Hi folks, I've previously build NetCDF libraries on my Mac with IBM XL Fortran extensions. However, I now need to use Absoft Fortran Pro 9.2 in order to compile 64-bit code. I've run into the problem Russ Rew described in January 2005 at the following website: msg02849.html As Russ mentions, './configure' and 'make' work, but 'make test' fails because the library has an extra ' after the NetCDF C functions, and hence they are not found. I've not been able to find any solutions to this issue in the discussion groups. I have this problem with v3.6.0, v3.6.0-p1, and v3.6.1-beta3. I've tried lots of different flag options.
These are the ones I've got right now: export CPPFLAGS='-DAbsoftProFortran' export CFLAGS=' export FLIBS='-lU77' export FC='/Applications/Absoft/bin/f90' export FFLAGS='-w -YEXTNAMES=LCS -YEXTSFX= -YCFRL=1' export F90='/Applications/Absoft/bin/f90' export F90FLAGS='-w -YEXTNAMES=LCS -YEXTSFX= -YCFRL=1' Does anyone know of a solution to this issue? -Mike Mills LASP, University of Colorado, Boulder.
This article was reprinted in OSCAR News, March 2018: If you want to receive, then you need a decent antenna, otherwise you will receive more noise than picture. For polar orbit satellites, one needs an antenna with a mushroom shaped radiation pattern. It needs to have strong gain towards the horizon where the satellites are distant, less gain upwards where they are close and as little as possible downwards, which would be wasted and a source of noise. Most satellites are spin stabilized and therefore the antenna also needs circular polarization, otherwise the received signal will flutter as the antennas rotate through nulls. The helical antenna, first proposed by Kraus in 1948, is the natural solution to circular polarized satellite communications. It is a simple twisted wire - there seems to be nothing to it. Various papers have been published on helix antennas, so the operation is pretty well understood.
Therefore, it is amazing that after more than half a century, there is still a new twist to the helical antenna. Backfire Helix The backfired quadrifilar helix array is especially popular for amateur satellite communications, but the results reported by Chris van Lindt and Julian Moss (G4ILO) regarding the antenna drawing on the right, left me curious and wondering whether we are dealing with an internet myth, or a comedy of errors, or a design that is too sensitive to build easily. Chris reported that the QFH exhibits nulls that are useful for tuning out terrestrial interference. How can an omni-directional antenna have a null? That comment rang a huge alarm bell in my mind that the commonly used QFH antenna was not designed or built right.
To figure out what is going on, I modeled the QFH in NEC2. First of all, I don't really like backfire helices, because that is not the way that Kraus intended them to be implemented and because much power is lost in the forward direction which will then hit the ground, while you are trying to talk to the sky.
The Kraus helix design calls for an earth plane / reflector, which will project the back lobe forward. Without the reflector, the radiation pattern of a helix is very messy, but since that is what lots of people are using, I modelled it this way. A model is never 100% the same as a real antenna, but the NEC cards presented below allows any true card carrying radio/computer geek (a.k.a. Radioham) to easily play around with it and get a feeling for the critical antenna constraints, before building one. The helical antenna work published by Kraus in 1948, shows that a thin helix radiates in normal mode, while a fat helix radiates in axial mode, as shown in his famous angle vs circumference graph.
Simple Thin Helix in Free Space - No Reflector The picture above, shows what a single turn thin helix radiation pattern looks like if there is no reflector - an upside down mushroom. The bulb at the bottom is turned skyward when the thing is flipped over in a backfire configuration, while the twirl at the top is then pointed to the ground. So while in backfire mode it is nicely circular polarized and nicely omni-directional, there is nevertheless significant radiation towards the ground. I plotted these with CocoaNEC on a Macbook (since it makes the prettiest plots) and it cannot rotate a helix in the x or y axis, so if you want to flip it, you got to turn your computer around. CocoaNEC also cannot handle a half turn helix, so I used one full turn. You could use xnec2c on Linux or BSD for the full set of NEC2 helix options, at the cost of uglier graphics.
Helical Arrays A monofilar helix is a very long and unwieldy thing. It is easier to handle a shorter antenna and there are various ways to achieve that. Every half wavelength, the current in an antenna goes to zero. When the current goes to zero, it doesn't matter if the wire is open or closed circuit, so one can cut an antenna every half wave length and it will still work the same. Similarly a long helix could be considered to be an array of identical little helices in a row.
