowHell
    00:??:00 Next transmission frame – 40m CWID
    00:??:00 Next transmission frame – 40m JT65B
    00:??:00 Beacon calibrates after each transmission cycle

    Notice I didn’t put times for the frames, because I have no idea how long each mode takes. I could sit down with a sharp pencil and a calculator and attempt to work it out, but hey it is just so much easier to actually program the above sequence and measure how long each one takes, and this is what I found.

    First, QRSS:

    Putting this all together I assembled the following cycle with a duration of less than 20 minutes:
    Start Duration Frame / Mode
    00:00:00 2 min First transmission frame – 40m WSPR
    00:02:00 6 min Next transmission frame – 40m QRSS
    00:07:00 8 min Next transmission frame – 40m SlowHell
    00:16:00 secs Next transmission frame – 40m CWID
    00:17:00 1 min Next transmission frame – 40m JT65B
    00:18:00 1 min Beacon calibrates after each transmission cycle
    18 minutes cycle time (more or less)
    To cut a long story short, if I set my cycle time to 20 minutes I should be able to get through all five frames and have a small safety margin. This is what I finally programmed (with approximate times):

    Figure 4: Mode-Hopping with Frequencies
    Conclusion
    This was a very interesting exercise and it worked out so well. I’m still changing some of the frequencies (e.g. SlowHell) to find locations that are easier to spot, but that is simply fine-tuning to the already working concept.
    Should you be interested in obtaining my “Cheat-Sheet” for the above setup, please do not hesitate to contact me and I’ll email you a copy.

    73s de ZR6LU Leon Uys from Johannesburg 0825735580

    Ends.

  • No Sound from my SDR

    PSDR
    PSDR
    And in other news, I’m trying to play with this cute little SDR receiver (the cuteness which I am sharing with you in another post), but I’m having mega problems.

    Don’t get me wrong: The issue is not SDR or this cute little Rx. I own and operate a Flex-1500 which has quietly become my almost all-time favourite desktop radio. Software Defined Radios are just awesome. I can install Virtual Audio Cables and serial port replicators and connectors in all the configurations I’m using. I have also played extensively with other variations of hardware kits over time and I would like to think that I’m not an expert but that I can make successful contacts with a SDR.

    Thus, when I needed to squeeze an experimental (not top-of-the-line) and not very good (yet) but definitely tiny (as in physically small) receiver into my Ultimate 3S beacon from Hans Summers over at QRP-Labs, I bought a PSDR module from my friend Anton Janovsky over at Giga. Measuring a fractional 30mm x 40mm the size was exactly right, and it requires a 12v input which I already feed to the Ultimate 3S so that wasn’t going to be a problem. The receiver itself wasn’t going to win any awards for noise or quality, the circuit is a simple Johnson counter with 7474 circuit group and Tayloe detector circuits – more info over at Pandatron. No filters or pre-selection or anything, but good enough for a proof of concept prototype. I might even use the pre-existing LPF filters with a bit of cutting and soldering to the boards.

    The really exciting thing is that in the latest Ultimate 3S from QRP-Labs with the Si5351A synthesizer, it is a piece of cake to tap another output from the frequency generator and use that as the LO (Local Oscillator) input to the PSDR module. A very elegant solution emerges! Forge ahead and spend the money!

    Coming home and temporally connecting it to an AD9851 DDS Function Signal Generator (also from Anton at Giga) and using my trusty Lenovo ThinkPad in the shack, I can’t decipher anything. Really? Nothing.

    To cut a long story short the issue is that the modern laptops don’t have stereo (yes, two channel) inputs. Google it and sift through the millions of hits. The best summary I found was at temporaryland dated 2008 over at his website of rm42 called “Consumer alert – Sound-Mix intentionally crippled laptops” in which he explains that for reasons that makes no sense, modern laptops can only record in MONO from their built-in sound cards. And in the case of Lenovo, maybe they are scared of the DRM police, but they made it a HARDWARE limitation.

    This is important to me, as the PSDR gives out I/Q signals similar to just about any other experimental SDR kit, it needs TWO signals to the processor. Ultimately (pun intended) in the Ultimate 3S I was going to consider using the Analogue inputs’ A/D converter to pick up the sounds for me although I’m not there yet in the design.

    But to hit the wall so early with such a silly limitation is simply stupid. There is a work-around – buy an external USB sound card like the STLab M330 (only 16 bits). But that is an unnecessary expense and extra wires to plug in and extra things that can go wrong. Needless to say, I’m no longer a Lenovo fan.

    So the point of this message is: For the moment, if you want to play with I/Q signals from a SDR receiver, make sure you have a stereo line input. From there, SDRSharp will make your life easy. But without the underlying hardware you are screwed.

    Let me know what you did as a work-around.