4NEC simulations + VNA measurements for vertical antenna design

image My old vertical tuner can’t withstand QRO power levels as the tuner is limited to approx 150W. I am therefore working on a new multiband vertical for QRO operation. Its best to try to be finished before winter sets in(soon approaching as I write this blog post). Instead of using traps, I will tune the antenna like a Marconi type antenna over a ground plane with switchable or tunable L/C networks down at the feed point. The challenge with multiband antennas that is going to cover all the 40, 30, 30, 20, 17, 15, 12 and 10m bands, is that there will be frequency ranges where the real impedance is very high. A high real impedance is not possible to tune out with L or C and also difficult to match with a L network. It can be fed and matched with a tapped parallel network, but  there will be high voltages present and vacuum capacitors will be needed for QRO operation. L networks are easier on most bands and I try to use only one HV capacitor in one parallel network for 18 MHz (at least that is the plan). The trick is to have a proper length radiator that is tuned so that the impedance peaks will lay outside the ham bands of use. At least one band will have high impedance, but it should be possible to have fairly low impedance above that band. I did a 4NEC numeric antenna simulation to investigate the expected impedance range before sizing the radiator in the real life. What to look for is the zero phase transitions (look at the pink curve above). The first zero phase transition is the quarter wave resonant point simulated in 4NEC to be around 8,5 MHz. The next zero phase transition is around 17 MHz. This is the half wave resonant point. The impedance is very high at this frequency. Then there is a zero phase transition  around 25,5 MHz. This is the 3/2 lambda resonant point. Here the impedance is low again. From the simulation graph it can be seen that 7, 10, 14, 21, 24 and 28 MHz will be possible to match with a L network. 18 MHz will have to be voltage fed because the impedance is very high.

IMG_0716_w800

To verify the simulations made with the Numerical Electromagnetic Code (4NEC) simulator I did some vector network analyzer measurements in the feed point end of the self supporting fiberglass mast that supports the vertical. The VNA S11 plot can be seen on the PC. The VNA unit is placed inside the tuner enclosure. (The ground plane is buried and is relatively extensive). The impedance peak of the half wave resonant point can be seen on the PC. However, there were some unexpected effects that affected the VNA measurements. I suspect that the master calibration was not good. Will have to look at that later. (The blue plastic sheet placed on the ground is laid there to be able to more comfortably work on the ground without becoming wet and dirty. The gray “ring” to the right is a concrete support for my soldering iron (ELRA ca. 1980 model still in good shape). I use a chair as a “PC support” to avoid placing the laptop on the ground. Cables to the house and control cables are routed below the surface in tubing.

How to upgrade your Windows installation without an internet connection

Sometimes the need arises to upgrade an old Windows installation. If you do have a slow internet connection or no internet connection, this may be a significant time problem. A full Microsoft download of SP3 and all hot fixes can take many hours on a slow Internet connection. Perhaps you now think: why is this relevant? I always have a fast internet connection, don’t I? But is this in fact true? What about at  a customer site with a slow DSL connection. What if the internet connection is down? What if it is an embedded system? What if you are installing from an old XP pre SP1 DVD where the new Microsoft Update methods are not supported? Well, in those cases you need WSUSOffline that can be downloaded from http://www.wsusoffline.net/ This is a set of scripts that automatically downloads the service packs, hot fixes, .NET frameworks and language support you need from Microsoft’s servers. You can select what components to install (se below image). The install files together with an installer script can be copied onto a USB memory stick. When you run the installer script on the machine you want to upgrade, everything happens automatically and you will, when the process is finished, have a fully updated Windows installation. I used this to upgrade an old machine with an old outdated XP installation on, for use with my CNC machine numeric control software.

How to control the plane when using the rectangle tool in Sketchup

Sketchup is a nice 3D drawing program. It is also free. (Lets hope it will stay that way after Trimble bought Sketchup from Google).

One very annoying “feature” of Sketchup that makes many new users abandon the tool is that there seems to be no way to control the plane you draw a rectangle onto (when using the rectangle tool). The arrow buttons don’t work (why?) and it seems arbitrary what  plane the rectangle ends up on. Thanks to the nice people over at Sketchuation, I learned a secret: the rectangle locks on to the PLANE THAT IS MOST PARALELL to the PLANE OF YOUR SCREEN! TRY IT!

image Now the rectangles are drawn on the blue-red plane.

image Now the rectangles are drawn on the blue green plane.