One could even take these little helices and put them side by side and it will still work the same, or one can rotate and interleave them into a multifilar helix. The main problem with a multifilar helix is hooking the filaments up with the correct phasing.
Bifilar Helix In a bifilar design, the one helix is rotated through 180 degrees. It also needs to be driven with a signal that is rotated 180 degrees. This is easy to do with a balun. Connect the centre wire to one helix, the shield to the other and then wind five to ten turns in the coax feed to increase the impedance of the sleeve. That makes a simple infinite balun. Quadrifilar Helix A quad design is the same idea as the bifilar, with four helices each rotated by 0, 90, 180 and 270 degrees.
A quad design is nice and compact, but getting the phasing right is much more of a chore. A 1/4 wave length of coaxial cable will give a 90 degree phase shift. This is easy to do for a hobbyist, since all you need is a calculator and a ruler. QFH - 4 Phased Driven Elements Most of the QFH designs on the wild wild web however, use one short and one long loop of wire (As from the design for the OSCAR 7 satellite).
The idea is to make two helices that are too long (inductive) and two helices that are too short (capacitive), then hook them up in parallel. One loop then leads 45 degrees, while the other one lags 45 degrees electrically, thus giving a 90 degree phase shift. See this However, if the wire dimensions are not exactly right, then it will be anything but - especially the capacitance. Hence that comment about the handy nulls in the omni-directional pattern.
QFH - 1 Driven, 3 Parasitic The above plot shows a quadrifilar helix in free space with one driven element and three parasitic elements. This plot doesn't look much different from the one above it and it eliminates a major head-ache, so you can then set your phasers to stun. The NEC model is the same, just remove the three transmission lines. Reflector The antenna god (a.k.a.
Kraus) intended helices to work with reflectors. If we expand the model to include a ground plane, the pattern turns right side up and the stem of the mushroom (almost) disappears, leaving only the bulb, so all the energy goes the right way, providing another dB or two of gain. QFH - 1 Driven, 3 Parasitic, Reflector It is the same as the one above, but you don't need to crick your neck. Similarly, you could make a helical array with any number of filaments and get any amount of gain (practically up to about 15 dBi), but the quad neatly solves the impedance matching problem, since it has an impedance of about 40 Ohms and can be hooked up with garden variety RG-58 co-ax without bothering with a tuning element.
Circular Polarization The electrical field is forced to rotate clockwise, when looking up at the sky, by the helix rotation. To confirm that you do the right hand polarization correctly, get a nice big wood screw. If the helix uses a reflector, then it needs to follow a normal right handed screw. If the helix is backfired without a reflector, then it needs to be opposite to the right handed screw. A wrong way polarized antenna will cause a big drop in signal strength. Opposite polarization is effectively a permanent null pointed at the satellite. To receive, you need a special antenna that will handle the rotating signal.
Dimitris Papadeas at SatNOGS built a variety of 2 meter band helical antennas: To see how well it works, I modeled his design with NEC2 using CocoaNEC on my Mac. The radiation pattern looks cool. With 12 dB gain, it would be good on a simple tracker or for permanent pointing at a Geo sat. You cannot just point it up at the sky to catch a polar bird, since then a satellite would have to pass almost directly over head, which doesn't happen very often. 2 m Band Helical Antenna Pattern At this size, a crossed Yagi would be rather easier to build though. A helix is more suitable for the 70 cm band, where it will be much smaller and easier to support.
CM Helix, SatNOGS, v4 CM Frequency: 434 MHz CM Wavelength: 691 mm CM c=299792458 m/s CM Radius = 110 mm CM Turns: 8 CM Circumference to wavelength ratio: 1 CM Reflector perimeter to wavelength ratio: 0.8 = 553 mm CM Winding diameter: 220mm CM Winding circumference: 691mm CM Winding spacing: 172 mm CM WInding length: 5696 mm CM Reflector perimeter: 553mm CM Total length = 172 mm x 8 t = 1376 mm CM Reflector plane 1 mm below zero to avoid a short with start of helix CM CM Feedpoint(1) - Z: (111.340 - i 1152.400) I: (0.0001 + i 0.0009) VSWR(Zo=50 立): 99.0:1 CM Antenna is in free space. CM Directivity: 11.08 dB CM Max gain: 12.51 dBi (azimuth 0 deg., elevation 90 deg.) CE GH 1 500 0.172 1.376 0.110 0.110 0.110 0.110 0.003 SM 10 10 0.277 -0.277 -0.001 0.277 0.277 -0.001 SC 0 0 -0.277 0.277 -0.001 GE EX 0 1 1 0 1 0 0 0 0 0 0 FR 0 1 0 0 434 0 RP 0 90 90 0 0 0 1 4 0 0 0 EN This design will work over the whole 2 m band and is good for Hamradio, Weather and Cubesats. What I like about satellite work, is that it is low power, sensitive work, so you need to know what you are doing, but you will not zap anyone touching your antennas when you happen to be transmitting at 3 or 5 Watt. The modern earth observation satellites produce amazing pictures and they change all the time, due to the sun angle, seasons and weather Notes Helical antennas superimpose nicely. That is, if you would wind four helixes together, each 2 turns, every 90 degrees, it would be equivalent to a single 8 turn helix, just much shorter. Here is the seminal work on the quadrifilar helix La voila! The default system is Raspbian, which is loosely based on Debian.
This is excellent. Years ago, I tried a Beaglebone Black and it came with a cripple version of Angstrom Linux which I didn't like and the board is consequently lying somewhere in my junk box. The Raspbian system is aimed at clueless newbies and the ssh daemon is disabled by default.
To use it as an embedded server, without having to plug in a keyboard and screen, you need to add one line to a configuration file, before you plug the SD card into it. Here is how to do all that. Get your RPi3 from here: Download a Raspbian image zip file from here: Open a terminal and unzip with: $ ark —batch filename.zip That will take a loooong time (On Linux machines, you probably have to do this on the command line. A graphical tool will very likely run out of memory and crash. Just double clicking it will work fine on a Mac since they usually have enough RAM installed.) Become super user: $ su - password Write the img file to a miniature SD card: # dd if=filename.img of=/dev/mmcblk0p bs=1M or on a Mac: $ sudo dd if=filename.img of=/dev/disk2 bs=1000000 Make a headless pi.
Now do Update followed by Advanced, Expand Filesystem. Then do Finish, Reboot, Yes. Solid State File Server With four 256 GB USB flash memory widgets plugged in, you can make a 1 TB solid state file server for about 1100 Dirhams - something that was unimaginable just a few years ago. A file server doesn't have to be fast.
It is limited by the network speed, not the processor. So a little Rpi makes a very cost effective file server. So far, I managed to get only two 256 GB Sandisk widgets. They came in perfectly idiotic packages, so I had to break all the plastic off to get them to fit in the USB sockets.
For protection, I wrapped one layer of self vulcanizing tape around them. I don't know what the clowns who designed the little enclosures were thinking, but it was clearly form over function - now it is function over form.
I always prefer doing things the simple way, so I formatted them with ext4 and mounted them using /etc/fstab in /mnt/sda1 and /mnt/sdb1 like this: $ sudo fdisk /dev/sda1 -t 83 -w $ sudo mkfs.ext4 -L sda1ext4 /dev/sda1 y $ sudo nano /etc/fstab /dev/sda1 /mnt/sda1 ext4 defaults,noatime 0 1 $ sudo mount -a.and ditto for the other one. I have never managed to figure out how to mount a disk so that a common user can write to it. My workaround is to make a directory on the thing and assign the user name and group to that, so now I have /mnt/sda1/dataa and /mnt/sdb1/datab and chowned them to pi. $ sudo mkdir -p /mnt/sda1/dataa $ sudo chown pi: /mnt/sda1/dataa So the access problem is solved without having to read another manual on disk mounting and with that, I now have 512 GB of online solid state storage, accessible over ssh and scp. Heat These Sandisk USB watchammacallits get very hot and there are long stories on the Sandisk forums about heat problems. So removing them from their plastic packaging is actually a good idea, since that improves the air flow over the chips.
The good news is that most people say they last for years, despite the heat. Rsync Backup Script I made a RSA key file with ssh-keygen and uploaded it with ssh-copy-id, as described here The IP address of the Rpi was added to /etc/hosts, so I don't have to keep typing it in. One's natural instinct is to make a backup script that includes all the files that one needs to backup - that is wrong! The trick with a backup script, is to keep it simple and include everything in your home directory and then exclude a few generic things.