By the way, the shift lock doesn’t seem to work properly even if the Sketchup documentation seems to indicate that it should

How to get ARRL AAT.EXE working under XP SP3

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I recently started to have problems with AAT.EXE from ARRL under XP. AAT.EXE is a DOS program used for calculating efficiencies of antenna tuners of L and T types. The user specifies QU of the inductor and capacitors, capacitor capacitance range, max voltage that the capacitor can tolerate, and some other parameters. AAT.EXE then makes two nice tables identifying where the tuner is most effective, where the tuner has a high loss, where the tuner will see a too high voltage values over the capacitor etc. The tables are generated in a .SUM file and a .LOG file. The problem is that the keyboard suddenly ddid not work in the XP dos box that is opened. I think this happened after upgrading to SP3 or after some security upgrade. I am not sure. What I did to solve it was to make a .BAT file containing this text:

mode con: cp select=865
aat.exe

This selects the codepage that is Norwegian. This solved the problem! If you have another keyboard layout you can find the codepage you will have to try here: http://www.kostis.net/charsets/

Here is an example of the output from AAT:

image

Does DX-WIRE DXW-174 meet published specs?

I Recently bought some DX-Wire DXW-174 cable from http://www.dx-wire.de/brit/ I was eager to check out if the cable meets the published specifications. (See below picture in yellow. This is the published specifications from the manufacturers DX-WIRE’s website )

To  verify the published specs, I took a roll of 100m and did a S21 measurement with my vector network analyzer. The VNA was calibrated with open, short, 50+jØ, crosstalk, thru, completely open loads. The S21 plot with dB scale and 5dB/division is shown below.

 Dx_wire_loss_100m

Results: the loss at 100kHz measures 1,29dB and the loss at 28 MHz measures 13,51dB.
Conclusion: this is almost exactly the spec that DX-Wire states on his webpage. I am satisfied with the accurate data published by this supplier. I therefore can recommend his product. However be aware of that 100m on HF with this cable will give you far too high loss even at 80meter. 10-15 meters should be no problem though. The loss on lower frequencies is lower than other cables made for higher frequencies with no solid copper core.

ALL NINE AZORES ISLANDS, CU1 – CU9, ACTIVATED AT ONCE!

 

Are You Ready to Fly to Azores for Free by Making Nine QSOs with CU stations?

Those of you willing to spend 24 hours or less on the radio are eligible to participate in an Azores lottery for two all-paid packages to the beautiful Azores Islands in the Atlantic, completely free of charge.

The project is organized by the Azores-Finland Friendship Consortium in partnership with the Amateur Radio Associations of the Azores Islands and supported by the Azores Promotion Agency (ATA) and Azorean Airlines (SATA). Just look at <www.visitazores.com> and make up your mind. Not many people know that the Azores consist of nine populated islands, stretching over a distance of 602 km (305mi) from East to West, next to USA and Europe. And it is not widely known that the Azores have their own airline (SATA) flying to each island, in addition to many destinations in Europe and North America. Each island has its own characteristics and its own blend and alone qualifies for your visit there. While these islands count for a single DXCC entity, they offer three (3) IOTA groupings.

With this unique AZORES 9 ISLANDS HUNT, an invited international group of amateur radio operators together with resident Azores amateurs will be activating the nine islands, offering an opportunity to the world to contact these islands all at once over one weekend.

Activity Weekend

Saturday, September 29, 1200 UTC to September 30, 1200 UTC (24 hours). These stations will be active starting Friday, September 28 as soon as they become operational.

Frequency Windows

CW:  7000-7015, 18080-18090 and 14050-14065 kHz

SSB:  7175-7195, 18120-18135 and 14250-14275 kHz

Nine Islands and their Stations

Santa Maria, CU1ARM;  San Miguel, CU2ARA; Terceira, CU3URA;  Graciosa, CU4ARG; Sao Jorge, CU5AM; Pico, CU6GRP;  Faial, CU7CRA; Flores, CU8ARF; Corvo, CU9AC.

Operators and Island Hosts

Sergio, CU1AAD; Jose, CU2CE; Francisco, CU2DX; Guilherme, CU2IF; Domingois, CU3CS; Guilherme, CU4AB; Jose, CU5AM; Jorge, CU6AB; Manuel, CU7CA; Claudio, CU8AAE; Joao, CU9AC; Franz, DJ9ZB; Richard, DF9TF; Nigel, G3TXF; Michael, G7VJR; Diane, K2DO; Rich, KE3Q; Mike, KI1U; Marius, LB3HC; George, N2GA; Martti, OH2BH; Juha, OH8NC; Ghis, ON5NT; Carine, ON7LX; Claude, ON7TK; Alex, OZ7AM; Kenneth, OZ1IKY; Yuri, VE3DZ and  Ed, VE3FWA.

Two Hunt Awards

Those making a QSO with at least 5 different islands will have a corresponding number of tickets placed into a lottery for a free trip to the Azores (e.g. if you have QSOs with 7 islands, you will get 7 lottery tickets). Additionally, the first 25 operators making QSOs with all 9 islands will be eligible for a second lottery. The free trips are from the closest airport served by SATA; including flight, accommodation and transfers..