That way, the script is maintenance free and will always work, irrespective of how you move files around. My Macbook rsync backup script now looks like this: #! /bin/bash rsync -avze ssh -progress -delete -max-delete=10 -max-size=20M -exclude '.Trash' /. The max-delete protects against catastrophes and max-size prevents making backups of large ISO files and movies, since those things can always be downloaded again from wherever they came from. Secure Shell SSH on Windows Note that Windows 10 now finally supports OpenSSH, so you could also connect securely to a sshd server with sftp from the latest Win10, but not from Win8.1 or Win7.
Deduplication with Hard Links Once you start to save backups, you will rapidly accumulate duplicate files on the server. You can eliminate these with the hardlink utility and regain many gigabytes of storage space: $ hardlink -c directoryname A hard link is an additional directory entry for the same file. When you delete hard links, the file will only disappear, once the last hard link is deleted. This is much better than soft links, where you can delete the file, leaving a bunch of broken links all over the place, with no easy way to clean up the litter. You can perhaps think of hard links as smart links and the other as soft in the head links.
Clouds in the UAE Desert Weather satellites are generally considered to be the most useful of the lot, since the data is open and not encrypted and the signals are quite strong. The NOAA operates both geostationary and polar observers. The geo satellites can only be received if you happen to live in its antenna footprint (North America), while the polar satellites pass overhead twice a day wherever you are. This article describes how to get an image from one of the NOAA polar satellites, using a cheap ($25) little RTL-SDR radio receiver. These pictures are interesting, since the weather is always changing. You also need to make a decent, else you may have more noise than picture. Interface Specifications NOAA-15, NOAA-18 and NOAA-19 are probably the easiest to interface to.
All three satellites broadcast using an ancient system termed Automatic Picture Transmission (APT). The APT signal is 2.4 kHz, frequency modulated, described here and here Each facsimilee line starts with a tone burst and the monochrome line is encoded onto a 2.4 kHz tone by frequency modulation at a rate of two scan lines per second.
To decode it, you need a phase locked loop to convert the FM signal into a varying brightness level - simple as that. Which Computer System To Use Most ordinary mortals use MS Windows computers.
These are generally good for playing games, writing letters and doing bookkeeping, but they are not very good for engineering use. The problems are many fold: The operating system scheduler is not real-time, the USB interface is buggy, scientific software invariably require specialized libraries of specific versions, which sometimes clash with libraries that are already installed - known as DLL Hell. The result is that if your special program happens to work, then you are in luck. If it doesn't work, then you are out of luck, there is nothing you can then do about it and your project is hung - Nuf sed. A Macintosh system is better, since it is based on FreeBSD, but it suffers from some of the same software library issues when using precompiled (non-Free) software. However, if you use Free software, then it is much the same as Linux/FreeBSD. In order to use Free scientific/engineering software, you need Xcode (The C compiler provided by Apple, in the App Store), Macports and Homebrew.
With these tools, you can compile specialized software, much the same as on FreeBSD/Linux. Linux and BSD have good real-time performance and gives one full control over everything. On these UNIX systems, Free software is installed by downloading the source code and compiling it on your machine. This sorts out all the library dependency issues for your system, with the result that specialized scientific and engineering software generally work much better than on other systems. Note that the future NOAA software systems will all run on Linux and other operating systems will be supported through Linux virtual machines only, as explained here So, for Linux users, it is the same idea as in this article. You need to install rtlsdr, gpredict and WXtoImg. All the same, just a bit easier, since the repositories have what you need and you won't need weird paths - everything will be in the usual places.
The Heavens Above The web site is very useful, but the best way to see when a satellite will pass overhead is with gpredict. Install gpredict from macports: $ sudo port selfupdate. $ sudo port install gpredict.even longer wait. Finally, you can run it: $ /opt/local/bin/gpredict. Gpredict Satellite Orbit Prediction You need to select the satellites that you want to track, but it is not immediately obvious how. There is a tiny down arrow at the top right, select Configure, then scroll down to the NOAA sats.
Enter your own ground station co-ordinates and then if you hover the mouse over a bird, you can see how many minutes are left to reach your position. There is also command line version called predict.
It can be used to get the pass data for a satellite for use in scripts, in order to automate a weather map system. UAE Desert Colour Image by Wxsat There are other decoders and renderers for Linux/BSD, but I have not tried them all yet. The secret seems to be to edit the file after recording it and trim the inaudible start and end and save only the good part in the middle in. On a Mac, you can trim a file with Quicktime, but it cannot save the result in.wav - it exports to.m4a. To trim, save and resample a.wav file to 11.025 kHz, you need to get from Sourceforge, or use sox.
RTL-SDR The software required for the RTL-SDR radio widget is described here: You need CubicSDR and rtlsdr as described in the above link - or gqrx on Linux. Frequencies: You can look at and listen to the satellite data with CubicSDR. NOAA15: 137.62 MHz. NOAA18: 137.9125 MHz. NOAA19: 137.10 MHz The actual frequency is 1.9 kHz lower than the above (the upper side band) and the modulation type is Wide Band FM (35 kHz).
Once tuned in correctly, you'll hear the fax lines go cheap-cheap-cheap. At two cheaps per second. If it doesn't sound good, then it also won't decode properly.
You need to play with the gain setting. My turnstile antenna is on the roof, hooked to a 15 meter 50 Ohm RG58U co-ax going in a window to the RTL SDR dongle plugged into a little netbook. I use '-g 49' to for NOAA15 and NOAA18. The NOAA19 satellite is more powerful and needs a lower gain setting of '-g 35'. The satellites also have other sensors on them and in future there will be other frequencies in the L and X band with much more data, as explained here Antennas If you would use a simple dipole antenna, then you would only be able to receive something when the bird is almost directly overhead. This may be good enough at first. A better receive antenna that you can build yourself using common commercial items, is described here: You need to know how to wield a drill, soldering iron and tin snips.
Do wear glasses, so you don't poke an eye out with the rods while working on the thing. The advantage of this antenna is higher signal gain upwards and less noise from the surroundings. However, the gain is not so high that you need to track the satellites with a mechanical rotator.
Just point it vertically up at the sky. A plastic, water filled umbrella base, is all you need to keep it standing up.
Weather Data Capture Once you figured out when a bird will fly overhead, go outside with your whole kit and kaboodle - you won't receive much indoors, if anything. It depends on what your roof is made of and you won't get a very interesting image at night either. So, horror of horrors, you have to get out of your cave in daylight! The 2400 Hz 'cheap-cheap' line data screeches can be received with the rtlfm program and transcoded to wav format with Sound Exchange ( sox), as below. Note that on my Macbook sox resides in /usr/local/bin and rtlfm in /opt/local/bin, probably since one was installed with homebrew and the other with macports. This kind of confusion is one reason I prefer Linux for engineering work.
The dangling dash tells sox to read from stdin - the piped data from rtlfm. Once you got the data, down sample it with sox to 11.025 kHz for decoding with wxsat. For example (NOAA15 137.62 MHz - 1.9 kHz, USB): $ /opt/local/bin/rtlfm -g 49 -d 0 -M fm -f 137.62M -s 55k -l 0 /usr/local/bin/sox -r 55k -t raw -e s -b 16 -c 1 - wxdata-55k.wav $ /usr/bin/sox wxdata-55k.wav -c 1 -r 11025 wxdata-11k.wav I got better results by setting the gain with -g 49, than by leaving it to automatic. Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: 00000001 Using device 0: Generic RTL2832U OEM Found Rafael Micro R820T tuner Tuner gain set to automatic. Tuned to 137618100 Hz. Oversampling input by: 19x. Oversampling output by: 1x.
Buffer size: 7.84ms Exact sample rate is: 1062 Hz Sampling at 1045000 S/s. Output at 55000 Hz.long wait.
Press Ctrl-C to stop and close the wxdata.wav file. You can pipe the signals straight into the wxsat rendering program and get the image in real-time, but making it work the simple way first, is hard enough for starters. Also note that there are multiple types of weather fax modulation modes used by polar sats, geo sats and HF radio. Russia also has different satellites. The above examples are for the older polar NOAA satellites only. $ sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.atrun.plist The recording will run forever, unless you stop it with a scheduled kill command!