During or immediately after the weekend, the logs will be posted on Club Log to display your band/mode slots. The lottery will be drawn on October 15, 2012.

QSL Cards

All QSOs will be confirmed through the bureau network with special full-color cards.  Direct QSL requests via Jose Melo, CU2CE.

The bandpass filters for Azores Island Hunt arrived

The bandpass filters for the Azores island hunt arrived today. The filters are of W3NQN design. Team Norway are going to have two stations on air at the same time from the same location in the Azores, so these filters will be crucialwe think. I will try to do some S21 measurements with my vector network analyzer on them to verify 1) Filter characteristic, 2) Stop band attenuation, 3) Return loss

Is lead based solder banned for all electronic purposes?

KESTER SOLDER24-6040-0066Many sources on the internet seems to indicate that lead based solder is no longer possible to purchase and is in fact banned for use in electronics. However, this is not the case. It is correct that the EU has passed a regulative that prohibits the use of lead based solder in new consumer electronic products. However, the use of lead based solder for repair of older equipment is still perfectly OK as far as I know. Also, new military electronics is ok to manufacture with lead based solder. I was starting to worry about soldering problems that may affect many amateur radio projects like soldering PL259 coax connectors, after my supply of solder went out. With leadfree solder, a much higher temperature is often necessary to use. The center of the non teflon PL259 connectors then melts and several other problems occur. The leadfree solder doesn’t flow as well as lead based. I us the 60 Sn / 40Pb variant that has been the standard for decades. Farnell sells it and has it in stock.  I have replenished the stock to last for several years in different thicknesses so i have for SMD, hole mounted, plugs and larger devices.

Here are Farnell’s ordering codes for good old lead based solder:

1610446 SOLDER, 40/60 2.36MM 453G;
419310 SOLDER WIRE, 60/40, 1.63MM, 500G;
453614 SOLDER WIRE, 60/40, 1.0MM, 500G;
5090787 SOLDER WIRE, 60/40, 0.5MM, 250G;
5090830 SOLDER WIRE, 60/40, 0.7MM, 500G;

Just go ahead and order so you have solder supplies for hobby use for 30 years. Not easy to know what the bureaucrats in EU will think up next!

Analysis of a tank circuit and notch circuit with the DG8SAQ VNA

image series lc dip IMG_0459

Experiment 1: I did an S11 analysis with my VNA on a 500pF transmitting capacitor in parallel with an airwound copper coil of good cross section. The question is how to interpret the first picture. The voltage over the parallel circuit is in phase with the drive voltage and almost as high in amplitude as the drive voltage when there is a real component present. (Blue trace, left image). The drive voltage cannot drive a current when the circuit is in steady state oscillation since the circuit has almost the same voltage over it as the drive voltage itself. Low voltage differential, results in low current. This is the definition of high impedance. Low in frequency the resultant voltage is not in phase however the voltage amplitude close to the resonance is almost as high as the drive voltage. The circuit presents a inductive load. Above the frequency there is a change from inductive to capacitive load. (Red trace). It looks like the phase changes abruptly, but I interpret it as a high impedance that occurs only due to a change from high inductive to high capacitive voltage. The phase goes “over the top” but only since someone defined capacitive reactance as minus. The impedance is still high and almost real close to resonance. |Z| represents the resistance to AC current in this context. It is the length of the R+jX vector.

Experiment 2: after that I did a S21 sweep of the same components in a series notch configuration as per VE2AZX’s paper http://www.arrl.org/files/file/QEX_Next_Issue/Jan-Feb_2012/QEX_1_12_Audet.pdf  to try to determine the Q (of the coil primarily – I assumed the Q of the capacitor very high compared to the coils Q).

The second picture gives the notch depth so the Q can be calculated as per VE2AZX’s QEX paper http://www.arrl.org/files/file/QEX_Next_Issue/Jan-Feb_2012/QEX_1_12_Audet.pdf

Note1: the picture to the right is of the S21 test, not of the parallel circuit and the frequency may have changed slightly as the coil were changed between the two experiments if I recall correctly.

Note2: don’t worry about the long leads. This is an exercise in understanding the design and operation of antenna trap circuits and loss in reap circuits due to resistive losses in the inductor primarily. The leads would be almost as long in a real trap.

G4WPW microphone connector database

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G4WPW has made a nice database covering microphone adapters for most amateur transceivers. This is a good tool for contesters and DX-ers adapting microphones and headsets for their new radios. You can check out his webpage here http://homepage.ntlworld.com/rg4wpw/date.html