So you can make a simple killall script like this: #!.bin/bash killall n19 and schedule it like this: $ at -f./n19stop now + 178 minutes To capture 10 minutes of data. Other Software There are also weather fax relays on HF radio for mariners. The encoding is somewhat different and fldigi can be used to decode them. The most comprehensive meteorological tool kit is probably gempack You can also look into wview Setting the above up will likely be quite an adventure.
More Information A detailed guide for tuning WxSat and making false colour pictures by combining the images from two cameras (visible and IR) in the satellites:. Group for Earth Observation (GEO):.
Satellite Networked Open Ground Station (SatNOGS):. Digital Weather Satellite Reception:. The middle elements are driven and the electrical field is forced to rotate clockwise, when looking up at the sky, by using a delay line. Wrap your right hand around the antenna rod, with your thumb pointing to the sky. You need the wave to travel from your knuckles to your finger tips.
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Therefore if you drive the element at your knuckle, the next one towards your fingertip needs a 90 degree (1/4 wave length) delay. Tape Measure Antenna The rod can be wood or metal. Wood is easier to work, but here in the desert, it can be harder to get. I bought a garden rake with a nice wooden varnished handle for 40 Dirhams and cut the ra ke off! A 1 inch wide 5 m Stanley tape measure was sacrificed for the elements. Tape Measure Turnstile Antenna The re flector is 1/2 wavelength long.
The driven element is 5% shorter and the director is another 5% shorter. The spacing from the reflector to the driven element is 1/4 wavelength. The spacing from the driven element to the director is 0.15 wavelength. This is a typical 3 element Yagi design. The dimensions are not very critical, since the frequency is low. The overall length of the reflector is 1027 mm. The length of each arm of the driven elements is 488 mm.
The overall length of the director is 927 mm. The spacing between the reflector to the driven elements is 513 mm. The spacing between the driven elements and the director is 308 mm.
The cabling is RG58, 50 Ohm or similar. The delay line is RG58, 342 mm in length. The balun is a clip on ferrite, or 5 to 10 wraps around the rod below the driven elements. The elements can be made from a 24 mm tape measure, or from 6 mm aluminium tubing from a clothes dry rack or whatever tubing you have on hand.
It will work with almost anything, since the frequency is low. It is easier if the elements are cut 50 mm longer and trimmed after mounting - for finger and eye safety, trim the corners 45 degrees and wrap the ends with tape or heat shrink tubing. A beach umbrella stand makes a handy upright support. The NEC2 Card deck: CM Turnstile Crossed Yagi, three element each, 2 meter band, 146 MHz CM Elements are made of 6 mm Al tube (r = 3 mm) CM CM CocoaNEC Summary: CM Frequency 146.000 MHz CM Feedpoint(1) - Z: (21.111 + i 4.130) I: (0.0456 - i 0.0089) VSWR(Zo=50 立): 2.4:1 CM Antenna is in free space. The coaxial cable is unbalanced, while the dipoles are balanced.
It is therefore necessary to add some inductance to the cable shield, by wrapping five to ten turns around the rod, just below the driven elements. Note that the wrap only affects the shield. The centre conductor is shielded and therefore is blissfully unaware that it is wrapped around a stick. Alternatively, clamp a ferrite around the cable. This will prevent the cable shield from radiating and disrupting the antenna pattern.
Again, the ferrite will only affect the shield, not the inner conductor. Conclusion A tape measure antenna is not rugged and sooner or later a wire connection will break, but the advantage is that one can fold it and get it in and out of a car, making it good for educational use. A quick check outside showed that it works. I could see a satellite signal get stronger over a period of time.
Unfortunately it is raining. It is the middle of the desert and it is a veritable rain storm - a misty drizzle - not good for my computer! The signal is stable, and doesn't fluctuate, so the circular polarization is working.0O0- I have subsequently also built an antenna from a laundry dry rack 6 mm aluminium tubes.
Customizations Update ForteMedia microphone effect library. Realtek drivers for mac. Posted by Anonymous on Dec 11, Fix recording issue for ALC Don’t use ‘ and by the help of this toll-free number you can contact to HP Printer tech support and get all the benefits by solving your all queries. HP Compaq Presario V And are they plugged into the correct jack? Many USB printers require you to install the software first without the printer connected to the computer.
This looks rather better and sturdier and there are enough tubes left over for a 70 cm turnstile transmit antenna also. Once I have both of them done, I'll build an electric screwdriver rotator mount for it.